Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
bgilb
member
Reged: 07/05/09
Posts: 79
|
|
I'm about ready to design my Obsession style telescope, but the mirror I'm making myself is very light weight.
12", and only 7 pounds. Obviously this is good for portability and thermal issues, but I've run into a problem. I like the low profile obsessions with smaller mirror boxes and smaller rocker boxes, But with a light-weight mirror the altitude bearings need to be so much higher. Short of making the UTA out of paper, what can I do?
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Add some metal bars or bits of flat to the bottom of the mirror box to move the centre of gravity lower.
Kinda defeats the purpose of a light weight mirror , but so will solid tube.
|
Luigi
Post Laureate
Reged: 07/03/07
Posts: 4938
Loc: MA
|
|
The alt axis needs to be higher. Larger diameter sectors can accomplish this without making the rocker taller. Look at ultra-light designs to see ways to keep the upper OTA as light as possible. Check out http://www.kineoptics.com/HC-2.html for ultralight helical Crayford focusers. Etc.
--------------------
17.5" f/5 Dob. IM-715 MCT. 120ED. Lunt 60mm Ha.
Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell bins
|
arpruss
scholastic sledgehammer
Reged: 05/23/08
Posts: 855
Loc: Waco, TX
|
|
I solved this, somewhat unsatisfactorily, with springs in my 8" travel scope.
Using fewer or lighter trusses will help, too, if you can do it.
--------------------
Coulter Odyssey 13.1" split-tube
Coulter Odyssey 8"
Home-made 7.8" F/4 dobsonian travel scope
Home-made 68mm F/5.3 achro (typically used as finder on 13.1")
Skymaster 15x70
BPTs4 8x30
32mm Plossl, 30mm Rini, 27mm Kellner, 13mm Hyperion, 6mm TMB/BO Planetary, Owl 2X Barlow
Palm TX with AstroInfo and RescoViewer
|
Sean Cunneen
Let Me Think
Reged: 08/01/07
Posts: 1222
Loc: Blue Island Illinois
|
|
You have to build your OTA(or model it) and find the Center of gravity. extend the radius down to where you want it and route the altitude bearings as needed. No one knows the radius of arc just by looking, so yours won't look out of place. I think you will enjoy the benefits of the lightweight and I would do theextra work to take advantange of that find!
--------------------
Sean Cunneen
Blue Island, IL
12.5" Ultralight Strut Dob
127mm f/9 refractor
35Pan, 10XW, 5XO
Member of the Calumet Astronomical Society
|
|
17 registered and 6 anonymous users are browsing this forum.
Moderator: Don W, Mike I. Jones
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 183
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 