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.

Here’s how to do it

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.

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.

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?

My favorite observing accessory

White duct tape. 

Okay, maybe not my favorite, but up there in the Top 10.

Why? Because it helps you find stuff at night. Not up there, down here. We worry about finding stuff in the sky, but when you drop something on the ground or walk into something in the dark, you’ll appreciate that being able to see stuff on Earth is almost as important as seeing stuff in the sky.

Few sites are so dark you won't see a piece of white duct tape more easily than something darker colored. I always keep a roll in the car.

Where to use it:

• On any equipment you don't want people bumping into in the dark, especially at public events with people unfamiliar with the size and shape of astro gear.
• Lens caps. Many lens caps are black. Drop one in the grass and you will need to turn a light on, not something you want to do unless you have to when you are observing. All my eyepiece caps and telescope covers have little squares of white duct tape on both sides so I can find them easily in the dark. Kudos to those companies that make the clear caps, but even they can benefit from a piece of white duct tape.
• Marking indicators. I have this thing about always forgetting to turn off red-dot finders. Always. So I put a couple of small pieces of white duct tape on the knob that turns it off. When they line up, it's off. Where to put the scope in the dovetail saddle? Mark it with white duct tape. Where does the telescope cap line up? Where do I grab something at night? White duct tape.
• At one site, we have a wooden fence gate that can be in various stages of open. I will invariably walk into it in the dark. Slap a piece of white duct tape on it.
• At another site, there was a big gopher hole. I stepped in it. You can be seriously injured by doing something like that. A stick with a piece of white duct tape on it kept me out of the hospital.
• Black telescope? Manufacturers love black telescopes, black binoculars, black cameras, black cases, black everything. A few strategically placed pieces of white duct tape will make it less likely to be stepped on, bumped, or run into at night, by you or someone else.
• Red LED flashlight. If it's dark colored, it's not going to do you much good if you can't find it in the dark. White duct tape.

And there's not much in the world you can't fix temporarily with duct tape, so it's always good to have it around.

I'm sure I've forgotten many other uses for it, and I'm sure you can come up with others.

Make a table for a tabletop telescope

If you or your child are just getting started in visual astronomy, I can recommend a tabletop telescope of 4.5" to 6", such as the Sky-Watcher Heritage 150 Tabletop Dobsonian. This telescope (reviewed here) has good quality optics, is compact and portable, and very comfortable to observe with. But it's missing a table.

Why make one

You would think that a tabletop telescope is designed so that you can use whatever table you may have handy: a picnic table, a foldup table, a stool, or just a small end table. That may have been the intention, or maybe just the marketing, but when you’re looking at objects in powers of 30x, 50x, 100x, or 200x, you need something very stable so the view isn’t all shaky.

Picnic table? Nope. When you sit on it, you’re going to make it shake. It is also unlikely to be in the best spot for observing and you can’t move around the telescope.

Foldup table? Nope. Really shaky unless you get one that’s built like a tank, and that defeats the portability factor that is often the main advantage of the table.

Stool? Maybe, if it’s solid and the right height. You could cut the legs to size, but will it be large enough to fit the telescope? It may also be bulky if you have to transport your telescope to a remote location.

End table? Three legs will be better for leveling on uneven ground, and you have the same problems listed above as a stool.

Well, that’s a bummer. You thought a tabletop scope would be just the thing for portability. Now you’ve got one and no good table to put it on.

Fear not. Some people use a milk crate, build a simple tripod, or buy something at Ikea like this stool.

Or...and you knew this was coming...you could have fun and build your own observing table. It’s not hard (if I can do it!), and you can customize it for your own observing needs. Continue reading to achieve tabletop nirvana.

How to do it

The table I built for my Sky-Watcher Virtuoso GTi 150P, a 6-inch collapsible tabletop telescope, is simply a round piece of 1/2” plywood with holes drilled in it to hold eyepieces and three legs made out of cheap 2x2 lumber that can be unscrewed so the table top lies flat for transport. The legs are cut with about a 10 degree angle so they provide a little more stability than straight legs, although you could make them straight to simplify things even further. Each leg has a 1/4-20 hanger bolt screwed into one end which allows it to be screwed into a t-nut fastened in the tabletop. Easy-peasy, and it takes up very little room in the car if you unscrew the legs.

I started by making a circular cutting jig for my jigsaw since I don’t have a router, the preferable way to cut circles. If you don’t even have a jigsaw, you can buy an edge-glued round piece of wood (I recommend 18”), although some reviewers have said they sometimes come unglued or split.

