Author Topic: first star photo  (Read 638 times)

barlaliblo

  • Active Astronomer
  • ***
  • Posts: 121
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: first star photo
« Reply #15 on: January 20, 2018, 11:40:17 PM »
Vignetting?

Jerome Fountain

  • Active Astronomer
  • ***
  • Posts: 112
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: first star photo
« Reply #16 on: January 23, 2018, 06:52:56 PM »
You can see it better here. I enlarged the extreme top left of another snap.Attached Thumbnails

Saul Zhang

  • Active Astronomer
  • ***
  • Posts: 114
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: first star photo
« Reply #17 on: February 03, 2018, 01:12:11 AM »
That, to me, looks like you are using a basic refractor. As it's a lens, it focuses light of different wavelengths at different focus points. Hence you see stars like that. Which is called as chromatic aberration.

therpomercu

  • Active Astronomer
  • ***
  • Posts: 113
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: first star photo
« Reply #18 on: February 03, 2018, 03:47:38 AM »
Quote
That, to me, looks like you are using a basic refractor. As it's a lens, it focuses light of different wavelengths at different focus points. Hence you see stars like that. Which is called as chromatic aberration.

Hi
Thanks. Yes, I agree with the chromatic false colour. It's the position of the same that I'm trying to get at. The enlargement is from the extreme top left of an image. You can see the chromatic aberration directing toward the centre. Away from the centre, all stars have the fale colour aiming at the centre. A star in the centre is perfectly round with the false colour evenly distributed around it.

Here is a crop from an overexposed Alnitak, slightly to the right and below centre of the rectangular camera crop. The camera cutts off a significant portion of the circular image produced by the main telescope. You can see it's almost circular.

Christopher Mendez

  • Active Astronomer
  • ***
  • Posts: 112
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: first star photo
« Reply #19 on: February 08, 2018, 11:23:17 PM »
Hi.

So you have a refractor. This looks like a combination of many different aberrations, and field curvature. Do you use a field flattener? Without one, only the center of the camera field of view will have pinpoint stars. Cheers!

--Christian

otisover

  • Active Astronomer
  • ***
  • Posts: 112
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: first star photo
« Reply #20 on: February 09, 2018, 09:03:41 AM »
Hi
Specifically, which is the aberration or combination of the same causing the colour to deviate toward the centre of the field?
Thanks