Many visual observers start small. Maybe a 4, 5, or 6 inch reflector, maybe a 60mm or 80mm refractor. Often the more inexpensive telescopes are smaller and they give a person a chance to try out the hobby to see if maybe somewhere down the line a bigger monetary and size investment would be worth it. Parents have also been known to get a small scope for junior, thinking maybe Dad or Mom might like one themselves, too. A decent first scope can make a nice portable second scope even if you move up to a larger one.
Regardless of type (reflector, refractor, catadioptric), aperture is aperture, and the bigger you have, generally the more you’ll see. Why? Because, all else being equal (quality and telescope design being major points), a larger mirror or lens will capture more light, thereby making dimmer objects look brighter, showing more detail, and allowing for the use of higher powers in good seeing, and therefore a larger image scale before the view gets too dim or blurry.
Downsides of a larger telescope are often cost, size, and weight. I always dreamed of having a big truss-tube dobsonian- say with a 20 or 24 inch mirror. Views through those can be spectacular, especiallly in a dark sky. But reality in terms of money, storage room, and ability to tote it around to dark sites or fit it in the car without buying a bigger car precluded ever getting one.
Still, after about 13 years of using my 4.5” reflector, I had a little more discretionary money and wanted the views I could get with a bigger telescope. So 20 years ago, I bought a Hardin 10” Deep Space Hunter dobsonian telescope for a whopping $490 shipped. It came with a Guan Sheng Optics (GSO - Taiwan) 32mm (39x) two-inch barrel eyepiece and a 9mm 1.25” eyepiece (139x), neither of which were as good quality as the .965” aftermarket eyepieces I had for the 4.5”. Most telescopes come with 1.25” focusers, but many now are 2” with an insert to allow use of 1.25” eyepieces. That is the case with my 10”.
My Tasco 11TR 4.5" reflector, repainted from the original red and remounted on a homemade dobsonian base.
My upgrade was not just going from a 4.5” mirror to a 10” mirror, with the accompanying light gathering ability, but also to the larger barrel 1.25” and 2” eyepieces. That’s a pretty big jump all told, and I’d like to share with you some of my first observations with the 10” to give you an idea of what more aperture will give you, and what it might take away, if you are contemplating a larger telescope.
Aside from a few sessions on our apartment balcony, my first observing trips with the 10” were out to some club observing sites between 30 and 50 miles from downtown Washington, DC, and back in 2004 they were fairly dark- maybe Bortle 3 and 4. Nowadays they are closer to Bortle 5 and 6, but still a good option to partially escape the ever expanding light pollution. One of the first things I noticed right away just from the apartment balcony was how much more color I could see in stars in the larger telescope.
Here are a few verbatim notes I took at the eyepiece on the first couple of nights that shed some light on the difference in views from the smaller to larger telescope. The sky was partly to mostly cloudy with poor seeing. I’ve added explanatory notes in brackets.
Observing notes:
My first view is somewhere in southern Gemini or northern Orion in the 32 mm eyepiece, and my first thought was, "My God, it's full of stars!" Wow, this is going to be a big difference from the 4.5".
My first object is M35 and NGC 2158 [the former a very large, bright open cluster, the latter a smaller dense one nearby]. Very nice in 39x, though the eyepiece leaves a lot of fuzziness around everywhere but the center, which is to be expected in a fast scope (f/5.0) like this [the 4.5” is f/7.9]. A nice wide view. I can't say I'm particularly impressed with the optics of this scope so far. Maybe it's the eyepieces. For example, with NGC 2158 I'm getting quite a bit of resolution on it- it's more half-moon or L-shaped rather than round, but I'm not getting good pinpoints on the stars. Quite a let-down really after seeing everything so sharp in the 4.5”, even on a bad night.
M37 is very nice with lots of stars in 139x. Just not dazzling, though. Little spots instead of little points. Kind of disappointing.
But looking at M51 [the Whirlpool Galaxy in Ursa Major, a bright, face-on spiral with a smaller galaxy next to it connected by a bridge of material]- that's more like it. That's what I got this thing for- deep sky. Real nice view. Definite spiral structure there, particularly one big bright arm that goes out from the main galaxy toward the smaller one, and then a dark lane inside of that, very well-defined in averted vision. Due east of the nucleus at the base of that arm is quite a bright area. On the SW side another bright knot. It's more difficult to see structure in the western side. But I can see structure in the smaller galaxy. The foreground star in the SW quadrant of the main galaxy is very plainly stellar in this scope. I can't quite make out the bridge between the galaxies.
I'll try M81 and M82 [showpiece galaxies in Ursa Major, one somewhat tilted from face on-M81, and the other an edge-on starburst galaxy with more readily visible detail]. M82 in 139x also very nice. What's peculiar is that it's similar to what I see in the 4.5", but a whole lot easier- much brighter. I'm seeing the same features, but they're much more distinct and I can tell the difference between a fuzzy spot and a star, and can see more detail in the bright sections, too. This scope will be nice for galaxies. I hardly recognize M81. Seems like the core is more prominent than in the 4.5". The galaxy shape is not so much an oval in this scope as a glow that diffuses out more slowly, and the extensions out to the north and south are more elongated. The fuzziness extends out further. No hint at all of any structure in there. Almost looks like an elliptical. A really nice view in 39x of the two galaxies- they fit easily in the 2" 39x eyepiece. M81 is just huge. I'm getting to like this scope a little bit more.
M33 [the Pinwheel Galaxy in Triangulum. This is visually a very large galaxy that can be seen easily with binoculars and may be glimpsed with the unaided eye in a reasonably dark sky.] In 39x it is a smooth fuzzball with a brighter core, no real nucleus to it. Couple of stars within it. In 139x there are two stars just NNE of the nucleus, and the nucleus itself isn't stellar. The rest fades out a bit. I was sweeping around the area, and thought I came up with another galaxy, but it's actually the nebula in M33, NGC 604! Looks like what a 10th mag galaxy looks like in my 4.5. It's slightly N of due west of about an 11th (?) mag star. Just a fuzzy patch, brightens a little bit toward the center. Rough edges, not cleanly round. Can see it now in 39x but it's better in higher power.
As you can see in the above examples, a larger aperture generally gives better views. However, there are situations where I prefer the 4.5”, for example on planets and double stars, mainly because where I am we rarely get really good steady seeing conditions, so most of the time I have to put an aperture mask on the 10” to make it act like a smaller scope to improve the sharpness of bright objects.
Eyepieces also make a huge difference in terms of sharpness, brightness, viewing comfort, apparent field of view (the viewing angle, i.e., like looking down a narrow tube versus wide open “floating in space” views), and true field of view (how much sky in degrees and minutes you can actually see. I have since gotten better eyepieces for the 10” that make the views more pleasing.
Also, it’s easier to move the 4.5”, so if my back or other body parts are acting up, or I’m just feeling lazy, I may choose to bring the smaller scope, or even stick to binoculars. Ditto if space is a premium in the car, although I’ve managed to fit the 10”, all my observing gear, and all my camping gear in some pretty small vehicles. Where there’s a will, there’s a way! At least to some degree.
All this being said, I recommend using your small scope to learn the sky well and learn what objects look like. Push the scope to its limit and see where it excels and where it falls short. See what difference darker skies make (hint: huge). Then consider a larger scope if it fits into your progression in the hobby, lifestyle, and budget. Some people stay with that 3.5” Questar tabletop scope because it fits them well and makes them happy. Bigger isn’t always better when you add the human factor, which is the most important one.
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