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Leica 20-60x or 25-50x or nikon zoom in F/5 newt?

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#1 btom

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Posted 23 January 2013 - 11:12 AM

I'm getting back into astronomy after a several year lay off. I have a 10" F/5 Royce mirror that I'm in the process of building a scope around. I currently have only pairs of 24 pans and 12.5 HD orthos that I used in my long gone bino. I've been seeing a lot of posts lately regarding 2 versions of the Leica zoom. I'd like to replace the 12.5 orthos with a zoom for deep sky observations and mate it to my barcon for planetary and lunar. I may replace the 24 pans as well with a cheaper wide field for star hopping. I don't think I'll get back into binoviewing for a long while. Now the question. If I'm not concerned with field size and am only concerned with highest contrast, lowest aberration, which of these zooms work best in a newtonian at F/5? Thanks!

#2 Aquarist

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Posted 23 January 2013 - 11:26 AM

Well for a moderately slow refractor it is highly recommended, for a fast scope, read this review: http://www.cloudynig...hp?item_id=2390

#3 btom

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Posted 23 January 2013 - 12:21 PM

Thanks Steve. Yes, I've read that review. The author apparently very much likes the newer aspheric version in an F/7 refractor. But the question I'm trying to get an answer to is which of the 2 versions would work best in an F/5 newtonian reflector? Or, is the price of the aspheric version warranted if AFOV is not of concern when using in an F/5 newtonian?

#4 johnnyha

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Posted 23 January 2013 - 10:39 PM

Tom the two Leica Zooms are reported to be the same superb image quality. Edge performance is not perfect at f5 but a Paracorr or barlow will clean it up nicely.

#5 t.r.

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Posted 24 January 2013 - 09:00 AM

Wouldn't the Vario outperform the Asph and be the better choice due to its smaller FOV as scope focal ratio gets faster? At least, as far as edge definition is concerned?

#6 btom

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Posted 24 January 2013 - 11:38 AM

Thanks Johnny and t.r. From you what you say, the Vario is probably the best choice for me. I'll be trying to locate one on Amart and I'm sure it will be quite a bit less expensive than the Asph. Also, I heard some folks have used a pair of Vario for binoviewing. Though I've also heard that the nikon may be better for that application...

#7 johnnyha

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Posted 24 January 2013 - 08:30 PM

Wouldn't the Vario outperform the Asph and be the better choice due to its smaller FOV as scope focal ratio gets faster? At least, as far as edge definition is concerned?

My guess is the size of the actual well-corrected area would be similar... :question:

#8 andydj5xp

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Posted 25 January 2013 - 03:14 AM

Wouldn't the Vario outperform the Asph and be the better choice due to its smaller FOV as scope focal ratio gets faster? At least, as far as edge definition is concerned?

My guess is the size of the actual well-corrected area would be similar... :question:


To add another thought: the OP's 10" F/5 reflector will yield 71x mag (exit pupil 3.6mm) and 142x mag (exit pupil 1.8mm) with the Leica ASPH zoom. These are fairly moderate mags where the fine tuning ability of the zoom isn't that neccessary as for higher mags. These lower mags are equally well covered with fixed focal length eyepieces.

The real advantage of the zoom will become apparent with higher mags which are easily available with a Barlow. And then the whole field of view is "cleaned up nicely" (to cite an earlier remark). The zoom will not see F/5 any more but F/10 in case of 2x Barlow.

Therefore, there are two distinctive advantages of the Leica 22-7.3mm zoom: the slimmer body if intended for bino viewing and the larger zoom range. Generally, the ASPH is better, in particular if used as the main eyepiece due to its way larger AFOV.

Andreas

#9 Víctor Martínez

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Posted 25 January 2013 - 04:22 AM

Has anyone compared the Leica Zoom 25x-50x ASPH with Ethos eyepieces saving, obviously, offering fields?. Do I understand that the Leica zoom then not generally perform well in an f/5 in comparison with, for example, an Ethos?. I was thinking for some time to sell my 13mm and 10mm Ethos, and buy the Leica zoom. What do you think about this?

#10 johnnyha

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Posted 25 January 2013 - 05:27 AM

Victor, when I got my Leica ASPH Zoom, I followed someone else's advice and sold my 10 Ethos but kept the 13, and I think it was a great decision. It's nice to have that 13 Ethos when I want the ultrawide view (and it barlows well). The barlowed Leica covers everything below the 13 Ethos. Even though the Ethos has a bigger corrected view than the Leica I find myself using the Zoom more and more. Hmm, maybe you don't need the 13 either... :lol:

Much has been said about the Leica's performance in a fast scope without a barlow, but it's not that bad. The outer 20% or so is soft in my scope at f4.5 but it doesn't bother me, I'm not looking there. :grin: Generally though I am using it in my dob with a Paracorr now instead of the barlow (the Paracorr at 1.15X gives me 110X-220X) and the view is sharp at least 95% to the edge.

#11 Víctor Martínez

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Posted 25 January 2013 - 06:52 AM

Thank you Johnny,
Actually I use these two Ethos, 13 and 10 mm, with an Antares 1,6X Barlow lens to obtain one each 8 and 6 mm virtual eyepieces.
I do not like the experiments, especially if they cost 800 €, so the thing is difficult to decide, and I do not know anyone who can lend me a Leica to test and compare my telescope.

