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I am making some headway into this complicated (for me) CMOS photometry.
Now I need software to calibrate raw FITS file photometry images.
There is much advice online. Most is centered around taking fantastic images.
Is there anything (perhaps user friendly for this old brain and less complicated)
suitable for calibration of images for photometry.
Everybody has their favourite so quite happy to take a poll.
I am in the AAVSO and they have some great stuff but as far as I can see, oddly nothing for this.
I have downloaded AIP4WIN initially as a viewer for FITS images, but can’t seem to get far with it.
Thanks again for invaluable advice on these forums
KevinHi Kevin,
There are quite a few choices for software packages that will calibrate your images, and some will calibrate and perform the photometry. Did I see somewhere that you are learning to use the AAVSO VPhot software? I don’t believe that has calibration facilities? It’s amazing on the calibration side of things.
I, personally, use AstroArt 8 (AA8) for my photometry and this is because it can be scripted and controlled by my Python programs. AA8 also performs the calibration. I prefer to use PixInsight to produce my calibration master files, but that’s only because I’m well versed in PI and it has an incredible set of calibration processes. AA8 would do the job too.
Having said all this, I’ve recently been using the excellent Tycho Tracker program to do photometry. This also copes with calibration. I would recommend looking at this and there are lots of very good videos on YouTube by the author of the Tycho software and he is very responsive with questions. There is a small one off cost for the Pro version but it is well worth a look.
Other than that, there is Maxim DL which is widely used for calibration and photometry. Also AstroImageJ (free) is incredible but takes a bit of learning.
You could use the free DeepSkyStacker for calibration.
I know lots of people swear by Siril which I believe is free.
A few links:
https://www.tycho-tracker.com/
https://siril.org/
https://www.astro.louisville.edu/software/astroimagej/
http://deepskystacker.free.fr/english/index.htmlCheers
Ian.Hi Kevin,
Another couple of other free options are:
MuniPack – https://c-munipack.sourceforge.net/
MetroPSF – https://github.com/blackhaz/MetroPSFThe advantage of these is they can produce output files of the photometry ready for uploading to the BAA Photometry Database. If you ultimately wish to submit to the BAA database then that is a distinct advantage. You can also do this with AstroImageJ and AIP4Win, though you have to use these in combination with the BAA Photometry Spreadsheet and that requires an Excel license.
Cheers,
AndyI really like Aperture Photometry Tool by Russ Laher. Written by a professional photometrist at Palomar it works extremely well, is very flexible and is still being maintained. The author is very open to suggestions for improvement and has implemented a couple of mine. It already has elliptical apertures (useful for photometry of galaxies, etc, or on slightly trailed stars/asteroids) and Russ is considering adding capsule apertures for asteroidal trails. Recently APT has made a start on PSF photometry, which works rather better than aperture photometry in crowded fields.
APT is written in Java and runs on essentially all current operating systems. I can provide assistance and a few useful help-scripts if desired, one of which creates a spreadsheet output which is fully compatible with the BAA-VSS database. I use LibreOffice, so no Excel license required..
Available from https://www.aperturephotometry.org/ and check out the Wikipedia page as well.
ASTAP is my favourite, free and can also write files in AAVSO and BAA format.
https://sourceforge.net/projects/astap-program/Thanks to everyone who has taken the time to advise on this post.
The main criteria for me is simplicity as I really only need calibration initially.
I have never done coding or written scripts.
I think I can do everything else I want with AAVSO packages.
Quite happy to spend some money on this but probably not as much as Maxim DL.
Clear Skies
KevinA few first impression comments about the suggestions. Working my way through them.
ASTAP intiates a Windows Defender warning.
Calibration Intro Tutorial for Tycho Tracker seems to suggest it’s for moving targets.
I have installed AstroImageJ, found the DP button but there is no option to process flat darks.
So I have found various tutorials but I’m getting the impression they are for CCDs which do use bias frames I believe.Trying not to be too negative but I think I need something with very basic tutorials that walks you through it.
Kevin
I don’t do photometry Kevin but I have noticed a couple of videos that might be useful to you. The Q&A sections cover a lot.
https://www.youtube.com/watch?v=ufbFaUywEBg&list=PLnZ_rvnR35rfGTaq4g3kzVOfkna1JeDyX&index=2
https://www.youtube.com/watch?v=gcE7c4CggFM&list=PLnZ_rvnR35re3ZxnumCnIesanWvUyy9eB&index=24
A few first impression comments about the suggestions. Working my way through them.
ASTAP intiates a Windows Defender warning.
Calibration Intro Tutorial for Tycho Tracker seems to suggest it’s for moving targets.
I have installed AstroImageJ, found the DP button but there is no option to process flat darks.
So I have found various tutorials but I’m getting the impression they are for CCDs which do use bias frames I believe.Trying not to be too negative but I think I need something with very basic tutorials that walks you through it.
Kevin
Hi Kevin,
I run ASTAP on 3 different PC’s and I’ve never seen a Windows Defender warning. ASTAP does deal with flat-darks as far as I can see but, as I said, I use PixInsight to create my master calibration files.