The base of my scope is about 14" in diameter. I decided on an 18” diameter circle so I would have a couple inches around the outside to drill holes for eyepieces and to put my cell phones and filters down. I used 1/2” plywood to keep the table as light as possible. With the scope feet directly over the table legs, it only needs to be stiff enough to keep the legs in place without bearing the weight of the scope. [9/22/2024 Update: Because the go-to on my scope is unreliable, I added an azimuth circle to the base of the telescope. The circle sticks out about 3/4" all around, so I built a new table, this time using 3/4" plywood and making it 20" in diameter. I like it better, and I recommend you go with those dimensions. It's a little heavier, but not by much. It also makes a great camping side table when you're not observing.]

My mistake in cutting the plywood circle with the jig and jigsaw was I trusted in a YouTube video that showed how easy and neat it was to use a cutting jig. In reality, the saw blade wants to either go inside or outside the circle unless you watch very closely. I had the saw run outside the circle on one part and inside on another, breaking two blades. 

Were I to do it again, I would only cut a couple inches at a time and check to make sure it was still cutting on the circle. Or I would just draw the circle on the wood and cut it freehand with the jigsaw. I’ve done that before and it comes out fine. I just might not do it if I need the precision necessary for an altitude bearing, for example, but for this purpose it’s fine.

Once I had a pseudo-circle cut out, I marked where the three feet of the telescope would go. You can simply place the telescope base in the center and mark where the legs go. To be more precise, you can divide the circle into three sections by drawing a diameter (1), then drawing lines (2 and 3) the length of the radius (9” in this case) from the outer point of the first line (1) to where it intersects the outer edge of the circle on both sides, then drawing the other two lines (4 and 5), as in the diagram.

To make sure I had the scope centered, I partially screwed a wood screw into the top of the circle in the center. Some of these tabletop telescopes have a threaded hole in the center of the base. I just placed that over the screw and marked where the three feet would go.

If you don’t have the center of the circle marked, you can find it by drawing a chord at any point on the circle (line 1) and drawing a second line (line 2) from the midpoint of that line using a carpenter's square or other object that will give you a 90 degree angle. Repeat in a different location (lines 3 and 4) and where lines 2 and 4 cross is the center.

To screw in the table legs you can get angled leg brackets, but I don't like the inserts they use and I wanted a nice flush surface so I could slide the tabletop in between stuff in the car easily. So I put three 1/4-20 t-nuts where the feet would sit. These need to go in from the top of the table so that when you screw in the legs from the bottom, they will be pulled in tighter, rather than pulled out of the wood. Make sure the t-nut barrel is long enough to grab at least a few threads of the hanger bolts in the legs but doesn’t stick out the bottom if it is inset about 1/8” (see below). You want the legs to contact the table when screwed in tightly to give a nice stable grip.

I used a 3/4” Forstner bit in my cordless drill to first inset the holes about 1/8” in the top of the table where the t-nuts would go. I didn’t want to go too deep in 1/2” plywood, but if you use thicker plywood you can go deeper. You just want them inset to give some edge for the telescope feet to catch on so it won’t slide easily.

Then I drilled a hole in the center of each inset with a 9/32” regular drill bit. If you don’t have that size, use a bit that’s just slightly larger than 1/4” because the threaded barrel of the t-nut will be a little larger than 1/4”. Hammer in the t-nuts from the top side until they sit below the surface of the table.

I wanted some eyepiece holders, so I marked off three holes along the outer edge of the table top in each of the three sectors. Test the fit by placing the telescope on the table and your eyepieces where the holes will be. Make sure the telescope clears the eyepieces through its full rotation of 360 degrees. When satisfied it would, I drilled holes with a 1-1/4" hole saw.  I also added a 2" hole to each sector, even though my telescope doesn't have a 2" focuser. I figured I might want to use the table for stuff while using my 10-inch, and I have a couple of 2" eyepieces. It would also lessen the weight further. [8/28/24 update: I may redo the top without the 2" holes. Twice now I've almost dropped an eyepiece through the 2" hole onto the driveway, thinking it was the 1.25" hole. Oops.]

I sanded both sides and the edge of the table top with a random orbital sander and the holes manually with small pieces of sandpaper and a scrap piece of PVC pipe.

As noted above, you can just make the legs straight at whatever height you prefer if you don't want to take the extra steps to angle the legs, although you will sacrifice a little stability. 2x2 lumber is cheap and you can make several sets if you like. I like to use balusters, which are the vertical pieces in a deck railing, because they tend to be straighter than the 8’ lengths of 2x2. Those can be horribly warped and actually cost more per linear foot at my local store.

