Build an air travel table mount for a tabletop dobsonian

A tabletop dobsonian is a great inexpensive but capable and portable telescope. The mount is a single arm hybrid dob base. The basic ones can be disassembled for air travel, and reassembled at the destination with a screwdriver, but you still have to have a suitable table at your destination to set it on.

However, the scope that I have, the Sky-Watcher Heritage GTi 150P (6-inch), has an electronic go-to mount that I would be very hesitant to try to take apart and reassemble. It's too big to fit in an average suitcase, but I wanted to take the telescope on a dark sky vacation via airline. What to do?

The optical tube assembly (OTA) can go in a 22-inch carry-on hard shell roller suitcase as long as it's well packed. The base that I built, consisting of a mount and table or tripod, would need to be disassembled to fit in a checked suitcase. I have a 26" roller suitcase that I used for this. 

The total weight of OTA, mount, and table is about 25 lbs.

While you may not want or need to build this entire table mount, I hope this will give you some ideas if you are putting together your own travel setup.

Why not a tripod?

Some people use a sturdy photo tripod for their travel scopes, such as the Innorel RT90C, a carbon fiber tripod that is often recommended for light travel scopes. I have a few problems with that, though. First, I don't like standing when observing, which would be the case if mounting my 6-inch Newtonian on one. It gets tiring very quickly if  you're out observing for several hours or more, and it's difficult to keep your eye steady at the eyepiece when standing. Second, I was concerned with the stability. Third, and you knew this was coming, a good, light tripod is not inexpensive, especially after buying a mount to put on it. 

Choosing the mount

I decided I would buy a lightweight mount and build a custom table for it. I chose the Svbony SV225 alt-az mount. It's relatively inexpensive and sold without a tripod. It handles the 10 lb. weight of the 6-inch tube with accessories very well. The SV225 is just over 5 lbs, so it's the heaviest piece of the table mount, but still quite manageable for air travel. The motions are smooth and the slow motion controls partly make up for the tracking I'd be missing by not having the go-to mount.

I chose not to adapt my existing table for the mount because I wanted to save a bit of weight and would also need to raise the mount so that the mirror end of the tube would clear the table when pointed at the zenith. With a spacer block raising it thus, the eyepiece still sits 2-1/2 " lower than with the stock Virtuoso GTi go-to mount. Also, at 20" in diameter, my existing table would not fit in the suitcase. Case closed.

Building the table

Instead, I built a new table out of 3/4" pine plywood in a triangle shape with the corners cut off, a pretty common design to save weight. for the center spacer block I used two pieces of 3/4" plywood and one piece of 1/4" plywood. This raises the mount just enough, 1-3/4", for the mirror end of the scope, including the adjustment screws, to clear the table at the zenith. The block is on the left in the image. The edges of the top pieces are rounded to provide clearance for the OTA. 

I inset 1/4-20 T-nuts into the top of the table, same as my previous tables. The legs have hanger bolts screwed into one end, so they just screw into the T-nuts from underneath. See my previous article on building a table for details. The paper azimuth circle is glued to the tabletop with contact cement and sprayed with a clear matte sealer.

Making the table triangular instead of round allows for a wider footprint for the three legs for greater stability, with a smaller width to fit in the suitcase. Instead of the corresponding circle's diameter, the width of the table is the measurement from the center of one side to the opposite corner, which is further decreased by nipping off the corners. So a triangle cut from a theoretical circle of a larger diameter can fit where that same circle wouldn't, if you follow me. Basically, you have three legs at the same distance as you would for the circle, but with a smaller width for packing (reduced by the width of the blue arrow in the diagram). I cut the triangle from a theoretical 20" circle. The width in green is 15-1/2", so I reduced it by the 4-1/2" in blue by making it a triangle with cutoff corners.

The problem with a typical alt-az mount like the SV225 is that it must be mounted in the center of the table, which then puts the center of gravity of the scope well away from center and makes it easier to tip over, especially when the back of the scope is positioned over a side without a leg immediately behind it. This would be the same if it were mounted on a tripod. To account for this, I angled the legs a little more this time, about 15 degrees versus 10 degrees, to make a larger footprint and give it more stability. The legs are also a little longer to make up for the difference in height of the go-to mount versus the SV225. I made the legs out of 2x2 balusters, just like my other table. They screw into T-nuts hammered into holes in the tabletop 13-1/2" apart.  

While it is more stable, it's still not as stable as I would like. The solution is to add weight below the mount. Yet I wanted to keep it light for travel. I'll get to the that in a minute.

The hardest part of this project was figuring out how to cut the triangular tabletop out of a piece of plywood without first cutting a circle and wasting a lot of the wood. After wrestling with the geometry of it all, I finally figured it out and made the cuts. Whew, I don't like my brain to have to work that hard.

Back to adding the weight for stability. Since I had my original 18" tabletop made from 1/2" plywood that had eyepiece holder holes already drilled into it, I decided it would make a great lower level rack for the table. Not only would it help stabilize the legs, but it would also provide a place to put a large rock (or bag of rocks, or some other "found" objects). Weight really does wonders for the stability of tripods, which is why they sell stone bags for them. Same for this arrangement. It would also give me a place to put eyepieces while observing, since the small amount of clearance of the OTA over the tabletop would not allow for storing eyepieces in holes there. It just fits in my 26" suitcase.

