Polar alignment changing

[knobby]

Hi all, can someone give me a reality check please 😁

I'm getting pa down to excellent using Sharpcap ... After imaging for a while and looking at PHD2 logs it's saying polar alignment error of around 3 to 4 arc mins ...

Guidescope is rigid / no play, could the wedge be slipping maybe ?

 

[Frank the Troll]

looks uncomfortable  too me, I would move the dovetail down a bit, seems to be riding bit high

[michael8554]

3 to 4 arcmins is fine, easily guided out, don't waste time trying to get it better. 

I doubt you could get PHD2, Polemaster, and Sharp Cap to come up with the same PA reading, they are trying to measure extremely small changes. 

I agree with Frank, maybe strap some weights to the front of the scope so you can find balance in the middle of the dovetail. 

Incidently your guidescope is on thumbscrews so definitely movement there, a few microns will translate to several pixels on your images. 

Michael 

[knobby]

Thanks for the suggestions chaps, the pic above is oldish - using a ZWO 120 mm screwed direct to guidescope now and I will look at using more of the dovetail ! although it does feel very secure as it is.