FIT Header - Maxim or ISIS issue?

[Peter Velez]

One for the Brains Trust

I have encountered a recurring error in ISIS of late. I attach a sample error message.

Looks like the FIT header does not display data in a format that ISIS likes - at least in relation to the date/time. I use Maxim DL for guiding and imaging. I'm uncertain whether this is a problem with Maxim or ISIS.

Can anyone shed any light on why this might be happening - and more importantly what I can do about it. For example, is it possible to correct the error using the FIT header editing tool in Maxim? To date, I have simply been excluding the problematic image from the data set.

This is becoming quite common for me. Its not an issue when I am taking short images of my reference stars but quite a pain when I have relatively few long exposures. For example, I had 13 images of SN 2020nvb last night - 2 of them failed to load which impacts on SNR of the final spectrum.

All suggestions would be gratefully accepted

Pete

[David Boyd]

I am not a Maxim DL user but I have heard from others who are that this is a bug in the latest version of Maxim. It sometimes writes rubbish in the DATE-OBS keyword in the FITS header and ISIS gets upset about that. I'm also told the supplier knows about it so presumably it will get fixed but maybe others with more information can add to this.

David

[Peter Velez]

Thanks David

good to know that the suppler is aware of it. I wonder whether I can alter it manually. Will give it a go

Pete

[David Boyd]

Here's more information I got from a user who received the following from the MaximDL people:

"We have an update coming out this week, which should resolve that.
In the meantime, we recommend trying these things:
Camera Control / Setup Tab / Options turn on threading for camera and filter wheel, for both guider and main camera
If using an ASCOM camera, try the patch in this post: https://forum.diffractionlimited.co...te-obs-fits-keyword-behavior.6695/#post-35927"

He got that last week so it may be worth checking their website for updates.

David

[Peter Velez]

Thanks David

there is an update that allows a user to set the DATE-OBS field to be populated by Maxim or ASCOM. This may fix it. I will test this out.

Looking at the FIT Header (which I should have done earlier) I see that the DATE-OBS field contains the observation time "No cooler control". Hard to work out where to include that in a sequence of images!

Pete

[Forrest Sims]

Hi Peter,

I am the user that David was referring to. Sorry I did not see your post earlier. The problem I had was identical to the problem you are having and is fixed in the latest vision of MaximDL 6.22. Diffraction Limited came out last Thursday afternoon with MaximDL 6.22. I only encountered the problem early last week when I upgraded from 6.20 to 6.21. I had all kinds of junk written into the DATE-OBS field. I had to hand edit 280 fit files from one evening, fortunately I had a good log. Doug George was very responsive when I reported the problem and sent me the information on the workaround David described and then the new version followed a couple of days later. This is my second night now using the new vision and no problems.

Cheers
Woody Sims

[Peter Velez]

Thanks Woody

I thought I had responded last night bit it seems my post didn't send - pilot error I am sure.

After upgrading to the latest version of Maxim its all working very smoothly now. Glad I was not alone in encountering difficulties

Pete