Hi All,

I have been trying to get autoguiding to work with my setup.

I have an unsupported mount so I have been trying to use the guider "on camera".

Guide Camera: ASI 120MM mini
Telescope: Questar on a fork mount (equatoirally set up), capable of guiding through ST-4 from the camera although, only in RA and not in DEC.
Software: EKOS on Stellarmate- using the internal guider.

The issue:

I can usually seamlessly polar align using EKOS. however when i guide i deal with a few different issues:
1) sometimes the star keeps getting lost even before calibration is completed: I have tried lengthening exposure time (seems to help)- the remedy the software suggests is expanding the box further (already set at 64 and i have tried 128) or shortening pulses (tried that too)
2) once calibration is completed when it starts autoguiding the RMS error is quite large- sometimes reaches threshold and starts all over again. other times it loses track of the star and then starts autoguiding again. doesnt seem to hold autoguiding constantly.

I have attached a screenshot that may give more detail below. settings I currently have: 1000ms pulses while guiding, 1 second exposures and GPG RA guiding checked in options, contrary to the image below, i have mostly used 2x2 binning. Any help would be much appreciated.
Best,
Omer

Hi Omer,

What guiding algorithm are you using? I couldn't see from your screenshots. I use SEP Multi Star and have good success with it.

My optical system is not as fast as yours but from your screen shot it looks like at a 1 second exposure EKOS only detected 2 stars. This seems abnormally low based on my experience. I have an F7 system and shoot 8 second guiding exposures (the long exposures are partly because I have a mount with high res encoders and they don't like to be 'over' guided). I usually see a few 10s of stars depending on where in the sky I'm shooting. Maybe a 2 or 4 second exposure would turn up more stars consistently?

Hello. Omer,
the Scope/Lens Info in the guiding tab, is set to FL=101mm and aperture=89mm, is that correct?

Regards

Dirk

Hi Fred,

Thanks for the suggestion I'll be sure to try longer exposures and report back. I think it only detects two stars because of poor seeing and the very light polluted skies of London. Not to mention my telescope has only a 3.5 inch aperture.

Could having only 2 stars cause the high RMS error? also any suggestions on the pulse duration?

Thanks,

Omer

Hi Dirk,

Yes the telescope has an aperture of 89mm and in finder mode (using the guider in the eyepiece port) has a FL of 101mm.

Thanks,

Omer

My posts are working again! Thank you

Hi Omer,
I use the ASI120mm mini on a 30/120mm guidescope. I have the following settings: 5 sec exposure, gain around 40 and delay between exposures is around 4 secs as well. I use the internal guider and the algorithm is SEP multistar. The exposure should be enough to get atleast 10 stars so that you have a reliable chance of guiding. Good luck.
BTW, what is the model of your mount?

Hi Omer,

In looking a bit at the recent posts and your telescope, what is the imaging camera and guide camera configuration on your scope?

Cheers,

The telescope I’m using is a questar 3.5. I’m using an asi120mm in the eyepiece port of the telescope in finder mode it has a 101mm focal length. The imaging camera is a Sony mirror less a6600 unmodified. It’s attached using a camera coupling set at a focal length of 1422mm. The telescope is a mak Casals design and as you can tell fairly slow.

The mount is a fork mount which is permanently attached to the ota. The telescope comes with legs that can be attached to the fork mount to be equatorially configured (akin to a wedge).

AFAIK the mount is not supported by ascom of indi hence using guiding through the camera and an st4 cable to the mount.

Thanks,

Omer

Hi Omer,

I'm afraid I'm not familiar with the kind of set up you are using - the scope has an enthusiastic following though! A couple of thoughts:

1) The difference in focal length between your guiding imaging path (101mm) and your main imaging path (1,422mm) is quite large. Forums and other resources are full of guidance and rules of thumb regarding what main imaging focal length to guiding focal length ratio should be. They vary between 3:1 and 10:1 - these days, technology likely allows ratios toward the higher end of the range. You're at 14:1 and that may provide you with some challenges. Of course, you've got to get to the point where you can guide in the first place - hence your post here!

2) When you look into the eyepiece port of the telescope in finder mode, are you able to visually see many stars?

2) Have you considered the use of a separate guide scope? You could mount a guide scope to your Questar and eliminate complications from the finder mode, if any.

Sorry I can't be more helpful!

Hi Fred,

Yes I could use a separate guidescope I know of one questar owner doing that. I was trying to creat the lightest weight/ most portable setup. I sort of can see more stars than just eyes up at the sky. My intent is to get 30 sec or so exposures. And targets being small galaxies and planetary nebulae given the high focal length of the scope.

Thanks,

Omer