Suitable materials for telescope components

[shahgazer (Shah)]

Hi all,

Being limited to only the internet for reviewing numerous wonderfull telescope designs, and not being able to see and test one, I am stuck in deciding which is the best materials for each of the telescope components, in case I would like to pursue ATMing myself

List below is some of the critical components which I need some ideas on materials:

1. Secondary cage/ring
2. Mirror Box
3. Rocker box.
4. Side bearings

The trusses will definitely be aluminium tubes, obviously.

Most of the materials I see is wood, and some aluminium-based telescope. Asides the esthetic look (which wood wins hands down), is there any advantages/disadvantages if I were to do an all-aluminium telescope?

Thanks

[Wavytone]

Have you trawled the photos scattered through this thread ?
http://www.iceinspace.com.au/forum/s...ad.php?t=19133

Pretty much shows all the techniques for building a dobsonian. OK his is probably bigger than what you have in mind and its a Nasmyth configuration but it shows how to make and finish the pieces.

[tnott]

Any hardwood veneer/hardwood core plywood would be good. I have used both Pacific Birch and Gaboon ply for my telescope construction. The Gaboon ply is about 20% lighter and has a nicer veneer. Got them from a local wooden boat supplier. Kydex is a brand name often given for the secondary cage baffle material but I think it is the same as any PVC plastic sheet.

[Blue Skies (Jacquie)]

The North Americans (USA and Canada) have an aversion to metal, and thats probably for a good reason. Here in Australia it is much more common to find all-metal telescopes, partly because nice wood is expensive. The problem that might arise using metal is expansion/contraction as it heats up with the ambient temperature of the day then shrinks again as it cools at night time, much like the glass in the mirrors. While its changing, either expanding/contracting, its not good for the optimal operation of the telescope (eg, you can use it but you wont achieve the best image possible until it has reached ambient temperature). North America can experience large temperature differences during the day, which makes wood a better option, but here in Australia the daily range is not always that large. As I see you are in a tropical area, I guess your temperature difference between day and night would be relatively small, so an all-aluminium metal scope would probably work ok.

[tnott]

Correction. The black plastic material I use in my scopes is black polypropylene- comes with a nice textured flat black finish. Kydex is another form of black plastic.

Another reason that big dob builders prefer wood is that it dampens vibrations. All metal truss scopes can ring like a bell for ages when they get bumped. Wood is also more forgiving to work with than metal. Starstucture made all aluminium scopes for ages though.