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

Moon through f/90 refractor

Moon Refractor
  • Please log in to reply
9 replies to this topic

#1 RyanC

RyanC

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 05 Jun 2021

Posted 13 January 2022 - 06:31 PM

Yes...the title is correct. F/90 telescope!

Last year I decided to have some fun and build a singlet refractor. The aperture is a mighty 27 mm with a focal ratio of 2500 mm. Singlet refractors have only a single lens (plano-convex, convex faces sky). This is nearly the optimal lens, but even still it has horrible aberrations. Hence the f/90 focal length. And it does successfully tame the chromatic aberration, mostly smile.gif

 

Here's my telescope "splinter" in all her glory.

 

singlet_refractor_reduced.jpg

 

 

I used my ZWO 1600mm over my 290mm for the larger sensor. But I still had to do a mosaic because of the immense focal length.

Binning 4x used and no filter.

 

Definitely happy with how it came out considering the rayleigh limit is around 4-5 arcseconds.

 

Ryan

 

moon_mosaic_crop_final.jpg


  • davidmcgo, John Miele, siriusandthepup and 18 others like this

#2 vtornado

vtornado

    Fly Me to the Moon

  • *****
  • Posts: 5,284
  • Joined: 22 Jan 2016
  • Loc: NE Illinois

Posted 13 January 2022 - 06:35 PM

Did you process out the CA?  

If not that is really good.  A camera is very sensitive to unfocused blue light.


  • Leia likes this

#3 RyanC

RyanC

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 05 Jun 2021

Posted 13 January 2022 - 06:41 PM

Did you process out the CA?  

If not that is really good.  A camera is very sensitive to unfocused blue light.

No I did not. There really isn't much chromatic aberration to begin with. Through an eyepiece the moon is sharp and pretty much free of color. Chromatic aberration probably reduces the sharpness a bit, so next time maybe I'll use a green filter or something. I didn't think to use it last night.


  • vtornado likes this

#4 Sleep Deprived

Sleep Deprived

    Apollo

  • *****
  • Posts: 1,204
  • Joined: 17 Apr 2019
  • Loc: Seattle Area

Posted 13 January 2022 - 07:04 PM

This is amazing!  Taking this idea to the n-th degree (which you did with this f90) is really interesting, yet none of us (???) have done it!  I can see the advantage of this approach.  Where did you get such a lens??  Is the lens home-made, too??



#5 RyanC

RyanC

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 05 Jun 2021

Posted 13 January 2022 - 07:12 PM

This is amazing!  Taking this idea to the n-th degree (which you did with this f90) is really interesting, yet none of us (???) have done it!  I can see the advantage of this approach.  Where did you get such a lens??  Is the lens home-made, too??

I got the lens from OptoSigma. I am not good enough to make my own optics :)



#6 JohnBear

JohnBear

    Surveyor 1

  • *****
  • Posts: 1,782
  • Joined: 08 Jul 2017
  • Loc: Sandy, Utah

Posted 13 January 2022 - 07:12 PM

I just love cute little table top Dobs!


  • vtornado likes this

#7 Look at the sky 101

Look at the sky 101

    Vanguard

  • -----
  • Posts: 2,389
  • Joined: 02 Nov 2021
  • Loc: Citizen of the earth .

Posted 13 January 2022 - 07:14 PM

Fantastic image,  love the scope. 



#8 highfnum

highfnum

    Fly Me to the Moon

  • *****
  • Posts: 5,733
  • Joined: 06 Sep 2006
  • Loc: NE USA

Posted 13 January 2022 - 07:46 PM

yea they work



#9 JoeyBaggo

JoeyBaggo

    Explorer 1

  • -----
  • Posts: 70
  • Joined: 13 Mar 2021
  • Loc: North Georgia

Posted 13 January 2022 - 11:55 PM

Wow!  Awesome ingenuity.  And great pic out of it too. 



#10 Stefano Delmonte

Stefano Delmonte

    Ranger 4

  • -----
  • Posts: 330
  • Joined: 17 Aug 2020
  • Loc: Salou (Spain) & Broni (Italy)

Posted 14 January 2022 - 05:07 AM

My congrats to your fantastic job both telescope and imagewaytogo.gif

 

Galileo, despite is not true, has been labeled the telescope inventor because understood that in order to reduce CA he must diaphragm and so enlarge the F ratio, his 20mm telescope was F50!  Since then the refractors start functioninglol.gif

 

Ste




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





Also tagged with one or more of these keywords: Moon, Refractor



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics