Free Shipping on ALL Products
camera reviewsbest cameraslens reviewsphotography tipscamera forumvideo toursphotography bookssupport me
It is currently Fri Aug 01, 2014 2:18 pm

All times are UTC




Post new topic Reply to topic  [ 18 posts ]  Go to page Previous  1, 2
Author Message
 Post subject:
PostPosted: Tue Mar 08, 2011 9:25 pm 
Offline
User avatar

Joined: Sun May 25, 2008 12:48 pm
Posts: 8022
Location: UK
On the polar finder, tonight I had a go at collimating it. My conclusion, I think I messed it up beyond repair.

To cut a long story short, I can't keep the main barrel on the correct optical axis relative to the mount.

I now know more about how it is built than I ever wanted to know... on the tip is a cemented doublet. It fell out as I disassembled it, and thankfully one side was dirty enough for me to tell it was the one facing outside!

The main barrel is a plastic tube with thread on both ends, the other end screws into the section holding the image overlay and light source. A mistake I made in the past is that there is a screw holding the barrel in place. When I last dropped it, I unscrewed and rescrewed it in without touching that screw, which stripped off a lot of thread on the plastic barrel. The thread on both ends of the barrel appears the same, but even if I reverse it to use the other good end, it screws in very loosely that even with the screw tightened, it wobbles.

Inside the assembly is the insert which has the overlay. That is held in place with three screws which you can adjust to collimate it, assuming you didn't mess up the rest as badly as I did. Finally is the rear section holding a lens assembly of relatively short focal length. This overall seems to produce a basic telescope with inverting image. I think the image overlay should sit at the common focal point in order for everything to be in focus.

I think right now, my best bet might be to try replacing the plastic barrel with something else more sturdy, but I'd need to get the thread and diameter exact. That'll be tough I think. The alternative is to buy a replacement polar finder. I wouldn't get the same one again, but I'm not sure if any other model would be mechanically compatible or would otherwise be easily modified as such.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


Top
 Profile  
 
 Post subject:
PostPosted: Tue Mar 08, 2011 11:09 pm 
Offline
Moderator
User avatar

Joined: Sat Sep 30, 2006 4:30 pm
Posts: 9805
Location: UK
Hi popo,

What a shame. No chance of a free replacement due to a manufacturing defect I suppose? :?

My guess, without ever having seen an AstroTrac in the flesh, is that while you could no doubt find polar finders that would fit through the mounting hole you would probably have to get someone with a lathe to make an adaptor to fix it in place. Or maybe you could adapt an AC602 Polarmate but they aren't exactly cheap. Or could you interest Astro Engineering in developing a version specifically for the AstroTrac and becoming a beta tester in return for a freebie! Sounds unlikely but if you don't ask....

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


Top
 Profile  
 
 Post subject:
PostPosted: Tue Mar 08, 2011 11:29 pm 
Offline
User avatar

Joined: Sun May 25, 2008 12:48 pm
Posts: 8022
Location: UK
The earlier dropping of it leading to it going badly out of alignment was entirely my fault, although thinking more I can try asking them if I can just purchase the long plastic section and have another go replacing it myself. Asking for a repair might be another option but I doubt that would be economic compared to re-buying new. I'm concerned I might also have damaged the bit the long bit screws into.

I have seen a relatively cheap Skywatcher but it's a bit lacking in detail as to what it offers.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 18 posts ]  Go to page Previous  1, 2

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  

All words, images, videos and layout, copyright 2005-2012 Gordon Laing. May not be used without permission.
/ How we test / Best Cameras / Advertising / Camera reviews / Supporting Camera Labs

Webdesign by Alphabase IT
Powered by phpBB® Forum Software © phpBB Group