7 replies to this topic

[ICit2]

I asked that question a number of times and decided to see for myself.  You can see for yourself here:

 

https://www.youtube....h?v=66-dfu2q1O8

 

Hope you find it useful. 

 

Richard

Dakota Starry Nights

[jayrome]

I'm thinking of doing a major aperture upgrade in a few years, when I turn 50 lol

 

For retirement, I envision a cabin by a lake  with a 32" out back in a dome observatory  

[AD14EM2]

Fun video...thanks!

[rachnoman]

I happily used a 12" for many years. But when my buddies started showing up with two 16" and a 20", it was all over for me and my little 12" !.

[Mazerski]

If you look at the numbers...

 

12” = 1896x the amount of light over naked eye // mirror area = 113 sq in

 

16” = 3370x the amount of light over naked eye // mirror area = 201 sq in

 

Verify the numbers.

 

I use night vision - Mod 3 and PVS7 and this has forever changed Astronomy. 

[ICit2]

If you look at the numbers...

 

12” = 1896x the amount of light over naked eye // mirror area = 113 sq in

 

16” = 3370x the amount of light over naked eye // mirror area = 201 sq in

 

Verify the numbers.

 

I use night vision - Mod 3 and PVS7 and this has forever changed Astronomy. 

Agreed.  Night vision has completely changed astronomy for me; to the point I no longer image. 

 

On paper a lot of things differ from real world experience.  While the numbers show a 1400+ additional increase in light gathering for a 16", I did not detect a 1400+ improvement over the 12"  Better, yes.  Just not as good as the numbers would have you believe.  The real advantage I found is the image scale increased along with delectable detail without the loss of brightness. The extra aperture enabled the longer focal length of the 16", which increased the image scale, to maintain the brightness.  If you were to increase the power on the 12" to get the same image scale the image would get much dimer.  But using the same eyepiece, as in the video, they appear somewhat similar in brightness. 

[Mazerski]

I agree on the numbers - if only things were that simple.

 

I sold a 15” and Ryan (NewMoon) is building me a 12.5” mostly due to moving scope in / out of house. 

I don’t know how much night vision adds (meaning magnitudes) but with an 8” f2.8 (or f/4) I can’t believe how much I can see compared to the 15” with glass eyepiece. Actually there is no comparison. 

Example: 15” with h-Beta filter at Star Alnitak— all I could see is bright star and black sky. With night vision (hand held with Nikon lens for 7x) I can see rage dust, dark notch and the Flame Nebula at Alnitak.

 

The drop from 15 to 12.5 will be worth it due to ease of moving the smaller scope.

[Jon Isaacs]

But using the same eyepiece, as in the video, they appear somewhat similar in brightness.

 

 

Assuming the scope's are the same focal ratio, nebulae and galaxies and the background sky will be identical in brightness if the same eyepiece/ exit pupil is used. Stars will be 78% brighter.

 

I've had my 12.5 inch for close to 20 years, my 16 inch for 12 years. I find the difference worthwhile, more than the numbers would suggest. Such judgments are subjective, it's a balance.. The 16 inch is more effort to set up but there's little difference in the effort required to actually observe to that tilts the decision towards the larger scope.  With the 22 inch and my previous 25 inch, the physical effort required during the actual observing process is substantially more,  a 16 inch is an "easy scope", the larger scopes are not.

 

They say a picture is worth a 1000 words. Here's a photo left to right, 25 inch F/5, 22 inch F/4.4, 16 inch F4.4, 12.5 inch F4.06.  

 

 

I will add this tidbit:  Ones biggest scope seems like a big hassle, the second biggest seems easy.. when my 12.5 inch was my biggest scope, it seemed like work. When the 16 inch arrived, the 12.5 inch seemed easy and the 16 inch was work.  When the 25 inch came on the scene, the 16 inch seemed easy.

 

Jon