Posts Made By: Mike Hosea

Did I miss something really interesting that got deleted? 8O

Well, there's no mention of any restriction on discussing said eyepieces on CN.
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Mike

I haven't seen any definitive responses. Although I have seen neither old nor new 6mm B/TMB, I have some reason to suspect that the original "garage-sale" 6mm might have had a 3-element doublet-singlet field group like the 9mm, while it would be reasonable if the newer one used a doublet like the 5mm and 7mm. So, this is perhaps a little bit difficult, but there is a way to examine this. One is to unscrew the barrel and shine a bright light on the lenses in the barrel (from either side). If you can see a spacer between two lens groups in the barrel or if you can count more than 3 reflections, including the one off the outer surface, then it's probably version 1. Obviously if you see a smooth retaining ring on the inside, yours has escaped upgrade, and it must be a version 1.

Like I said, most of this is somewhat speculative on my part, although not totally off the wall. At present it's like a Foxworthy "Youuuu might be a redneck" thing. It would help if people who actually have these eyepieces and know that they have a garage sale or know that they bought from a dealer in the last several months would try this and report their findings.
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Mike

Greg Nowell said:
I'm curious about it because I have seen it in a very high end eyepiece line that I consider to have excellent contrast and great light control, well baffled too; for example when you're looking directly at Jupiter, it's excellent.

No, it's actually inadequate baffling. Looking directly at Jupiter the baffling of an eyepiece is irrelevant as all the bright light is well-contained on the lenses. In that case the surface polish and coating performance are important. Baffling an eyepiece is different from baffling a scope because all the light for given point in the view uses each eyepiece lens only locally. What's happening when you see this "glare" in an eyepiece is that light from outside the view hits some piece of hardware inside the eyepiece that isn't blackened or masked off properly, and it reflects back into the view.

It is not significant for planetary targets like Jupiter and Saturn, but it can affect usage around the moon and it may affect contrast for DSO usage because one unnecessarily integrates background glow from outside the view.

I, too, have seen this in many eyepieces. The B/TMB Planetaries became famous for it because the initial versions had a somewhat more pronounced problem with it and because expectations were quite high based on what had been written about them beforehand. Some may remember my exploits to remove the problem from my B/TMBs (mostly because I care a lot about lunar observation in particular). As you know, it was unfair to regard the B/TMBs as special in this regard, but there nevertheless was room for improvement.
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Mike

I dislike them, also. I have taken to filling mine in with aluminum tape. It's not the most durable thing, but I use Nylon thumbscrews in a Dob-Newt (it's not capable of dumping an eyepiece), and it seems to hold up OK, and it's easy to remove cleanly and replace if I want.

Michael Tencza said:

No big deal but I never expected to get vignetting with a plossl in a barlow, yet that's what I got. Are these barlow's only made for orthoscopics or am I living wrong?

Actually, Tele Vue Plossls are very INTOLERANT of the divergence of short focal-length Barlows. It's because the DCX elements in the doublets limit the diameter of the lenses. If the lenses could be made larger without making them thicker, then the design would be more forgiving. Sometimes it works OK, but it usually doesn't with the longer focal length Plossls. The 5-element Ultrascopics/Ultimas/Parks Gold design will take more divergence from a Barlow without vignetting, but the longest focal lengths are still susceptible.
Somebody mentioned a Pentax XL--an eyepiece design highly TOLERANT of divergence. The Barlow is presenting the challenge, not causing the vignetting directly. It's a greater challenge the wider the field stop, but in the final analysis whether the divergence challenge is met is up to the eyepiece design.
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Mike

Bill Meyers said:
Has anyone tried Barlowing an Ethos?

Yep, do it a lot. It's 5.9mm with the 2x TV Barlow, which is the best combo I've tried. I've also tried the 2x Tak (almost as good, but inferior at the edge), 2.2x Klee (OK, but the Klee needs baffling improvements, IMO, and I sent it back after one session), and Meade #126 (good on-axis but quite bad at the edge of field). To give you some idea of the view with the 2x TV Barlow, I set this up in my 7" f/6.7 Newt and watched the E and F stars in the trapezium as it drifted literally from one edge of the view to the other. It's not even that good without the Barlow. There's some lateral color, but I haven't really compared the amount to that without the Barlow to ascertain what role the Barlow may be playing in this. I should add that with the 2x TV Barlow it has given some of the best views of Mars I've had this year.

I can only imagine that it would be as good or better in a 2.5x Powermate. I have considered it, but I don't want the extra weight or to move the eyepiece farther out from the focuser.
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Mike

Hi, Matt. Welcome back. The 20XW has a bit of field curvature like the 21XL. I don't remember if I tried it in a Paracorr or not, but I wouldn't have it straight up in my old 10" f/5 dob. Haven't heard any good things about the 21 Hyperion/Stratus, all bad. The 24 Hyperion is a new thing, and I haven't tried one. The 22LVW is very good, and they can sometimes be had for less than $150 here. That was the last eyepiece I had that met your description. I sold it (and almost everything else) to get a 13mm Ethos.
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Mike

Warren James said:
Looking for 10-20mm range for lunar/planetary use.

I don't know about "ultimate" anything, but this is what comes to mind off the top of my head:

10mm, 12mm, 14mm, or 16mm TMB Supermono (especially the last two focal lengths), but these longer focal lengths are increasingly hard to come by.

12mm or 18mm University Optics HD or Baader Genuine Orthos

11mm, 15mm, and 20mm Tele Vue Plossls

Some people like Brandons, too. I remember Jeff Medkeff speaking highly of the 16mm Brandon.

Right. It's not uncommon for a newbie to come in with expectations that haven't been calibrated to the market. Your expectations are more realistic. Personally, I prefer the newbies who ask for too little, but they come in both varieties.
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Mike