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Fit Image Header

Acquisition Bias Frames Deep Sky
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Jerry Gerber avatar
Jerry Gerber avatar
Hi!

I just took 30 BIAS frames at 1ms each.  When I examined the .FIT header it reads:

2024-07-09_01-35-44_Dark Filter_-0.50_0.00s_0000.fits

The time is showing 0 seconds rather than 1ms.  Is this a readout limitation of the FIT header or should I be concerned?

Thanks,
Jerry
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andrea tasselli avatar
andrea tasselli avatar
That's not a FITS header. The file naming is showing precision up to 0.01s or one hundreth of a second, so 1 thousandth of a second it is rounded off to zero. The actual FITS header should show the real number.
Jerry Gerber avatar
Jerry Gerber avatar
andrea tasselli:
That's not a FITS header. The file naming is showing precision up to 0.01s or one hundreth of a second, so 1 thousandth of a second it is rounded off to zero. The actual FITS header should show the real number.


Oh, OK, I didn't know that.   Is there a way to see the actual FIT header for confirmation?

Thanks Andrea!
Christian Großmann avatar
Christian Großmann avatar
What software did you use? I use Nina and you have to specify the type of frame you record. This is then written to the fits header. I remember this setting in other software as well. The "Dark Filter" string may also be the name of the filter that's used. Did you use this to generate darks? Have you named a filter like that and this is currently used?

It seems, the software can store exposure time values in hundreths of a second. 1ms is even less. So the value is rounded to 0.00. I saw this in some of my own images as well.

CS
Christian
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Jerry Gerber avatar
Jerry Gerber avatar
It's resolved. I found the process in Pixinsight where I could inspect the FIT header. I confirmed that the exposure is 1 ms as expected.

Thanks..
Brian Puhl avatar
Brian Puhl avatar
Side note, I'd recommend longer bias frames, especially on CMOS.    0.2 second exposures minimum is what we've been recommending.
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