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How to center a Polar scope Reticle the easy way.

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#1 will1384

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Posted 25 April 2013 - 12:15 AM

I have been having problems getting my Celestron VX mount aligned for astrophotography, and wanted to try a Polar scope, so I got one and tried aligning it during the day, but one of the tiny screws fell out and got lost, so I looked on the internet to find out what size they were, turns out they were metric M3 grub screws, and I don’t have them, but then I found a link: Permanent Polar scope Reticle Centring and he used rubber O-Ring to center the polar scope reticle, and I have few assortment boxes of rubber O-Rings, so I removed the two remaining reticle adjustment grub screws, and removed the reticle, its a small lens set inside a brass ring, the brass ring has a concave edge, that fits a O-Ring perfect.

I used two O-Rings:

AS568A-112 rubber o-ring on the reticle lens

AS568A-210 rubber o-ring as a spacer between the eyepice and the reticle lens

And now it looks to be perfectly center, one thing I will say is that you are likely to have to clean the reticle lens after you put the o-ring on because its a tight fit, and when pressing it on you will touch the lens.

#2 Pinbout

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Posted 25 April 2013 - 06:48 AM

any pics? sometimes I have a hard time understanding easy things... :grin:

#3 will1384

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Posted 26 April 2013 - 12:24 AM

OK, Here is a "little" :lol: how-to image.

Posted Image

and a link to a larger image because of the 800x800 size limit.

http://lh5.googleuse...ACVI/Xr0RsnY...

#4 John Carruthers

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Posted 26 April 2013 - 02:36 AM

Fine for visual but how do you then adjust it for concentricity? or do you just rely on the housing/ring/reticle all being concentric? if that were the case they wouldn't need provision for adjustment in the first place?

I put a thin O ring behind the reticle (thanks Dion) to stop it falling out should the grub screws accidentally be loosened too much.
Replacing the grubs with thumb screws (another tip from Dion) is a great help, no more fiddling with little Allen keys in the dark.

adjusting polar scope;
http://www.awrtech.c....htm#POLARSCOPE

adjusting and mods;
http://www.astronomy...php?f=19&t=4006

Attached Files



#5 will1384

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Posted 26 April 2013 - 11:23 AM

When I rotate the RA axis from left to right the cross hairs stay centred, I could have done the same with the grub screws but this was a lot easier.

do you just rely on the housing/ring/reticle all being concentric?


Yep.

if that were the case they wouldn't need provision for adjustment in the first place?


I am not sure, maybe the aliment is slightly off using this method, even if it looks good, but its no better than I would have done using the grub screws.

#6 donnie3

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Posted 03 May 2013 - 06:01 PM

will1384, where did you get your o rings. I tried to find them at atwoods and lowes and all they had was plumbing o rings. im going to try true value tomorrow. thanks, donnie

#7 MartinTreadgold

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Posted 05 May 2013 - 04:19 PM

i like the thumb screws... great tip.. thanks

#8 will1384

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Posted 14 May 2013 - 04:01 PM

will1384, where did you get your o rings. I tried to find them at atwoods and lowes and all they had was plumbing o rings. im going to try true value tomorrow. thanks, donnie


I had got some cheap O-Ring assortments at Harbor Freight Tools, they were under $10 for almost 400 O-rings, I had also ordered some from Amazon in the past for around the same.

I got playing with my polar scope today, and decided to get it exactly centered, not just very close, and tried using some metric screws I saved from an old laptop I disassembled, took very little time to get it centered, less than 10 minutes, I also rotated the polar scope reticle to better line up with what the night sky looks like now, I left the O-Rings installed.






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