>How to do Asteroid screening

  • Posted on: 25 June 2019
  • By: tihomiry

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:

NGC 7000, South America nebula in Cygnus, taken by me from NAO Rozhen. 2 shots composed by 45 frames @ 30s, ISO 51200 with SW 200pds and Pentax k-5. Same processing with DeepSky Stacker and LightRoom.

To check the polar alignment of your telescope look trough the polar scope. When turning the Ra axis the polar star should move in the exact circle in the eyepiece without any deviation.

Removing the DSLR build in IR-cut filter will give you at least 50% more sensitivity for hydrogen alpha emissions of the nebulas. Also the camera will be more light sensitive at dark allowing you to shoot more faint objects.

We can check what is like to process day shot with similar to astrophotography techniques. It is cloudy in Bulgaria for the next week or so and I took shots of the nearby mountain trough the fog with 200mm lens.

Most of the modern LED backlight screens including Laptops, TV and smart phones use PAM technique for Pulse-amplitude modulation. This means that they switch on and off state very rapidly.

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