Image of the day

Captured by
Normand Rivard


My Account

New to Astromart?

Register an account...

Need Help?


Started by Inge_S, 12/13/2002 03:31PM
Posted 12/13/2002 03:31PM Opening Post
There has been quite some discussion about wide-angle eyepieces lately. Do anyone know about the Sieberts in the f.l. range 20 - 30mm? How do they perform with short f.l. Newtonians?

Another question, maybe a bit off topic: What is the origin of the "Erfle" designation. How is it pronounced in English (or German or Russian if anyone knows)? If pronounced as written in Norwegian it sounds stupid.
Posted 12/13/2002 07:12PM #1
Don't know about the origins of "Erfle," but it's pronounced "ur-full", with the second "u" barely vocalized.

Jeff Verona
Whose M.A. in English occasionally comes in useful
Posted 12/14/2002 12:00AM #2
I've talked to Harry about that very thing, since I've a Portaball on order ( and I think you have one, Inge? ).

The Ultra Plus and Observatory lines apparently are made for faster dobs.. while the Ultra's are tuned for SCTs. So if you get a review you may want to make sure which they are talking about.

I've got the Ultra Plus 32mm's and 17.5's on order.... but I'm actually using it on an F/10 right now ( nice contrast, nice sharpness ) so can't give you direct experience. *grin* Mention this to Peter and maybe he'll expedite my order? *cought*


Posted 12/16/2002 02:53PM #3
I have two Siebert 21mm, the standard and the premium deep sky. I've been using them in f/6 scopes, faster scopes may not work as well. I also have a standard 12.5.

The premium deep sky's "flaws" show up most at the edges when used as a 21 mm. I used it quite a lot as a finding eyepiece in at Tak 130 epsilon. The edge is not as sharp as say a 22 panoptic, but some of that is wide angle in newtonians. It is better in my MN 56. I had less trouble with ghosting than Chris, though it is certainly there on Jupiter or saturn (and probably Sirius). The on axis sharpness is better than the 22 Panoptic I use now. The panoptic is emotionally a better view. But, when I have alternated the eyepieces, it's been very hard to say why. In the MN 56, the Panoptic maintains a flatter field and possibly better contrast. For some reason everthing looks bigger (though it isn't). So you get something for the extra $200.00.

Barlowed, the 21 mm just gets better. Edge sharpness is very good as is throughput. I've been using it with The Siebert variable barlow (which is optically excellent, though it requires a considerable range of focus to be fully utilized). It works very well in my 8" f/6 Dob, and those two pieces, 21 mm and barlow, could be used as my only eyepieces (but I'm too greedy for that). The problem is more the inconvienence of of switching to the Barlow and then pulling it out to adjust the mangification and then extensively refocusing. The rest of the Premium deep sky line is simply a barlowed 21 mm.

The Standard 21 mm does not have the Ghosting problem. Harry says that the edge is not as well corrected, but I haven't been able to observe that.

The 12.5 mm is a damn good eyepiece. It's in the same league as the TV plossls (I have a 15 and a 10.5), at least out to 50 degrees, and barlows very well. I would give an edge to the TV plossls, but I suspect that it comes from the flocking in the eyepiece barrel.

Finally, Harry Siebert is very honest and fair about his eyepieces. He will take it back if you don't like it (up to 30 days, which ought to be enough).