Meade Super Plossl 56mm Question

[refractordude]

Returned the Orion Q70 38mm and Q70 32mm. How would the Meade 56mm Super Plossl do with a 120mm f/8 refractor? What do you think of the Astromania 56mm Plossl?

[Ruud]

The Meade Super Plössls have been around for a long time and have a good reputation. I think they should give a very decent view in an f/8.

But for an F/8 I think 56mm is too long a focal length. You'd get an exit pupil of 56/8 = 7 mm. Only young eyes can fully benefit from that and even then, a 7 mm exit pupil amplifies any light pollution to visibility, so you need really dark skies. Of course, if you're young and have pitch black skies then go for a 56mm. Otherwise, if it's wide views you're after, consider a 40mm 68° eyepiece, like a used Meade SWA or a Maxvision.

Usually, for astronomy, exit pupils up to around 5 mm are recommended. On an f/8 refractor that would mean a 40mm eyepiece.

I've never even heard of the Astromania, so can't say anything about that.

I have heard of the Orion Q70s. Some seem to like them. Evidently they came short of your expectations. What were you hoping for, and what did you get from them?

 

[F15Rules]

The Meade 56mm is a nice eyepiece of its type, but I'd second Ruud's comments on this very long focal length. 

The eye relief is long, so you may get problems with blackouts and comfort holding your eye some distance from the eyepiece, and contrast under any real light pollution will make the sky background very brightght.

I don't even get much use from my nice 40mm 68degree TMB clone in the summer months as it's not often dark enough..

Dave

[DRT]

I have never had a Meade 56mm Plossl but I did own a Tele Vue 55mm Plossl and the only real practical use I found for it was in SCT/Mak scopes with very long focal lengths. In shorter fl scopes the magnification is very low and light pollution and lack of contrast result in a very washed out view.

[25585]

Long FL have more use on shorter FL scopes as they can turn the main scope into a guide scope.

My 500mm TV Genesis uses a 55mm TV Plossl giving 9x instead of a separate little frac or RDF on top. It has an UHC filter to darken & increase contrast. 

 

[Ruud]

I had a 55mm TV Plössl for my Genesis for just that purpose: as a finder eyepiece.

It's a personal thing of course, but this is the only eyepiece that I ever sold. I found a RACI with cross-hairs more effective. The RACI is also more convenient: no switching is needed. On top of that, it looks nice to have a baby scope piggybacking on your refractor. So it was goodbye to my 55mm Plössl.

During the day, the 11 mm exit pupil combined with my 2 mm observers pupil had a peculiar effect. If I moved my head, staying within the exit pupil, there was an obvious parallactic  shift of closer objects with respect to more distant ones. I always thought that was special. It was no reason to hang on to the eyepiece though, so it went to someone with a big SCT.