Constructing a dob

Initially, to keep the bearings from falling off the ground box, I had steel plates attached onto the bearings. However, in hindsight, this wasn't a good idea as they kept bumping off the ground box when the bearings rotated.
This evening, I switched the plates around and attached them to the ground box instead. Now, they remain stationary and work perfectly.

www.astroshot.com/Dob/19.jpg

I also weighed the telescope this evening:
Ground Box: 6.4kg
Bearings and mirror cell: 8.9kg
Secondary Cage (UTA): 2.4kg
Poles: 2.4kg
Primary Mirror: 12.2kg

Total weight excluding primary mirror: 20.1kg
Total weight including primary mirror: 32.3kg
For comparison, the 16" Lightbridge has a total weight of 58kg (nearly twice as heavy)

Well, I've used the scope a few times now and am extremely happy with it. I think I've got the collimation sussed now and it holds very well right through the night. Last night I collimated the scope around 7.30pm; by 3am, it had fallen out of collimation by only a small margin. It also holds collimation well irrespective of the angle of altitude which the bearings are at.
I bought some speaker material in Maplin last week to act as a shroud. I've this cut to length and plan to attach some sort of fasteners to it this evening so that it can be easily attached to the scope. I'm not gong to have a full length shroud - only around 15" length so as to boost contrast to the secondary mirror and eyepiece. I don't think there is much more to gain by having a full length shroud.
So, now that I've this scope sorted, I guess I'll have to start work on a real dob with real aperture!

So, now that I've this scope sorted, I guess I'll have to start work on a real dob with real aperture!

You're off your trolley ! :lol:

BTW, how has the speaker material worked out ?

Dave,
I tested it this evening before the Moon cast too much light. Made a noticable difference, expecially when there was a light source directly oposite the focuser. Well worth using.

I was in contact with a company called Consort Cases in Mooncoin, Co. Kilkenny recently and they can custom-make cases - their web address is www.consortcases.ie
Anyway, after much discussion with Kevin Duggan there who was very helpful and answered all my queries, I placed my order late last week. Today, the case arrived - very quick service.
I wanted the case to be designed around the mirror and not excessively big. For my 16" mirror, I have a case with external dimensions of 17" x 17" x 4.5"
The case is fitted with very dense foam cut to a precise measure. I asked that a couple of cutouts be made in the foam for me to get my hands in under the mirror and also wanted an 80mm diameter extrusion on the top section so that only an 80mm diameter piece of foam would press against the centre of the mirror surface. Why 80mm?...well, the secondary is 88mm diameter and so in this area of the mirror, no light falls on it. Therefore, if any of the foam on the 80mm piece does get something stuck to it and scratches the mirror it won't matter. Meanwhile, the remainder of the mirror surface is protected. Make sense?

Here are a couple of pics:

www.astroshot.com/Dob/20.jpg

www.astroshot.com/Dob/21.jpg

Total cost including delivery was €147.50, which I think was great value, especially as it was custom made to my specification, includes delivery and was all done very quickly.

Clear Skies,

ohhh, very nice and very professional looking. !