To make straight legs, drill a hole in the center of one end, as straight as possible, a little deeper than the length of the wood screw part of a 2" 1/4-20 hanger bolt. Use a drill bit a little smaller than 1/4” so the screw will have plenty of wood to bite and hold tight. Screw it in by threading two 1/4-20 nuts and tightening the upper nut with a 7/16” wrench until you get the length sticking out that will work with your t-nuts, roughly 3/8 to 1/2 inch. You can unscrew it if you overdid it by putting the wrench on the lower nut and twisting counterclockwise.

To make angled legs, which will add stability to the whole setup, I found an easy way is to take a typical mitre box and lay the uncut piece of 2x2 diagonally so that one side is up against the top of the box as seen from above and the other against the bottom. Clamp it down. If you cut along the 90 degree slot in the middle you’ll get about a 10 degree angled end. For the first and the last cut, you’ll have to estimate and just clamp the wood down. 

Cut three legs so the ends are all at parallel 10 degree angles, i.e., the piece looks like a parallelogram from the side. I cut my legs 10-5/8” long, which, with the 1/2” plywood top and the 10 degree angle, gives me a table top height of about 11 inches, just right for my adjustable observing chair at the height I like to sit.

Now put each leg in a vise if you have one, so that the angled face is horizontal. Then just drill your hole in the center vertically. Screw in the hanger bolts as described above using two 1/4-20 nuts and a 7/16” wrench. When you screw the leg into the table, the other end will trace a small circle, but it will work. 

I adjusted the depth of each screw so that the leg would screw in tight to a particular t-nut where it points outward, and just marked each pair with painter’s tape on the table and leg so I could easily match the leg to the hole. Later I’ll use a Sharpie once I’m sure everything fits well. You can always readjust the screw depths as things wear.

If you use outdoor plywood, you don’t really need to paint it because you're not going to leave it out in the rain, but I got a spray can of spar varnish and gave the table a few coats. A cheaper option would be paint. I recommend white so it's easy to see at night and you can see where to put your eyepieces. If you use treated wood for the legs, they don't need to be painted but you can paint them. If a few drops of water soak in, they are dry enough to be painted, otherwise wait a week or two for the chemical treatment to dry completely before painting. Use a tack cloth after sanding everything to remove any sawdust and grit.

Lastly, I put a piece of white duct tape on the table top at each point where the legs go to assist setting the scope on the table so the feet are directly over the t-nuts.

That’s it. If you mess up, all the parts are cheap and you can redo any or all of it. You can also make legs of different lengths if needed.

My Sky-Watcher Virtuoso GTi 150P tabletop telescope (same as the recommended scope at the beginning of this article but with an electronic mount) on the table I built for it. It looks happy, doesn't it?

[9/22/2024 Update]: Here's the new table I built to accomodate the addition of an azimuth circle to replace the go-to. I made all the eyepiece holes 1.25" and painted it white. 20" diameter using 3/4" plywood. The scope is even happier now!

Materials:

Piece of Plywood 1/2" to 3/4" thick big enough to cut a suitable sized circle (18" is usually good) or precut wood circle

One or two 2x2" stair balusters

Three 1/4-20 t-nuts, short enough not to stick out from the plywood, depending on the thickness

Three 2" x 1/4-20 hanger bolts

Two 1/4-20 hex nuts

Paint or varnish

Tools:

Mitre box and hand saw

Power drill with 9/32" (for t-nut holes),  1/8" or 3/16" bit (for hanger bolt holes), 3/4" Forstner bit, 1-1/4" hole saw

Jigsaw (unless you are buying a precut wood circle)

7/16" wrench

Sandpaper, sander (or sanding block), and dust mask (I like this one for sanding, painting, and gluing)

Tack cloth

Two bar clamps or C clamps large enough to clamp a 2x2 in your mitre box and to the workbench surface (which could be a piece of plywood laid over two saw horses if necessary).

Bench vise

Hammer (a big, short bolt helps to hammer the t-nuts below level so you don't damage the table surface)

Carpenter's Square or L-Square 

Pencil or X-acto knife (makes more precise measuring marks for cutting)

A simple dolly for moving a Dobsonian telescope from the garage or shed

Reader Pete suggested I write up something about my dob dolly pictured in the post on making the heavy 10-inch Dobsonian telescope more easily transportable. A dolly or hand truck is useful if you are using a heavy telescope at home or next to where it is stored, versus disassembling it and moving it by hand or transporting it to a dark sky site.

