• Posted on: 14 February 2019
  • By: tihomiry

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. Orange is for very polluted sky, for yellow – you do not see the milky way, for green – sky is polluted of some degree up to the zenith, for blue – there is a shining at the horizon and grey is for a dark sky. The second map is for how much light each village emit. You can switch between the years.

1. http://darksitefinder.com/maps/world.html

2. http://www.lightpollutionmap.info/#zoom=8&lat=5183204&lon=2785360&layers=B0TFFFF

I went to Kara Tepe at the heart of the Rhodope mountains 1600m above the sea level. It is in the grey area and the sky was outstanding. You can get great shots with ease. Full if stars and details.
I will continue my research and use such locations to shoot faint objects. Here are some new photos of Lagoon nebula (40x30s ISO 25600) and M22 cluster (1x30s ISO 25600):

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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