Author Topic: "Planetary" Eyepieces  (Read 1214 times)

ceusesugua

  • Active Astronomer
  • ***
  • Posts: 119
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
"Planetary" Eyepieces
« on: December 30, 2017, 12:49:07 PM »
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

  • Active Astronomer
  • ***
  • Posts: 113
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #1 on: December 30, 2017, 11:35:00 PM »
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

  • Active Astronomer
  • ***
  • Posts: 130
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #2 on: January 04, 2018, 04:39:31 PM »
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.

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

  • Active Astronomer
  • ***
  • Posts: 134
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #3 on: January 08, 2018, 09:31:52 PM »
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.

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.
Ok, perhaps other owners of that particular scope can give you better advice. Which scope?

Jeffrey Hunter

  • Active Astronomer
  • ***
  • Posts: 116
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #4 on: January 11, 2018, 08:51:37 AM »
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?

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.

tissuppgunre

  • Active Astronomer
  • ***
  • Posts: 105
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #5 on: January 11, 2018, 08:51:57 AM »
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?

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.

asexdalo

  • Active Astronomer
  • ***
  • Posts: 118
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #6 on: January 12, 2018, 09:22:55 AM »
Most TMB's for sale new today are china made clones with 5 elements and they are not what they used to be.The original TMB's were just a little less good than Televue Radians, which are a step below current Delos, Delites, Pentax XW's.Oldies that can surpass the aboves are Zeiss, Clave, TMB Monos, some Japan made orthos that you will almost never run into that are just as expensive as TV's and XW's.So what can you buy new today, Plossls man, made in Taiwan, Brandon made in usa(?).Almost nothing made in China would I consider good enough for planets.

Chris Jiles

  • Active Astronomer
  • ***
  • Posts: 116
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #7 on: January 13, 2018, 08:45:54 AM »
Since the seeing is the most important factor that determines whether you'll get to observe the fine details visible in our solar system or not, the use of fixed focal length eyepieces may not always be the best choice. On the other hand, an excellent zoom eyepiece can give you the right power at the right time when the seeing changes for the better or the worse. That's of course for some of us who would rather observe than switch eyepieces all the time. Fine zooming eyepieces such as the Leica, Baader and Televue Nagler 3-6 solved the aforementioned issue years ago. You can always equip yourself with a high quality ocular of a specific focal length that usually matches your best seeing conditions, but chances are the good zoom will be used more often than this luxury item. In addition, the difference in visible details and presentation between the high end less glass eyepiece and the quality zoom will most definitely not make your jaw drop !

George

cytiwitqua

  • Active Astronomer
  • ***
  • Posts: 115
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #8 on: January 13, 2018, 12:23:12 PM »
Even though they have a very narrow FOV I still think my University Optics Orthos have always out performed other eyepieces for planets. I do have a set of pre-Chinese TMB planetaries and in my opinion the UO still out perform them. For me common sense tells me less glass, less chance for reflection in the eyepiece.

sanddotshanpens

  • Active Astronomer
  • ***
  • Posts: 112
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #9 on: January 13, 2018, 04:07:00 PM »
Is your tube flocked? Do you let the cooling fan cool the interior to ambient before settling in to view the planets? Is your viewing site free from neighborhood house and street lights? If not, an extension light shield on the front of your tube might preserve image contrast.

It should go without saying how critical collimation is to avoid smearing out of fine details.

Good used orthos show up on the classifieds here fairly often, and moderately priced that you might want to try them first. Perhaps a 6mm or 7mm?

OTOH, with an untracked scope like yours, the narrow FOV of orthos might be a negative, compared to planetary EPs with ~60 degree FOVs.

ciomapicsta

  • Active Astronomer
  • ***
  • Posts: 128
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #10 on: January 16, 2018, 01:53:19 AM »
Nothing wrong with "good" old fashioned ORTHOS (unless you need long ER), especially if it's just the planets and you have a 'tracking' scope. 4 elements / a few ounces / and NOT a lot of $$$. If you need longer eye relief - well, then you need a more modern/sophisticated design / more elements and a LOT more $$$. Just my two cents. M11Mike

Mark Rivera

  • Active Astronomer
  • ***
  • Posts: 123
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #11 on: January 23, 2018, 08:02:24 AM »
Quote
Even though they have a very narrow FOV I still think my University Optics Orthos have always out performed other eyepieces for planets. I do have a set of pre-Chinese TMB planetaries and in my opinion the UO still out perform them. For me common sense tells me less glass, less chance for reflection in the eyepiece.

Sadly, University Optics has closed, as the owner has retired. Their orthos may be available used. The last generation of orthos they sold are identical to the Kokusai Kohki, Fujiyama HD-OR Orthoscopics available from Agena Astro Products. They are good eyepieces if you don't mind the 42 degree AFOV, and the eye relief gets awfully tight at focal lengths of 7 mm and below. They are still noticeably better on eye relief than Plössls though.

slotiniphin

  • Active Astronomer
  • ***
  • Posts: 116
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #12 on: January 30, 2018, 06:05:59 AM »
Quote
Since the seeing is the most important factor that determines whether you'll get to observe the fine details visible in our solar system or not, the use of fixed focal length eyepieces may not always be the best choice. On the other hand, an excellent zoom eyepiece can give you the right power at the right time when the seeing changes for the better or the worse. That's of course for some of us who would rather observe than switch eyepieces all the time. Fine zooming eyepieces such as the Leica, Baader and Televue Nagler 3-6 solved the aforementioned issue years ago. You can always equip yourself with a high quality ocular of a specific focal length that usually matches your best seeing conditions, but chances are the good zoom will be used more often than this luxury item. In addition, the difference in visible details and presentation between the high end less glass eyepiece and the quality zoom will most definitely not make your jaw drop !

George


George:

Your jaw may well drop when you realize there's little or no difference in the detail seen in the zoom and the less glass eyepiece.

My definition of a planetary eyepiece is any decent eyepiece of the appropriate focal length placed in the focuser of a telescope with decent optics and sufficient aperture during periods of good seeing.

In the 16 inch Dob that the OP is considering, well corrected, wide field eyepieces with a reasonable amount of eye relief have many benefits...

Jon

Kyle Styles

  • Active Astronomer
  • ***
  • Posts: 119
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #13 on: January 30, 2018, 02:49:16 PM »
A planetary eyepiece is the one in the focuser at the time.

unllamerblood

  • Active Astronomer
  • ***
  • Posts: 132
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: "Planetary" Eyepieces
« Reply #14 on: February 04, 2018, 11:26:26 AM »
.......and its likely to be in the focuser if I find it comfortable and like looking through it.