My home is around Bortle 8 (badly light polluted), but I still like to get the 10-inch dob out sometimes because it shows more in a light polluted sky than either my 4.5 inch or my new 6-inch reflector. So rather than heft the base and tube out onto the driveway every time I want to observe, I built a crude but effective flat dolly for it, as detailed below.

Option 1: buy a hand truck

If you don’t want to build a little dolly, you can simply buy a hand truck such as this one at Harbor Freight for somewhere between $50 and $100 and make a few minor modification to carry your Dobsonian. Usually this involves adding a plywood piece to make the toeplate larger (the flat part that the object sits on), adding padding for the scope tube about halfway up the frame, and a strap to hold the scope tube to the hand truck. 

In fact, this is what I am recommending for my brother who has a 6-inch Orion SkyQuest XT6. The scope is not very heavy, 31.5 lbs. total, but to get to a decent park in the city to observe he has to tote it about six blocks (he doesn't drive). Ugh. So a hand truck makes sense for him. Here’s a Cloudy Nights post that might give you some ideas.

Another advantage of a hand truck is that it's very useful around the house (toting bags of yard waste around, moving furniture, etc.).

Option 2: build a flat rolling dolly

Here’s how I built a very simple but also very crude rolling dolly for my 10-inch Dobsonian. Caveat- there are no handles, so I just push and pull on the scope base to move it. Also, mine has front and rear wheels that are different sizes because my driveway is on a three percent slope. This makes it level without any further adjustment so I can use my azimuth circle/digital angle gauge setup to find objects. Using a hand truck in this case would involve too much fuss and potential trouble. If your driveway or path is level or if you don’t need the scope to be level, you can use the same size wheels. If your driveway or path is not paved, or if you have to negotiate steps or anything taller than an inch or so, you are probably better off with a hand truck with 6” or larger wheels.

I had some scrap pieces of 5/8” roof sheathing plywood leftover from a roofing job. (Always see what your workers are throwing away and ask them to save it if you might find it useful.) The base of my 10-inch is a 22” diameter circle, so the dimensions are optimized for that.

I cut a 22” x 26” rectangle from the plywood. The extra 2 inches in front and back provide room to fasten the wheels on without getting in the way of the feet on the scope base or having the bolts sticking out and scraping the base.

I needed the front of the dolly to be 1” higher than the back to compensate for my sloped driveway. I bought a pair of 3” rubber rigid casters and a pair of 2” rubber swivel casters at Harbor Freight. These are 3-5/8” and 2-5/8” high, respectively, which gave me the just about the right adjustment for my sloped driveway. I thought about getting casters with brake levers on them, but these aren't strong enough to hold anything on a slope, just keep it from rolling on a level floor. The casters bolt through the plywood with four bolts each. You’ll need a drill and a pair of wrenches. Make sure you buy bolts that fit the caster holes.

I was able to put the nuts on the bottom of the fixed casters, but the swivel casters were smaller and the threaded bolt ends sticking up would have prevented them from swiveling, so I had to have them sticking up on the upper side of the plywood. It’s not optimal, but that’s what I had to do.

With an azimuth circle on the dob base, I wanted to make it easy to align with the cardinal directions, so I put a mark on the dob ground board that would align with a mark on the dolly to position the base so it would be roughly aligned in azimuth and I would just need to fine tune it each session.

I put the scope base where I would be placing it on the plywood and painted a white circle all the way around on the dolly’s surface to help me align it when plunking it down. 

To keep the base from sliding around, because I would be pushing and pulling it, I glued pieces of wood just outside each dob foot. Normally dobs have three feet, but I found adding three more feet from wood made it more stable on uneven ground, so I have six little pieces of wood glued to the dolly. Just make sure they are shorter than the dob feet so they don’t touch the ground board.

That’s pretty much it. I didn’t even waste paint on it, since it will be spending most of the time in my garage, and paint is often one of the more costly parts of any woodworking project.

So how well does it work?

My only real complaint is that it’s a little hard to maneuver with the two swivel wheels, so I just have to go slowly when pulling/pushing it in and out of the garage. To keep the scope from rolling down into the street, I use a rubber wheel chock from Harbor Freight and a rubber sanding block under each front wheel. If you use something different, make sure it's not going to just slide down the slope. I always stand on the downhill side of the scope when rolling it to and from the driveway.

