Narrowband Color Shift in my Astrophotos

Revised Feb 5th, 2022 Recently I noticed that, in my narrowband astrophotos, the red color of the stars in my calibrated LIGHT frames seems shifted a few pixels. The blue pixels are also shifted but by a much smaller amount. I decided to invent a visualization tool for CaLIGHTs that makes it easy to study this color shift. In CaLIGHTs V3.1.6 I introduced a feature called SatGuard. This feature requires CaLIGHTs to be able to identify bright stars and determine what pixels need to be modified. I had already created…

QHY294C Cooler Performance

I log lots of information about my astrophotography system for every photo taken. I do this so I can go back at some later date and study what happened and learn what works and what doesn’t work. I have been using my QHY294C camera for 2 years now. In 2020 I used a cooler setpoint of 0 Celsius. I had no idea what to expect from the cooler and I certainly didn’t want to wreck it by driving it too hard. The QHYCCD folks talk about the possibility of a…

My LIGHT Table Solution

In 2021 I bought a LIGHT Table on Amazon which I believe works very well. It also caused me to develop a method for taking FLATs that is quick, accurate and easy. Background A key aspect of Astrophotography is taking quality FLATs. Vignetting caused by lens or telescopes is not simple. Even though your telescope, focuser, filters and camera all look like they are perfectly aligned…they typically are not. The center of your LIGHT frames is not always the location where the vignetting is at it’s minimum. This “sweet spot”…

Read Noise and Dark Current Using CaLIGHTs v3.1.6

I am going to build on my last post “Counting Electrons with CaLIGHT v3.1.6” where I demonstrated how you can evaluate your astrophotos at the electron level. Read Noise Here I have gone ahead and called up a BIAS frame for my QHY294C using a GAIN=1600. This is a 1/10000th second exposure. I am not using any master frames here…no masterDARK or masterBIAS. I am also not using the Noise Filter, Bad Pixel Filter or Row Noise Filter. I chose a very large area for calculating statistics because I am…

Counting Electrons with CaLIGHTs v3.1.6

Starting with CaLIGHTs V3.1.6 it is now possible to select a custom output pedestal value. This creates an interesting opportunity to study your astrophotos at the electron level. You can now determine how many electrons have been collected at any given location in your astrophoto. You can also evaluate how much the CaLIGHTs noise filter can dramatically improve your astrophotos. One piece of information you need to determine is the system gain of your camera. The system gain tells you how to convert the pixels values into electrons. This can…