Astrophotography forum > Eyepieces Questions & Recommendations

"Planetary" Eyepieces

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ceusesugua:
One reads a lot of about "planetary" eyepieces on these forums. The key features seem to be low scatter and high transmission, to prevent damaging the most delicate contrast. Conventional wisdom says that you get this from four things: few pieces of glass, extremely good coatings, very smooth polish and good internal baffles.

This seems to culiminate in recommendations of orthos or other low lens count optics, such as supermonocentrics. The top end recommendations seem to be Pentax XO, ZAO and TMB Supermonocentrics.

How does this square with other lines, such as TMB Optical Planetary II? These seem to be used to meet the above goals, but have far more lenses (6!). This would seem to defeat the idea of low glass count optics, at which point wouldn't a well executed eyepiece of any kind (such as Delos) be just as good as TMB Optical Planetary II?

Finally, many other users advocate that well executed high-lens count designs (such as the Delos, Delites or XW lines) can look just as good on axis as the older traditional planetaries such as TMB Supermonos. I get a bit confused by this - is there a contrast enhancement available in such expensive and limited eyepieces, or not?

Artavius Murphy:
Oh, you've poked the bees nest now

There is no truth. Go to a star party, try simple and multi-glass, see what works for you.

tioteyclasbeat:

--- Quote ---Oh, you've poked the bees nest now

There is no truth. Go to a star party, try simple and multi-glass, see what works for you.


--- End quote ---
True, but with two toddlers at home I don't have time yet to get to a serious star party. My next major investment in improved planetary performance is probably a 16" scope, but I've been trying to untangle the arcane web of these near mythical EPs that I see get talked about.

Michael Shen:

--- Quote ---
--- Quote ---
Oh, you've poked the bees nest now

There is no truth. Go to a star party, try simple and multi-glass, see what works for you.


--- End quote ---
True, but with two toddlers at home I don't have time yet to get to a serious star party. My next major investment in improved planetary performance is probably a 16" scope, but I've been trying to untangle the arcane web of these near mythical EPs that I see get talked about.
--- End quote ---
Ok, perhaps other owners of that particular scope can give you better advice. Which scope?

Jeffrey Hunter:

--- Quote ---One reads a lot of about "planetary" eyepieces on these forums. The key features seem to be low scatter and high transmission, to prevent damaging the most delicate contrast. Conventional wisdom says that you get this from four things: few pieces of glass, extremely good coatings, very smooth polish and good internal baffles.

This seems to culiminate in recommendations of orthos or other low lens count optics, such as supermonocentrics. The top end recommendations seem to be Pentax XO, ZAO and TMB Supermonocentrics.

How does this square with other lines, such as TMB Optical Planetary II? These seem to be used to meet the above goals, but have far more lenses (6!). This would seem to defeat the idea of low glass count optics, at which point wouldn't a well executed eyepiece of any kind (such as Delos) be just as good as TMB Optical Planetary II?

Finally, many other users advocate that well executed high-lens count designs (such as the Delos, Delites or XW lines) can look just as good on axis as the older traditional planetaries such as TMB Supermonos. I get a bit confused by this - is there a contrast enhancement available in such expensive and limited eyepieces, or not?


--- End quote ---
The 6-element eyepieces are just the 4-element design with a 2-element barlow lens inserted in front. This makes the eye relief much longer and provides a wider FOV.  The "planetary" designation is marketing terminology. Just understand what you're getting.

Longer eye relief is good for "planetary" too, since you tend to stare for long periods vs. DSO. I do believe that eyepieces with 3 or 4 elements can offer superior contrast & performance. But many other factors can override this! For example if you move from a 12 inch scope to a 15-inch you'll see more, it won't matter which eyepiece you're using.

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