# How do I design a good telescope to observe nebulae and other deep sky objects [closed]

How can I make a good telescope that is powerful enough show nebulae and other deep sky objects ? (consider low budget build)

• Does "low budget" mean you have plenty of time? And are willing to put in the hours? – James K May 17 at 16:39
• Yes, you are looking for an amateur telescope. Amateur doesn't mean low quality. It means that you are not being paid (usually by a university or a government) to be an astronomer. Professionals telescopes are not owned by astronomers. They are owned by governments and universities. So you want a low cost, good telescope. – James K May 17 at 18:05
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• Watch this video youtube.com/watch?v=snz7JJlSZvw "Telescope Building with John Dobson" – Aaron F May 18 at 10:40
• @Aaron F thanks buddy – Amrith Adithya May 18 at 13:22

# Absurdly cheap and (potentially) very fun!

The absolute cheapest telescope to make would be extremely hard to make, you'd be doing something for the first time, but it would at least be fun!

Make your objective lens out of ice, and find a way to polish it smooth. Don't make it as big as these though. You can then use an eyepiece out of a pair of old binoculars or a toy telescope or use a dime-store jeweler's loupe for an eyepiece.

These are solar collector projects, a telescope objective would have to be polished to a much better shape.

Here is a functioning camera lens made from ice for example, from this answer there:

click images for larger

Source: Mathieu Stern

Chromatic abberation is a problem, so use a filter that removes blue and green (I guess you'd call it a red filter) and look at things that are mostly hydrogen.

From Alex Kozik's Orion Nebula spectral composition we can infer that the Orion Nebula would still have the shape of the Orion Nebula in the presence of chromatic aberration if got rid of green and blue light.

1Professor Emeritus of Astronomy, University of Illinois

# But seriously folks

If we throw out any hope of an electronically driven and computer controlled equatorial mount and just want to look at things as they slowly drift then spend most of your budget on an f/8 spherical mirror, either a second hand one from a discarded telescope or one out of a catalog like an Edmund Scientific from the 1970's. Seriously I don't know if there are catalogs where you can order premade mirrors any more, but it was fun to dream!

You may have to invest in a telescope mirror making kit. There are an abundance of resources on how to make home-made mirrors, and as long as you are f/8 or longer you don't need to worry about figure correction (making it a parabola instead of the natural spherical shape it will want to have)

Next, put your mirror in a Dobsonian mount made from plywood or scrap metal, depending on your materials and particular skills and tastes.

You'll need a diagonal mirror or prism to send the light out the side and a stick or spider to hold it near the center of the aperture. If you are only going to use one eyepiece then you can find a simple way to hold it in place, but you've got to do some reading about how to align the whole thing.

That would be an excellent follow-up question here!

You can also take a cue from Sir William Herschel and instead of using a diagonal in the center of the aperture, just peer over one edge with the eyepiece and (since your telescope will be a lot smaller) use a diagonal mirror or prism attached to the edge. You'll have more distortion, but if you increase your f/ number (the one below was f/10) and stick with low magnification, you'll see some nebula, at least as opposed to not seeing them. :-)

I used a small front-surface mirror, some alligator clips, an eyepiece from an old pair of binoculars, a cardboard tube (a la Clyde Tombaugh) and a weak concave magnifying mirror for my first 10 cm Herschellian reflector telescope and had a truly thrilling time!

From here:

click for larger

left: Source, right: "Two Dobsonian telescopes on display at Stellafane in the early 1980s." Source

• – uhoh May 17 at 22:52
• Thank You very much ! – Amrith Adithya May 18 at 6:55
• @AmrithAdithya sure! I think you can browse this site for more questions and answers about telescope making and there are plenty of resources out there, old books (that last image is from the 1980's) or old books or articles on the internet. – uhoh May 18 at 11:33