12" Dob or greater, buy or build

[jquin]

Hi All
I would start out with an 8" dob but I have been spoilt by looking through a 10" and I would like a big light bucket.

Are there many people who build Dob's anymore or does everyone buy one of the shelf and modify it?

I don't mind getting my hands dirty and building something challenging but is it more trouble that it is worth?:eyepop:

Otherwise the large Bintel Dobs look good.
Any advice?

[hickny]

Hi John,
Have a look at the ATM site in the forum.
Mental4Astro and I have built a few dob. Yeah we get our hands dirty.
Check out http://www.iceinspace.com.au/forum/showthread.php?t=54572
Today we did more modifications and the updated post should go up in the next few days.

[Paddy]

Hi John and welcome. I found my 12" gso/bintel dob to be very good and this seems a common opinion. I would think that the main advantage of building one would be the portability of a truss design. Mind you, the 12" GSO is not too much of a problem to move around.

There are some lovely truss dob designs around though. Price wise you would lose little to buy a GSO dob and building a new assembly for the optics if it takes your fancy or you find the tube set up cumbersome.

Whatever way, I reckon you'll have a good time.

[torana68]

It could cost more, could mean more to you, could provide a excellent time waster making it, could end up looking better. It would be yours :) it could turn out better than any you buy or could be a disaster if your a nu nu with tools :) your choice.

[Vanda]

Don't truss designs suffer from dust/stray light more than enclosed tubes? :)

[mental4astro]

They can, but there are ways around this.

*One is designing the truss dob to minimise stray light.

*Useing a 'light shroud' to enclose the 'tube' when assembled- this is really only needed in a light polluted location. In a dark site, there really is no stray light around.

*Light baffels can be fitted to the mirror box and the secondary cage to reduce stray light. They act like lens shade on a camera lens.

Dust is no bigger problem than an open tube. Both will collect dust while they have their mirrors exposed. The inside of a solid tube gets really, really dirty over time, which acts a source of dust as it gets shaken off the inside of the tube, only to settle on the primary.

What truss dobs are more suceptible to is dew forming on the primary mirror. In an enclosed tube, the tube helps maintain the moist air away from the mirror much more effectively. Dew control heating can, and is readily added to truss dobs to stop this problem.

I can tell you from my experience, a 17.5" dob is much easier to transport as a truss dob than a solid tube scope! Man, is it ever! The truss dob in the process to finishing is the exact same scope in the solid tube pic. What ever 'problems' an open truss design may present, comes nowhere near the single problem of a big solid tube. Just finding a spot to store the sucker is a task in itself.

[ManOnTheMoon]

Holy crap Alex that sucker is huge! and I thought my 8" skywatcher was big lol...:)

[Vanda]

Thanks for the explanation alex.

[Migmo]

Im new to this a have recently purchaesd a 12 in saxon dob....I just love it