Tycho Tracker handles both static and moving targets, but I’m not sure it deals with flat-darks – I might be wrong.
I think you’re right about AstroImageJ – why not experiment with Bias frames and see what you get?
Lastly, I’ve found this calibration tool which looks interesting:
https://astrohobby.ca/my-software/calights/
Cheers
Ian.I thought it was the case that when Windows Defender objected to something you could bypass it by choosing the other option (which isn’t highlighted and doesn’t say “bypass” 🙂 ).
Last version I used, Tycho handled flats and darks, but not flat-darks.
Could AIP4WIN make your flat and master dark?
I use AstroArt8 instead.
I would suggest the PPARC Starlink package CCDPACK (I’m biased) but thats under Linux and a lot of it command line.
I thought it was the case that when Windows Defender objected to something you could bypass it by choosing the other option (which isn’t highlighted and doesn’t say “bypass” 🙂 ).
Ah, I know the one you mean now – the one where you have to go into an option and choose “Run anyway”. Yes, that often happens.
Ian.Hello Kevin,
I’ve attached a screenshot – this builds master-flat for me in AstroImageJ using bias and flat-darks. When you process lights, change the file reference to relevant master-dark for lights and change “build” to “enable” for master-flat.
john sAttachments:
Hi Kevin,
I Use AstroImajeJ for calibration and photometry. Perhaps you might find this guide helpful :https://britastro.org/2018/a-guide-to-astroimagej-differential-photometry
I don’t use plate solved images for alignment/photometry, I prefer to use apertures (see the “Process” tab and “Align stack using WCS or apertures”). Also I haven’t found it to be good at stacking. It can do it but the stacked file has a FITS header lacking essential data ( eg time !) . This can be dealt with by copying a FITS header from another file. So if I know I’m going to need to stack, I would choose and odd number of images and pick the middle one then copy its FITS header to the stacked image. However the calibration is fairly straightforward I think. Hope this helps !
Update
I threw caution to the wind and ignored the Defender warning for Astap.After I have had literally a play with the following with a view to just being able to just calibrate.
AstroimageJ
TychoTracker
DeepSkyStacker
AIP4Windows
AstapASTAP seems at first to be the most user friendly for someone of my limited experience of image processing and has
a dedicated routine for flat darks which seems to be missing from the others.
I loaded some lights, flats, darks and flat darks and ran the program which seemed to work(Furthest I have got so far).
It output a pretty nice “looking” (but huge image 62Meg)
I would have liked to upload it for inspection but it’s way to big, so I have attached the text file that appeared in the window.
I assume this is the FITS header. Only concern is the opening line which states:SIMPLE = T / file does conform to FITS standard
Which I know is a bit of a deal breaker as they have to conform. So that’s where I am. Any thoughts please?I’m sure that the others may prove much more powerful and useful when I am a bit more advanced.
The problem for me is that the more advanced and versatile the software the more parameters there are to play with.
Thanks to everyone for useful input for future plans. I will almost certainly ask some more questions.
KevinSIMPLE = T / file does conform to FITS standard
Which I know is a bit of a deal breaker as they have to conform. So that’s where I am. Any thoughts please?Hi Kevin,
I don’t understand the problem. It all looks OK to me. Here, for comparison, is one of my FITs headers after it’s been calibrated. (Captured in SG Pro, calibrated by AA8).
Cheers
Ian.SIMPLE = T / file does conform to FITS standard
BITPIX = 16
NAXIS = 2
NAXIS1 = 2750
NAXIS2 = 2200
BZERO = 32768.0
BSCALE = 1.0
CRPIX1 = 1375.999999978
CRPIX2 = 1100.999999981
CTYPE1 = ‘RA—TAN’
CTYPE2 = ‘DEC–TAN’
OBJECT = ‘CF PEG ‘ / Object name
DATE-LOC= ‘2023-10-08T21:50:30.3930000’ / Local observation date
DATE-OBS= ‘2023-10-08T19:50:30.3930000’ / UTC observation date
IMAGETYP= ‘LIGHT ‘ / Type of frame
CREATOR = ‘Sequence Generator Pro v4.2.0.1158’ / Capture software
INSTRUME= ‘Starlight Xpress H694’ / Instrument name
ROWORDER= ‘BOTTOM-UP’
OBSERVER= ‘Ian Sharp’ / Observer name
SITENAME= ‘PixelSkies’ / Observatory name
SITEELEV= 850 / Elevation of the imaging site in meters
SITELAT = ’37 44 23.000′ / Latitude of the imaging site in degrees
SITELONG= ‘-0 38 38.000’ / Longitude of the imaging site in degrees
FOCUSER = ‘PegasusAstro ProdigyMF’ / Focuser name
FOCPOS = 5489 / Absolute focuser position
FOCTEMP = 19.48 / Focuser temperature
FWHEEL = ‘Starlight Xpress Filter Wheels’ / Filter Wheel name
