CGEM Periodic error correction

Lognic04 (Logan) · #1 14-06-2017, 08:25 PM

Continuing with the theme of the CGEM...

Does the CGEM utilize Permanent Periodic error correction? if so i should be able to do better unguided shots. If not does it have a function to store PEC and playback at least? I have heard actually moving the mount manually can upset this though?

ChrisV (Chris) · #2 14-06-2017, 10:40 PM

I can't get it to work on mine. If you figure it out let me know. Whenever I start PEC training on the mount (using guiding pulses from PHD2) it just starts shuddering and I have to shut down the mount !

Instead, I've downloaded a beta version of PHD2 which has PEC prediction/correction. After a few cycles it reduces the periodic error.

LewisM · #3 15-06-2017, 10:39 AM

Having BRIEFLY owned a CGEM, all I can say is "May the Force be with you" - you'll need it.

It was the first and only mount I actually contemplated turfing into the wheelie bin.

Tony_ (Tony) · #4 20-06-2017, 10:41 PM

I've used a CGEM for about 5 years. With guiding I can get round stars with 2 minutes subs and I could go higher - but light pollution limits my exposure times. If I tried harder I'm sure I could go to 10 minutes - but with a lack of clear skies I don't get much time to experiment.
Without guiding I have been able to get 30sec subs at a focal length of 2300mm with about 15% reject subs at the worst PE points due to excessive elongation. At 600mm I can get 2 minutes unguided.
With your scope at 1000mm you should be able to get close to 90-120s if your polar alignment is good.
For the price I think it is quite a good mount - remember in general the top end mounts are $10k+ or maybe $6k for a G11 - if that is considered top end? You should be able to get reasonably good images with your set-up - but not comparable to the top images here, especially from the suburbs.
As far as PEC goes - yes it is permanent. You have to set the mount to the index point before you record and playback. I've never used it.
There are a lot of factors involved in this hobby and the only one that matters is the fun factor and your set up is good enough to achieve that.

Tony.