Jump to content


Photo

Double Star Colours and Aperture

  • Please log in to reply
4 replies to this topic

#1 Cepheus Elf

Cepheus Elf

    Explorer 1

  • -----
  • Posts: 94
  • Joined: 01 Aug 2010
  • Loc: Rainy, Cloudy Lancashire UK

Posted 28 December 2012 - 10:33 AM

Hi Folks,

I have read a couple of independent authors who advise that large aperture scopes can be detrimental when observing colourful doubles as their light gathering power can bleach out the stars' colors and they recommend 4-6" scopes as the optimim aperture for observing bright colourful doubles.
My own observations over the last three years with scopes ranging from 3" to 12" do not agree with this view and I have to say that in every case (wide and close, bright and faint pairs), the colours of the doubles I observed were much more intense in the bigger aperture scopes - even the very bright pairs like Albireo. Just wondering if anyone else found aperture to be a an advantage when observing colourful doubles :question:

All the bset and clear skies,
Mick

#2 Darren Drake

Darren Drake

    Mercury-Atlas

  • *****
  • Posts: 2782
  • Joined: 09 Oct 2002
  • Loc: Chicagoland

Posted 28 December 2012 - 11:08 AM

More aperture is definitely better for seeing colors. Sometimes it helps to defocus the image a little to spread out the colors instead of just seeing them concentrated into a point source.

#3 azure1961p

azure1961p

    Voyager 1

  • *****
  • Posts: 10363
  • Joined: 17 Jan 2009
  • Loc: USA

Posted 28 December 2012 - 07:09 PM

I know what they are trying to say and unfortunately they didn't really say it. Yes when a star like Vega or Betelgeuse is seen thru a 20" scope it's terrifically bright but the orange leans more toward yellow as the reds are bleached out a bit. Now here's what they didn't finish saying: a larger scope sees MORE stars and puts color in stars a 6" might reveal as simply grey. So you see more color with more choices to pick from while the 4" list is comparatively short to the 20" for example. When you have that much light gathering power you aren't restricted to naked eye magnitudes and the multitude of stars now showing color is in another realm.

Pete

#4 Cepheus Elf

Cepheus Elf

    Explorer 1

  • -----
  • Posts: 94
  • Joined: 01 Aug 2010
  • Loc: Rainy, Cloudy Lancashire UK

Posted 30 December 2012 - 03:48 PM

Thanks for your thoughts on this Darren and Pete.

Mick

#5 Rich (RLTYS)

Rich (RLTYS)

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 5171
  • Joined: 18 Dec 2004
  • Loc: New York (Long Island)

Posted 01 January 2013 - 10:11 AM

I have observed a number of colorful doubles with my 10" refl. I then tried a 4" apature stop and could see no real difference in color. Admitedly my eyesight is not the best but this was my personal experience.

Rich (RLTYS)






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics