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

Further Adventures Without Many Seagulls

  • Please log in to reply
2 replies to this topic

#1 Shorty Barlow

Shorty Barlow

    Apollo

  • -----
  • topic starter
  • Posts: 1,446
  • Joined: 15 Sep 2015
  • Loc: Lloegyr

Posted 10 November 2019 - 08:20 AM

I finally got to test the 32mm GSO Kellner in my Sky-Watcher Evostar 80ED DS Pro Friday night. Actually I have used it before in the same scope but it was in conjunction with a GSO Barlow element threaded into it, effectively making the 32mm EP into around a 20mm one. I used it with the Barlow element as there was noticeable astigmatism when the eyepiece was used 'on its tod' in my f/5.8, ED72. And we're talking serious seagulls here! The GSO got shelved for a while and I kind of forgot about it. The 32mm GSO was originally purchased on back order in October 2018. I’ve experimented with swapping the original barrel with an undercut for a ‘smoothie’ although as it is now primarily used in a Baader twist-lock dielectric diagonal the undercut isn’t so problematical. These eyepieces used to be marketed in both Meade and Celestron kits. I’m not actually sure if GSO still manufactures them. Apparently they’re not very popular and don’t perform well in fast Newtonians.

 

sml_gallery_249298_10131_261870.jpg

 

 

You may be wondering at this stage why I’m bothering with this 'Kellner' at all. It's a good question. There are more capable EP’s and I even own some, such as the 31mm Baader Hyperion Aspheric, which could probably do the job much better. This is true, however, the 32mm GSO has a wide field stop of around 35mm. It’s also a physically light (240g), three element design, with a correspondingly bright and well contrasted image. Furthermore, I quite like its ergonomics including the very soft rubber eyeguard that forms well to the face. This does an excellent job of masking any external light sources that could possibly cause reflections in the large eye lens. Did I mention it was also under fifty quid (60 USD)?

 

sml_gallery_249298_10131_99349.jpg

 

The GSO has an AFOV of 56º, regardless of any spurious retailer claims of it being 65º. This gave a TFOV of just under three arc degrees (2º: 59’: 10”) with a magnification of 18.75x and an exit pupil of 4.2mm. Used in the 80mm Evostar without a Barlow it displays very little astigmatism and  there was a definite paucity of seagulls. It is usually claimed that f/8 and slower are the best focal ratios for Kellner or modified Kellner type eyepieces. So I reckon the ED80, at f/7.5, gets away with it. I’ve been told the 40mm version performs well in slower refractors. Perhaps I should have ordered that as well while I had the chance.

 

sml_gallery_249298_10131_42247.jpg

 

Conditions weren’t brilliant, but despite the bright Moon, and before the inevitable clouds came, I got to view a few deep sky objects. These included a low M42 and additionally mainly open clusters like the Orion Belt Cluster (Cr 70), the Pleiades and Hyades clusters, and whatever I could see in between rapidly encroaching cloud. I was actually pretty impressed with viewing Cr 70 and the Pleiades with the 32mm GSO RK Wide Field eyepiece. Not bad for under fifty quid.


  • j.gardavsky likes this

#2 SloMoe

SloMoe

    Mercury-Atlas

  • *****
  • Posts: 2,622
  • Joined: 23 Dec 2016
  • Loc: Washington State

Posted 10 November 2019 - 09:07 AM

Morning Shorty, well for you it's early evening but that's not really important,,,,, so anyway fighting the physics of slow eyepieces in fast scopes I started thinking about this and you using a Barlow on a long eyepiece, I would think that a three element or four element magnifier like a Powermate might get those seagulls to roost elsewhere instead of your fov.


  • Serpentarius likes this

#3 Shorty Barlow

Shorty Barlow

    Apollo

  • -----
  • topic starter
  • Posts: 1,446
  • Joined: 15 Sep 2015
  • Loc: Lloegyr

Posted 10 November 2019 - 09:35 AM

Morning Shorty, well for you it's early evening but that's not really important,,,,, so anyway fighting the physics of slow eyepieces in fast scopes I started thinking about this and you using a Barlow on a long eyepiece, I would think that a three element or four element magnifier like a Powermate might get those seagulls to roost elsewhere instead of your fov.

Good afternoon SloMoe. Technically it's afternoon here lol. I think it's possible, but a 2" Powermate would add considerably to the weight on my ED72. At present I'm using the ED72 on a Vixen Porta II/Polaris combo.

 

sml_gallery_249298_10284_27190.jpg

 

Heavy 2" eyepieces in conjunction with a prism diagonal require the altitude clutch to be tightened slightly more to prevent altitude drift. Which means that when I switch to lighter eyepieces the altitude can be a bit stiff and jerky to move. The 36mm Baader Hyperion Aspheric is fine, the 19mm Celestron Luminos (which weighs about a metric tonne) isn't.

 

sml_gallery_249298_10131_181356.jpg

 

The bloody thing's ginourmous! 

 

sml_gallery_249298_10131_64742.jpg

 

I have experimented with weight/balance trials with a 2" GSO Barlow. Weight and balance are important to me as I'm physically disabled and my right arm is now partially paralysed. So I don't believe in making things more difficult for myself lol.




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