Meade Series 5000 Plossls

[MortonH]

Hi Michael, agree with everything you said.

The reason I started this thread is that I'm weighing up which eyepieces could give a field of view around 2 degrees when used with a scope of around 1200 focal length (i.e. 8" f/6, 10" f/5, or 8" SCT with focal reducer) and keep the exit pupil under 7mm.

I certainly felt some pain when I bought a 35mm Panoptic a few years back, but it was a fantastic eyepiece. I only ever used it in a TV-85 and the view was almost too wide. Wish I'd kept it, cos I imagine it would be excellent in any of the scopes I mentioned above.

Morton

[DobDobDob (Ron)]

Originally Posted by Apocrisiary

That pain will go away when you look through it and if you keep it for 10 years and see lots of really good things through it you will look back and chuckle. The pain of how much you paid will be a distant memory compared to the window it opens on the Universe.
Michael
BINTEL

Hi Michael, most of what you said is still a little beyond me, although I follow your drift, however more important than all the technical opinion from my viewpoint is the last two sentences, quoted above. Those sentences are IMHO priceless and the endgame, regardless of how we get there

I'm looking forward to meeting you, naturally you will be delighted to know I have a healthy Visa card

[janoskiss (Steve H)]

Originally Posted by Apocrisiary

Where does this information come from??

http://www.televue.com/ask_al/barlows/0049.html
- also discussions on CN, esp comments from Mike Hosea

In just about any scope, stick a 15mm TV plossl in a 2x Televue barlow (or any other barlow) and the edge of field goes black, usable FOV reduced to around 40-45 degrees. Try it in daylight, it is most obvious. This is something entirely different from the overall dimming of the image from halving of the exit pupil, i.e. increase in magnification due to barlow. When not barlowed the edge is not dark, but noticeably dimmer than the centre of field.

[Apocrisiary (Michael)]

Thanks Janokiss, as suspected the vignetting is caused by a separate factor - not by the eyepiece.
There is a really nice list called the "wobbly stack" that lists all the factors that intervene between Reality (what we should see) and Perception (what we "see") when evaluating the view. They include:
Bandwidth of Light, atmospheric turbulence and absorption, ground turbulence, aperture pupil, aberrations, alignment, spider obstruction, secondary obstruction, tube currents or air pudding, dirty and absorptive optics, internal reflections between lenses, vignetting, incomplete baffling of stray light, eyepiece aberrations, defocusing, improper eye placement, monocular input, eye aberrations, internal scattering and absorption in the eye, damaged and insensitive areas of the retina, local retinal processing faults, non uniform distribution of rods and cones and mental processing errors.
This is lifted from Dick Suiter's book Star Testing but it is good to keep in mind how many different factors are involved in testing optics. I think the last one on the list accounts for most differences of opinion.
Anyway I only just realised this morning that this thread is about Meade Series 5000 Plossls. They are 5 element eyepieces so I'm not sure if it really is a Plossl...but Meade don't follow convention there anyway. Maybe they should have called it the Advanced Plossl. I've looked through the 32, 26, 20, 14, 9 and 5.5 in daylight. Under the sky I have only looked through a 26mm and 9mm from memory. They are OK. Of them all the 26 down to 14mm seem most comfortable. The 32mm is like a hand grenade and the wind up eyepiece thingy seems a bit silly - they use that sticky grease on it to make it smooth but I worry this is a dust trap and you can easily put your finger in it. On the big eyepieces you cant get your eye in close enough because the top of the eyepiece is TOOO big. This goes for the SWA and UWAs too. They are not as contrasty as the older Japanese lenses.

[rockit]

As the same principle of exit pupil size at high mag, you are constrained by maximum permissible field of view. Unless you own a astrograph with 4" focuser more than 50deg at 40mm ep will be poorly illuminated. Why pay for what you can't see. And I personally are very tired of the nagler celebration, go to america already. Using open eyes I have been trying to discover what will live in my ep collection. And I can emphatically state that there will be no naggypoo's unless I end up with a very large and desirable DOB, which is the only place I have seen them work beautifully. As of the Meade 5000's I have 2uwa, the 14mm is very nice and the 4.7mm I wish I never owned and bought a UO HD orthoscopic or two for it's price. Purely one mans opinion , but when you ask a question about ep's there is not going to be a friendly out come. I am seriously going to Takahashi ep's if weather permits(waiting for a money shower). One birdy told another birdy that his Tak smoked the nagler(The lower case is not an over site!!!)

[Don Pensack]

I recently reviewed the entire S5000 group. The "Plossls" (they aren't really) were a disappointment. The 60 degree field is too wide for the correction of the design and all had serious edge-of-field astigmatism and aberrations.
The SWA and UWA were much better and in a different class of eyepieces, IMO.
TeleVue Plossls are better, and recommended.
As are the "Pseudo-Masuyama" designs: Antares Elite, Celestron Ultima, Orion Ultrascopic, Parks Gold Series, Takahashi LE, Baader Eudiascopic and the pre-1994 meade 5-element Plossls, Tuthill 5-element Plossls, Omcon Ultima 5-element; and the original Masuyamas, of course.

PS, the 32mm TeleVue Plossl (not other sizes), IIRC, has a field stop size that allows for slight edge-of-field vignetting. It is usually not noticeable in modern scopes, optimized for 2" eyepieces.