Eyepiece

[Connor brad]

Hi what is better eyepiece in performance and better edge of field star sharpness out of televue Panoptics or 68 explore Scientific? What is a better choice? 

[toshapetriji]

They are both very fine eyepieces the differences are likely to be dependant on the individual.

[Connor brad]

1 minute ago, toshapetriji said:

They are both very fine eyepieces the differences are likely to be dependant on the individual.

I hear the Panoptics are better than the explore Scientific in performance and edge of field sharpness 

[Louis D]

As the scope gets faster (lower f-ratio), the Panoptic line pulls away from the ES-68 line.  If your scope is f/8 or slower, the difference would be minimal.  Around f/5 to f/6 differences start to appear, and by f/4.5 or faster, Panoptics generally have a significant edge.  The downside to this improved edge performance is increased pincushion distortion.  The moon gets stretched into an egg shape and stars appear to move across a globe during panning.  This also happens in the ES-68 line, but not to the same degree.

[NGC 1502]

28 minutes ago, Louis D said:

  The downside to this improved edge performance is increased pincushion distortion.

Agreed, Panoptics do have edge of field pincushion.  When David Nagler was at Astrofest in London I was able to speak to him about eyepiece design.  He said it’s a trade off to get better sharpness towards edge of field. He further explained that  there’s no way round this  idea of trade off, for instance if we want wide field and long eyerelief we generally have to accept a larger more expensive design. If we sacrifice eyerelief we can get a smaller more compact wide field eyepiece- the T6 Naglers are an example of this.....etc.

David is very approachable and happy to discuss, just like his dad.

 

Edited September 28, 2020 by NGC 1502
Extra info

[Louis D]

32 minutes ago, NGC 1502 said:

Agreed, Panoptics do have edge of field pincushion.  When David Nagler was at Astrofest in London I was able to speak to him about eyepiece design.  He said it’s a trade off to get better sharpness towards edge of field. He further explained that  there’s no way round this  idea of trade off, for instance if we want wide field and long eyerelief we generally have to accept a larger more expensive design. If we sacrifice eyerelief we can get a smaller more compact wide field eyepiece- the T6 Naglers are an example of this.....etc.

David is very approachable and happy to discuss, just like his dad.

 

And yet the original NT2 eyepieces and their NT5/NT6 equivalents have similar eye reliefs around 10mm to 12mm despite the NT2s being much larger than their NT5/NT6 nearest equivalents.  Sometimes it is possible to reduce size and weight while maintaining eye relief through improved designs.

[NGC 1502]

3 hours ago, Louis D said:

And yet the original NT2 eyepieces and their NT5/NT6 equivalents have similar eye reliefs around 10mm to 12mm despite the NT2s being much larger than their NT5/NT6 nearest equivalents.  Sometimes it is possible to reduce size and weight while maintaining eye relief through improved designs.

Yes, I think your point about improved designs is relevant here.  Of course that’s just what TeleVue have done since Al Nagler started the company so long ago.

[Second Time Around]

This in depth article by Bill Paolini, the author of a book on eyepieces, is a shootout between 12 different eyepieces with focal lengths between 24 and 26mm. Go to https://www.cloudynights.com/articles/cat/user-reviews/24-26-mm-eyepiece-comparison-r2651

Since then the 24mm APM Ultra Flat Field has come on to the market.  This 65 degree FOV has particularly long eye relief (approx 20mm useable rather than the claimed 29mm), and is one of the few wide field eyepieces at this focal length where the full FOV can be seen with glasses (this being one of the problems with the 24mm Panoptic).  It also accepts a Televue Dioptrx astigmatism corrector.  It's garnered a fine reputation for quality and is often recommended here on SGL.  It's also not expensive at less than £150.