The next problem was how to attach this 18" circular eyepiece/weight rack to the three table legs below the main tabletop. I solved this by wrapping a cam buckle strap around the outside of the legs (the orange strap visible in the image above). The circular board sits nicely on the strap, leaving the eyepiece holes clear. Easy to set up and break down with no tools, screws, bolts or nuts.

I don't use straight-through finders, so I have a right angle correct image (RACI) finder mounted on the OTA's dovetail bar. I've been adding azimuth circles to all of my scopes, so I added one to this table, too, printing an 8" outer diameter circle from Blocklayer.com. See my article on adding an azimuth circle for details. I use the same magnetic digital angle gauge for all of them. The azimuth pointer is a long strip about 1/2" wide cut from a piece of aluminum roof flashing. It had to reach from the rotating top part of the SV225 base down to the tabletop, while clearing the spacer block. I attached it to the SV225 with Velcro so it is movable when aligning the table mount in azimuth at the beginning of an observing session. The SV225 has altitude and azimuth scales (the black circle below the slow motion cable in the image), but they are very small and pretty much impossible to view while observing.

The legs are 14-1/4" long, cut from 2x2 treated deck balusters, with the ends cut at 15 degree angles. I used a cheap plastic protractor to mark the angles and a mitre box with bar clamps to cut them with a hand saw. This puts the table height at 14-5/8" and the max eyepiece height around 42". 

The whole table mount setup breaks down and fits with a bunch of other gear in a 26" suitcase. I do set the arm of the SV225 in the more compact position that it came shipped in, and that requires an Allen wrench that comes with the mount. I also need a small socket wrench with a 3/8" socket to remove the 3/8" center bolt holding the mount and spacer block to the table. It screws in from underneath. This is not something I would want to do every night, but for air travel to and from my destination it's fine. 

Finding a suitable chair

You really have to consider everything when traveling for astronomy. One of the biggest issues was not having a suitable observing chair. Regular folding chairs are too big and heavy for a suitcase. The place I was staying at didn't have any suitable chairs. I normally use a Denver style adjustable observing chair, but an adjustable chair isn't necessary for a scope this small and there's no way I would try to take one on a plane. So I found a small folding tripod chair with the sitting height that I wanted, and added a round stool cushion, fastened to the seat with sheet stays, as well as tennis balls to the legs so it wouldn't sink into soft ground. The stool is only 1.4 lbs. and folds up to into a 17" bag. It's going to be great for short sits while birding and hiking, too (minus the cushion and tennis balls).

This setup worked great on my trip to Arizona Sky Village, and my brother and I were really glad to have the 6-inch along!

Bino Body Mount - build a travel mount for binocular astronomy

I recently took a dark sky vacation to Arizona. I wanted to bring my 15x70 Garrett Optical binoculars, but they are 5.5 lbs., and I can't hand hold that with any kind of steadiness. I had previously built a zero gravity chair mount, but I wouldn't have access to a zero gravity chair. 

I was pondering compact and, of course, inexpensive solutions, and came upon this post on Stargazers Lounge. The observer uses a mini-tripod with one leg removed, resting the other two legs on his shoulders. This seemed like a great idea, except you still have to keep your elbows raised, which introduces both unsteadiness and fatigue. 

Taking that idea a step further, I devised a very simple apparatus that I call the Bino Body Mount, which solves the problem of having to raise your arms by adding a 90 degree handle to each side of a basic wood frame. You don't have to buy a mini-tripod, just a cheap 1x2 furring strip (my go-to wood for this kind of thing), a binocular tripod adapter, a 1" 1/4-20 stud knob, two star knobs, two hanger bolts, a flat washer, two fender washers, two neoprene washers, four wood screws, and two tennis balls (well, three really because they come in 3-packs). See parts and tools list at the end.

The mount breaks down flat for packing by removing three knobs. It's very lightweight, and can be used standing or sitting in any type of chair. Your arms stay at your side to provide comfortable support when standing and rest on the arms of your chair when sitting. As you recline further back toward the zenith, the shoulder bars transfer more and more of the weight to your shoulders, resolving the problem of raising your arms and tiring quickly. The Bino Body Mount also improves the view and fatigue factor with any size binoculars because you don't have to hold them in front of your face with your arms raised. 

For Comet C2023/A3 (Tsuchinshan-ATLAS), I sometimes used the mount standing because it was relatively low to the horizon and I really didn't need a chair. It worked great. I wouldn't recommend standing and looking anywhere near the zenith with binoculars, whether handheld, on a Bino Body Mount, or on a tripod. That's just painful and awkward.

For objects near the horizon, you can sit up and rest your arms on the chair arms. 

Note: That's a Bino Bandit around the eyepieces. It's a neoprene eyepiece light shield that I highly recommend despite it's relatively high cost because it works so well. 

You're not going to get rock steady views with this, but surprisingly close, and your arms and neck won't get tired. My brother and I spent many hours on our Arizona vacation using these, and they worked great with almost no fatigue. You will primarily see a jiggle from your heartbeat. You can look around anywhere in the sky that you could just handholding the binoculars. You can loosen the knobs to tilt the bino bar at whatever angle works best for you. You can adjust focus with one or both hands.

