Suggestions for a Home-Built Telescope

hodet asks: "I would like to know if anyone here has built or are planning to build their own telescope. My plan right now is to build an 8" F/6 Dobsonion Reflector based on these plans. The same design can also be found here. The base has been cut and the primary and secondary mirrors are to be ordered shortly. Since I plan on making a few modifications to this design I'd like to know if anyone here has done anything similar or totally original and what thoughts and suggestions you may have. I know it may be cheaper and easier to buy one from Meade, but that's not what I'm looking for."

Comments

Make vs. Buy

[DynaSoar]

I've made a 6" reflector, and I've bought one. You don't make a telescope to have a telescope, you make it to make it. It's the process that's important. The fact that you end up with a telescope is almost secondary. It's sort of a spiritual thing, when you spend hours and hours grinding, and consider those who've done the same over the centuries.

Re:Make vs. Buy

[Glonoinha]

24 comments and nobody has offered up a way to overclock this thing yet? Heck, the only reason I read it was to get a grasp of just how bad /. was going to crank this guy's handle : simple ways to create a 48" parabolic back mirror, ways to create a 48" diameter tube for that mirror, maybe someone would come up with a four bounce set of mirrors set up between two houses as a way to use even larger mirrors or a longer focal length or a wider field of view ...

Surely somebody is going to figure out a way to turn a kiddy-pool into a 84" reflector for one of these things ...

a few links

[Councilor Hart]

can be found at dumbo
Although a few might be outdated.
Good luck.

Focuser

[Uma Thurman]

Instead of making a focuser, you might be happy buying a really nice one instead. Out of everything you put on the scope, the focuser and the mount will be either a source of pleasure, or a source of annoyance. A good focuser will make it much easier to get the best views of the stars, and proper balance and stability of the mount will make it easier to point the scope.

It really makes a difference, more than anything else.

http://www.scsastro.co.uk/it060013.htm

Re:Focuser

[battjt]

Dad built a new mount for his 13" dob that was lighter than the original.

He started with the standard cardboard tube, but other than that tried to make it as light as possible for mobilility.

What he found was that ballance isn't so hard, just use large washers for counter weights, but the lightweight scope jiggles more that the heaver scope. Also the force to break the teflon bearings loose jars everything more when there is less mass to move.

Joe

Re:a few suggestions

[battjt]

Dad has a 13" dob. He put kid's bike tires on it. To move it, he locks the tube in the base with a wing nut and bolt, then tips the whole thing over onto the wheels.

Before this, when I was in high school, he would wake me up at 3 am to help him put the scope away. (now I'm 32)

Joe

The Amateur Sky Survey

[Dammital]

There are some interesting photos and information on Tom Droege's TASS site. Not sure how active they are at the moment, but there are some knowledgeable people there.

Re:Optics

[seanmeister]

I beg to differ - the mount is very important also. Top-of-the-line optics won't do you much good if you can't aim the telescope because it's all attached to a shaky mount. The dob mount design itself is solid - just don't skimp on the materials used to build it.

Sincerely,
a guy who recently bought a telescope with a shaky mount

Other options

[pease1]

While John's design is good and will work great, there are others - many others. One good source is this book.

Build the scope yourself, don't spend all that much money on the focuser (better yet make your own focuser) and spend the saved dough on additional eyepieces. You can get a "better" focuser later.

A 6-inch f/8 scope is a wonderful starter - much better then the junk you find in stores. Hundreds of deep sky objects, craters on the moon, moons of Jupiter and rings are Saturn are all easy to see.

Final advise. Locate and join your local astronomy club, go to a regional star party (can you find both here and get out under dark skies.. sorry, this requires getting out of the city.

It's cheaper than cyberage!

[NanoGator]

"Suggestions for a Home-Built Telescope"

Move into an apartment complex with attractive tenants.

