Celestron Omni 32mm Plossl

[Mak the Night]

I've noticed that Celestron Plossls tend to have longer eye relief than ones with equivalent focal lengths from other manufacturers.

[John]

I've noticed that Celestron Plossls tend to have longer eye relief than ones with equivalent focal lengths from other manufacturers.

According to the manufacturer specs:

Celestron Omni 32mm plossl: eye relief = 22mm

Meade 4000 32mm plossl: eye relief = 20mm

Tele Vue 32mm plossl: eye relief = 22mm

GSO 32mm plossl: eye relief = 22mm

The plossl design sets eye relief at more or less 70% of the focal length. With some designs issues like the eye cup height, shape and flexibility and the extent to which the eye lens is recessed will affect the actual amount of useable eye relief.

[Mak the Night]

According to the manufacturer specs:

Celestron Omni 32mm plossl: eye relief = 22mm

Meade 4000 32mm plossl: eye relief = 20mm

Tele Vue 32mm plossl: eye relief = 22mm

GSO 32mm plossl: eye relief = 22mm

The plossl design sets eye relief at more or less 70% of the focal length. With some designs issues like the eye cup height, shape and flexibility and the extent to which the eye lens is recessed will affect the actual amount of useable eye relief.

I think I was thinking of EP's with shorter f/l's than 32mm, particularly the 15mm TV and Celestron Omni Plossls, which have an ER of 10mm and 13mm respectively. 

[AndresEsteban]

Update folks! 32mm 1.25" plössls!!!

I finally get my Meade Series 4000 32mm plössl. Now I have three 32mm plössls that I can compare:
Meade Series 4000 32mm plössl - FMC, blackened lens edges. (Series 4000 typical body design -straight black cilinder)
Celestron OMNI 32mm plössl - FMC, blackened lens edges. (Celestron and GSO share the same ep. body)
GSO Superplössl 32mm - FMC, blackened lens edges. (Celestron and GSO share the same ep. body)

Tested the bunch a few days ago.
Object tested: Beehive Cluster, also known as Praesepe or M44.
Telescopes used: a 200mm f/5 reflector (hand made with excellent mirrors) and a vintage japanese Dan Beam 76.2mm f/16.4 achromat (OKKK OEM). This achromat is comparable to a 75mm f/15 Polarex. If I'd give grades to scopes a Polarex would be 100 and the Dan Beam achromat 90.
Despite the deformations at field borders when using the 200 f/5 reflector, conclussions were, from best to good:


Celestron OMNI 32mm: Excelent coatings, sharp images and pinpoint stars with f/16 achro. In both telescopes excellent star colour differences. With f/5 reflector, deformation at borders but otherwise excellent images at center field. By far the brightest eyepiece of the bunch and superb colors!! Best coatings of the trio also! Celestron and Meade seem to have same type of coating, a deep dark mate green so light transmission is quite similar, but Celestron is 20% brighter. AFoV 50º. Eyepiece rating: 100

Meade Series 4000 32mm: Same as above although it seems the eyepiece has a litle bit more longer focal length (35mm?) than the Celestron Omni . Also AFoV a bit smaller than Celestron, 47º?. Otherwise excelent images, but stars on Celestron seem to have more colour. Like the Celestron, admisible correction with f/5 reflector on field borders. Ep. rating: 90

GSO Superplössl 32mm: Coatings are light brilliant green and I think is not so efficient as the Celstron and Meade. Not so bright eyepieces as the Celestron or Meade. With f/5 scope more deformation on borders. Pinpoint stars on both scopes at center. AFoV and focal distance similar to Celestron OMNI. Fainter stars that were super-easy to spot with Celestron, easy with the Meade, are not so easy with this EP. Ep. rating: 75-80

On daylight use, there's almost no difference between the three eps. Objects snap into focus easily, being easier on GSO (?). But daylight images seem more "vivid" with Celestron and Meade. At night things are completely different and Celestron OMNI clearly ourperforms the others in low light star fields.

Heavy clouds prevent from comparing the three eyepieces observing the Moon. On previous tests with the Moon between GSO and Celestron OMNI results were quite similar, but strangely GSO ep was able to show more details on craters than the Celestron... No Moon tests with the Meade 32mm yet.

Conclussions: The winner is Celestron Omni 32mm plössl, that's the one I'll keep. The GSO is not a bad ep. at all. As I've said Moon crater's detail seemed a little sharper on this GSO than with the Celestron, but noy by far. On low light conditions the Celestron excels, the Meade get close although as I've said it seems it has a longer focal length this fact dissapointed me because views with the Meade S4000 32mm are quite close to the ones given by the Meade Series 4000 40mm eyepiece , which I like a lot. Knowing this I'd keep the Meade Series 4000 40mm and the Celestron Omni 32mm and sell the Meade 32mm and the GSO 32mm.