At this point, I am using the Bino Body Mount for all of my binocular astronomy observations, regardless of whether I'm traveling or not. It's simple, it's lightweight, it's compact, it's inexpensive, it's easy to build, and it works very well.

Build it

The critical measurement is the distance from the tripod threads in between the barrels of your binoculars to the end of the eyecups, what I call the "thread-to-eye" measurement. The correct distance places the binocular eyepieces exactly where they would be if you were handholding them. This doesn't need to be super precise- within 1/2 or 1/4" is fine. You can tilt the bino bar when observing to make up for any slight error.

If you have multiple binoculars with different thread-to-eye distances, as is the case with my Meade roof prism binoculars, you just drill a pair of holes in the shoulder bars at the correct distances and you can easily reposition the bino bar as needed. Or you could just make two mounts!

See the parts and tools list at bottom of the post.

Step 1:

Measure and cut

Measure and cut a 1x2 furring strip into five pieces. You can make them whatever lengths that work for you, but I made the two shoulder bars 12" long, which accomodates most porro prism binoculars with an approximately 4" thread-to-eye distance. On a second Bino Body Mount, I cut the bars 13-1/2" long for my Meade roof prisms, since the measurement is about 6" for them. The bino bar (the crosspiece that holds the binoculars) is 11". The two handles are 12". One six or eight foot furring strip will be plenty and leaves some extra in case of "constructor error."

Step 2:

Bino bar

Drill a roughly 11/64" hole in the center of both ends of the bino bar (the 11" piece) and insert a 2" 1/4-20 hanger bolt into each, using the "two-nut" technique (thread two nuts on the end, tighten them together, then screw in by turning the upper nut, screw out by turning the lower nut). The threaded end of the hanger bolt should stick out far enough to accomodate the 5/8" width of a furring strip, another 1/8" for a neoprene washer, 1/16" for a flat washer, leaving about 1/4" for the knob to screw onto. So leave about one screw thread of the wood screw part showing and you should be fine. You can always adjust it.

Drill a 1/4" hole in the middle of the bino bar. This will hold the tripod adapter using the 1" stud knob and flat washer.

Step 3:

Shoulder bars

Drill a 1/4" hole in each shoulder bar where the bino bar crosspiece hanger bolts will be inserted. This should be the measurement above plus about 6 inches. So for a 4" thread-to-eye measurement, drill the hole about 10" from the end of the shoulder bar that will rest on your shoulder. Put a neoprene washer between the bino bar and the shoulder bar, then on the outside of the shoulder bar, a 1/4" flat or fender washer and the knob.  

Step 4:

Test the fit. People's bodies vary, so if the above calculation doesn't work, make an adjustment by drilling a hole a little closer or further from the end. This is the important part, so make sure you get it right and it's comfortable for you. Adding tennis balls will give you a little more distance, and putting a thicker pillow behind your head or wearing a hood will give you a little less. It doesn't have to be perfect, just close enough to work for you. 

Remember you can make minor adjustments by loosening the side knobs and changing the bino bar tilt slightly. I like to have the binoculars tilting slightly downward compared to the shoulder bars (see images above), except when observing near the zenith. In that case, I like to have the binoculars pretty much pointing straight out parallel with the shoulder bars, especially when observing in a chair that doesn't recline very far.

Cut an X or hole in two tennis balls and stick them on the ends of the shoulder bars so they fit snugly and won't fall off easily. This is harder than it sounds. Tennis balls are tough! I used a large folding knife to poke an initial hole, then cut the rest until it fit snugly on the end of the 1x2. See this video, or if  you have an electric carving knife, this video. I always wear heavy leather gloves when working with sharp things near my hands that could slip. 

Step 5:

Handle bars

Attach the handle bars on the outside of the shoulder bars about 7" from the ends that rest on your shoulders with two wood screws per side. You can also add tennis balls to the handle bars for the ultimate in opulence.

Step 5:

Finishing touches

With fender washers under the two side knobs, a flat washer under the bino mount knob, and neoprene washers on each end of the bino bar (to help keep it from slipping without having to overtighten the knobs), test it all and if no further adjustments are needed, sand and paint the wood pieces. 

The final assembled Bino Body Mount (with my 15x70s mounted).

Front view showing placement of the neoprene washers.

The pieces disassembled for packing in a suitcase. This mount has longer shoulder bars with two sets of holes to accomodate both my porro and roof prism binoculars. No tools required to assemble and disassemble. Just unscrew three knobs.

What's better than one Bino Body Mount? Two Bino Body Mounts! One for me and one for my brother. I hope you enjoy yours!

[1/27/2025 update] Some tips on use:

• Always carry the apparatus by holding the binoculars. That way, if you forgot to tighten something or it got loose, it's the mount that will hit something, not your binoculars.
• Apropos the above, periodically check that the three knobs are tight.
• Some tilting of the binoculars from side to side on the tripod adapter is desirable so that if you are looking off to the side a bit it will stay lined up better with your eyes. 
• When observing near the horizon while sitting, I like to rest my palms on the side knobs with my fingers curled around the ends of the handle bars, tucking my elbows in for support

Parts list

1x2 furring strip (6 ft.)

