Posts Made By: Mike Hosea

I got a 20mm Ultra-wide of this type and thought it looked and acted like a $50 eyepiece. The coatings looked pretty, but as multi-coatings they were badly done with too much reflectivity. There were ghost images also (no surprise), and the exit pupil wasn't very cleanly formed. I disliked using it in my f/13.8 ETX as much as I disliked it in my f/6.7 and f/5 Newts. I'm no great fan of big Naglers myself, mostly because I refuse to use a Paracorr for convenience reasons in my 10" f/5 Newt, but from what I saw in the 20mm Ultra-wide, I wouldn't bet 25 cents that the 6mm Ultra-wide would stand up for 5 seconds against a 7mm or 5mm Nagler Type 6. Anybody wants to send me a 6mm Pro-optic, I'll be glad to do the comparison, but like I said, extrapolating from the 22mm, it doesn't make the cut on my list of things to do with $50.
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Mike

No. I mean, theoretically it will scatter a little light and cause diffraction damage about like so much dust, but the level of damage here is too small to see. With several dozen of those on a mirror I'd probably have it recoated, but just a few can wait until the next recoating some years down the road.
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Mike

I don't think people should get so hung up on color rendition. You will notice these differences primarily when switching back and forth during eyepiece comparisons. If you will just make a choice and stay with it for an extended time, I very much doubt that the amount of discernable detail and color differences will be significantly different, but you must give your eye/brain system time to adjust. I'm not saying that it doesn't make a difference--in fact it does slightly increase the contrast of some colors at the expense of others, just like a very weak color filter, but WEAK is the operative word.

For people who can't hold their head and eye steady, sometimes long eye relief is a bad idea because it leads to substandard performance that other observers with a steadier gaze needn't suffer. For example, you can generate "lateral" color on-axis in many eyepieces by moving your eye a bit off-axis. Not much detail is lost, generally, but this can't be good.

Sharpness does vary a bit, particularly at fast focal ratios where many designs may end up being a bit undercorrected. Smoothness of polish, quality of coatings, and design affect contrast and internal reflections. I sometimes do not like a very wide field when doing lunar viewing because the extra light will scatter a bit in my eye. It's the whole system, from objective/primary to the eyepiece to the eyeball and brain that we care about in visual astronomy. It may not be any technical fault of the eyepiece that it isn't the best choice for me in a certain situation.

Among currently available production eyepieces an inexpensive eyepiece may be the best choice in some cases. But I think it's just that rarely have eyepiece manufacturers devoted themselves to the task of designing and manufacturing planetary eyepieces that deliver uncompromised performance, particularly at today's faster focal ratios. That's why many of us are excited that TMB and AP are BOTH moving into the void. I really expect that the new TMB Monocentrics, which are better corrected with modern glass than classical monocentrics, will outperform all the inexpensive competition for planetary use, probably all the expensive competition as well, but that will no doubt be a hot topic of future debates, and I exclude the AP eyepieces being designed now from this comment because no sample currently exists and so no comparison has been done. However, we do expect great things from AP as well.
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Mike

I got one a couple of months ago.
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Mike

Terry,

Assuming the eyepiece is clean, it's a defect whether other people have it or not. If your scope is collimated, you should get the same softness as you approach the edge of field from any direction. Assymetrical performance is a smoking gun indicating a problem somewhere. An easier way to rule out the OTA is to rotate the eyepiece. If the bad portion of the edge rotates with the eyepiece, then you have it: there's a defect in the eyepiece. It may be fixable if a lens element is tilted, or cleanable, if a lens element is dirty, but I'd probably just return it for a replacement.
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Mike

Your 10" Dob should bury ANY 90mm scope on the planets if it is cooled and collimated. Of course a lot depends on the quality of the primary mirror (and secondary mirror for that matter). If you're not an ace at collimation, learn the ins and outs of collimation. It will be cheaper than a scope purchase and more rewarding. If you are an ace at collimation already and you're still not satisfied with the Newt, try an off-axis aperture mask, i.e. make a piece of cardboard to cover your scope's aperture. Then cut a hole off to the side of about 4" diameter, maybe a little less depending on the size of your secondary mirror, and position the mask so that looking through this hole you don't see either the secondary mirror or any spider vanes. Here is a very fancy example that is made to also hold a solar filter (just forget about the filter).

http://www.teleporttelescopes.com/Access/10MasFilNew.jpg

With the mask in place, your scope is now an unobstructed, off-axis Newtonian. Technically there is a tweak you might make to the collimation from this point, but it should be darn good if the scope is in collimation without the mask.
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Mike

Although the context is primarily microscopy, these are just fabulous.

http://www.microscopyu.com/tutorials/java/aberrations/curvatureoffield/index.html

http://www.microscopyu.com/tutorials/java/aberrations/astigmatism/index.html

http://www.microscopyu.com/tutorials/java/aberrations/distortion/index.html

Aside from the "matched coatings" that Nagler is using now and the extra cost of exotic glasses, there is the expense of working with some of these exotic glasses in the first place. Some of them require more skill and patience, and they can generate more scrap. The consumer MUST ultimately pay for all manufacturing costs, including labor and scrap. Personally, I think the price on the type 6 Naglers is very reasonable and you are just asking for a steal if you expect them to be near in price to the shorter type 1's. For one thing, type 6 Naglers are not scaled designs, and they are all about the same size and weight. Not surprisingly, the asking price is the same across the different focal lengths. The price isn't even that much more than the longer type 1's (maybe even a little less in the case of the 13mm).
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Mike