Build Your Own Dobsonian...

[kashi]

I've read that it's quite feasible to build Dobsonians that can outperform commercial, mass produced scopes of simular aperture. Can anyone provide some more information about this?

[FVAS]

Sure check out the Fraser Valley Astronomers Society at www.fvas.net they have a series of links that show everything from Mirror making to building a Dobsonian.

Good Stuff..

Paul

[Bluewolf027]

The quality of the telescope is all about the quality of the mirrors. If you purchase higher quality mirrors - or make your own you can make a much better scope than most that you would buy. Most manufacturers make their mirrors so that they are 'good enough' so many times they are not properly parobolized.

For a basic Dobsonian Design
Try:

http://members.aol.com/sfsidewalk/intro.htm

For lots of links and info on mirrors and grinding your own try:

http://www.starastronomy.org/TelescopeMaking/Links/
http://ben.davies.net/telescope.htm

[seeker372011]

Kashi:

I was talking to the people at BinTel here in Sydney and the advice was that you don't make a scope because it is going to be more economical. You build a scope because that's what you want to do. It will probably cost more and take from 12 to 18 months for most people who have day jobs to get around to finishing the project. (I am sure there are people who did it in a long weekend but is this for the average person).So you have to be prepared for delayed gratification-you can't use the scope tonight, as you could do with a commercial .

If you build a Dob you would use plywood which is straightaway better compared to the chipboard that commercial scopes use so the mount will certainly be better

When it comes to mirrors the make or buy decision is rather more difficult especially at smaller sizes. There is a company in Canada advertising mirrors in Sky and Telescope -8 inch for $139 US. I can't find anywhere in Australia where I could buy a blank for that kind of money let alone a finished mirror. Buying a finished mirror will cut the project time dramatically of course.

Hope this helps. If you decide to go ahead keep us posted on how you go
seeker

[kashi]

Thanks for all your suggestions guys! I noticed the the Astronomical Society of Victoria runs telescope making workshops every month and you can get the materials through them at cost price. They also have equipment for testing and refining your mirrors to ensure that they are of good quality. Could be worth attending.

To my way of thinking there would be no point building a scope unless you were going to grind your own mirror. I'm glad you've talked some sense into me with regard to cost. When you take time into account, it works out a lot more expensive.

[Dave Mitsky]

You can indeed build a Dobsonian that is superior optically and mechanically to the typical mass market offering. However, you will probably save little or no money in doing so.

Have a look at the ATM links listed here:

http://www.efn.org/~mbartels/tm/atm.html

There are also several good books on telescope building available.

Dave Mitsky

[kashi]

Check out this beast:

http://www.hanf-poos.de/stathis/atm/erhard...dob_itv2003.htm (http://www.hanf-poos.de/stathis/atm/erhard_1meter_dob_itv2003.htm)

Someone's built a 1.07 metre dobsonian!

[LaughingJaguar]

Without knowing your skills with tools and fabrication methods, it's hard to address this question. I also have no knowledge of your past experience as an ATM. So I will assume, lots of ability but no experience.

You don't state what type of viewing you enjoy doing. Is it deep space or do you prefer planetary work?

You don't need a big mirror to view most planets as they are plenty bright. Sometimes TOO bright! You will need aperture to gather the light needed to magnify targets and do any serious deep space viewing.

My first home built telescope was a 6" f 8 dobsonian. The tube was a 4 foot section of 8 inch PVC sewer pipe from the local commercial plumbing supply house.

Cardboard "Sonotubes" are popular for this application but I wanted something more novel and robust.

The center section is an 8 inch coupler (it's used for "coupling" sections of pipe). You want the main tube to be able to slide up and down though, so you must first grind out the inside ridge. With that removed, saw a slit the length of the coupling. That allows the coupler to be tightened around the pipe with stainless hose clamps. after balancing.

Trunnions were made from two 4 inch PVC caps that were cut on the open end and then sanded to match the OD of the coupler. First they were epoxied in place and then quarter by twenty bolts and washers added for redundancy.

The base isn't rocket science either: two vertical sections notched for the trunions. Ecah side is fitted to a 24 inch round base each with a piano hinge so it can folded flat for transport. The surface of the notches are covered with narrow strips of Star Ebony laminate. The trunions need no treatment.

The round base rotates on a second, similar piece of 24 inch OD plywood fitted with a 24 inch diameter sheet of Star Ebony laminate. Three plastic "feet" for use on chair legs are perfect.

The focuser is merely a chrome "Stove Pipe" assembly, also from the plumbing supply house. One piece of scotch tape folded over the edge makes it a perfect fit for any 1.25 inch eye-piece.

The spider was made using steel strapping band as described at Steve Swazy web site (Spelling? Steve Swazie?) Google will find him, promise. They are thicker but you could use hack saw blades instead.

The center post for the secondary mirror is a short section of copper pipe cut at a 45 degree angle with the mirror simply glued on with silicon.

Primary mirror is also siliconed in place to a bathroom "riser" fitted with bracket angles, short lengths of rubber tubing and fasteners so it can be columated. (A "riser"is a disk of PVC with slots and grooves that enable you to raise the toilet bowel when adding tiles to the bathroom floor.

The whole thing, sans mirror was about $50.oo and works remarkably well in spite of my ignorance of design, construction and the novel materials employed. It still gets used even though I now own two 6" Criterions, a 13" f5 and a 12.5 Inch f8.

Current project is a 15 inch f.4.5 mirror which I am polishing and figuring myself and which will be housed in an all carbon fiber system with provisions for multiple mounts: Dobsonian, German Equatorial, etc.

Please, buy a good primary mirror! I urge you to budget heavily for it and for good eye pieces too. DON"T SCRIMP ON DOLLARS HERE!

A good mirror is forever as are the eye pieces which will most certaintly travel with you should you outgrow your home built OTA and go to something more powerful.

It will take a committed builder about two 8 hour sessions to complete; more if you have "help". Good luck!

[Agro]

Hi Kashi,

The previous respondents are quite correct when they say to build a scope if you want that experience. If your main objective is observing then you will waste a lot of observing time building it, getting it working, working out what accessories you require etc.
I have, over the last 6 months, built an 8" newtonian on an equatorial mount. I designed it, manufactured mirror mounts, tube and other items, bought the mirrors (from Newport Glass in USA, but I'm in Adelaide Aust.), assembled it all. It was for me a very satisfying experience. I now have a scope that is better than anything I could have bought for the same money. Having said that, for about AU$1000 more I could have had a Meade 10" LX200 off the shelf and working and spent that 6 months observing. Mind you - I now know a lot more about scopes than I did before!
If you want to build one - don't be frightened off by the work, the technical requirements etc. Just learn as you go and talk to lots of people in the field (The Vic Astronomical Society is really good for that!). There are plenty of people around who will help you with ideas, equipment, tools, techniques etc. It can be done "cheap and nasty" or "high quality, moderate cost".

If you really just want to observe, my advice would be charge in and buy a good scope that will meet your requirements (planetary, deep sky or compromise) but of good repute so that it retains it's resale value.

Best regards and clear skies. :ph34r:

[kashi]

Thanks everyone. I think I will attend one of the Astronomical Society of Victoria's telescope making workshops before I make a decision about this. I already have too many hobbies!