Binocular tripod adapter (example)

1" 1/4-20 stud knob (most come in multi-packs- good for lots of projects)

Two 1/4-20 2" diameter threaded five-star knobs

Two 1/4-20 2" hanger bolts

Three 1/4" hole flat washers 

two 1/4" neoprene washers

Four 1-1/4" wood screws

Two tennis balls

Tools:

Tape measure or ruler

Power drill with 1/4" and 11/64" (or close) drill bits, and phillips head bit (or screwdriver, or both)

Hand or power saw

Two 1/4" hex nuts and two 7/16" combination wrenches or pliers (to screw in the hanger bolts)

Sturdy pointed knife to make holes/cuts in tennis balls

Sandpaper, tack cloth, paint, and paintbrush

Nice to have but not essential: 

    Mitre box (to make straight cuts)

    Clamps (to hold the wood for sawing and drilling)

Add an azimuth circle to a your Dobsonian and ditch that straight-through finder

A couple of years ago I added azimuth circles to the bases of my two Dobsonian telescopes, and recently added one to a go-to tabletop dob to replace the often unreliable go-to system. Coupled with a digital angle gauge, available in hardware stores or online for about $20-30, this allows me to dial in the altitude and azimuth coordinates for any object, creating a "push-to" system. I can literally find anything anywhere now without straining to look through a straight-through finder, as long as I can see it in my scope and it's included in my sky charting app. 

The main advantages are:

• No neck strain looking through a straight-through finderscope or red-dot finder (this was the impetus for me)
• Ability to find objects in areas of sky without a lot of bright stars for starhopping, or in light pollution
• Quick and easily repeatable
• No finicky and power-hungry electronics (the angle gauge takes two AA batteries that last a long time)
• Inexpensive

What you need and how you use it

You will need an app to look up the alt-az coordinates for an object in real time. As the earth rotates, these coordinates constantly change, and are based on your location and time. As always, I recommend Sky Safari Pro (Android or iOS) as a great all-round app that will list the coordinates and show you the star field once you've gotten close to an object. Even the Basic version has the alt-az coordinates, but for a smaller database of objects.

In the Sky Safari Pro screenshot at left, I have selected galaxy NGC 7331, centered it, and the current azimuth (88.5) and altitude (62.4) are shown in the upper left. Make sure you center the object. If you don't, it will not show the correct alt-az coordinates. Then move your scope tube so the pointer on your azimuth circle is set on 88.5 and your digital angle gauge shows 62.4. Look in the eyepiece and, if you have properly leveled and aligned the scope, the object should be in there somewhere. If not, check the wider view in the RACI finderscope if you have one, find the object, and adjust the pointer as needed.

The following are the steps required to find an object with the azimuth circle/angle gauge method. Steps 1-6 are done at the beginning of each observing session. Step 7 is repeated for each object you want to observe.

1. Set the telescope base so that the azimuth circle is roughly aligned with either the Sun or Moon during daylight, or any bright object at night.
2. Level the scope. A cheap bubble level will do fine. I use an app. I made some plywood squares with tread tape on them for rough leveling and use composite shims for fine tuning.
3. Put in a low power eyepiece and find a bright object that's easy to align on without a finderscope. Just sight along the tube at something not too high in the sky. Once centered in the eyepiece, adjust your RACI finderscope, if you have one, to match.
4. Look up the alt-az coordinates of the object in Sky Safari or your preferred app. The altitude should match your digital angle gauge plus or minus the accuracy of the gauge. Make sure your gauge is sitting evenly on the top of the scope tube.
5. Adjust the azimuth pointer to match the azimuth shown in the app. Don't wait too long, as this will be constantly changing.
6. Look in the eyepiece and you should see the object, or at least the star field around or near the object. Identify the exact location within the field by comparing your view with the star chart.
7. To move to another object, look up the new object's coordinates and move the scope until they show on the gauge and circle. You may have to adjust the azimuth pointer slightly for inherent inaccuracies if you are in a different part of the sky, but you will be close.

I added right angle correct image (RACI) finderscopes to my scopes to verify I dialed the coordinates in correctly, help identify dim objects among star patterns, or move around an area to look for other nearby objects. You can get by with just having one RACI finderscope and putting a shoe on each telescope, then moving the finderscope between scopes. I do that with a 6x30 finder for my 4.5 inch and 6 inch scopes. I prefer an 8x50 for my 10 inch, and it can handle the extra weight of the bigger finderscope better.

Get a digital angle gauge

This is the easy part. If you have a telescope with a metal tube, pretty much any digital angle gauge will have a magnetic base that will work well with it. If you don't have a metal tube, you can stick on a metal plate or design some other system to attach the angle gauge. You'll need to cover the display with transparent red tape or something to dim it down to acceptable levels.

I chose a Klein Digital Angle Gauge because it has white numbers on a black background, so minimal light, and all I needed to do was cover it with a tranparent red material. I used the plastic pack that the gauge came in as a holder for the red material, and duct taped in a scrap piece of red acrylic I had leftover from resizing a laptop shield and some craft foam. It slips over the gauge with a friction fit. Just make sure the red material doesn't blur the display making it unreadable. The Wixey is another popular digital angle gauge. You can try to find one without a backlight if you are just going to use a red flashlight to look at it.

Making and installing an azimuth circle

There are many variations on the azimuth circle because telescopes are different and observers are different. Check out the megathread Degree Circles on Cloudy Nights for ideas and pictures. The standard way is to make the azimuth pointer movable, usually using magnets. You can also make the circle movable, but that's usually more complicated. You decide how you want to do it, but here's what I did.