FILTER = ‘L ‘ / Filter name
EXPOSURE= 60 / Exposure time in seconds
CCD-TEMP= -10.2 / Camera cooler temperature
SET-TEMP= -10 / Camera cooler target temperature
XBINNING= 1 / Camera X Bin
CCDXBIN = 1 / Camera X Bin
YBINNING= 1 / Camera Y Bin
CCDYBIN = 1 / Camera Y Bin
XPIXSZ = 4.5390625 / Pixel Width in microns (with binning)
YPIXSZ = 4.5390625 / Pixel Height in microns (with binning)
STRSZ1x1= 6 / SGPro minimum star size filter
READOUTM= ‘Standard Readout Mode’ / Camera readout mode
TELESCOP= ’10Micron Mount’ / Telescope name
RA = 325.297497442515 / Object Right Ascension in degrees
DEC = 26.2268339926879 / Object Declination in degrees
CRVAL1 = 325.2979715357
CRVAL2 = 26.20068031717
OBJCTRA = ’21 41 11.399′ / Object Right Ascension in hms
OBJCTDEC= ‘+26 13 36.602’ / Object Declination in degrees
PIERSIDE= ‘West ‘ / Side of Pier the objective is on
AIRMASS = 1.04170531837155 / Average airmass
OBJCTALT= 73.8212777777778 / Altitude of the object
CENTALT = 73.8212777777778 / Altitude of the object
FOCALLEN= 1956 / The focal length of the telescope in mm
FLIPPED = F / Is image flipped
ANGLE = 267.83 / Image angle
SCALE = 0.472905 / Image scale (arcsec / pixel)
PIXSCALE= 0.472905 / Image scale (arcsec / pixel)
AOCDEW = 10.3 / Dew Point in degrees C
AOCHUM = 75 / Humidity in %
AOCRAIN = 0 / Rain Rate in mm/hr
AOCSKYT = -28.5 / Sky Temperature in degrees C
AOCAMBT = 18.7 / Ambient Temperature in degrees C
AOCWIND = 12.5833333333333 / Wind Speed in m/s
EGAIN = 0.3 / Electrons Per ADU
STAR = ‘CF PEG’
PROCESS = ‘DK+FLAT’
CALSTAT = ‘BDF’
EQUINOX = 2000.0
CD1_1 = 4.981204779451E-006
CD1_2 = -0.0001310849482926
CD2_1 = -0.0001310385252376
CD2_2 = -4.948753747364E-006
CDELT1 = -0.0001311331670384
CDELT2 = 0.0001311783283646
CROTA1 = 0.0
CROTA2 = -87.83051432587
AVISUMIN= -33.0
AVISUMAX= 467.0
AVISUTYP= 0.0
ENDYour right Ian,
Thanks for your patience.I had been playing with various files and I felt sure that I had read one that stated that it did not conform.
Obviously not that one. That’s great. Have moved forward another small step.I think my worry was that maybe I had done something wrong.
I was expecting to have an output of master flats, master darks and master flat darks and then having to do something with them.
Subtraction I assumed.So the image it outputs, is that a calibrated image? Is it possible to tell?
What does the software do to the original uncalibrated lights?I have no feel for what’s going on under the bonnet.
ThanksKevin
I’m not familiar with ASTAP but the file appears to have a WCS and has a record of some lights darks and flats. The keyword CALSTAT is also suggestive ie DFBS – dark, flat, bias, stack?
When you display it does it look like the original frames but with less noise? If so I would assume its your stacked image. You could check that by using a different stacking method (SUM? ADD? Total?) and see if the sky count jumps up. Has any vignetting present diminished? Those would be big hints.
So the image it outputs, is that a calibrated image? Is it possible to tell?
What does the software do to the original uncalibrated lights?Hi Kevin,
ASTAP does nothing to your uncalibrated lights and it creates calibrated copies with “_cal” on the end of the file names.
If you look at the FITS headers of the calibrated files, you will see something as shown below towards the end of the header. In my test I only selected my master dark and master flat files and you can see resulting CALSTAT = ‘DF’. Also the COMMENT 1 field indicates it was calibrated by ASTAP.
What do you see in the CALSTAT field when you use your flat-darks?
Cheers
Ian.COMMENT 1 Calibrated by ASTAP. http://www.hnsky.org
PEDESTAL= 5.000000000000E+002 / Value added during calibration or stacking
CALSTAT = ‘DF’
DARK_CNT= 1 / Darks used for luminance.
FLAT_CNT= 1 / Flats used for luminance.Hi Kevin,
Further to this, as Grant has mentioned, compare your uncalibrated lights to your calibrated lights. See my attached image where I show three heavily stretched images. Top left is uncalibrated – note the gradients and the dust marks. Top right is calibrated – note it looks pretty flat. Bottom is the flat frame with a big stretch.
Not the most dramatic example because my C11 has a pretty flat field over this sensor to start with. But – I must try and get rid of that horrible splodge on the sensor!
Cheers
Ian.Attachments:
I believe the flat-darks calibrate the flats so you get master darks and calibrated-flats.
Platesolve your stacked image and you can do photometry on the stars and also any comets. If you do the Tools – Calibrate Photometry command it also creates MZero in the fits header (which I recently checked against Astrometrica’s version and it closely agrees).
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