I made a scope from these plans

[ghamerly]

I made a a scope from these plans -- pretty much the same scope that you want to build (8"). I built it in summer 2002. You can see my scope (including pics) here: http://www.cs.ucsd.edu/~ghamerly/personal/astro/te lescopes.html I have some advice on this page, which I will repeat/expand on here:

• For me, making the telescope was all about the experience of learning & having a project -- not saving money. I believe I could've bought a better telescope for less money than I spent on making mine (not including the cost of time spent).
• The plans are quite good and complete -- though I still had to improvise quite a bit when I didn't have exactly the same materials. However, improvising turned out to be some of the most fun, since it was problem-solving.
• On a more technical note, one of my improvisations forced me to place the secondary mirror closer to the main mirror than it really should have been, therefore I lost about 3/4" of the main mirror. This is something to be aware of. This was mostly due to my naivete, and the plans don't really mention this issue. When placing the secondary mirror, take time to really consider your main mirror, focal length, and *the size of your secondary mirror*.
• The mirror collimation design (3 bolts on a board) works really well, I think, for how simple the design is.
• I bought my mirrors from E-scopes, and was happy with them. I bought teflon from Rob Teeter at Teeter's Telescopes, and I recommend them.
• The tube can be had from a local construction surplus store -- it's called Sonotube (brand name) in the industry, and it's used to pour concrete pillars. I was afraid that 1/8"-thick would be too thin, and I considered going with 1/4", but 1/8" turned out to be fine (and much lighter).
• I'm extremely happy with my telescope, and while it isn't perfect, I had so much fun making it, and it's so easy to use. I had no sooner finished it than I wanted to make a larger one. :)
• Here are 6 pictures taken of the moon with this telescope (just holding my camera up to the eyepiece with my hand): 1 2 3 4 5 6

Good luck, and have fun!

Spinning Mercury Mirror

[justanyone]

If you want a large but immobile telescope, there's a way to do it with a large spinning pool of Mercury. Some canadian university built a nice observatory doing this.

The limitations are that they have to wear breathing protection around it due to Mercury outgassing vapor and them (understandably) wanting to avoid heavy metal poisoning.

However, it apparently makes a wonderful mirror, albeit a parabolic one. It would be interesting if someone could set up a manufacturing process whereby we would spin up Aluminum as a mirror base then spray a thin layer of Silver or chromium onto it to give a polished surface.

Of course I don't know jack about mirrors except that grinding glass ones is a pain in the butt and therefore costly.

Anyone know more?

Re:Spinning Mercury Mirror

[dfranks]

It would be very difficult to maintain an accurate surface in aluminum. The current state of the art (afaik) in exotic mirrors is thin carbon-fiber composite mirrors molded on a mandril, then silvered.

The fast majority of homebuilt telescopes are built using glass, pyrex or zerodur (all glasses of various compositions) mirrors. All newtonian telescopes f/8 or slower can sometimes be made with spherical mirrors, everything faster than that requires a parabolic mirror.

Many amateurs polish their own mirrors. A great project if you have the time, and a great project if you have kids, but you'd have to be working at a McJob to come close to breaking even on the time vs purchasing a prefab mirror.

Mel Bartel's system, and other designs

[dfranks]

You might want to take a look at Mel Bartels Telescope home page. It contains lots of references on mount design, and a home-brew system for adding computerized goto capabilities to dob scopes.

Depending on your fabrication skills and facilities, you might also want to look into a truss dobson (probably not necessary at 8"), or a split ring mount. The split ring mount is an equatorial mount, making it easy to add a motor to track objects against the earth's rotation. Even if you want to learn the sky for yourself (rather than use a goto system), tracking is very very useful, particularly when sharing the views with others. The split ring also avoids field-rotation at the eyepiece allowing long exposure astro-photography using film or digital cameras.

I started out with a 10" meade starfinder dob, rebuilt it as a truss scope (goto), then rebuilt it as a split ring (motorized but not goto). The Meade starfinder design is very similar to the one you referenced, and is by far the easiest to build.

Be aware that astronomy is a disease, I don't know anyone who uses a telescope regularly and only owns a single telescope.

Dean

Mirror Grinding

[Ann Elk]

I know you're planning to buy your primary mirror, but you might like to read Ed Grinds a Mirror from Ed Ting's excellent astronomy site. Also, if you ever need advice on production scopes and accessories (like eyepieces), Ed's site is the place to go.