For my 10 inch, I cut a notch in the round bottom of the rocker box and glued a paper azimuth circle to the round ground board beneath that. The azimuth pointer rides on a magnetic strip in the notch so I can adjust it during initial alignment and make subsequent fine adjustments.

For my 4.5 inch, my design of the base did not lend itself to simply gluing on a paper circle and cutting a notch, so I cut a circle out of a 1/8" thick sheet of FPVC, which is a light, semi-flexible vinyl, using a craft knife. I made the cut slowly and wore leather gloves for protection. I had to go over the cut mark multiple times until it cut all the way through. Then I glued a printed paper azimuth circle to the FPVC circle and assembled it below the bearing material disk. I drilled a hole in the center through which the bearing bolt passes. Here's my post on Cloudy Nights about my 4.5 inch project, with additional pictures.

For the 6 inch, I couldn't separate the round bottom of the rocker box from the triangular ground board for fear of messing up the electronics, so I cut the FPVC into a ring shape, glued on the paper azimuth circle, then sliced the ring in two places and attached it to the ground board with some double sided foam tape.

The cuts are next to 55 degrees and 295 degrees so I could attach the ends of the pieces to the "ears" of the ground board that you can see sticking out slightly from below the azimuth circle. I used small pieces of double-sided foam tape. You only need to make two cuts, 120 degrees apart, so you can position the bigger ring piece and then the smaller one to complete the circle.

The azimuth circle added 3/4" to the radius all the way around the base. I had to make a new, larger table for the scope because the circle now blocked the eyepiece holders. This new one is 20" in diameter. The original was 18". I took the opportunity to eliminate the unused 2" holes that I had on the old one and make four 1.25" holes on each side, so no matter where I am sitting, I have lots of places to store eyepieces. I also used 3/4" plywood. White paint makes it easy to see where you're putting stuff and makes it less likely someone will walk into it in the dark. See my post on making a table for a tabletop telescope .

Use the website blocklayer.com to design and print an azimuth circle that fits your telescope. Some people take it to a FedEx or another store that will print it for you. I tried that and they printed it slightly oversized, so I just printed it in several pages on my home printer and fit them together. That introduces a tiny bit of inaccuracy, but you're likely not going to get it perfect anyway. It'll still work fine.

The Blocklayer site has a huge number of templates of all types, and it's fun to browse. But for this project, I used Circle Divider templates. There is a green "Metric Version" indicator at the top, which is actually a button to change it to Metric from the default "Inch Version." Leave it showing Metric.

Due to the popularity of creating azimuth circles for telescopes, Blocklayer has added a template for this specifically: Protractor - Setting Circle. It does essentially the same thing as the Circle Divider template, and you could use that instead. It appears they have removed the option to set the scale counterclockwise, which you would need if you had a movable circle and a fixed pointer.

You have many options, including having the numbers on the inside or outside of the scale, black-on-white or white-on-black, size and length of tick marks, numbering of every 10 or every 5 degrees, etc. Choose what you like, but think about readability from where you are observing and using a red light to see it. Change the "Diameter inches" setting to what will work for your scope, then hit "Calculate" or use the slider. The circle needs to fit on your lower ground board or fabricated circle or ring.

These are the settings I prefer:

• Black print on white background
• Tick lines (default)
• Primary increments 10 degrees (default)
• Number orientation = Radial -90 (so you can read the numbers correctly at the eyepiece)
• Outer marks - note that if you choose Outer marks, the diameter you chose becomes the inner diameter, so you need to adjust the size so the outer diameter is the diameter you need (e.g., your ground board is 22 inches, and so you need a 22 inch outer diameter circle, or a tiny bit smaller). Font size, tick thickness, etc. will affect this, so check the info in the center of the circle on the Blocklayer page and adjust everything with the sliders until you have it the way you want it and your outer diameter is the correct size.

If you like my suggested settings and have the same scope, you can download the azimuth circle PDF that I used for my Sky Watcher Virtuoso GTi 150P here. If you need a 22 inch outer diameter azimuth circle, here is the one I created for my 10-inch Hardin Deep Space Hunter. The Cloudy Nights Degree Circle megathread has a bunch of other files created for different scopes.

Once you have the circle the way you want it in Blocklayer, select "diagrams to PDF" at the top, and in the page that comes up, select the paper size you will be printing on, put in the file name, and hit the "Trim" button. Full printing instructions are at the bottom of the Blocklayer page. Hit the "PDF 1" button in the lower right below the circle (to exclude printing the tape that otherwise would also print out). 

Your own computer's settings will determine how you print it once downloaded, but make sure you are printing at 100% and select "tile large pages" or a similar setting that will print the circle over several pages. If you have it commercially printed, make sure they print at 100%. If it doesn't come out right, just adjust in Blocklayer and try again. I like to print a little smaller than the diameter of the ground board so the edge doesn't peel up.

Once printed, check the fit against your FPVC circle or ring. If it's good, glue it carefully onto the circle or ring using contact cement, making sure you get complete coverage with no bubbles or bare spots. Then spray the paper with several coats of a fixative (I use Aleene's Acrylic Sealer - Matte Finish) outdoors because these often have really bad fumes, especially Aleene's. 

