NGC1931 - 20230128 - StarTravel 80 - Achromat Experiment with Ha (altazastro)

Celestial hemisphere: Northern · Constellation: Auriga (Aur) · Contains: NGC 1931

NGC1931 - 20230128 - StarTravel 80 - Achromat Experiment with Ha, altazastro

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NGC1931 - 20230128 - StarTravel 80 - Achromat Experiment with Ha

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NGC1931 - 20230128 - StarTravel 80 - Achromat Experiment with Ha

I wanted to see how much an achromat can come close to an apochromat when using a narrowband filter.
There was some mechanical issue with the rather coarse focuser lock, that probably caused a misalignment of the optical train: bright stars were not really round and had to be corrected in post-processing.
Moreover some spherical aberration in the cheap doublet cannot be ruled out.
I should possibly have settled for a lower exposure time: 30 seconds with 2.4 um pixels are probably too much for this setup and I had to keep just 140 frames out of 220.
Finally I would have thought that an 80 mm lens at F5 would have revealed more nebulosity in such an integration time:maybe the sky was not all that transparent, but perhaps it is also a matter of coating, transmission and diffused light in a cheap achromat double.

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NGC1931 - 20230128 - StarTravel 80 - Achromat Experiment with Ha

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NGC1931 - 20230128 - StarTravel 80 - Achromat Experiment with Ha

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