>The Great Orion nebula and the filters

  • Posted on: 11 November 2020
  • By: tihomiry

Some shots from Sofia. A very bright sky place. Zenith sky brightness info (2015): SQM 19.13 mag./arc sec2 Brightness 2.41 mcd/m2, Artif. bright. 2230 μcd/m2, Bortle class 6.

However I think that with the LED lights nowadays it is much worse as I can see only the 7 bright stars of Orion.
So I did another comparison of different filters to compare which one is best for my observations.

You can notice that the IR image gives the most stars, as most of the artificial LED lights do not emit IR. However IR is less then 20% of the QE of the sensor and we do not have much details here. The best details and colours we have with the UHC-S as it is narrow band for hydrogen and oxygen. The nebula is reach of those elements. The general light pollution filter (Omegon city lights filter) is also good but my one do not have AR coating and cast some glows. However it is my default choice when shooting at sky with any kind of pollution. It is more universal then UHC-S and I can use it for galaxies as well. Here is the place to check your sky : light pollution map

Orion nebula comparison

No fake :) My filters tested with my hand made spectrum analyser and looks good. The light pollution filter cuts all the yellow. UHC-s cuts IR but pass blue light.

Mars spectrum with filters

Satellites, cosmic trash or UFOs, the moving spots are everywhere on the sky. Typical satellite behavior is to reflect sun light. It should be yellow or white and could fade and shine due to its rotation.

If you have used DeepSky stacker to stack RAW files, maybe you have notice that the resulting image is poor of color saturation. This is because it has a higher number of bits then the display could show.

Last test from passed night put an end of the questions witch is better CCD or CMOS. My old CCD K-m fall back compared to CMOS K-5.

HDR stands from High Dynamic Range. In short it is the number of tones that compose the image. The larger it is, the best capability we have to see details in the bright and dark regions of a scene.

Witch is better. Stack or long exposure? It depends…

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