Astroart Forum

Hi,

First off, I just want to say that Astroart is working extremely well for me - very happy. I have my rig fully automated, which AstroArt makes extremely easy! Now, the main reason for my post

I am working in a heavily light polluted area, and also have a very small guiding fov (approx 0.2_deg). So, finding a guide star can be difficult, but is manageable when working semi-manually (i.e. selecting a guide star by manually 'searching'). However, for my fully automated sessions I would like astroart to find a suitable guide star for me (i.e. Camera.StartAutoguide() )

Now, In order to help astroart find a good guide star I have programmed a spiral search out from the centre of the target. The spiral search stops once Camera.StartAutoguide returns successfully. Unfortunately the problem is that astroart often tries 'too hard' to find a guide star and appears to selects on either noise, which forces my spiral search to stop 'early'. Of course a can choose to ignore the successful StartAutoguide and keep running the search, but at the moment I have no way of knowning when a 'good' star is found.

So I was wondering if there was a way to set the threshold for what StartAutoguide would see as a 'good' choice. Or alternatively, maybe rather than just returning 0 or 1, StartAutoguide could return a confidence level - possibly 0-5? I could then test multiple coordinates (i.e. run my full spiral search) and select on the best option.

I guess an alternative approach might be to somehow use my primary camera (much wider field) to return coordinates for 'good' stars, and then move the mount in such a way that it puts a good star in the guiders field of view. Unfortunately my OAG guiding FOV is outside the FOV of my main camera though so this approach would be a little painful.

Any suggestions welcomed

Cheers,
Andrew.

Hi,
At the moment I don't see a solution, but:
It would be very easy to add a parameter to StartAutoguide, defined as the minimum S/N acceptable. I think that this will solve the problem.
Returning the actual S/N instead of 0..1 is too complex at the moment, but another solution could be a command to download the guider full frame, where the user could calculate statistics on the brighter star.

there could be another solution yet, but my lateral thinking is not very good.

Hey Fabio,

I think a S/N parameter would probably do the job quite nicely.
Having the option to download the guider frame would also be a nice option.
Could I be greedy and ask for both

Cheers,
Andrew.

OK, it will be added in 2-3 days. To receive a prerelease please write me by email, otherwise I expect to release a new camera interface at the end of the year.

Wonderful!

Hi.
It's possible to know the exact syntax of the command Camera.Startautoguide() with the definition of the S/N threshold?

Many thanks

Hi,
for the camera interface 6.2:

Camera.StartAutoguide()
Camera.StartAutoguide(radius, snRel)
Camera.StartAutoguide(radius, snRel, saturationMax, exposureTime)

snRel means "S/N relative" , relative to an "optimal - minimum" S/N of stars to be used for autoguide, which for the camera interface 6.2 is 8.0.
So, setting snRel = 2.0, means that only stars with S/N better than 16.0 will be used. (Obviously if many stars are found, only the one with the highest S/N will be used).