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5mm eyepiece for planatary views


ddtwelve12
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The Hyperion will be softer at the edges of the field of view but should be pretty sharp in the central area. Maybe 240x is just too much magnification with the seeing conditions not having been that great lately and Jupiter (if thats been your main target) not being too receptive to high magnifcations ?

I'm just wondering if the eyepiece is really the issue here ?

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My X-Cel LX is pretty good.

Certainly no softening, I can let Jupiter drift from side to side with no decrease in clarity.

But I'd agree with John, It's not one I use much.

On the moon I tend to use an 8mm with a 2x barlow.

On Jupiter, most of the time, the 6mm is as good as it gets.

Lately, I've been using the 7mm and 8mm more.

But just to be perverse!

The other night I managed to put the 8mm and 2x barlow together and get some pretty decent views as the image drifted in and out of clarity.

I was pleased with it because it had been what I'd been seeing through the 7mm and 8mm on previous occasions anyway.

The 5mm was good too, on that night, but I think the 6mm still gave the stillest and clearest views.

It'll be totally dependent on the seeing conditions.

I bought my X-Cel LX second hand, so it has been worth the investment.

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At a reasonable budget the 2 options would seem to be the X-Cel or the BST at 5mm.

They seem to perform very much the same (as in identical) and perform well.

The X-Cel may have a slight advantage in that they do a 7mm as well, so when the 5mm was too much the 7mm might pro0duce the views.

If a 6mm were optional then the WO 6mm planetary seems to get consistantly good reports.

After that you are likely looking at ES, and similar, eyepieces and no experience of these.

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I agree with John, the most probable reason of soft image (assuming you were watching Jupiter with the 5mm) is that seeing didn't support it.

5mm eyepiece gives 0.83mm exit pupil in your f6 scope (5/6), that's about the smallest exit pupil (or maximum magnification, whichever way you want to put it) you want to use for planetary observation, and it works only in very good seeing, which happens a couples of times a year, if you do observations regularly, ie.

Buying a new 5mm eyepiece looks like throwing money away to me.

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With your scope I would use a 6mm (200x, 1.0mm e.p) when the seeing is good. I would not go shorter than 7mm (171x, 1.2mm e.p.) on average seeing. 

5mm seems just too much as others already pointed out, unless the seeing is excellent.

If you don't have a 12mm and are considering a barlow, I would go for a good 12mm. In this way, you get a good 100x, 2.0mm e.p for DSO, and 200x, 1.0mm for planets and doubles.

Just a thought   :rolleyes:

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A few months ago an observing buddy brought his TSA 120 triplet round to my observatory with the purpose of trying out my eyepieces. I use Pentax XW's for lunar and planetary observing, my friend used a collection of Hyperion eyepieces. Bear in mind that he is a seasoned planetary observer with over 40years experience. He's also a Brummi who lives in Yorkshire and suffers from the Short Arms, Long Pockets Syndrome. (He doesn't like to spend much!).

After a rather prolonged trial using both his Tak' triplet and my 120 ED doublet, and plenty of cursing on his part, he departed. A week or so later his eyepiece collection had three new additions comprising of a Pentax XW 10mm, XW 5mm and XW 3.5mm. He is still thrilled with his purchase. They are not cheap but well worth considering if you want one of the best eyepieces available.

If you have the book "The Backyard Astronomers Guide" by Dickinson & Dyer, on page 75 author Dyer states that "We love the Pentax XW's, especially the higher power models.....14 to 3.5mm." He then goes on to state that "they provide both razor sharp, high contrast views of both deep-sky and planets." Dyer goes on to say that if he were restricted to just one eyepiece line, it would be Pentax XW'S.

Mike :-)

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The 5mm in my collection is for when the seeing is really good. It doesn't get used much. But on those rare occasions..... Worth every penny. If I were restricted to just one, I would head for a 6 to 8mm offering.

If you are not in the XW / Delos spending league, have a look at the Vixen SLV range. I am very happy with mine as planetary eye pieces.

