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What IS a Planetary eyepiece?

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#1 tag1260

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Posted 08 January 2013 - 12:53 PM

What make an eyepiece a so called Planetary? Is it the size, the design, or what? Is a 5mm TMB Planetary just a 5mm eyepiece with a gimmicky name or is there something special that make it a planetary. Inquiring minds need to know!!!

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#2 dpwoos

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Posted 08 January 2013 - 01:07 PM

What makes a "sports" car?
 

#3 keroppilee

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Posted 08 January 2013 - 02:21 PM

the only factor i can think of that ISNT up for personal preference (FOV and such) would be fairly high magnification.
 

#4 dpwoos

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Posted 08 January 2013 - 02:31 PM

Even magnification depends on the focal length of the scope.
 

#5 Jim Rosenstock

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Posted 08 January 2013 - 02:46 PM

Heck, we don't even know what a Planet is, anymore.

I had a great planetary eyepiece, but I made the mistake of looking at Pluto with it.

Now it's just a "minor eyepiece".... :tonofbricks:
 

#6 Dave Ittner

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Posted 08 January 2013 - 02:48 PM

+1
 

#7 David Knisely

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Posted 08 January 2013 - 02:50 PM

What make an eyepiece a so called Planetary? Is it the size, the design, or what? Is a 5mm TMB Planetary just a 5mm eyepiece with a gimmicky name or is there something special that make it a planetary. Inquiring minds need to know!!!

Thanks


It is just an eyepiece that yields the higher power needed to view detail on the moon and planets. Some people require it to be limited in design complexity (as few elements as feasible) and high in coating quality to reduce the amount of scattered light in the field, but other people use "planetary" eyepieces that have many elements. Many so-called "planetary" eyepieces have focal lengths smaller than around 15mm, but in a very long focal length telescope, this may not be true. The same goes for apparent field of view, as some people who call an eyepiece a "Planetary" eyepiece often feel their fields of view are less than around 60 degrees. Again, this isn't universally so. One of my favorite eyepieces for planetary viewing is my 8-element 5-8mm Speers Waler variable focal length eyepiece with a whopping 78 degree apparent field of view. It violates both ideas of limiting the number of elements and limiting the field of view. In the end, whatever eyepiece you like to use to get the powers you need for viewing the planets will be a "planetary" eyepiece for you. Clear skies to you.
 

#8 tag1260

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Posted 08 January 2013 - 02:54 PM

OK. Sounds like it's just a marketing hype when you use the term "Planetary Eyepiece". As was stated it could be anything in your arsenal.

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#9 Tank

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Posted 08 January 2013 - 02:55 PM

Best in these areas:
light transmission
scatter control
Contrast

Main due to:
minimal glass elements
coatings
polish
 

#10 BillP

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Posted 08 January 2013 - 02:57 PM

A "planetary" eyepiece is one that is optimized for the task of planetary observing - simple as that. Classically, this has been considered to be an eyepiece that shows the least distortion to the image (hence the Abbe design becoming popular for this as it has an "orthoscopic" field of view), and an eyepiece which best preserves image brightness and contrast (hence why minimum amount of glass is usually noted as less glass means brighter and higher contrast since less optical elements and surfaces to scatter and absorb light).

So those are IMO the classical views of planetary eyepieces. Today however, with technology marching on, this is getting challenged. With latest multicoating technologies element count "can be" increased and still retain outstanding transmission and contrast. More elements also means wider AFOVs and better eye relief also, which can be benefitial traits for a planetary eyepiece. So today there are some challengers to the classic planetary such as the Pentax XW series, Leica Vario ASPH Zoom, and the TV Ethos for many.

