Quote:
Originally Posted by Stonius
Last time I used a short (4mm) Plossl, was with the 60mm Tasco Refractor I had as a kid, and I remember it being quite an uncomfortable experience.
Now to be fair, that scope wasn't built for that kind of magnification, and without a tracking mount it was an exercise in futility that has scared me off Plossls ever since. There was also something incredibly annoying about having your eyelashes hit the lens every time you blink.
But the 'less glass' thing makes sense to me, plus they're fairly cheap, but the TV ones only go up to focal lengths of 8mm with 6mm eye relief.
Yes you can barlow it, but then you might as well use a Nagler because you're introducing more glass anyway, but if you don't then, 8mm isn't really *all that* short, is it? If conditions suffice, wouldn't you *want* shorter focal lengths?
I also struggle to understand the use for a 50mm Plossl for? My understanding is that wouldn't even work in a binoviewer. Surely at those focal lengths it's outperformed by other EP's with similar field of view?
So I guess what I'm asking is whether my FOMO is justified? People who have tried / own them, was it a slight incremental improvement, or was it an 'Aha' moment?
So far I've been pretty happy with my Pentax XW's, but maybe my memories of that 4mm in my tiny refractor are making me unfairly biased?
Markus
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The "less glass" idea only works if the optics are equal.
I think the idea got started by people comparing cheap 3 and 4 element eyepieces with cheap 6 and 7 element eyepieces.
If, on the other hand, the lens polish and coatings are superior on the multi-element eyepiece, it might be the case, and I've seen this, that the multi-element eyepiece might actually yield a better image. My TeleVue Delites yield a better planetary image in my 4" apo than Plössls do.
Add to that the fact that most eyepieces are pretty much the same on axis, i.e. yield a spot size smaller than the Airy disc, and the differences are largely outside of the on-axis view.
That would matter a lot if you use a non-tracking mount and want to watch the planet or Moon image as it drifts across the field. If you do that, then there are definitely some 70° eyepieces that are better than the "less glass" types.
The light loss through an 8 element eyepiece might be as much as 1-2% more than a simple 4 element eyepiece, and that is unnoticeable to the eye and hard to measure in a lab, so we can ignore that difference. It simply won't matter.
So, stick to your XWs (the eyepieces Daniel Mounsey on cloudynights.com called the "best widefield planetary eyepieces" in a couple reviews a few years ago.[He's a hardcore planetary and double star observer].
4mm and 5mm Plössls are best used as telescope "dustplugs".