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Stargazing Is it nebulosity or an artefact?

  1. Dec 18, 2017 #26

    Tom.G

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    Perhaps you could use an "Artificial Star", typically used for telescope collimation. It could also be adapted to get an idea of the camera sensor overload characteristics (blooming) by giving a spot source without the telescope. With a stable source and no atmospherics to get in the way, you could likely get a beam profile across the image using PS.

    Using a Google search for - telescope star simulator - turned up this site with some explanations and links: http://www.hubbleoptics.com/artificial-stars.html
     
  2. Dec 18, 2017 #27

    sophiecentaur

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    Hmm. Any reflection would involve the shape of the back end of the objective which is not flat and, moreover, it is expensively coated.
     
  3. Dec 18, 2017 #28

    sophiecentaur

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    It would need to be a pretty high powered little star, though as this effect only happens on a few stars. The other stars on my above images don't show it. The ones in the trapezium are such a jumble the the halo effect wouldn't be spotted, I think. I will soon be able to try and see if I get the effect on a Zwo bottom of the range guide camera I have ordered. Cmos may be different again.
     
  4. Dec 18, 2017 #29

    Tom.G

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    Think LASER pointer at whatever distance is appropriate, perhaps shining thru a pinhole in some aluminium foil.

    Cmos may be different again. Very noisy, low sensitivity.
     
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