In the end, IMO, the general characteristics of a "planetary" eyepiece would be:

1. Maximum Transmission possible compared to other eyepieces (i.e., best coatings and least glass)

2. Maximum Contrast compared to other eyepieces (i.e., best polish for least scatter, best application of the coatings for least scatter, elimination of all stray light within the eyepiece for least scatter)

3. Lack of Visible Distortions (or greatly minimized) compared to other eyepieces (i.e., an orthoscopic field of view and so the view stays as true to what the telescope is producing; no/little visible AMD and RD so planets stay round and linear features do not bend when near field stop)

4. Neutral Tonal Quality compared to other eyepieces (i.e., does not impart a hue or coloration to the view in any way so the view stays as true to what the telescope is producing)

------Nice to Haves------

5. Longer eye relief for more comfortable extended viewing

6. Larger AFOV for longer drift times in non-tracking scope mounts

Note - while there may be planetary eyepieces here and there, most all eyepiece lines I do not consider planetary because they do not offer focal lengths that are very close together. TMB Supermonos are an exception with focal lengths in 1mm increments from 4mm to 10mm. But in reality, when considering both fast APOs and slow SCTs, really need 1mm increments from 3mm to 14mm IMO to be considered a planetary "line"...or a zoom with this range.
 

#11 Monoeil

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Posted 08 January 2013 - 03:06 PM

You are lucky. My planetary eyepieces show me planets ONLY, unless it is because of the light pollution... I am not sure. Maybe I should buy some deep sky eyepieces? :question:
 

#12 tag1260

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Posted 08 January 2013 - 03:16 PM

Well, you all knew this was leading up to another question. What is a good planetary to consider under $100 ? I already have a 12mm Paradigm and I have an 8mm on it's way. I use a 12" f/5 dob scope which I'm sure will make a difference. I have enough money left in my eyepiece fund for one more.

Thanks
 

#13 JohnMurphyRN

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Posted 08 January 2013 - 03:34 PM

Well, you all knew this was leading up to another question. What is a good planetary to consider under $100 ? I already have a 12mm Paradigm and I have an 8mm on it's way. I use a 12" f/5 dob scope which I'm sure will make a difference. I have enough money left in my eyepiece fund for one more.

Thanks


ES82 6.7mm or just maybe 4.7mm
 

#14 Starman1

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Posted 08 January 2013 - 03:38 PM

Well, you all knew this was leading up to another question. What is a good planetary to consider under $100 ? I already have a 12mm Paradigm and I have an 8mm on it's way. I use a 12" f/5 dob scope which I'm sure will make a difference. I have enough money left in my eyepiece fund for one more.

Thanks

Well, the Paradigm should be OK.

What is a planetary eyepiece? Any eyepiece you use to look at planets with.
A non-planetary eyepiece can become one with a Barlow lens to up the magnification. Your 12mm becomes a shorter focal length when used with a Barlow.

The sad truth is that the difference between the very best and only average eyepiece is of a considerably smaller scale than the difference in seeing from night to night and even hour to hour. My lifetime-best view of Jupiter was with 18 elements in the focuser (!) at 456X. But seeing was essentially perfect in every way. Even my 12.5" was "aperture-limited" at that time.
It's a shame there was no really big scope nearby on that night.

What you need, when the seeing is like that is:
--sufficient aperture
--high magnification
--a cooled and collimated scope.
--a decent eyepiece and scope.

That's about it.
 

#15 dpwoos

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Posted 08 January 2013 - 03:45 PM

One of my favorite eyepieces for planetary viewing is my 8-element 5-8mm Speers Waler variable focal length eyepiece with a whopping 78 degree apparent field of view.


Not being an eyepiece "collector" I don't covet a lot of eyepieces. However, the SW 5-8 variable is one I would love to try! These are hard to come by, and I have never even seen one. Enjoy it!
 

#16 BillP

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Posted 08 January 2013 - 05:08 PM

The sad truth is that the difference between the very best and only average eyepiece is of a considerably smaller scale than the difference in seeing from night to night and even hour to hour.


This is very true! However, I do not consider it a sad truth but a wonderful truth to be capitalized on because it means with the proper "planetary" eyepiece I can see a planet both a little better and a little more :D

To give an example of the other side of the scale...my all time best view of Mars was with a singlet sphere lens...one element contrast rocks :rockon:

btw, isn't it cool when the views become aperture-limited instead of atmosphere-limited! I had an evening a few years ago where I ran out of eyepieces and multiply stacked Barlows as the view just stayed crystal clear no matter what insane magnification I was using. It was 3am and I was looking at my scopes (had a 5" and a 10" out) wondering how they were doing what they were doing. Moments like these makes one understand just how much we are limited by the atmosphere.
 

