It has a been a while, but last night I finally had some time to play with my gear. So I thought I'd test it on the Pinwheel since it's now in season. Everything seemed to go smoothly but when I checked my subs I saw star trails. Unfortunately I had already packed up for the night so I didn't have a chance to do any trouble shooting.
My initial thought is that my alignment was off, but according to Sharp Cap the alignment was true. It's the first time I've used Sharp Cap so I'm not sure how accurate or reliable it is.
If it's not the alignment then could it be the balance?
A quick rough check of your PA without fancy software
Do a drift test on a 1 or 2 magnitude Star
You should be able to track and keep it centered in a crosshair for a few minutes
If not your PA is not good enough
And don't forget to tighten the latitude control after PA.
Recently I saw small trails on all sub frames, but when breaking up the setup after imaging, I realized I forgot that after proper PA, so when pointing to a star, the latitude was 'changed' somewhat, resulting in tracking errors.
Polar alignment is crucial. The south pole is even easier for me, because when I center the +6.9 BQ Octantis (not Sigma !), only 10' off the real south pole, it is accurate enough to make 4 minute subs on 600mm without trails.
At the north pole I have to know the sidereal time to get Polaris at the correct direction 40' off the real north pole.
How long was the exposure? was it guided or unguided?
+1
If you're unguided and doing long subs it could just be a bit of periodic error. Easiest way to tell if it is that is if each sub stays in the same frame and yet you have the trails.
Thanks for the replies. I should have provided a little more info. The sub is a 5 minute guided exposure at 920mm (refractor, no reducer/flattener) on a NEQ6. Usually I drift align but this time I thought that I’d try something new and give SharpCap a go. I did check the latitude/azimuth bolts and they were definitely tight. I’m OCD about this as I’ve been burned too many times in the past. ��
I didn’t think about tilt, but maybe this might be the culprit. I did remove the reducer prior to imaging so maybe I left something loose in the imaging train.
Last edited by LostInSp_ce; 13-04-2019 at 01:11 PM.
Reason: Fixed typo
I managed to get out this morning and do some troubleshooting. My rotator must have loosened when I removed the reducer. So when I attached my camera back to rotator the weight was causing it to tilt just a fraction. Unfortunately the clouds were out and seeing was terrible so I couldn't redo my previous session. However, I did manage to take a 20 minute test sub and the stars look much better now. I still thought I'd process my junk subs with tilt to get some practice with this target. Here are the results.
