CaLIGHTs Version released

I decided to stay with a 32b application for this version of CaLIGHTs. Microsoft had discontinued support for Windows 7 a while ago but I just learned that Microsoft has made changes to Windows 11 that prevents programming environments from building applications that can be supported not only for Windows 7 but for all 32 bit operating systems. The error messages I have seen indicate that the minimum requirement is now Windows 10. I didn’t want to leave Windows 7 users or 32b operating system users out in the cold so I had to go back to an old laptop computer to build this version. It will run just fine on modern 64b operating systems. My plan is to switch to Microsoft’s new scheme for the next major revision of CaLIGHTs. Let me know if you have problems using this version…I can make bug fixes to this version using my old laptop so that Windows 7 will be able to run CaLIGHTs v3.1.8.x.

Click here to download CaLIGHTs


How CaLIGHTs works with masterDARKs and masterFLATs  I have been doing some very careful analysis of how CaLIGHTs calibrates your LIGHT frames and I decided to make two changes which should improve your results. When you use the Preference button to change the Pedestal Priority to Master DARK, CaLIGHTs was using the mean values of the masterDARK to determine this pedestal. Amp Glow can be a significant issue with masterDARKs which can increase the calculated mean values of the masterDARK. All of the benefits of using a masterDARK were being achieved but the calibrated LIGHT frame could end up being slightly darker. I decided to change the Pedestal calculation so that, for masterDARKs, the pedestal values are determined by using only the pixel values in the center of the masterDARK. This avoids any influence of Amp Glow and also eliminates the slight darkening I was detecting.

The vignetting effects that are corrected by using a masterFLAT can be dramatic. Pixel values at the edges of your LIGHT frames can need to be increased by 30% or more to compensate for vignetting. Up to this point I had decided to “split-the-difference” and distribute the masterFLAT compensation over the entire image. The 30% or more increase was re-distributed such that the center of the image was darkened and the edges were brightened so that the 30% or more vignetting compensation would still be applied. I decided that I wanted the brightness of the center pixels to not be affected by FLAT compensation. The FLAT compensation now only brightens the outer pixels of your LIGHT frames and preserves the brightness of the center pixels. This means that bright stars located at the edges of your LIGHT frame can be saturated solely because of FLAT compensation. I would encourage everyone to use the StarSatGuard feature which understands this issue and will limit the brightness of these affected stars so that they are not saturated and their color can be preserved.

Don’t allow Negative values  During the calibration process, specifically masterDARK subtraction, there is a grey area where some pixels in the masterDARK are slightly HOT but are not HOT enough to be detected statistically.  When you throw in random noise from shot noise and camera noise and combine this will LIGHT frames taken at a dark site you can get a situation where a pixel’s calibrated value can be smaller than the camera’s BlackADU value. The BlackADU value is defined as the value equal to complete darkness…so values less than BlackADU don’t make any practical sense.  These very dark pixels look like black specs that are very pronounced in the darkest portions of your LIGHT frame.

I have added a Don’t allow Negative values option to mark these very dark pixels as bad pixels so that their pixel values are substituted using the values of their nearest neighbours. This new option can be enabled via the Preferences button on the main screen.

Image Viewer  You can now use the F9 function key to save a screen capture of the image to your computer. This may be useful to document issues you experience with your astrophotos. The title is not included in the screen capture but the statistics (right-clicking on the image displays stats where you clicked) are included.

Image Viewer Statistics  When you are using the Image Viewer you still can right-click anywhere on the displayed image and some statistics will appear. I have modified the statistics to make them more useful. Here is what the statistics look like now…

N=1024  dX x dY = 32 x 32

Range(X,Y)=(1700,1306) to (1732,1338)

 RED       SNR=0.21  SD=  18

 Min=  32 Avg=  76 Max= 128

 GREEN  SNR=0.47  SD=21.2132

 Min=  60 Avg= 108 Max= 208

 BLUE     SNR=0.21  SD=  18

 Min=  36 Avg=  84 Max= 212

The values displayed for “SD=” are still standard deviation values but they are calculated using what I call a graphical method. This is the same graphical method I use for the StdDevg statistics displayed on the Make Averaged Master Histogram. The graphical method is more immune to hot or cold pixel values which, I believe, improves the usefulness of the SD values. Hot and Cold pixel values still influence the Min and Max values.

Image Preview I split the Shift HFD Rnd Angle feature into two features. There is now a Show Color Shift feature which generates the Shift image. I also created a Show Star Statistics feature which performs the HFD, Rnd and Angle analysis.  I also made the Show Star Statistics feature the default when you first call up the Image Preview.

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