So, how many have the Siebert Observatory EPs?

I am interested in your impressions for the 34-36mm Siebert Observatory EPs.

Floyd Blue said:

I am interested in your impressions for the 34-36mm Siebert Observatory EPs.

Hi Floyd.

I have a 34mm Siebert Observatory Series that I use with a 12" f/4.9 dobsonian. It gives me just about the largest useful exit pupil for my tired eyes, and the 70 AFOV and long focal length make for a very large TFOV to boot.

On the A-F scale, I would give it a strong B+. I base this rating on the following factors:

The Good:

The FOV is flat. Nice and flat. Flatter and sharper at the edge than say a 27mm Panoptic.

Nice wide FOV.

Stars stay pinpoint to the field stop which is a generous 38mm.

The Not So Good:

Contrast isn't on par with the Panoptics by a long shot. I blame the coatings, which are fairly reflective. For example when you view a very bright object like Sirius, the reflection of the object off of your eyeball will re-reflect off of the surface of the eyelens and make it look like a tiny "companion star" dancing all around the object.

Price. At $200, it is not inexpensive. At $150 I would have given it an A-. At $200, for just a bit more money you can get some excellent second tier premiums like the Vixen LVWs.

Jim

I have the Siebert 36 mm observatory eyepiece. I found it to be quite competitive with the 35 mm panoptic that an observing friend owned. Stars stayed as pinpoints quite as well, and the field stop is certainly wider than the panoptic.

Jim's observations may wind up hurting my enjoyment of the eyepiece, but I have not (yet) had his negative experiences with it. I should note that with the eye shield off it has significant reflection issue, and with the eyeshield on I have had no trouble with balckout.

Unfortunately, or perhaps fortunately, I no longer have access to a 35 mm panoptic to compare it with. When my friend had his 16 inch f 6 dob, we used the Siebert in it a lot because the Panoptic required rebalaning. I put a retaining ring on the barrel to make it parfocal with TV eyepieces.

Floyd Blue said:

I am interested in your impressions for the 34-36mm Siebert Observatory EPs.

Floyd, I received a used 34mm Siebert Observatory eyepiece yesterday, purchased for $149. And strangely enough was able to use it last night. In the light polluted backyard, with the 16" f/4.9 dob. The air was cooling down fast. I have a 3" fan blowing upward into the mirror back, but there were some some thermals evident when defocusing. Seeing wasn't too bad. Saturn showed the Cassini division pretty easily at 100x-150x with other eyepieces. Collimation was checked with Tectron tools.

I don't have a 35mm Panoptic for comparison, only a 32mm Televue plossl.

First impressions: the coatings are minimal, in fact I couldn't see any of the blues, greens and purples you would normally see on Televue and other premium eyepieces. However when viewing against a 32mm Televue plossl I could not see any obvious contrast differences. But mind you it was not a dark site.

It does provide a better FOV than the plossl, but I'm suspicious of the 70 degree AFOV value, seems much smaller than the two Naglers I have now.

Sharpness: the central area is very sharp. But I was seeing astigmatism in the outer areas, but so does the plossl. I didn't see the totally sharp stars all the way across like the other poster on this thread, at least for brighter stars. I used to have a 35mm Panoptic and remember there being less astigmatism.

It is light and easy to handle, seems reasonably well made.

For now it's a keeper due to the wider FOV, especially for $149.

Mike