>How to do Asteroid screening
While cleaning up my PC I found sequences of shots of Virgo galaxy cluster taken during springs of the last 2 years. Those were attempts to shot this object, but I was not satisfied with the result and left them. Having shots with the same equipment from long period of time are valuable as you can check for any changes in the filed that might lead to a discovery. So I do. I got all of them and stack. Since recently I am using algorithm in DeepSkyStacker that do not clear the movements on the shots. It is Entropy Weighed Averege.
After did the stack of about 112 frames of 30s, I saw something that is very similar to the behavior of asteroid. It was present only on the shots from 9th of April 2018. Using Stelarium, I estimated the coordinates of the object and the approximate brittleness of 16 by compare it to the nearby stars. I asked for help in order to recognise the object in the Bulgarian astro forum forum.starrydreams.com, as I am not an expert in asteroid tracking and the shots were taken more then year ago. They show me the Minor Planet Checker site and the asteroid was mached to (1558) Jarnefelt with is 65 km of diameter. It is typical to observer asteroids beyond Mars orbit near the ecliptic. Here is one example at Astrobin. By cpmparing the stacked result with a single shot, what also amaze is how much data you can retrieve from the noisy background of the 14bit RAW file. Each faint spot is a galaxy that is only visible in the stacked image and only few fotons have been recorded at a single frame. The setup is as usual: Pentax k5, 112x30s, ISO 12800, SkyWatcher 200pds.
So here are the shots:
1. Single frame crop:
2. Stack 112x30s crop. The trace is not a solid line as the stack algoritm have excluded some bad frames.
3. Final image:
I am so impressed with the K5 ability to quickly gather signal from nebulas (Quantum efficiency) and galaxies, so I decide to take one more K5 and to remove the IR-cut Filter of the old one.
Recently I got one very good lens the Asahi Takumar 135mm 1:2.5. This is fast telephoto lens and from my point of view a good lens should be with aperture from 1:1,2 to 1:2,8.
Moon at 45% illumination and 70x magnification. With aperture of 200mm,14,1 stops dynamic range, color depth of 23.7 bits at this image there are slight color variation on the moon surface that reveals it’s structure.
This is the beginning of my research on how dark the sky could be and what is benefit of a dark sky for astrophotography. I was inspired from those 2 sites. First one presents mathematical model of how dark the sky is.
You can find my last DSLR Astrophotography article in Bulgarian at page 76. I am sharing my last findings for this publication, Specially written for the Institute of Astronomy.