BTW, about 40mm plössl, although soem complain about the narrow field, about 43º - 44º and say it's better to buy instead a 32mm with wider field, these 40mm have a greater exit pupil than the 32mm. With fast scopes the difference of exit pupil between 40 and 32mm increases, so a 40mm is absolutely worth it despite the narrower field (and even if you don't have a 7mm exit pupil!)

Don't know if Celestron OMNI 40mm is better than the Meade Series 4000 40mm. But a friend of mine told me Vixen NPL 40mm give better contrast and sharpness than the Meade 4000 40mm. If that's the case then perhaps the Celestron OMNI 40mm and the Vixen NPL 40mm are quite similar. It would be nice to hear others' experiences about these brands, I mean:
Meade Series 4000 plössl - GSO Superplössl - Celestron Omni plössl and Vixen NPL plössl.
Regards, Andy
 

[Mak the Night]

I've always rated the Celestron 32mm Plossl, I normally use my TeleVue 32mm nowadays, but a few nights ago I was observing M42 mainly and I'd only taken one of my cases out with me. It now houses my Delos and Panoptics, but I wanted a butcher's hook at the Pleiades amongst others with a low power Plossl and as it's an old modified Celestron case it still has the 32mm Celestron Plossl in it. AFAIK it's the same as the Omni apart from the finish.

[John]

Interesting review Andy - thanks for posting it

I'm not sure about using a 40mm over a 32mm in a fast scope though. If the exit pupil exceeds your dilated pupil size it's not going to help with fainter deep sky objects and the paler background sky that the lower magnification gives is similarly not a positive thing to have. In slower scopes these factors are not such issues although I still prefer an apparent field of view of 50/52 degrees over the 43/44 degrees that is the best that a 40mm eyepiece in the 1.25" fitting can do.

I've read that Vixen use a slightly modified optcial designs for their NPL range, similar to the Tele Vue plossls. I've compared the Vixen NPL 30mm with a Tele Vue 32mm plossl on a few occasions and the Vixen does pretty well although the Tele Vue maintains field sharpness over a larger % of it's field of view when the scope gets faster than around F/6.

[Dave In Vermont]

Nice write-up, Andy! I'm always interested in good reviews of eyepieces that don't cost as much as the national-deficit. And I am looking about for a lower cost EP in the 32mm range. Between you and Mak there, my choices are more finite now.

Thanks to both of you!

Dave

[AndresEsteban]

Interesting review Andy - thanks for posting it

I'm not sure about using a 40mm over a 32mm in a fast scope though. If the exit pupil exceeds your dilated pupil size it's not going to help with fainter deep sky objects and the paler background sky that the lower magnification gives is similarly not a positive thing to have. In slower scopes these factors are not such issues although I still prefer an apparent field of view of 50/52 degrees over the 43/44 degrees that is the best that a 40mm eyepiece in the 1.25" fitting can do.

I've read that Vixen use a slightly modified optcial designs for their NPL range, similar to the Tele Vue plossls. I've compared the Vixen NPL 30mm with a Tele Vue 32mm plossl on a few occasions and the Vixen does pretty well although the Tele Vue maintains field sharpness over a larger % of it's field of view when the scope gets faster than around F/6.

Technically, I agree with you John!

1) On my 200 f/5 reflector the Meade 40mm gives: 40mm/5 = 8mm exit pupil and 32mm ep gives 32/5 = 6.4mm . I'm 54 and certainly my pupils when fully dilated have not 8mm! So yes, technically it's a waste.

2) But with the 76.2mm f/16 refractor the 40mm ep gives 40/16.4 = 2.4mm and the 32mm, 32/16.4= 1.95mm. Although the field is narrower with the 40mm ep there's a gain in exit pupil than is perceptible in this slow scope (from 1.95 to 2.4mm).

Well, what about the f/5 reflector and my actual pupil size when dilated? Being 54 years old I don't have 8mm for sure!!!  Don't know my actual pupil diameter when fully dilated (5, 6mm?) but I know there's a small difference still perceptible for me when using the 200 f/5 and switching between the 40 and 32mm eps. That's why I still think the 40mm is worth keeping. I did all this reasoning that you did, and totally agree with you but... two nights ago looking at M44 through both telescopes and switching from 40 to 32mm, the maths proved right with the slower one but then, with the f/5 I was still convinced the 40mm gave a brighter image despite the narrow field. Subjective perception? Self-suggestion? Honestly: don't know!

But the Celestron Omni 32mm was without any doubt the brighter 32mm ep of the trio! Excellent!

Regards John, and again thanks for your observations!

Andy

[PESKYWAABBIT]

Been looking for my first proper eyepiece other than the ones that came with my SW 200p, I think I've found it... 

Thanks for all the info guys!