15th Feb 2024: Astro Pixel Processor 2.0.0-beta29 released - macOS native File Chooser, macOS CMD-Q fixed, read-only Fits on network fixed and other bug fixes
7th December 2023: added payment option Alipay to purchase Astro Pixel Processor from China, Hong Kong, Macau, Taiwan, Korea, Japan and other countries where Alipay is used.
Hi Mabula,
I've invested the better part of the last 2 days writing a web app to help me select frames I captured for a mosaic of M31.
The app ensures that white balance is maintained across RGB according to predetermined ratios I measured for my camera and filters: 1.62 : 1.00 : 1.34. (Those ratios are user inputs to the app.) The app also asks for the desired total integration time of luminance and of color.
The app uses an open source JavaScript library (fitsjs) to read the FITS file headers of files you select on your computer. It calculates Altitude, Airmass, and Extinction given the RA and DEC of the object, UT of capture time, observer's Latitude and Longitude, and the Filter used. Then it sorts all files by Extinction so that the files having the highest signal-to-noise ratio are chosen first.
With a few clicks I selected all LRGB files I've captured so far for "Panel F" of my M31 mosaic. Finally, I export the results.
Here is an example when I ask for 30 minutes of L and 90 minutes of R+G+B while maintaining white balance:
filter,file,include
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-17-28_001.fits,
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-19-00_002.fits,
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-20-32_003.fits,
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-22-03_004.fits,
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-23-35_005.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-25-07_006.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-26-39_007.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-28-11_008.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-29-42_009.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-31-14_010.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-32-46_011.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-34-18_012.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-35-49_013.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-37-21_014.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-38-53_015.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-40-25_016.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-41-57_017.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-43-29_018.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-45-01_019.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-46-33_020.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-48-05_021.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-49-37_022.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-51-09_023.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-52-40_024.fits,x
opB,M31-Panel-F_Light_opB_90.500_secs_2019-08-26T01-54-12_025.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-44-21_001.fits,
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-45-30_002.fits,
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-46-39_003.fits,
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-47-47_004.fits,
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-48-56_005.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-50-05_006.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-51-14_007.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-52-23_008.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-53-32_009.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-54-40_010.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-55-50_011.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-56-58_012.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-58-07_013.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T00-59-16_014.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-00-25_015.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-01-33_016.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-02-42_017.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-03-51_018.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-05-00_019.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-06-08_020.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-07-17_021.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-08-26_022.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-09-35_023.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-10-43_024.fits,x
opG,M31-Panel-F_Light_opG_67.500_secs_2019-08-26T01-11-52_025.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-38-57_001.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-40-30_002.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-42-03_003.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-43-36_004.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-45-08_005.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-46-41_006.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-48-14_007.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-51-19_009.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-52-52_010.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-54-25_011.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-55-57_012.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-57-30_013.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T02-59-03_014.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T03-43-24_018.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T03-44-57_019.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T03-46-30_020.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T03-48-03_021.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T03-55-47_026.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T03-57-20_027.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T03-58-53_028.fits,x
opL,M31-Panel-F_Light_opL_90_secs_2019-08-05T04-00-25_029.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-25T23-52-04_001.fits,
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-25T23-53-57_002.fits,
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-25T23-55-47_003.fits,
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-25T23-57-38_004.fits,
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-25T23-59-29_005.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-01-19_006.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-03-10_007.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-05-01_008.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-06-51_009.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-08-43_010.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-10-34_011.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-12-24_012.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-14-15_013.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-16-06_014.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-17-57_015.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-19-48_016.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-21-39_017.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-23-29_018.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-25-20_019.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-27-11_020.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-29-02_021.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-30-53_022.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-32-43_023.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-34-34_024.fits,x
opR,M31-Panel-F_Light_opR_109.400_secs_2019-08-26T00-36-25_025.fits,x
It is easy to import this into a spreadsheet.
When processing I launch APP 1.074. At this point I have two options:
1) Add only the files marked with the "x" shown above, or
2) Add all files but then uncheck the ones without the "x"
My question is: Will APP 1.075 offer something akin to Deep Sky Stacker's "File Lists"?
Thanks for a great product!
That looks really impressive! Is it indeed needed I'd like to know? As in, do you see differences in the end result for APP when doing it this way?
Hi Vincent,
It's been a long slog becoming proficient using a mono camera for color imaging. My first attempt is documented here:
https://astrotuna.com/ngc-6791/
As you can see the blue stars are horribly bloated. Take a look at the details, I exposed R, G, B the same: 80x50s. That was the problem. I learned later that the key to getting a balanced image is to adjust exposure and/or frame count to compensate for the shape of the sensor's QE curve. The 290M mono camera is most sensitive to red and least sensitive to blue (by a large factor!) By using the same integration time across all channels, blue was guaranteed to have a much lower signal-to-noise ratio than the red channel. That's why blue stars are so bloated in that image.
The breakthrough for me came from reading this article by Al Kelly:
http://kellysky.net/White%20Balancing%20RGB%20Filters.pdf
Thankfully, I took a course at AAVSO on CCD Photometry so a lot of the terminology was familiar to me.
Recently I took what I learned and wrote up instructions for performing it using AstroImageJ:
https://u235.herokuapp.com/color-balance-calculator-instructions.html
The last couple days I added a new "calculator" called the "LRGB Stack Balancer" to take an existing set of LRGB frames and rebalance them differently from how they were originally captured.
https://u235.herokuapp.com/lrgb-stack-balancer.html
The topic of the post you are reading has to do with experiments with my "LRGB Stack Balancer". Specifically I wanted to know how much color integration time (i.e. R+G+B) I needed in order to accurately show color in a final LRGB image. It turns out "very little". I was getting acceptable results with as little as 30 minutes total of RGB (white balanced, of course.)
Regarding cameras and white balancing, I see that very high-end cameras ($5,000+) have sensors with desirable QE characteristics where the response is relatively constant from 400nm to 700nm. For those cameras, white balancing is not as critical. I, on the other hand, am cheap. I haven't spent more than $400 on a camera. My latest is a 10 year old Atik 314E. Works great but it's not very sensitive to red, so I need to compensate.
Finally, I welcome everyone to play with my calculators, however, the latest one "LRGB Stack Balancer" relies on well-structured FITS files containing accurate information. I've tested it with Ekos and it works great but I can't guarantee other capture software will work with it. There is no documentation as of yet. Please feel free to play with it but keep an eye on the "Altitude" field. If it shows some nonsensical value then there is missing or inaccurate data in the FITS header. I need to work all this out with adequate validation checks and warnings. Something for me to work on.