Once dry, mount the circle or ring between the ground board and the lower rocker box. For my 4.5 inch, I drilled a 1/4 inch hole to fit the 1/4-20 center bolt, and the circle sits underneath the azimuth bearing plate. Yours might be different. For the Sky Watcher Virtuoso GTi 150P (6 inch), I had to make two cuts to remove an arc 1/3 of the circumference because I couldn't separate the ground board and rocker box. I then reassembled it into a ring and attached it to the ground board with a few small pieces of double sided foam tape. I tried larger pieces of foam tape, but fitting them under the rocker box board was a mess because they would stick before I could get the pieces in position. Smaller foam tape pieces worked much better and it still holds well.

You'll need to make an azimuth pointer. I made mine from a scrap of thin aluminum flashing material I had from a roof job, but you can pretty much use anything. I attached a tiny rare earth magnet to it using duct tape. I couldn't find any glue that would hold permanently- duct tape to the rescue again! Then I took a piece of magnetic tape and attached that to the rocker box board, so that the pointer will move with the rocker box. The azimuth circle is fixed on the ground board and the pointer rotates with the scope. 

For the Sky Watcher Virtuoso GTi 150P, I switched to using a strip of Velcro instead of magnets, because I kept knocking the pointer when reaching for the azimuth bearing lock knob. You can use anything as long as the pointer can be moved over an arc of about 30 degrees. Any less and it will be harder to rough align the scope when you first set it down and still be able to put the pointer within range. Put the pointer where you'll see it easily from your normal observing position. 

The Sky Watcher Virtuoso GTi 150P with new azimuth circle and larger table. The digital angle gauge sits on the top front of the metal lower half of the tube.

Mounting a RACI finderscope on a collapsible tabletop telescope

I recently bought a Sky-Watcher Virtuoso GTi 150P tabletop 150mm (6-inch) telescope. This is a slightly larger variation, with a go-to mount, of a popular design sold by Astronomers Without Borders as the OneSky, a 130mm (5-inch) altitude-azimuth mounted collapsible tabletop telescope, shown at left.

These telescopes have a Vixen-style dovetail bar attached to the solid part of the tube—the green thing in the pictures of my telescope below. This is how the tube attaches to the mount, which has a Dobsonian style groundboard for the azimuth (side to side) axis and a half-fork with dovetail saddle for the altitude (up and down) axis. The tube can be removed from the saddle and clamped back on with a single threaded knob, the knob sticking up from the blue tube in the picture of the OneSky, making this portable design even more portable.

The problem

For finding objects, or in the case of the go-to model, aligning the mount or finding objects when the go-to isn't cutting it, the scopes are equipped with a straight-through red dot finder that projects a red dot on a window in front of the stars. A clever design with many variations, but like some people, I have trouble—no, make that pain—bending my neck enough to comfortably look through one, especially at objects high in the sky. 

On my other two scopes I have added azimuth circles and a digital angle gauge to find objects by looking up their alt-az coordinates in an app like Sky Safari Pro, moving the scope so that the coordinates are set on the azimuth circle and the gauge, and then using a right angle correct image (RACI) finderscope to zero in on the target. A RACI finder doesn’t require neck contortions and shows a correctly oriented view like you would see in binoculars.

I wanted to add a RACI finder to the Sky-Watcher tabletop telescope, but the problem is that the front ring that holds the secondary mirror and focuser is extended out on two truss tubes so that the whole front half can collapse into the solid rear half that holds the primary mirror, making it quite compact. There is no good place to add a finder on the front ring and it would make the scope quite front-heavy, requiring some sort of counterweight for manual operation. Others have added reinforcement to the front plastic ring or have drilled holes in the tube to add a finderscope, but I didn’t want to do either of these things. 

The solution

I added a universal dovetail shoe (base) to a block of wood attached to the scope's dovetail bar (the green thing) and swap my RACI finder between my 4.5-inch and this telescope. Looking at the design, the long dovetail bar attached to the telescope tube has two channels that run its length and a single 1/4-20 threaded hole close to the front end of the bar. The hole is presumably for mounting on a tripod, but it’s at a very poor location for balance. I had seen others mount a laser pointer and finder on that part of the dovetail bar, so I experimented with mounting a Svbony SV182 6x30 RACI finder that I have on my 4.5-inch reflector. I zip tied it in place to see how it worked. The problem was that, sticking out straight from the dovetail bar, the finder was too far from the observer’s position and I had to get up and either lean over or walk around the back of the scope to the other side to use it.

If I were to fasten a block of wood to the end of the dovetail bar at a 90 degree angle, then I could mount the RACI finder on the end of it, bringing the eyepiece to a much better position, even better than if I had drilled a couple of holes in the solid tube to mount it. After doing just that, I noted a post on the OneSky megathread on Cloudy Nights that did something similar, but by drilling and tapping a dovetail clamp instead of using a block of wood. Same end result.

10-19-2024 Update: I wasn't happy with how far I had to scrunch down to look through the finder at or near the zenith, so I added an 8-1/2" extension bar made out of a piece of 1x2 furring strip where the dovetail shoe was and put the dovetail shoe on the end of the new bar, moving the finderscope forward and closer to the eyepiece. Wood screws all around. Shifts the balance slightly, but I just move the scope down the dovetail bar a small amount to compensate.

