CGEM hypertune

[Tony_ (Tony)]

Can you use PHD to manually send adjustment commands to the mount to check that the correct signals are being sent?
Is it possible that the RA control autoguide has been reversed? If you are losing the guide star after only 15 seconds it may be guiding in the wrong direction? Even when I have forgotten to plug my autoguider into the mount head (stupid) it still takes several minutes to lose the guide star.

Regards,
Tony.

[toc (Tim)]

Originally Posted by Tony_

Can you use PHD to manually send adjustment commands to the mount to check that the correct signals are being sent?
Is it possible that the RA control autoguide has been reversed? If you are losing the guide star after only 15 seconds it may be guiding in the wrong direction? Even when I have forgotten to plug my autoguider into the mount head (stupid) it still takes several minutes to lose the guide star.

Regards,
Tony.

Actually its not losing the guide star - it stays locked on, but the graph shows drift, and the images show oval stars.

The calibration step works fine, so I am assuming that the communication is working.

[Tony_ (Tony)]

Did you have this problem prior to the hypertune?
It happens to me most of the time - I have always thought it is caused by differential flexure, backlash or just ineffective guiding?
My biggest problem is trying to guide 2350mm fl with a 400mm fl guidescope and the nexguide which doesn't guide to sub-pixel. Sometimes it guides perfectly - other time I get drift.
Are the stars oval in any particular direction (RA or DEC) - that may give more clues.
I think I have read a report that the CGEM mount doesn't have good guiding in DEC the latest mc firmware is supposed to improve this?

Regard,
Tony.

[Rod771 (Rod)]

Tim and Tony

Which motor control firmware versions are currently running on your mounts?

You can download the MC update software here if you don't already have it. 6.50 is the latest version which has the dec bug sorted.

Set the custom rate 9 setting (in the menu section) in the hand control to 4.00 degrees per second or lower if needed. CGEM users have have mixed results with 6.50 , Celestron suspect this could be due to different motherboards used during manufacturing. The main problem reported was heavy vibrations during high speed slews, setting the rate to 4.00 fixed this. It is also better to have more counter weight higher on the counter weight shaft than less weight lower.

When or if you update , definitely test the mount before loading it up with imaging gear to be safe , that's what I did anyway

I was able to get nice 10 min subs at 1960mm FL with OAG/Lodestar.

[Tony_ (Tony)]

I have the latest firmware. I think the guiding only uses much lower rates? - not the custom rate. Isn't that only for slewing or does using a lower slew speed improve the initial calibration?
The problem I have with guiding is that even when the guide star stays right on the middle of the crosshairs and the RA/DEC adjustments seem minimal, I get drift in the imaging scope. It doesn't happen everytime - but often enough. I have always though it to be caused by differential flexure or some other movement?

Regards,
Tony.

[Rod771 (Rod)]

Originally Posted by Tony_

Isn't that only for slewing

Correct, I just wanted to make sure that in the case you had not had the latest firmware and then updated, that the custom rate was set to 4.00 to avoid reported vibrations

Originally Posted by Tony_

The problem I have with guiding is that even when the guide star stays right on the middle of the crosshairs and the RA/DEC adjustments seem minimal, I get drift in the imaging scope. It doesn't happen everytime - but often enough. I have always though it to be caused by differential flexure or some other movement?

Sounds like flexure to me. Imaging at 2350mm you'd be better off looking into an OAG

Cheers

Rod

[toc (Tim)]

Originally Posted by Rod771

Tim and Tony

Which motor control firmware versions are currently running on your mounts?

Im running the latest. My DEC seems fine.

[Tony_ (Tony)]

Tim,

Have you had another chance to try out your mount?
Do you think the hypertune has made much difference - was it worth doing?

Regards,
Tony.