If you have to roll the scope over a threshold, for example I have a 1” bump from my driveway into the garage, use a piece of baseboard molding a bit longer than the width of the dolly. It has a tapered profile that works nicely as a little ramp. Tip: Save some pieces of any molding you replace. I’ve found multiple uses for this.

Just be aware that you’ll be adding about 4” or so to the height of the eyepiece when observing. Even my adjustable observing chair needs a booster cushion at its highest adjustment for some positions when the scope is on the dolly. I don’t notice any instability or shaking in the views from being on the dolly.

If you have a telescope on a heavy tripod and mount and want to build a dolly, here's an article from BBC Sky at Night that might give you some ideas.

Bonus Tip: If you have a store like Harbor Freight or Northern Tool near you, or can order from one, you can save a lot of money on many items, including tools that you’ll only use occasionally. Better to have the right cheap tool than the wrong high quality tool. I don’t have any affiliation with them, I just like to save money if I can.

AstroHopper - using your phone as a free push-to finder system

 

Screen shot from AstroHopper by Artyom Beilis showing the basic concept.

In my quest for different means of pointing the telescope, I tried a freeware progressive web application called AstroHopper last night with my 4.5-inch Tasco 11TR dob-mounted reflector. This app is designed and supported by Israeli amateur astronomer Artyom (Artik) Beilis, and has been around for several years. It was previously known as SkyHopper. In a nutshell, you load it on your phone, attach your phone to your telescope so the top of the phone points where your scope points, align it with a star, and you’re off to the races. I decided to take it for a spin and see what it can do.

Bottom line:

If you are new to astronomy and got a new telescope, or finally starting to use that telescope that’s been sitting in the closet, and you have a halfway decent cell phone, this app will get you observing. It’s easy and it’s fun. It’s also free!

For visual astronomy, there are really only two ways you can point your telescope:

1. Manually by pushing or pulling it with your hands or unclamping knobs and moving it around, then clamping the knobs down and using the slow motion controls for finer adjustments.
2. If equipped, using a computerized mount, moving, or slewing the scope by means of a paddle or controller with arrow buttons.

To actually find something, though, you need to either compare what you are seeing in the finderscope and eyepiece with some kind of chart, be it on paper or an app, have a system that contains a database of objects where you select an object and tell it to “go-to” that object electronically, or some kind of “push-to” system that gives you some indication of either what coordinates you need to dial in or what direction and distance you need to push it to get the object into the field of view. It’s the latter technique that this app uses.

The app runs in a browser but is installed like a regular app, and Artik gives instructions for both Android and iOS phones to install it. While you could just use it by going to the web page when you have an internet connection, I recommend installing it so you don’t have to worry about being somewhere with a signal. I put it on an old phone that no longer has service. I found that Brave browser does not work with it, so I used Google Chrome instead, and that worked [8/15/24 update: except I needed a WiFi connection to start it. Firefox does work without a connection on my phone]. Safari should work. 

Another caveat is that your phone needs to have decent gyro and compass sensors, accelerometers, and GPS. Most phones made within the last decade or so should include these. Make sure location services are turned on.

Once I installed it on my older phone, a Google Pixel 3a XL, I attached the phone temporarily to the top of my telescope so that the top of the phone pointed with the telescope as in the image above from the app. I just used Velcro, but most people won’t want a big honking piece of fuzzy Velcro permanently attached to the back of their phone, so you can try large rubber or elastic bands or other means. Just be sure your phone isn’t going to slide out and hit the ground.

Then it was time to take it outside. I have Bortle 7 skies at best in my neighborhood, and tonight was also getting murkier by the minute. Still, I had enough stars, and Jupiter out, to test the app.

You need to calibrate the compass of your phone first. This entails moving the phone in a big figure-8 pattern (vertically) several times. I found this part a bit finicky, as it took a few tries to get the star chart in the app to be even close to pointing to what it was showing in the sky. Remember, unlike other star charting apps, you don’t hold the screen up to the sky to match it up with what you are seeing. You point the top the the phone toward the object, and if it’s then within the screen view, you’re close enough.

I reattached the phone to the telescope and picked a bright star that was easy to get in my low power eyepiece (50x in this case) just by sighting along the tube of the scope. I chose the orange star Aldebaran, in the familiar V-shaped asterism of the Hyades, in the constellation Taurus. Once centered, I hit “Align” on the app and then tapped Aldebaran on the chart. In a few seconds it did a calculation and centered the dot on Aldebaran. Then I moved the scope around and off of Aldebaran. Now the moment of truth: how close would it actually be when I followed the guiding line back to Aldebaran?

