Calibrating a polar scope

[iamjulian]

Blimey, how hard is it to set up/calibrate a polar scope! I set up my mount last night, pointed up stairs with a post-it note and a dot stuck to the bathroom door. I was kneeling on the floor looking through the polar scope, trying to adjust the three little screws to centre the cross hair. About fifteen minutes later I had lost the ability to walk and wasn't getting anywhere so I took the polar scope apart to see how it works. Better understanding what the three little screws were doing I put it back in the mount and tried again, only to have one screw fall out (on the inside) and the little diagram showing the cross hair came loose.

I re-assembled it and had another go but now when the counter weight arm is at the bottom, the little circle for centring polaris is to one side, in a different place to when I started. Does this matter?

I still didn't manage to get it set up. I'll start the cross hair on the dot, rotate the RA 180 degrees, then adjust so that the cross hair moves half way to the target. But I was following Astro Baby's guide from memory, so when I rotated back to where I started and the cross hair was no longer centred I was scratching my head - I had forgotten to re-align the mount at that point using the slow motion controls.

I'll have to have another go tonight, but wouldn't mind hearing whether it matters that the part with the cross hair and markings (within the polar scope) has now rotated within the polar scope?

[dark knight]

It shouldn't matter, however if using the setting/date circles, these will need to be recalibrated.

HTH

[iamjulian]

Thank you Dark Knight, that will be good if/when I get past the first step.

I have been defeated again. I cannot get my head around the first bit of the calibration of this polar scope. Please see diagram. I centre the cross hair on a distant point (A). Then I rotate the RA axis through 180 degrees to see how far off the cross hair is (. Then I use the 3 tiny screws to adjust the cross hair so that it moves half way back to the distant point ©. Then what!? I know I am supposed to rotate the RA back to the centre but the point has moved accordingly (D). The instructions I am reading on Astro Baby's tutorial say that at this point I need to re-centre the cross hair on the distant point. But how? I must be missing something obvious. Any help greatly appreciated. Thanks!

[dark knight]

After achieving step "D" you use the adjusters on the mount (Latitude and Azimuth) not the polar scope to recentre the star in the middle, then repeat the whole process until the star stays in the middle of the polar scope.

[iamjulian]

ah yes, that makes sense.

Thank you once again!

[dark knight]

Your very welcome Julian.