Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

5" APO verses BEST 7" MAK CASS

  • Please log in to reply
129 replies to this topic

#126 Richard Whalen

Richard Whalen

    Mercury-Atlas

  • *****
  • Posts: 2547
  • Joined: 24 Sep 2007
  • Loc: Florida

Posted 06 February 2019 - 12:33 PM

I compared my 8" f15.5 at WSP years ago with three 8" APOs. Early in the evening two of the three APOs gave better views, (I left my scope out in the sun all day uncovered for people taking photos) but after midnight when the seeing dropped well below .5 arc seconds and my scope cooled down only 1 of the APOs I would rate as very slightly better, perhaps very fine detail in Jupiters polar regions a tiny bit clearer. The other APO was a wash or perhaps a tad less sharp, the third was several steps down from my MCT and the other two APOs. We were all around 350x to 450x most of the time on Jupiter except the one APO, which struggled above 260x. Used up to 525x on Jupiter in the MCT with no hint of image breakdown or image getting to washed out or dim.

 

My MCT has no CA and less higher order abberations than any 8" APO that is F10 or faster. Also has a better figure than most. In excellent conditions 6" and 7" APOs dont come close from 20 years of comparrisions, hard to beat the resolution of a outstanding 8"  with a smaller scope with just very good optics. 

 

Where smaller APOs shine is when conditions are bad, wide field or imaging wide field is on the menu or you have temperatures dropping like a rock. If you live in an area that has generally poor conditions, get an APO. 

 

And remember, not all APOs or MCTs are created equally. There can be significant variation even from the top manufacterures within a single brand and product line. Nobody makes perfect every time, though the top guys try harder to be close more often.


  • Darren Drake, Eddgie, Paul Morow and 1 other like this

#127 Eddgie

Eddgie

    ISS

  • *****
  • Posts: 23529
  • Joined: 01 Feb 2006

Posted 06 February 2019 - 12:59 PM

I had a few Maks that were super on the planets. I still like a well made Newt the best for high power planet work and the best bang for the buck.

Yes, if planetary performance is the ultimate application of the telescope, 99.9% of CN members would not have enough money to buy an Apo that could beat a 10" f/6 with high quality mirrors.

 

What difference is the theory of the argument if you can't actually be realized in practical application?

 

My mass produced 12" Newtonian has given me the best planetary views I have had in 30 years of observing and I have owned 6" Astro-Physics and C14.   Now the mirrors on my sample came out of the box with a level of quality I was surprised to see, so I would not say the everyone would be fortunate enough to share this experience. 

 

I have owned 5" Apo and while it is very sharp and contrasty, at very high powers, the types you can use on nights of superb seeing, the view gets far too dim The colors loose saturation, and the image gets grainy due to the very small exit pupil.   People dismiss the role of luminance on the observer's ability to resolve low contrast detail and to me, that is unfortunate.   The larger aperture produces a much brighter image (for a given power) and stimulates more cones in the observer's eye, and this is the real key to seeing low contrast planetary detail.   You have to fire as many cones as possible. 


Edited by Eddgie, 06 February 2019 - 01:00 PM.

  • Darren Drake, De Lorme, Paul Morow and 1 other like this

#128 De Lorme

De Lorme

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1939
  • Joined: 30 Dec 2008

Posted 06 February 2019 - 01:47 PM

Eddgie,

 

That's exactly what I'm hoping the .82% more light from the 7" SW will fire more cones to get me over the thresh hold.

So far everybody's comments lean toward that way.



#129 salico

salico

    Viking 1

  • -----
  • Posts: 521
  • Joined: 12 Jul 2016
  • Loc: Germany

Posted 06 February 2019 - 02:53 PM

Eddgie,

 

thanks for that. Encourages me to go for the Mewlon210 over the ED 120 in soso seeing...



#130 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 14654
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 06 February 2019 - 05:22 PM

"The colors loose saturation, and the image gets grainy due to the very small exit pupil. People dismiss the role of luminance on the observer's ability to resolve low contrast detail..."

Right on. It's not always about the scope itself, it's also physiology of the observer and the physics of image surface brightness. The afocal telescopic image may be just fine, but our ability to see it at small exit pupils may not be.

Edited by Asbytec, 06 February 2019 - 05:25 PM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics