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What is a planetary eyepiece?


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Is there something special about an eyepiece that is advertised as "planetary"?

If you have two eyepieces that are same focal length and FOV, but one is planetary, aren't they the same?

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"All the same" is not my experience at all. I use Orion (USA) 'Edge-On" planetary EP's with my f/12 'frac. On nights of excellent seeing, I see a big difference between these and the otherwise excellent Parks plossls I usually use.

I don't have Naglers - and will probably never be able to afford one, but that isn't an issue for me. The detail on Saturn was amazing - and my views with my 133mm 'frac and a 6mm planetary were crushing the views to be had with a 250mm dob that night. Far more contrast, and much better resolution of detail.

Can't speak to their performance in a fast dob - haven't compared them side by side, so to speak. Maybe a project for the summer when I'm done grading exams...... :D

Dan

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I think in general you are quite right about your 'all the same' comment but good quality is easier to achieve across the field if you use less glass and a narrower field of view plus offer tighter eye relief.

thankfully planets are small and take less field up so you can use a narrow field and short eye relief and this means less glass which in principle allows more light through, more contrast and more detail.

if you can spend the value of an Ethos/Nagler/Nirvana/UWAN etc, you will get all of the above and more eye relief and a wide field.

if you want to get the same quality much more cheaply and can observe with short eye relief then Orthoscopics (I use Baader Genuine Orthos) and Plossls (I use TV Plossls) of good quality will give just as good a view on planets, in some opinions, better.

BUT don't make the mistake of thinking that a planetary eyepiece is restricted in anything other than field of view. I find Orthos to be excellent for all objects as long as they fit in the narrow field.

the key is the basic quality of the eyepiece, whether you can use short eye relief and whether or not you have a driven mount - there's no doubt that it's easier to use orthos with a driven mount.

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Basically just sales pitch. Short focal length ep's all do the same.

My response was in answer to your question "If you have two eyepieces that are same focal length and FOV, but one is planetary, aren't they the same?" Forgive me if I have caused confusion by my first post due to my reading the question wrong :D

What I meant is that short FL EP's are short FL EP's. They all do the same in that they will in any given scope give you the same magnification showing the same size planet "planetary" or not "planetary". As Dan & Shane said there are better qualities to some brands over others regards eye relief or contrast but as far as "planetary eyepiece" is concerned this is just a sales pitch and as said by others any good quality EP will do the job.

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I agree with you matey. in fact what you said is correct. the do all do the same - they provide the same magnification and size of image. where they differ is in the quality/field of view/contrast/sharpness etc (and of course price!) as we all mention. we were all singing from the same hymn sheet but each from a different corner :D

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Precisely correct, lads!

I have an old 5mm ortho I gave $35 for brand new, and it gives the same magnification and image size as the pricey EP's. I've also drooled over the $600 TeleView offerings... who hasn't??? 20x the cost doesn't give 20x the image quality, however - the law of diminishing returns is in full force here; and it is that last 5% that will really cause you a smoking hole in the wallet. ;)

There's also the spouse question for many of us - how to convince the love of our lives that we need that last 5% of performance - no matter what the cost! :p

Dan

I agree with you matey. in fact what you said is correct. the do all do the same - they provide the same magnification and size of image. where they differ is in the quality/field of view/contrast/sharpness etc (and of course price!) as we all mention. we were all singing from the same hymn sheet but each from a different corner :D
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definitely the case Dan with optics. Look through a £100 pair of binoculars and a £1000 pair and you'll see a difference but not by a factor of 10!

I'm lucky as my wife Julie, always needs a new pair of shoes or a Pandora bead and I think gradually she's coming over to our way of thinking! In some ways, I find the wider field eyepieces a bit distracting when it comes to planetary observing.

Also, I sometimes find the moon tricky to observe with the 13mm Ethos I have and much prefer the narrower fields for that sort of image.

We all have slightly different preferences of course and thankfully the manufacturers also see this as a sales opportunity and have created a vast range of eyepieces to match those preferences.

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Thanks so much for your responses. As you'll see in my other thread, "GSO eyepieces - bargain or false economy?", I'm narrowing my target on some budget EPs as my first upgrade. Thanks again.

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