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Polar scope centering screws


catman161
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Hi guys, just thought I'd share some pics of the little mod that I found on one of Dions tutorial videos on Astronomy shed.

Now Dion says that M3 x 10mm thumb screws are needed but I couldn't find these anywhere and when i did for just 3 units including delivery it came up with silly prices.

So I ordered 3 M3 x 8mm thumb screws from 365astronomy.com. For less than £8 delivered.

7ejy8eby.jpg

As you can see they have a straight edge to them before the thread. I found that this catches on the polar scope a little when rotating (hence why Dion said 10mm were needed doh!) so I got out the trusty old Dremel multi tool and just shaved a little off around the edges of the bottom of the thumb grips on all three whilst being careful to avoid slipping and hitting the thread which would obviously have ruined them. You can just about see the effect in this picture:

9adebage.jpg

Then I set to placing the other 2 in where the grub screws were. To do this you have to remove the polar scope eyepiece and take care to catch the reticule as with no grub screws in place it also comes out with the eyepiece. Being careful not to touch the reticule directly, I used a pair of tweezers for this.I then screwed out the thumb screws so that they did not ingress into the polar scope tube at all and with the tweezers placed the reticule back in in the correct orientation and tightened the thumb screws so that they gripped the reticule. I then replaced the eyepiece:

mu2e8ehu.jpg

and then setup the mount up in my yard and used the TV aerial method as described in Dions video "Polar Scope Centering & Mods" to center the reticule with the three newly installed thumb screws. It takes a little time and patience but eventually you can make it so that when you rotate the RA axis 360 degrees the Polaris circle touches the tip of the TV aerial each time indicating the reticule is perfectly centred :) I attempted to use my iPhone to take a picture through the polar scope to illustrate this am came up with the pretty poor image below but I think you can just make it out :)

e7y5avu8.jpg

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Did it not come with the centering screws? I thought they are supposed to as standard, thanks for the link to 365 though as I lost one on my cg5 and just used some horrible looking one I found in the shed :lol:


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Did it not come with the centering screws? I thought they are supposed to as standard, thanks for the link to 365 though as I lost one on my cg5 and just used some horrible looking one I found in the shed :lol:

Nope they come with tiny, annoying grub screws that you need to use Allen keys with which is ridiculously fiddly!

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There's a hardware store up Welford Road Felix - one of the old traditional types - they have hundreds of boxes of nuts 'n' bolts of all shapes and sizes from polar scope to M10 bolts for attaching mount to tripod. On the corner of Welford Rd and Wordsworth Street (Called Welford Ironmongers) right opposite Grimsby Fisheries (best fish 'n' chip shop in Leicester).


 


You could've got 3 for a £1 there. Nice mod though - I think they use grub screws cos the polar scope shouldn't need regular adjustment. But as allways that's never the case. :)


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Oh man! Thanks though Kim, should've just asked you first! Ha ha! Oh well it's done now an I hope it will help make polar alignment and tracking more accurate-it was bad before but hey ho :)

Am hoping for it to stay clear so I can set up in the yard tonight and see what I can see :)

Edited by catman161
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Just make sure you try the chip shop - it really is dead scrummy haha! :)

Will do! We tried a new one last night on narborough road run by an old Italian family and its fantastic. The lighter batter I've ever had I think and cooked to order in front of you and the chip portions are good but not ridiculously big like some places

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Guest Ely Ellis

Done the mod on both for my EQ-4 and EQ-5 polarscopes.


But the fitting that was already on both mounts had them already there. I just removed them and fitted them to the polarscopes.


 


I thought all mounts had these on the fitting you have to remove from the scope! Maybe just Celestron!


 


Yep, makes life easy to set-up, but found they do come loose, so you need a dob of cement or something to keep them in place. (Not that I got round to doing that on mine yet!).


 


Martin


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