Posts Made By: Mike Hosea

In the Equipment Forum, I wrote "Who is who", and Randy Roy writes "Who is whom?".

Well, I'm not sure what you can get away with these days. Rules regarding use of the objective and nominative cases are relaxed in common speech. Technically, "Who is who" is correct since the first "Who" is the subject, "is" is a linking verb, and the second "who" is the predicate nominative, which naturally should be in the nominative, not objective, case. But when asked "Who is it?" and voice recognition is expected, few in spoken English would answer the correct "It is I." Rather, the answer would more likely be "It's me." So, I wouldn't quibble about it.
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Mike

I'm taking a break from a night of okay seeing. I've been out with my 10" Teleport and testing my new 21.5mm, 15mm and 12mm Edmund RKEs, mostly in the 5x Powermate. I purchased these RKEs new from Edmund, and the first thing that I noticed was that this 15mm has the same "ragged" field stop that the one I owned years ago had. It's partly because it is sharp as a knife (cut my finger on it, actually).

One thing about these RKEs that I hadn't remembered is how generous the eye relief is for a scaled design. The 12mm is okay still--no chance of getting eyelashes on the eye lens. Coatings look great--just like single-layer MgF2 coatings are supposed to look. This is the way the cheap Chinese eyepieces ought to look. When you attach an eyepiece to a powerful Barlow or Powermate and point it at a light, you can see the sillouettes and diffraction effects of imperfections in the optical path, usually dust. The RKEs arrived in their yellow boxes, but inside they were just wrapped in paper (no caps), so there were paper particles that needed to be removed. There are little indications here and there that they could be cleaner inside, but the problem is small enough that it cannot be detected without a Barlow's assistance.

I'm fairly pleased with them at f/25 in the 10" Teleport w/the 5x Powermate. I thought the 21.5mm would be interesting to compare to the 20mm Tele Vue Plossl, but I'm afraid I can't choose between them very easily. Sometimes it seems like the Tele Vue is better, but other times they seem the same.

It turned out that the night was a pretty good one for viewing the Alpine rille, which I could see most of in the higher magnifications. If there's anything lacking in quality and performance of the modern RKEs versus those manufactured long ago, I didn't see any evidence of it. Didn't see any internal reflections, either.

I tried them without the Powermate in the Teleport and viewed M42 and Saturn. Loss of sharpness near the edge of field was only slightly worse than in the 20mm Tele Vue Plossl (slightly wider field there, though), and the image in the center of the field was fine. E.g. The E and F stars in the trapezium were bright and clear with direct vision, especially in the 15mm and 12mm.

I like the RKEs, but on the other hand, I don't think there is anything unique about them as compared to UO orthos, Ultrascopics, and other quality 1.25" eyepieces.
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Mike

I don't know about exceeding the Dawes limit, but once upon a time:

http://www.astromart.com/forums/viewpost.asp?forum_post_id=165035&poll_id=&news_id=&page=

I have yet to see a 1.25" Tele Vue Plossl that wasn't made in Japan, but then again, I haven't seen one that was made in the last few years. Does anybody have a 1.25" Tele Vue Plossl that is stamped Taiwan?

Probably the similarities are a matter of imitation. When the Orion Tri-Mag Barlow came out, others and myself noted the similarity in appearance to the 3x Tele Vue Barlow, which cost a lot more. Speculation became moot, however, when the reports on the Tri-Mag started rolling in--not Tele Vue quality.
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Mike

Is it really necessary to go back and forth on the Meade 5000 Plossl issue? I read about 2/3 of that thread (until I got tired of just getting one line of text per click), and it seems to me that there is really no mystery left. Am I missing anything here:

1) Meade's marketing strategies can be annoying. They don't seem to have broken any laws, but these guys are going to be the first up against the wall when the revolution comes. (c.f. Hitchhiker's Guide to the Galaxy, re. the marketing division of the Sirius Cybernetics Corporation).
2) The Meade 5000 Plossls aren't Plossls in the classical sense.
3) They reportedly work pretty well at f/10, not well at f/6.
4) They have 60 degree fields, so direct comparison with eyepieces having a more narrow or a wider apparent field is tricky and impinges on some differences of opinion about what is important. To be more specific, some people are interested in degree-for-degree comparisons, others are annoyed by useless edges enough to care only about a qualitative assessment of the full field, and still others prefer to categorize eyepieces by their specifications and only compare eyepieces within a category. I think all these points of view have merit.
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Mike

Don't know, but they don't look like bargains or undiscovered gems to me. If they are like the UO MK-70s in correction, that would be okay at f/6 but perhaps not very satisfying at f/5. Twice I've tried the 40mm UO MK-70 and just wasn't happy with it in my 10" f/5, although my dissatisfaction with seagulls at the edge of field was rivaled by my frustration with the very thin, undersized barrel with the safety undercut in just the wrong spot for me to parfocalize the eyepiece (ended up wobbly in the focuser).
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Mike

Michael, you use the word "resolution" and then you gave an example that seemed to imply a difference in "transmission". To sort this out you need a clear understanding of what "resolution", "transmission", and "contrast" mean and how these things can relate to the number of elements/surfaces in an eyepieces. I say "can relate" because it really comes down to specifics. The generalization that your laboring under is an oversimplification. That less glass SHOULD be associated with greater resolution (or contrast, or throughput) is at best a coarse generalization that is usually true yet often false, at best. A given eyepiece may have greater resolution, transmission, or contrast than another, but counting elements won't take you very far along the path to understanding why. On the other hand, from the designer's perspective, the number of elements and surfaces is a factor that they take into account as they design the eyepiece. When they resort to adding additional lenses, it is always because they want something in exchange versus their best design so far using fewer lenses. I don't see anybody offering Tolles eyepieces these days, nor do I see any 2-element eyepieces on the market. If less glass is really that directly connected to better performance, why would that be?
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Mike

I strongly dislike safety undercuts.
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Mike

I got Clyde's 5mm Tak LE today and disassembled it. As the Anacortes web site says, it is indeed 5 elements in 3 groups. From telescope to eye, a negative doublet, a 10mm internal field stop, a plano-convex doublet (i.e. plano facing the field end), and a convex-plano (i.e. convex facing the field end) singlet. As I look closely at it, the eye lens surface does seem to be ever so slightly convex, so the eye lens might be DCX, but that top surface is relatively flat.
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Mike

The 12mm UO Konig isn't very good at f/5. I'm not very good in this range of focal lengths, so perhaps I will overlook something obvious. The 12mm Nagler T4 is a 6-element/4-group eyepiece. Panoptics and Radians are also 6/4.
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Mike