Planetary Eyepiece for 8 inch dob?
I'm having trouble deciding which planetary eyepiece to get for my 8 inch dobsonian, my budget is around 150$ and I was wondering whether a good amount of eye relief is too much of a quality sacrifice.
The four that I have been looking at are;
Celestron Ultima LX - 5mm
Vixen NLV Lanthanum - 5mm and 6mm
Baader Hyperion - 5mm
Baader Genuine Orthoscopic - 5mm and 6mm
Any advice for about these or suggestions for others in my budget?
Do you already own a barlow lens? If not, you might consider getting one. I'm partial to Orthoscopics, and many will tell you give the best planetary performance but eye relief IS important, especially when you go below 9mm, it begins to get pretty uncomfortable (but Plossls are worse in that regard). With a decent quality Barlow lens you could use a longer focal length Orthoscopic and have a much more comfortable viewing experience.
You might balk at using a barlow, preferring a more "pure" viewing experience without the possibility of further lens elements degrading the image, but the fact is that these other types with the long eye relief ALL incorporate a barlow-type lens element in their design.
The only advantage that these other designs have over a barlowed Ortho is a significantly larger field of view. This translates to not having to nudge the telescope quite as frequently to place the target back in the field of view, and at 5 or 6mm that is a significant consideration. On the other hand, while decent, they may not be quite as sharp as with an Ortho, especially getting out from the center of field. If you're concerned with eking out the most detail from a well collimated scope in excellent seeing conditions (think steady air, hardly any twinkling from stars) then I personally think that Orthos are worth the other disadvantages.
However, I have not had any personal experience with the other eyepiece types in discussion. You might want to check out Cloudynights.com and their forum for other possible viewpoints/reviews.
Vixen 2 NLV Lanthanum Eyepiece 50mm 39302
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