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Excellent review!

Not only was this review very well-written, it was done so in a manner that users of all levels can understand and appreciate. The use of photographs aid in the overall review as well as the results of observing several objects through this particular EP.

Nice job!

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Good job, Tom.

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I'm very much encouraged by the photo where you hold the eyepiece up and show the "exit pupil". I don't see any signs of glare around that. I really can't use a 3mm (my scope is f/6.7), but I've been eyeing the 6mm and 12.5mm.

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What about your scope being F/6.7 makes a 3mm eyepiece unusable? Just curious what you mean by that.

Thanks!

Timm

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It's generally thought that, when an eyepiece's exit pupil gets below .5mm or so, you're getting into the realm of "wasted magnification", that no more useful detail will be seen despite the larger image size.

An eyepiece's exit pupil in a given scope is calculated by dividing the eyepiece's focal length by the scope's f/ratio. So, a 3mm eyepiece in a f/6 scope--regardless of aperture!--will give an exit pupil of .5mm. A slower scope (higher f/ratio) will result in a smaller exit pupil, and wasted magnification.

Now personally, I have gotten "nicer" views with higher magnifications and smaller exit pupils than the "standard" limit of .5mm. Perhaps if my own eyes were a bit sharper, I'd see it as wasted magnification, too....but maybe I just like obscenely big planetary images!

Very nice article, BTW. Unfortunately, I already have a couple of nice "ridiculous magnification" eyepieces, and am not in the market for any more, since they only come in to play during nights of the very best seeing, anyway....but it's nice to know there's another good option out there!

Clkear, steady skies,

Jim

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QUESTION AUTHORITY!
"errr....sez who??"

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What about your scope being F/6.7 makes a 3mm eyepiece unusable? Just curious what you mean by that.

Thanks!

Timm

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It's generally thought that, when an eyepiece's exit pupil gets below .5mm or so, you're getting into the realm of "wasted magnification", that no more useful detail will be seen despite the larger image size.

An eyepiece's exit pupil in a given scope is calculated by dividing the eyepiece's focal length by the scope's f/ratio. So, a 3mm eyepiece in a f/6 scope--regardless of aperture!--will give an exit pupil of .5mm. A slower scope (higher f/ratio) will result in a smaller exit pupil, and wasted magnification.

Now personally, I have gotten "nicer" views with higher magnifications and smaller exit pupils than the "standard" limit of .5mm. Perhaps if my own eyes were a bit sharper, I'd see it as wasted magnification, too....but maybe I just like obscenely big planetary images!

Very nice article, BTW. Unfortunately, I already have a couple of nice "ridiculous magnification" eyepieces, and am not in the market for any more, since they only come in to play during nights of the very best seeing, anyway....but it's nice to know there's another good option out there!

Clkear, steady skies,

Jim

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Thanks Jim,

Got it! Yes, in my scope the 3mm is producing 185X at an exit pupil of .43mm in my F/6.9 80mm scope. I find it to be usable, but only because of the comfort of the eye relief and size of the lens nearest my eye. I accomplished the same thing more or less with barlowed plossls but I found them to be extremely hard to get comfortable with to get to this magnification. Barlowing an Orion 6.3mm Highlight plossl is not a fun thing to use.

I tried the 6mm and 3mm SPLs on the comet last night and both worked well, but the atmosphere was wiggly looking in the 3mm, lots of twinkling stars, etc so the 6mm actually seemed to be the best eyepiece for it last night. On a steady night earlier in Summer, I had some suberb looks at Saturn with the 3mm SPL, but I found Jupiter to almost always be better with the 6mm SPL.

Clear skies,

Timm

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WO Megrez 80FD, Celestron C8
WO SWAN 33mm, UWANs 4mm, 7mm, 16mm, WO SPLs 3mm, 6mm, 12.5mm, WO Zoom II 7.5-22.5
WO EZTouch & Celestron Nexstar GT modified mounts
SV F50B2 Finder in WO Quick Release 50mm bracket

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