TheSkySearchers

The Celestron Ultima eyepieces, if I understand things correctly, are a copy of a Massuyama designed Astroplan. The Astroplan originally came from Zeiss and was derived from the Erfle design to perform like an Orthoscopic, but with a wider field of view of maybe 50 degrees instead of the middle 40s of the Orthos.

The Baader Classic Orthoscopic is a wider field ortho, based on information from Zeiss research, that has a 50 degree field.

Understanding that the two eyepieces have different numbers and configurations of elements, with most likely different types of glass, I expect them to have different focal points, but wonder how they differ in behavior to the human eye, given that the goal of their designs are basically the same and the research came from the same source.

I am thinking specifically of the Celestron Ultima 18mm and the Baader Classic Ortho 18mm. One is rare and the other is common.

Any thoughts?

If they are Masuyama clones then they are a 2-1-2 configuration.
Anything different than that is not a pseudo Masuyama
Both 18mm eyepieces are 2-2 design (Plossl) and not pseudos (if I recall correctly). Orthoscopic is just a term meaning free of aberrations, not a actual design like Masuyama, Plossl or Abbe.
I may be wrong with Celestron, I will have to check

Bigzmey did a 18mm comparison a while ago, perhaps ask him?

From looking around the Celestron is a 5 element so possibly a pseudo Masuyama but the Baader is a standard 2-2 Plossl/ Symmetrical design.

Personally I love my pseudos so I am biased towards them.

Never had a chance to look through pseudo Masuyama. From what I read they should be good performers. However, form my hands on experience BCOs are great EPs. After observing with them for a few years, they are my gold standard I compare other EPs with and have now two sets to use in BVs.

Here is the thing though. One good EP is good, more even better! This is why I have Old TV smothie Plossl 17mm, BCO 18mm, Pentax XW 20mm and Vixen SLV 20mm.

A little insight into the Ultima line. Note post #2 where Don lists the versions:
https://www.cloudynights.com/topic/4524 ... on-ultima/

And some older related material:
https://www.cloudynights.com/topic/4988 ... ntry649359

Lady Fraktor wrote: ↑Sun Aug 22, 2021 9:23 pm From looking around the Celestron is a 5 element so possibly a pseudo Masuyama but the Baader is a standard 2-2 Plossl/ Symmetrical design.

Personally I love my pseudos so I am biased towards them.

According to a review by @WilliamPaolini only the 32mm BCO is a 2-2 Plössl heritage design and the other BCOs are 3-1 Abbe based.

https://www.cloudynights.com/topic/3822 ... try4893450

I tend to agree with BillP on this but I could always dissect my 18mm to make sure.

That is strange as Baader calls them Plossl.
https://www.baader-planetarium.com/en/c ... t-mc).html

Either way they work well

Lady Fraktor wrote: ↑Mon Aug 23, 2021 3:48 am That is strange as Baader calls them Plossl.
https://www.baader-planetarium.com/en/c ... t-mc).html

Either way they work well

Agreed that they work well and are just about the best bang per unit of currency out there! But on the page you link there is the ambiguous:

Baader Classic Ortho/Plössl (Q-Turret) 1¼" Eyepieces

which is clarified(?) further

The lens assembly consists of a triplet-element and one plano-convex eye lens, so there are only four glass-air-surfaces. The interior has been blackened for a very good suppression of stray light. Of course, the hard anodised barrel has got a filter thread.

So a 3-1 design.

Technical data of the Baader Classic (Q-Turret) eyepieces

Focal length (mm) Optical design Barrel Lens elements / groups Apparent field of view Parfocal EyeRelief
(mm) Field stop (mm) Height (mm) Diameter Weight
6 Classic Ortho 1¼" 4 / 2 52° yes 5 5 34,2 34,8 37g
10 Classic Ortho 1¼" 4 / 2 52° yes 8 8,7 41,12 34,8 48g
18 Classic Ortho 1¼" 4 / 2 52° yes 14,67 16,8 54,46 34,8 81g
32 Classic Plössl 1¼" 4 / 2 50° yes 21 26 78,8 34,8 94g

So they are using "Classic Ortho" to mean Abbe and "Classic Plössl" to mean Plössl. Sorry, the formatting of the specification table isn't getting preserved. I recommend the link.

I plead lack of caffeine!

Lady Fraktor wrote: ↑Mon Aug 23, 2021 4:07 am I plead lack of caffeine!

I've often pleaded that as well. Completely understandable!

I will restate my question with different words. Assume I have a Celestron Ultima 18mm and a Baader Classic Ortho to compare. The Ultima was derived from an Erfle, sacrificing AFOV and concentrating on the quality of the remaining area to get an orthoscopic view. The Baader Classic Ortho was adapted in unknown ways (to me) from an Abbe to arrive at a wider field of view. Both have a 50ish field of view. The Ultima has an extra lens to manipulate and the Japanese passion for perfection going for it. The Baader has time, improved technology, an two less air/glass surfaces going for it. There may be other advantages or disadvantages with each.

The Question: If I were to look through both on the same high quality refractor, what differences in the view do you think I would see?

Define in the view

Both are good eyepieces, differences would be more subtle.
Possibly a slight difference in colour rendition from coatings, light scatter though this should be minimal with these eyepieces.
A lot depends on the telescope. A Masuyama is designed for f/7 and longer though using one in a shorter telescope can start showing some aberrations along the FOV edge, the Abbe would be good for f/5-6.

Either one would work well

Lady Fraktor wrote: ↑Mon Aug 23, 2021 4:11 pm Define in the view

Both are good eyepieces, differences would be more subtle.
Possibly a slight difference in colour rendition from coatings, light scatter though this should be minimal with these eyepieces.
A lot depends on the telescope. A Masuyama is designed for f/7 and longer though using one in a shorter telescope can start showing some aberrations along the FOV edge, the Abbe would be good for f/5-6.

Either one would work well

Also, what are you viewing? If a stellar DSO at f7 or longer I'd not expect any differences. I've noticed that on nebular DSOs that the coatings on the BCOs present a slightly darker but more contrasty view with richer internal detail than other fine eyepieces.

I've not done a comparison on lunar/planetary targets. So I wouldn't hazard a guess.

One difference of note is correction at the edge of the field, which is better in the Ultima than in the BCO.
I think Baader pushed the Abbe design a bit too far to gain a wider field, but at the loss of some edge sharpness.
Though, at f/7+, this difference will be less noticeable than at f/6-

Thanks everyone for the input!

The scopes I am planning for the astroplans are two f/8 refractors (60 and 100mm) and a 90mm f/11. They have all been worked over for reflection control with flocking, collimation, better focusers, even though the achromatic objectives are not top end in terms of money. All work nicely. The 60mm will be used for wider views, large star clusters, nebula, etc. The 90mm mostly planetary and lunar viewing. The 100mm for anything I can find with it. All will be used for star splitting fun as I am able. Conditions will be the low light end of Bortle 6, but on the edge of a city light dome at 700 ft elevation.

I love my achromats
At the stated focal lengths either eyepiece will perform well.

Lady Fraktor wrote: ↑Mon Aug 23, 2021 7:20 pm I love my achromats
At the stated focal lengths either eyepiece will perform well.

Agreed. You really can't go wrong with either type. The only way is to be unlucky and get something that is a bad example. QC on both is quite good I believe.