Guiding Issues

johnpd

Guiding is driving me crazy. I can see a little trailing in some as stars especially around the edges which seem a little oblong. This could also be a product of my focal reducer.

My RMS numbers can be below 1.00, but occasionally pop over that. The Dec seems usually OK, but I get some nasty spikes in RA which sometimes come in pairs or triplets or more. When looking at the guide star selected by my ASIAIR Pro, it has like a cloud around part of it in the guide star display. I am using an ASI290MM Mini as my guide camera and I have focused it with a Bahtinov mask. One thing that seemed to help guiding was increasing the gain on the guide camera. Any ideas are appreciated.

JohnD

This image of IC1396 had a little better tracking. This is where I set the guide camera gain up a little.

PMTeam@ZWO

johnpd Hello, the guide curve looks normal.
The introduction of dark guiding Library in version 2.0 may be helpful to you

johnpd

The screen print of the guiding at that point in time show good guiding. However, this shows the spikes I was referring to.

JohnD

Walf@ZWO

What main telescope and guide telescope you use？

johnpd

The main scope is an Explore Scientific 127ED (952mm F/L using a .065x focal reducer giving an effective f/4.8).
Camera is an ASI533MC Pro.

Guide scope is a Williams Optics Uniguide 32mm diameter with a 120mm F/L.
Guide camera is an ASI290MM Mini.

JohnD

Walf@ZWO

I think the problem is that main scope and guide scope is not sync, because the focal length of main scope is too longer than guide scope, you could reduce strength of RA and have a try.

ckoos

I disagree with the ZWO answer, you should be able to guide with a reduced ED127 and a 120mm guide scope. I see two things, first, the star size of 5.9 is way too large. Minimally the size should be below 4, ideally the size should be below 3. You need to figure out why it's so large. Second, because of how regular and large they are, to me, those spikes look like a mechanical issue with the mount or guide scope. Maybe a drive train issue in the mount or a loose mounting of the guide scope. I suggest searching on Cloudy Nights or a mount specific forum for clues.

I guide a ED127/ASI533MC with a 240mm/ASI120mm mini, EQ6R-Pro set up and get consistent .35-.45 RMS guiding.

And check this for ideas: https://openphdguiding.org/Analyzing_PHD2_Guide_Logs.pdf

-chuck-

johnpd

ckoos

Thanks for your reply. The reason the star is large is that I doubled the gain. Increasing the gain did help somewhat stabilize the guiding. I am leaning towards an issue with the mount as I have seen others comment about their CEM40s having spiking problems. Below is my telescope setup.

JohnD

johnpd

I have talked to my local astronomy store and sent them information. They were willing to do some investigation. Here is the log in case you would like to look at it. The last entry had the best guiding as I had doubled the gain on the guide camera. In looking at the RA corrections and referring to that Analyzing Guide, it almost looks like a backlash issue although that guide says that RA backlash is rare.

JohnD

phd2-guidelog-2022-09-05-202205.txt

701kB

johnpd

I brought my mount up to the local astronomy store and they took a look at it. They said that the RA gear was tight. So they loosened it and I will pick it up Friday and try it out Friday night to see if there was any improvement.

JohnD