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

Brain fart...what’s the configuration called? Newtonian where the light goes through a hole in the primary?

  • Please log in to reply
26 replies to this topic

#26 KLWalsh

KLWalsh

    Viking 1

  • -----
  • Posts: 531
  • Joined: 19 Feb 2014
  • Loc: North Georgia, USA

Posted 07 May 2019 - 02:32 AM

OK - is this what you were thinking? wsDK - weak secondary Dall Kirkham telescope

If you fold a Newt back through the primary with a flat you are automatically folding over half the focal length, which in turn means that you need a flat that is OVER 50% of the diameter of the primary. You can do that, but it is not pretty!

The wsDK is the better version. It compromises a weakly curved secondary to get a 34%, plus or minus, secondary size and utilizes a tertiary to give you the eyepiece height that allows viewing without a ladder. (And no hole required in the primary)


Yes; in my post above I gave a link to an article about the US Naval Observatory astrometric reflector. The 60 inch f/10 design required a secondary flat with a diameter of 35 inches.

#27 siriusandthepup

siriusandthepup

    Apollo

  • *****
  • Posts: 1049
  • Joined: 14 Feb 2006
  • Loc: Central Texas, USA

Posted 07 May 2019 - 03:48 AM

 

Yes; in my post above I gave a link to an article about the US Naval Observatory astrometric reflector. The 60 inch f/10 design required a secondary flat with a diameter of 35 inches.

Wow - I didn't know that such a beast existed!




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