Filter Number in FITS header

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GregL
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Filter Number in FITS header

Post by GregL » Sun Jul 14, 2019 7:07 pm

I am just getting started with narrowband imaging -- using either SGP or Sharpcap to manage my QHY183M camera and filter wheel. It would be really nice if there was (or could be) a way to log the filter number being used for the exposure. I see the RA&DEC, binning, exposure -- all good, although I am used to seeing RA in H:M:S format. And the timestamp. But I would like some way of recording the filter slot being used, please.

greg latiak

nexusjeep
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Re: Filter Number in FITS header

Post by nexusjeep » Sun Jul 14, 2019 8:52 pm

Not sure if it can be added in the header but you can add it to the filename automatically and create a new folder for each filter.

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Nick

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Re: Filter Number in FITS header

Post by admin » Mon Jul 15, 2019 9:31 pm

Hi,

If you're using an Ascom filter wheel then this should already happen when saving to fits files. Actually the name of the filter rather than the index of the filter will be what gets put into the filter header in the fits file, but hopefully that will be sufficient.

I think it may also work for filter wheels that are controlled directly by the camera without an Ascom driver, but I'm not hundred percent sure from looking at the code – it would require a quick test. If you find that this doesn't work as it should, please let me know.

Cheers, Robin

GregL
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Re: Filter Number in FITS header

Post by GregL » Fri Aug 09, 2019 12:45 pm

Robin,

A couple of days ago I did a series of exposures with LRGB and Ha filters. The filter wheel is a QHYCFW3, the names of the filters are defined to ASCOM and are visible through a number of different programs. What I find is that the FIT header on the image file and the camera settings file in the capture directory record the same information ... 'Filter7' for the filter wheel position 7, not 'B'. I suspect its not actually talking to ASCOM for this as the tag recorded for filter 1 is blank. And the ASCOM definition for that slot is 'Lum'.

greg

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Re: Filter Number in FITS header

Post by admin » Fri Aug 09, 2019 7:58 pm

Hi Greg,

That's odd because I've had another report that the names of the filters are not showing up correctly for a qhy filter wheel. Do the names of the filters show up in the filter wheel change buttons in the control panel?

Cheers, Robin

GregL
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Re: Filter Number in FITS header

Post by GregL » Sun Aug 11, 2019 1:00 pm

Robin,

No, they don't. The grid just shows 'filter 1', etc. What is funny about this is that if I look at 'properties' for the filterwheel in 'settings', all the filters are named correctly. As an aside, is there any commercial filterwheel with the number of slots allotted in the grid?

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Re: Filter Number in FITS header

Post by admin » Sun Aug 11, 2019 7:15 pm

Hi Greg,

Please can you send me your SharpCap log file – please capture it after you have opened the camera and move the filter wheel a bit.

Cheers, Robin

GregL
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Re: Filter Number in FITS header

Post by GregL » Mon Aug 12, 2019 5:37 pm

Robin,

Here is the log from my last captures -- a set of five groups of L, R, G, B, Ha. Used the exposure calc for L, R, Ha was a guess based on the L. Process was to select filter from the list, run captures, change tot he next filter, repeat. Clouds were closing in so I was a bit rushed. The filters used were 1,5,6,7,2 in that order.

greg
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Log_2019-08-04T23_33_59-10448.log
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Re: Filter Number in FITS header

Post by admin » Mon Aug 12, 2019 9:51 pm

Hi,

Thanks for the log – I have a couple of ideas now and will try to put some extra logging code into the next update that will help me to work out exactly where things are going wrong.

Cheers, Robin

GregL
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Re: Filter Number in FITS header

Post by GregL » Mon Aug 12, 2019 11:26 pm

Robin,

Glad you are having fun... brings back memories of writing this sort of code myself. But that was a long time ago and it was a mix of Vax Macro-32 and C/Basic. Gave it up when I retired. Now I am just a grumpy ex-techie...

g

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