Paul

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I've recently bought a 12.5 mm Altair Lightwave LER  "planetary" eyepiece from Green Witch for £45. I believe they are "similar"  (but maybe not the same) as the Williams Optics SPLs. Altair do them in 5mm and 6mm. The guy at Green Witch said they compared well with the X-Cel LXs but they are 55 as opposed to 60 degree afov. Typically I cannot tell you how it performs cos of the usual curse so all I can do is flag it as another option. Good solid looking and nicely turned out EP though at the price.

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If you can buy a second hand 6mm WO SPL you wont be disappointed. That will give a 1mm exit pupil, as the 6mm matches your focal ratio, a good starting point,  ideal for Planetary  work at 200x power  ( under the right conditions?)  but atmospheric conditions and our own eyes can be the culprits. I don't bother looking of axis too much. I can track very smoothly, so I tend to view primarily on axis, I have too, as the image scale is small on an 8".

 We can advise all night, and will,  but no matter what the eyepiece, it can only be your eyes and perception that makes it the 'best eyepiece'

Edited by Charic
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The 5mm in my collection is for when the seeing is really good. It doesn't get used much. But on those rare occasions..... Worth every penny.

Paul, your experience more or less confirm the exit pupil I mentioned, your scope is f4.7, 5mm eyepiece gives 1mm exit pupil in yours, and it still doesn't get used much. 5mm eyepiece in OP's f6 scope gives about the same exit pupil as 4mm eyepiece in a f4.7 scope, i.e, the same usefulness.

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Paul, your experience more or less confirm the exit pupil I mentioned, your scope is f4.7, 5mm eyepiece gives 1mm exit pupil in yours, and it still doesn't get used much. 5mm eyepiece in OP's f6 scope gives about the same exit pupil as 4mm eyepiece in a f4.7 scope, i.e, the same usefulness.

The 1mm exit pupil seems fine. It is the atmosphere that lets the side down. I thought that image degradation due to atmospheric stability was independent of exit pupil limitations.

I am a novice in this area (ok. And the other areas too). Happy to stand corrected.

Paul

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Yes, it is seeing doing the degradation, but why your 6mm handles the same bad seeing better than 5mm? The difference is the exit pupil size. :smiley:

I'm sorry, but I'm not sure what you are talking about. :)

So, when the seeing is worse so I can't use the 6mm and have to drop back to the 8mm, that's the exit pupil?

And when the conditions are so bad that not even my 20mm gives any clarity, that's down to the exit pupil?

And, and when the other night an 8mm and a 2x barlow (300x) was as good as the 6mm had been the previous night, that's the exit pupil too?! :D

Now I'm confused.

The WO SPL 6mm is smashing. :)

Edited by bingevader
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Thinking in terms of exit pupil is a valuable thing to do, as our eyes are diffraction limited from about 2mm - .8mm exit pupil. http://www.telescope-optics.net/combined_eye_aberrations.htm I find that my own eyes operate well down to .8mm exit pupil, which of course gives different magnifications in different scopes.

If thinking in terms of one telescope, the mag can be figured out at whatever exit pupil and then just use the proper mag EP for the conditions.

Exit pupil can used for whatever telescope discussed, eventhough the mags will most likely be different. This concept is important for choosing EP's for filter use, for galaxy observing and of course for lunar/planetary. http://www.lumicon.com/pdf/3filterspec_prnt.pdf

In my VX10 a .8mm exit pupil gives about 311x and when seeing permits I use this often, on the planets and the moon.

Edited by jetstream
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I agree with Jules. Steer clear. I have a Skywatcher 9mm UWA  66 degree (which is what these are) and it was "disappointing" on my  F5 scope and not that much better on my Mak. You should be able to put £35.00 to something much better.

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I would go for the 6mm Delos, a fine eyepiece which I reviewed some time back. I have the 5mm XW as well which is in the same class but this F/L for me on your scope is a bit too much for everyday views. The 5.5mm Meade was also reviewed by me and as NicK said is a very good eyepiece without emptying the pockets, it may even be in the same report as the Delos.

Alan 

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