#17 Starman1

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Posted 08 January 2013 - 06:15 PM

2003 apparition of Mars. 5" Maksutov, 1540mm focal length, 4.7mm Meade Series 4000 UWA eyepiece, magnification 328X.
NO scintilation of the image at all for 29 out of 30 seconds and so much detail visible in albedo features I decided to try something I'm not good at--sketching.
I made a map showing everything I could see and, using a good map later, identified about 50 named features on the planet. I really got to see what "aperture-limited" really meant.

October, 1987, Saturn high in the sky, 7" f/12 AstroPhysics refractor, Parks 3.8mm eyepiece in 2X Barlow, 1123X (!). We saw spokes hovering above the grooved rings, many belts and storms on the disk, Cassini's division all the way around, the Encke Minima, and, every now and then, a glimpse of the Encke Gap at the ends of the oval. Seeing contrast variations within the rings was unexpected, and the image is burned into my brain. Again, no scintillation of the image at all, and aperture-limited.

Eyepieces used? Garden-variety, whatever-was-available types.
Images seen? Stupendipity!
 

#18 SteveTheSwede

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Posted 08 January 2013 - 06:42 PM

Heck, we don't even know what a Planet is, anymore.


I know this was a joke, but I can't help pointing out that it's the exact other way around. Prior to when Pluto lost its status as a planet there existed no official definition of a planet at all. Since then there is one, so it's truer to say finally we know what a planet is :D

Steve
 

#19 csrlice12

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Posted 08 January 2013 - 06:50 PM

No definition created by man has withstood the passage of time.......
 

#20 Rick Woods

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Posted 08 January 2013 - 07:26 PM

Someone once asked me if his guitar was a "jazz guitar". I said it was if he played jazz on it.
Same principle here.
 

#21 Paul G

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Posted 08 January 2013 - 07:52 PM

Someone once asked me if his guitar was a "jazz guitar". I said it was if he played jazz on it.
Same principle here.


+1
 

#22 Paul G

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Posted 08 January 2013 - 07:55 PM

Best in these areas:
light transmission
scatter control
Contrast

Main due to:
minimal glass elements
coatings
polish


Planets are usually so bright that light transmission isn't really important. 10% either way shouldn't make any difference. Scatter control and its effect on contrast is most important IMO.
 

#23 ibase

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Posted 08 January 2013 - 08:00 PM

Viewing a planet entails a lot of EP time to glimpse those otherwise unseen surface details which are visible in those fleeting moments of atmospheric stability. If one is not viewing comfortably, then the tendency is to call the night earlier than what would have been a longer run if the EP used was a high-comfort one (i.e., with good eye relief). Retiring earlier means missing out on those prized minute planetary details altogether even if one were using the uber-premium "planetary" EP. If scope used does not track, a wider AFoV EP is a plus (at least 70-deg AFoV where "widefield" starts). Couple that with good power and great transmission & contrast for a clear crisp image and sharp to the edge view that stays longer to observe before nudging, and you've got the ideal "planetary eyepiece." Among the EP's that I own & use frequently for this purpose, Televue's Delos 6mm fits the bill - generous eye relief (20mm), wide AFoV (72-deg), good power to pull in details, and great crisp images up to the edge of view. Just my 2 cents.

Best,
 

#24 Tank

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Posted 08 January 2013 - 08:02 PM

One of my favorite eyepieces for planetary viewing is my 8-element 5-8mm Speers Waler variable focal length eyepiece with a whopping 78 degree apparent field of view.


Not being an eyepiece "collector" I don't covet a lot of eyepieces. However, the SW 5-8 variable is one I would love to try! These are hard to come by, and I have never even seen one. Enjoy it!


Its a very good planetary performer and a very great all round EP:

Attached Files


 

#25 johnnyha

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Posted 08 January 2013 - 08:04 PM

For actual viewing of planets I prefer binoviewing, I can bino ortho and plossl pairs for hours with no strain at all. I see more detail with two eyes and floaters are virtually eliminated.
 






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