Observing colour through telescopes

  • I
  • Thread starter PEGELLA
  • Start date
  • #1
10
2

Main Question or Discussion Point

Excluding planets and given normal dark skies, what minimum aperture size of a (non-refractor) telescope is required to just start getting hints of colour in deep sky objects like nebulae and galaxies? I mean in real time, unaided eye, no photography.
 

Answers and Replies

  • #2
Drakkith
Staff Emeritus
Science Advisor
20,854
4,599
My practical experience with my own telescopes tells me that anything 10 inches (254 mm) and below yields virtually no color for deep sky objects. My largest is a 10 inch Newtonian and I can't remember seeing any color in any DSO's except perhaps M42.
 
  • Like
Likes sophiecentaur, russ_watters and davenn
  • #3
davenn
Science Advisor
Gold Member
2019 Award
9,228
7,482
^^What Drakkith said ^^
 
  • Like
Likes russ_watters
  • #4
238
99
I have used 38 to 60 cm telescopes under good skies and only planetary nebula with high surface brightness will show a color and it is always turquoise since the eye is the most sensitive there. Maybe a hint of turquoise in the center of the Orion nebula.
 
  • Like
Likes sophiecentaur and Drakkith
  • #5
10
2
Thanks for the comments. Any idea of how long an exposure time would be required to record colour from some of the larger, brighter DSO like M42? Using a 12 inch - 16 inch scope and a simple DSLR camera hook up?
 
  • #6
Drakkith
Staff Emeritus
Science Advisor
20,854
4,599
Thanks for the comments. Any idea of how long an exposure time would be required to record colour from some of the larger, brighter DSO like M42? Using a 12 inch - 16 inch scope and a simple DSLR camera hook up?
Not long at all. Perhaps as little as a few seconds depending on the camera's sensitivity, the surface brightness of the target object, and the f-ratio of the telescope (perceived surface brightness is determined by the f-ratio, not the diameter of the scope). But you probably don't want to use a 12-16 inch telescope for astrophotography if you're just starting out. The focal lengths of these telescopes is so large that it's difficult to record exposures thanks to the high zoom. Any little error in the tracking of the mount, the alignment of the scope, or other issues like wind is magnified by high zoom levels. It is MUCH easier to use a small, short focal length telescope starting out.

Also, once you get into imaging, you can do stacking and processing, which means that even short exposures can be added together to get the equivalent of a long exposure.
 
  • Like
Likes russ_watters
  • #7
sophiecentaur
Science Advisor
Gold Member
24,606
4,517
I mean in real time, unaided eye, no photography.
Using a 12 inch - 16 inch scope and a simple DSLR camera hook up?
You have moved the goalposts a bit here. We are discussing two vastly different issues now.
given normal dark skies,
And what do you mean by that? Normal skies are only dark skies for some very lucky people.
If you want to do visual astronomy you will probably need to transport your kit to a suitable site. That could mean you would see things for which you would need a camera to use from your back garden.
I bought a 200mm Dobsonian Skywatcher (second hand for less than £200) which was good enough to see some definite colours (of course the Orion nebula but some others and some delightful contrasting colours of adjacent stars). Some pretty stunning views from my home (no street lights) I used a friend's 150mm Newtonian but that was noticeably worse for visual). The eyepieces supplied with most cheap kits are pretty disappointing and do not do justice to a fair quality parabolic reflector. I spent a fair bit on some 2inch eyepieces and I have never regretted that as I still have them and use them with my 120mm refractor. The stars look tiny which, to my mind, means that the resolution and flare are good.
If you start to go into AstroPhotography you will end up spending a lot of money, take a long time setting up all your kit each time and every free hour tinkering with the hundreds of images that you take. (Just letting you know - it's a brilliant hobby but very demanding.)
 
  • Like
Likes collinsmark
  • #8
Drakkith
Staff Emeritus
Science Advisor
20,854
4,599
If you start to go into AstroPhotography you will end up spending a lot of money, take a long time setting up all your kit each time and every free hour tinkering with the hundreds of images that you take. (Just letting you know - it's a brilliant hobby but very demanding.)
This, a thousand times!
 
  • Like
Likes collinsmark
  • #9
chemisttree
Science Advisor
Homework Helper
Gold Member
3,399
427
I see color in my 1974 60mm Montgomery Ward f11 scope with the 0.965” Huygenian eyepieces. Albireo is beautiful!
 
  • #10
DaveC426913
Gold Member
18,776
2,256
While not a star, I was able to pick out the colour gradients of Mars in my scope well enough to illustrate it.

I drew them by hand, then (afterwards!) checked on NASA's site for what Mars looked like at the times of my observtions.

Rather pleased I was:


pic_marssketch.jpg


(If I'd partially masked the aperture to bring down the light level, I might have picked up even more detail. Maybe next time.)
 
  • Like
Likes sophiecentaur
  • #11
sophiecentaur
Science Advisor
Gold Member
24,606
4,517
Seeing colour through a telescope mis depend a lot on the individual's vision. As you get older it gets worse and worse and worse. Damned young whippersnappers can see and hear stuff that just totally passes me by.
 
  • #12
chemisttree
Science Advisor
Homework Helper
Gold Member
3,399
427
Of course the original question was about DSOs like galaxies and nebulas.
 

Related Threads on Observing colour through telescopes

Replies
1
Views
2K
  • Last Post
Replies
2
Views
3K
Replies
10
Views
7K
Replies
4
Views
4K
Replies
1
Views
714
Replies
2
Views
952
Replies
17
Views
4K
Replies
18
Views
2K
Top