>10" aperture on double stars?
Posted 06 July 2013 - 12:37 AM
Is there such a thing as too much aperture for double star observing? I have a 16" scope and am curious.
Thanks for any experiences,
Posted 06 July 2013 - 03:06 AM
Posted 06 July 2013 - 04:31 AM
Posted 06 July 2013 - 08:14 AM
When you go to that great an aperture many if the colorful doubles that are swell in an 8" tend to get bleached out due to excessive brightness. Reds tend to look orange and oranges tend to look yellow and blue looks like cool white. What becomes of great importance than is choosing doubles that fit that aperture bracket. My 70mm seems to prefer magnitude 4 while my 8" is around 6- 7v . I'd guess you'd find the best color saturation around magnitude 10. Too, the diffraction pattern is clearer due to lack of irradiation. If I had a 16" aperture reflector Id draft up a new list of doubles entirely and bypass the 80mm refractor "gems" . You will likely have more to choose from as well since the list for fainter but appropriate doubles becomes so much longer. At the very least it would seem a variable polarizer or ND filter is in order if you want to observe mag 6 doubles in a 16".
Good luck. I am envious of the wide list of doubles that are available to you and the inevitable jewels that await discovery that probably most people are t aware of simply because they lack enough brightness and color in lesser apertures.
Posted 06 July 2013 - 09:50 AM
And that was also pretty much what I found years ago with a C14 I used a lot some years back. Around mag 8, rather than near 10, was where colour showed well - not too faint, not too bright. The light gathering difference between 14 and 16 inches is small; less than a half magnitude.
Of course, some folk have better colour vision and see fainter than many of us, so they might find stars a bit fainter still looking good for colour.
And whether or not the colours show at their best, bigger telescopes will show far more doubles as Pete has said, including showing well and easily doubles that are dim or invisible in smaller telescopes. And on the steadier nights, pairs too close for smaller scopes become possible as well.
Posted 06 July 2013 - 04:51 PM
Posted 06 July 2013 - 08:45 PM
Posted 06 July 2013 - 08:58 PM
Again thanks for the input!
Posted 08 July 2013 - 09:54 AM
Posted 08 July 2013 - 12:05 PM
If I want to, I can always stop the aperture down--the attached photo shows a 6 inch off axis mask I made for my 15 inch scope--its ugly, but it works!
As Pete alluded to earlier, the smaller apertures can offer more pleasing views of colorful doubles--I saw this first hand the other night with the 6 inch mask in place--Izar, Cor Caroli, Rasalgethi and many others came alive! I can see why folks love their refractors.
Interestingly, on this same night of quite poor seeing, Antares B showed better as a disk separated from the primary when using the 6 inch off-axis mask versus unmasked to the full 15 inches. So, there exists practical utility with its use as well.
Posted 08 July 2013 - 05:59 PM
Posted 10 July 2013 - 07:37 PM