Here’s how to do it

[Note: See 10-19-204 updates below for an improved version that puts the finder closer to the eyepiece.] I cut all the pieces using a basic mitre box and a hand saw.

I cut a 5” piece of 2x2 baluster (vertical railing piece) that I had left over from making the legs for the telescope’s table mount. I cut a 45 degree corner on one end so I wouldn’t have a sharp corner sticking out. These balusters tend to vary slightly in cross section width, so I checked a few pieces before I found one where the dovetail finder shoe, or base, fits tightly in one direction—one more way to make it even more solid. Note: I used balusters rather than the 8’ lengths of 2x2 that they have because the balusters tend not to be as warped as the long pieces and they were actually cheaper per foot.

I glued and screwed two small pieces of wood to the block to sit in the bar channels and keep the block from rotating on the single bolt. I cut the two little pieces from a large size paint stirring stick (1/4” thick). The pieces are 7/16” wide and 2-1/4” long. I sanded them so they fit tightly into the bar channels.

This side will face the observer sitting at the telescope.

I dry fit the block and the two channel pieces to make sure they fit tightly in the dovetail bar. There are two screws in the dovetail bar at the bottom of each channel 1/8” from the front end of the bar. The block would need to sit behind these screws with the channel pieces butting up against them to add stability. I marked where the bolt would go through the block into the dovetail bar and also where I would need to glue the small channel pieces that would fit snugly into the two channels in the bar. I had cut them a little long just to give a bit more twist resistance in the channel.

Where the bolt would go through the block and screw into the dovetail bar, I countersank a 3/4” diameter hole about 3/16” deep, enough so the bolt head, with a 5/8” outer diameter - 1/4” inner diameter washer, would be flush or nearly flush with the surface, using a 3/4” Forstner bit. (3/4” because my wrench socket would fit in it so I could tighten the bolt.) You must do this before drilling the hole for the bolt so that the bit can center properly. It’s not essential to countersink the bolt head, but I thought it would be better than having it sticking out, and I recently got the Forstner bit set, so I’m eager to find reasons to use it! I then drilled a 1/4” hole all the way through the block, centered in the 3/4” countersunk hole.

I inserted the two little channel pieces into the channels and pushed them tight up against the screws in the bar channels. I inserted the bolt and tightened it to make sure the fit was good. Then I removed the bolt, put wood glue on the two channel pieces where they would join the block and bolted the block into place. Once the glue had dried for about 45 minutes, I removed the assembly and cleaned off some glue that got on the dovetail bar. It removes easily.

The dovetail shoe for the finder has four slots for screws. I screwed it into the top of the block with four 1-1/4” #6 wood screws. Everything looked good, so I took the shoe off the block assembly, painted the block assembly black, reattached the shoe, and attached the whole assembly to the dovetail bar. The shoe stays on the bar and the finderscope is removed for transport. This modification is also entirely reversible with no alteration to the telescope. [Note: With the updated extension, you'll screw the extension bar in here and screw the dovetail shoe to the forward end of the extension bar.]

The finished mount. Note the four screws added to the channel bars. I found glue alone did not hold. Make sure you recess the screw heads into the wood with a countersink bit so they don't scrape the dovetail bar. 

The finder is at a more comfortable, although still not optimum, location. I can also fit my head in there to use the red dot if necessary. The scope can rotate through the entire range of altitude motion without anything bumping or binding, but be careful when pointing above 50 degrees, as the additional weight of the finder will want to flip the tube backwards.

Packed up, the finder mount is out of the way and adds very little weight or volume to the overall package. Just loosen the two thumbscrews, slide the finderscope on, and tighten the thumbscrews. 

View from above when collapsed. The finderscope mount does not stick out beyond the round baseboard of the telescope mount. The dovetail shoe is mounted so that the thumbscrews point inward and are less likely to catch on a cover or other item.

Now I can use the RACI finder more easily and swap it between the two telescopes. It's still not an optimum viewing position especially at higher altitudes, although being able to rotate the diagonal on the finderscope helps. But for these collapsible telescopes, this makes a useful addition or alternative to the red dot finder.

10-19-2024 Update: The scope with the new extended mount for the finder. Because it sticks out further when the scope is collapsed, I plan on getting a 1-1/2" knob to replace the bolt holding the bracket to the dovetail bar, making it easy to remove for transportation.

Recording your observations

 

Jupiter-Venus conjunction, March 2023

 

July 3, 1990 (Miami, Florida)

Picked out major stars: Vega, Altair, Deneb, Arcturus, Spica, and Antares (near Moon). Found the “Teapot” and figured that was Saturn to the left (west) of it. Mosquitoes were fierce and it’s only July! Looked for M19- too washed out to spot it. Also M4. Traced out some of the constellations. Moon is gibbous—some good crater action on the “tan line”.

That was the first observation I ever recorded. I didn't even have celestial east and west sorted out yet. Not that I hadn't observed the sky with a variety of telescopes, binoculars, or the unaided eye before that. But this was my first year of "getting serious" with amateur astronomy.

But how serious are you about Sirius?

It's what you make it. It's a hobby. For some people it's a passion. But it's still a hobby. Most of your observations matter only to you, so consider that, when and if you record them. I do strongly suggest you keep some kind of observing log, for the following reasons:

• It will jog your memory to bring back specific nights and events
• You can compare observations made at different times, in different skies, through different instruments
• It's interesting to see your progress in the hobby, and your failures
• It will tell you if you've observed something before or if it's new to you
• You'll remember people (and critters) you would otherwise have forgotten

That's just a few, and it really varies depending upon the person.

I can only tell you how I log my observations. I don't always log details, especially for objects I've seen many times, unless I see something new in them. I like to keep it conversational and not too technical. I like to have fun. I don't like to be bothered recording the seeing, transparency, exact eyepieces and powers I was using, data from a sky quality meter, etc. for every observation. I'll note the sky conditions at the beginning of a session and if they change, as they often do. I keep it simple- who, what, where, and when. I already know the why. See my post on the Comet Shoemaker-Levy 9 impacts on Jupiter log entries to get an idea of what I put in there and how a log makes a great memento of a memorable observing session or event.

Two bins

My observing records end up in two bins: an observing log in narrative form, which includes notes taken while at the eyepiece that I then extract from the log and group together by object over time in a separate collection of notes files.

My actual observing log, as in the example above and at left, is a session by session narrative. I keep it in a series of Microsoft Word compatible documents, usually one document per year or half year, depending on how much observing I've done, and I'll add images from the internet for many of the objects. 

I note the situation, the people, animal sounds, big gusts of wind, spectacular lightning on the horizon—all those things that bring back the memory like it was yesterday. I'll also make notes at the eyepiece about specific objects. At the beginning of each session, I note the date, day of the week, location, and what equipment I'm observing with.

Periodically I'll extract the notes on specific objects, which I highlight in bold in the log to make them easier to find, and collect them in text files, which I call my observing notes. With this collection of notes, I can look up an object and compare what I'm currently seeing with what I have seen in the past from a variety of locations, in different sky conditions, and with different instruments. I aggregate the notes for each object into a single entry, as in the following example:

Veil Nebula (western portion), NGC 6960

Oct. 13-14, 1993, Chiefland Star Fest, Chiefland, FL

(4.5-inch) Quite bright- tried for dimmer side near the bright star in my scope- only a hint of its brightest part in 100x. Low power would be better if I had it.

Nov. 13-14, 1993, Lake Kissimmee State Park Star Party, FL

(10-inch) Nice view of the fainter section in the 10-inch SCT. Very bright with the nebula filter. Seems like there's a dark lane down the center of the nebulosity (this is the W section). E end visible with the filter.

Sep. 24-25, 2003, Skyline Drive, Shenandoah National Park

(4.5-inch) It's just such a nice transparent night I had to go for the Veil Nebula, and sure enough, it's pretty easy to see around 52 Cygni on both sides, not just the one brighter side, and I can see more than I usually can in those areas. I can see the other segment on the opposite side (NGC 6992) in the finderscope! It shows up nicely in 50x. I gotta say that's about as well as I've seen the Veil show up in this scope. I can trace the whole crescent shape of 6992 for at least 2 fields of view in 50x (almost 2 degrees).

...and so on.

Decades ago I wrote my notes at the eyepiece in pencil or pen. Then I used a handheld tape recorder. Then a digital recorder. Now I dictate in Google Keep using the voice typing feature, copy and paste into my log at a later date, and clean up the dictation errors. Google voice typing has particular difficulty with certain astronomical names, such as when I say "Ophiuchus," and it writes "all for you because," "ophelucas" (huh?), or the usual "off of Lucas." I'm used to correcting such phrases such as "and you see," for "NGC." A recent favorite is "IHOP address" for Saturn's moon Iapetus. 

Find a way to make it easy

Ideally, I would have a charting app at the telescope in which I could click on an object and it would bring up these observing notes for that object. Sky Safari falls short for me in that respect, in that it forces you to organize your notes by observing session, much like my observing log. But I want to see all my notes over the years for a single object in one place. I've tried to use one Sky Safari "session" to put all the observations for a single object in the comments, but the box has no scroll bar, there's no way to add images, and it's very clunky. 

I just wanted a simple app that I can update easily, add images, and most important, import and export through a standard format. 

I think I found just that in the Memento Database app. I started with an astro log template available through the app and modified it to include just two fields: notes and images. While it requires going between the Sky Safari and Memento apps, it's a pretty good second best solution. I use the app Twilight to dim and redden the screen while observing. iPhones do this natively.

I was able to export my notes from Sky Safari on the 1200+ objects I've recorded over the years, then import them to Memento, all via a .csv file. Cool beans. 

I downloaded images of the objects, resized them to keep the database small (the Memento cloud has 100MB free storage), and attached them to each file. Tedious, but fun and it helps me remember some of the objects I haven't observed in a while and should revisit. I like having images at the eyepiece to help determine if what I think I'm seeing is actually there.

Apps will come and go, so one of the keys is to be able to backup your notes and store them in a standard format like text or xml. I figure text is about as standard as you can get, so I stick to that.

Sometimes I just like to read through my old logs on my computer, and now the notes are portable so I can look them up at the eyepiece and even browse them while I'm waiting at the doctor's office. I did that today, reading my observing notes on the Comet Shoemaker-Levy 9 impacts on Jupiter, which were 30 years ago. I cherish the memories that I've preserved through my observing log and notes. How much would I remember without them?