138 replies to this topic

[areyoukiddingme]

Just 24 more posts, and someone will implode!

[Starman1]

If they go to a 2" barrel. The odd focal length of the 18.2 implies a constrant in the design, assuming it is a scaled design across the focal lengths.

It's not scaled or the 3mm would be 1/6 the size of the 18.2mm.
But you're right...any Delite over 20mm would be a 2".

[jrmacl]

It's not scaled or the 3mm would be 1/6 the size of the 18.2mm.
But you're right...any Delite over 20mm would be a 2".

I always just divide by 5 then multiply by 8 to try and figure out what 2" size TV "could" make; for instance 18.2/5=3.64, 3.64x8=29.12. So 29mm is as big as they should be able to make a 2" Delite (and they "could" have made a 27mm Deloes). But that math never plays out with what TV has- a 32mm Plossl, which everyone says is the largest you can make a 1.25", would mean a 51.2mm 2". For scaled designs the 31 Nagler means they "could" make a 19.375 in 1.25" (which if they can, they should- now that the 20mm 2" is off the market).

Edited by jrmacl, 21 April 2025 - 12:52 PM.

[Spikey131]

The 24 Panoptic isn’t going anywhere.

 

It gives a maximum possible FOV in a 1.25” EP, with a 68 degree aFOV, with unquestionable Tele Vue quality.  Nothing does this, and no 2” EP will replace it.

[JoeBlow]

Does the 24mm Pan vignette when used with filters? I had that problem with the Meade 24/68 SWA (same optics as the ES 24/68) when used with my Astronomik uhc filter. That was one of the main reasons I replaced it with a 22 LVW.

[Mike W]

Does the 24mm Pan vignette when used with filters? I had that problem with the Meade 24/68 SWA (same optics as the ES 24/68) when used with my Astronomik uhc filter. That was one of the main reasons I replaced it with a 22 LVW.

I've used it with a Lumicon OIII and a TV Nebustar and never saw any.................................

[25585]

It's not scaled or the 3mm would be 1/6 the size of the 18.2mm.
But you're right...any Delite over 20mm would be a 2".

Why 2"? 

Edited by 25585, 21 April 2025 - 05:11 PM.

[davidgmd]

Why 2"? 

  
Barrel diameter in mm (D) = eyepiece focal length/tan(AFOV/2)

Eyepiece focal length = D*(tan(AFOV/2))

For a 1.25” (31.75 mm) barrel

Assume a 2 mm wall thickness, leaving a 27.75 mm inside diameter

Focal length = 27.75 x tan(72/2) = 27.75 x tan36 = 27.75 x 0.726 = 20.15 mm

 
Any 72 degree AFOV eyepiece longer than 20.15 mm wont fit in a 1.25” barrel.
​

[Starman1]

Why 2"?

The design would likely vignette severely. It's possible to make 62° eyepieces as long as 26mm, but not of the design of the Delites.

[25585]

The design would likely vignette severely. It's possible to make 62° eyepieces as long as 26mm, but not of the design of the Delites.

Please explain how a Delite's optical design would prevent a low to mid-20s mm being 1.25"as Delites are only 62 AFOV.

[JoeBlow]

Please explain how a Delite's optical design would prevent a low to mid-20s mm being 1.25"as Delites are only 62 AFOV.

If it were possible, wouldn't Al Nagler have already produced one by now?

 

Btw, I would love a 26mm 62deg Delite. I like the bright and usable exit pupil it would produce for looking at clusters and scanning the milk way. Unfortunately I hear the ES version is not well corrected for fast telescopes. 

Edited by JoeBlow, 22 April 2025 - 08:17 PM.

[jrmacl]

Please explain how a Delite's optical design would prevent a low to mid-20s mm being 1.25"as Delites are only 62 AFOV.

Don't the Delites have a built in Barlow/Smyth lens? They get taller as they drop in size, so I would think so. Would we be getting something like the 24mm Hyperion then, a Delite with no Smyth lens? I don't think that would meet TV's standards.

Edited by jrmacl, 22 April 2025 - 08:51 PM.

[jrmacl]

Please explain how a Delite's optical design would prevent a low to mid-20s mm being 1.25"as Delites are only 62 AFOV.

By the way, I banged my head off the sidewalk trying to wrap my brain around this topic a couple of months ago:

 

https://www.cloudyni...rter-than-24mm/

 

You can be the first to try out triplemon's radical idea:

 

"There is nothing stopping anyone taking the 2" 20mm Masuyama, chop of the 2" barrel really short and put an 1.25"  barrel inside it. It would end just short of the actual field stop, but its OD still safely larrger than it, so to not slide in and damage the field lens.

Most scopes would also be able to still come to focus - which would be just a few millimeters above the new 1.25 inch barrel shoulder."

[Starman1]

Please explain how a Delite's optical design would prevent a low to mid-20s mm being 1.25"as Delites are only 62 AFOV.

You know, this has been explained many times.  Negative/positive designs need a larger space on the inside to avoid vignetting.

So their maximum field stops are a lot smaller in the same barrel.

All-positive designs do not need that internal space.

So a 68° Panoptic can be 1.25", while a 22mm 700° with a negative/positive design must be 2".

It's why the 14mm Nagler T7 and the 14mm Long Perng 80° are 2" eyepieces.