I was pleasantly shocked that Aldebaran was actually again within the 50x field of view, which is nearly a degree in my telescope. So it works! Now the question is, what to look at? I chose the Pleiades star cluster, figuring it would still show through the ever-increasing murky clouds. So I tapped on the Pleiades on the app’s star chart and a circle with a line appeared. At this point, all I had to do was move the telescope in the direction of the line until the circle was centered over the Pleiades. When I looked back in the eyepiece, there were the Pleiades, at least some of them, since they don’t all fit into the 50x field of view.

That’s all there is to it. Once calibrated and aligned on a bright star, the phone’s sensors guide you to a nearby object. It’s important to realign on a new star if your object is outside the area, basically off-screen if you have it zoomed in to just one or two constellations. As Artik explains, you need to re-align every time you move to a different object, although I found that nearby ones will generally still be close to the expected position until you’ve moved a few times. Then the accuracy degrades. But still, it’s not a big deal to re-align and once you get the hang of it, it’s easy. I moved over to Jupiter, re-aligned, and easily found it. The app includes a manual override mode if you just can’t get your phone’s compass to behave. Rather than frustrating, this was actually fun. I like that in an app!

The star chart in the app is quite rudimentary, only displaying the brightest stars and very few deep sky objects. This is a navigation app, not a star charting planetarium app with extensive information on each object, and that keeps it uncluttered. Therefore you’ll primarily be using the search button. Object data that displays when you search for an object includes its designation, magnitude, size, and perhaps common name, for example, “NGC 457, m=6.4, 7’ Owl Cluster”. However, the included database, OpenNGC, includes the entire NGC and IC catalogs- a very large list of deep sky objects. If you want to add more obscure objects, you can do so in the app: Settings > User Objects > edit. Artik explains the formatting in his README file on Github. [8/15/24 update: I found I could create a great custom night mode keyboard with the app "Keyboard Designer" by Gerritt Humberg to get around the default keyboard's lack of night mode. The app takes a while to figure out but is well worth the effort.] 

Because this is not a star charting app, you’ll need a more detailed chart available to decide what objects you want to look for in a particular area of the sky and then search for them using AstroHopper. Then you can refer to the charting app for more information on what you are looking at. Not the most user-friendly experience in that regard, but still quite workable. You will probably need a second device for the charting app, unless you’ve created an observing list in advance, which you can do by going into Settings > List > edit.

 

Conclusion

With the caveat that I only tried AstroHopper out for about an hour, I would say it’s very useful for someone just starting out who doesn’t know how to find anything, doesn’t have go-to or a plate-solving system like StarSense for navigation, and is having trouble with or doesn’t want to spend time starhopping. It’s also a useful app to have as a backup to your normal object-finding routine, as long as you manage expectations.

However, you have to have a little knowledge of what is feasible for you to look for at your level of experience and in your sky, and where in the sky that might be, hence my recommendation to use a second, more detailed star charting app such as Stellarium (free for the fully featured desktop version), Stellarium Mobile (free) or Plus, or Sky Safari Basic, Plus, or Pro, where objects populate the screen more densely as you zoom in.

A big advantage of freeware like this is that as long as the developer doesn’t get bored with it or sidetracked by, well, life, it will continually improve over time and it’s still free. Despite all those who feel they have to monetize everything, here’s an example of how doors can open up for people if not everyone buys into that ethic. I say give it a try!

 

Note that AstroHopper does not use the plate-solving technique that something like Celestron’s StarSense system uses. In other words, it doesn’t compare what’s coming into the phone’s camera with a database to determine where the scope is pointed. Instead you align the phone with a star and the phone’s accelerometer and gyro sensors compare the movement of the telescope with the position the app thinks an object should be. Two different systems, both with advantages and disadvantages, and you’re probably not going to get the level of accuracy and sophistication of the StarSense system with this. However, you will get a sense of the way a push-to system works and whether it works for you. You’ll also likely be motivated to learn the sky better. And most important, you’ll be able to find stuff! For me, I’ll stick with my azimuth setting circle and digital angle gauge to push my scope to the coordinates of specific objects. But this will make a nice backup, and will be fun to show at public outreach events.

This is the actual app running in your browser. It will look similar on your phone:

https://artyom-beilis.github.io/astrohopper.html

Instructions on installing and using AstroHopper (formerly SkyHopper):

https://github.com/artyom-beilis/skyhopper

AstroHopper manual:

https://artyom-beilis.github.io/manual.html

Artik is also active on the Cloudy Nights forums if you have any questions or comments.