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

How Good Are ED-APO Telescopes for Imaging?

  • Please log in to reply
3 replies to this topic

#1 tom_fowler

tom_fowler

    Lift Off

  • *****
  • topic starter
  • Posts: 18
  • Joined: 31 Oct 2011

Posted 29 August 2020 - 12:23 PM

I decided to compare three telescopes to determine how they image two stars: Vega (type A0) and Albireo (types K3 and B9). Albireo turns out to be the difficult test because of the color contrast of its two components. The fainter component, Albireo B, is coincidentally a B-type star, which accounts for its readily observed blue color. The brighter star, Albireo A, is a K type star, with a yellowish-orange color typical of such cooler stars. Vega, as a type A star, is not as hot and not as blue as Albireo B. This turned out to be apparent in course of the tests that I did.

Click here to view the article
  • BruceNewEngland likes this

#2 MakoVette

MakoVette

    Lift Off

  • -----
  • Posts: 2
  • Joined: 14 Jul 2016

Posted 29 August 2020 - 09:26 PM

Remarkable and thoughtful work.  I greatly appreciate the time and effort you put into this project. I will be keeping this in mind as I consider ED vs. APO for my next scope purchase.



#3 drd715

drd715

    Viking 1

  • *****
  • Posts: 612
  • Joined: 07 Jan 2015
  • Loc: Fort Lauderdale

Posted 06 September 2020 - 08:33 PM

A most interesting comparison in actual results - especially since I have an APM152ED and a 102ed (F-11) .   It seems to show the effects of aperture also separately with the effects of refraction compared to reflection.  The little 102mm doesn't seem to have the resolution/tighterspot performance of the larger diameter objectives. Not really a concern for wider field imaging,  but obvious when pushing resolution to the seeing limits.   In pushing the limits of resolution both aperture and objective quality would seem to stand out.  A direct comparison between the 152 doublet ed and a 152 triplet would be interesting on these same objects. 



#4 BruceNewEngland

BruceNewEngland

    Explorer 1

  • *****
  • Posts: 51
  • Joined: 19 Jun 2020
  • Loc: New England, USA

Posted 16 September 2020 - 07:47 PM

Excellent work Tom, It’ll help inform my next purchase.

 

Thank you.

Bruce




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