M57 number 2

Managed a second attempt at M57. just managed to get it before Mr Cheese appeared above the clouds on the horizon. Tracking was pretty poor so I cropped the worst of it out.
LX90.
DSI-C.
22 images @ 25 seconds combined in Autostar Suite.

www.irishastronomy.org/user_resources/fi...1122257508-M57-2.jpg
Bill.

Nice one Bill! ... Big improvement on the first attempt. Keep up the good work!

Agreed! The tracking doesn't look that bad from the images you salvaged at all! I like the colour you managed to capture especially! Nice Work Bill!

cheers guys. I was quite pleased with it.
Seanie, here's the uncroped version. Once you move away from the actual target you can see the deteriation in tracking. does a Polar wedge reduce this?

www.irishastronomy.org/user_resources/fi...1122292030-M57-2.jpg

Bill.

A polar wedge would definitely help, I've seen them in action and giving better results.

Bill - that's not tracking - that's field rotation - inherent in alt-az mounts (including fork mounts).

If it was pure tracking, all objects in the image would 'trail'. Rotation is evident in that the objects closer to the edges of the field trail whilst those in the center do not (at least for short-ish exposures).

There are three solutions:
1. Polar wedge (attach to mount)
2. Field de-rotator (attach to OTA)
3. Buy a DSI-Pro (field de-rotation software built in)

The wedge is probably the best solution. It basically turns your mount into a German Equatorial by tilting the forks so you can align them to the celestial pole (ie polar align).

Cheers

Dave McD