Robotarget selection criteria

A question about Advanced and RoboTarget, but I am not able to post in that section.

I have been using Voyager Advanced for a few weeks now trying to improve the level of automation of my observatory. It has worked fine on initial trials, but I have not yet understood some of the nuances.

Last night was clear, but with a bright moon. I expected RoboTarget to select narrowband targets some distance from the moon which it did. It started with NGC6888 until that fell below my local horizon limit, then switched to NGC7380 (Wizard Nebula) and collected data until that fell too low. I then expected it to switch to IC1795 (Fish Head Nebula) which was high in the sky an reasonably far from the moon.

Instead the scheduler said it could not find a viable target and the reason given for rejection was “cannot intersect interval(s) or interval(s) empty”. I had the moon avoidance algorithm set for Lorentzian narrowband.

I can understand why many of the targets listed in RoboTarget were not selected - either too close to the moon in narrowband (e.g. Horsehead Nebula), or broadband and suffering from strong moonlight. But I wondered if there was anything else going on? I assume the error message means that the criteria for selection are not met, but i am not sure how I can find out which criteria is the problem.

Whilst I was still playing around after midnight, the clouds rolled in and I decided to abandon the session (heavy rain forecast).

I clearly need to add more targets in different parts of the sky, but would like to understand a bit more about the scheduling algorithm. For example, if IC 1795 was rejected because of moon avoidance, I might have been tempted to try it anyway to see what the results looked like. I had no other narrowband targets that were more favourably placed.


I added your user to the Advanced group in forum and now you can write.
You can found more information on video tutorial about RoboTarget.

“cannot intersect interval(s) or interval(s) empty” means that the time of scheduling is not inside any of the possible time intervals where the constraints are satisfied. In particular lorentzian moon avoidance algorithm work on coupling of distance from the moon and moon phases.

All the best

Thanks Leonardo - I thought that might be the case.

I need to fill out my RoboTarget list with more targets, and accept that there will be times when the moon is up and close to full, where no imaging will take place.