#12 johnnyha

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Posted 25 January 2013 - 06:02 PM

Yeh it's pricey which makes it a tough call, but I'm glad I got mine.

#13 dscarpa

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Posted 25 January 2013 - 08:59 PM

I've got a Teeter STS with a Zambuto 11" F/5 on the way. I wouldn't have a problem with the outer FOV being less than optimal at F/5 provided it cleaned up when barlowed. I've got premium low and mid FL eyepieces that perform well at F/5. Not that I'll be buying the zoom any time soon what with the newt setting me back a bit. David

#14 Bob S.

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Posted 26 January 2013 - 12:49 AM

I use the Leica ASPH in f/3 and f/5 Newts as well as a 6" f/6 solar scope and a f/7 refractor. In the monocular mode, I generally prefer using the Leica over my TV Ethos ep's and I own all of the Ethos. A mild barlow does tighten up the view but even without the barlow, you can dial in just the right magnification for a given moment with the Leica that you can never do with a fixed focal length ep. What is spectacular, especially for the large solar scope is that the higher the magnification, the larger the field of view on the zoom which is ideal for capturing the entire disk of the sun in the eyepiece even at high mag. For my tastes, I pretty much prefer my Leica 25x-50x Vario zoom over fixed focal length ep's including my Ethos and Pentax XW ep's. As always, YMMV. Bob

#15 Víctor Martínez

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Posted 26 January 2013 - 04:13 AM

Bob, I undestand that the Leica is well corrected in your short focal telescopes?. If yes, within a time I would consider sell my 10mm Ethos and purchase the Leica ASPH, I would not get rid of my 13mm Ethos.

#16 Bob S.

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Posted 26 January 2013 - 07:16 AM

Bob, I undestand that the Leica is well corrected in your short focal telescopes?. If yes, within a time I would consider sell my 10mm Ethos and purchase the Leica ASPH, I would not get rid of my 13mm Ethos.


Victor, I use a TeleVue Paracorr with both the f/3 and even the f/5 which adds a magnification factor of 1.15x and significantly reduces coma. Additionally, I find that the ASPH does benefit slightly in terms of the tightness of the star points from a low to medium barlow in the 1.5-2.0x range. The barlow to me is not critical for viewing but is a slight additive. I haven't sold any Ethos ep's but in the next year, I plan to evaluate that and determine if I need most of my Ethos eps? I like the ASPH so much that I worried about accidentally disabling it and so I bought a second one. I had to gulp when buying a backup $900 ep but I like it so much that I would not want to have to wait several weeks for another one from Germany. It turns out that the spare is perfect for staying resident in my Lunt 152 solar scope. Bob

#17 Víctor Martínez

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Posted 26 January 2013 - 07:22 AM

Ok Bob, and without Paracorr, what would be your impressions about the Leica Eyepiece in the f5 reflector?.

#18 Bob S.

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Posted 26 January 2013 - 09:00 AM

Ok Bob, and without Paracorr, what would be your impressions about the Leica Eyepiece in the f5 reflector?.


Victor, I have not had enough time with the ASPH in the f/5 with our without the Paracorr. I have used it mostly with my 20" f/3 with SIPS, 6.3" Apo at f/7 and 6" solar scope at f/6. For a brief time, I had the Leica 7-22mm predecessor and did not like the smaller FOV. It did not give me as much wow factor in my f/6 solar scope as well. The ASPH is to me the finest eyepiece that I have ever used due to its incredible versatility. The problem with people giving their impressions as you know is that everyones receptor systems are different and what looks great to one person does not look as good to another. For example, I very early on abandoned Naglers in favor of Pentax XL's and XW's because my eyes preferred the Pentax's. It sort of comes down to preferences. My thought is that the eyepiece is ultra popular and if you don't like it for any reason, it will not cost you much to resell it. Bob

#19 Víctor Martínez

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Posted 26 January 2013 - 05:01 PM

Ok Bob, thank you. We are talking about this eyepiece, isn't it?:
Leica 41021 Zoom Eyepiece 25-50x WW ASPH
Regards.

#20 sixela

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Posted 30 January 2013 - 06:42 PM

I'd say I'm a nit (I always chuckle when someone says their wide field eyepiece is 'perfect to the edge of the field' in an f/5, since I've yet to see _any_ eyepiece that is), and I'm not using the Leica without a barlow too often at f/5, except in my travel scope. When I don't travel, I complement it with a 13E and 21E (and for some large nebulae a 16T5).

But at f/5, a zoom sees a lot more use with a mild barlow anyway, especially when hunting galaxies and planetary nebulae. For the larger objects or groups of objects for which I tend to use longer focal lengths, I like the 100° AFOV of the Ethos anyway, and the Leica's field of view is narrow in perspective (even if it's definitely 'T4' Nagler-like at the low focal length end).

When I travel I only have the Leica plus a BarAdv, plus an f/5 Dob. Perfect if you want only one eyepiece. You do have to live with some edge of field astigmatism, the kind that you'd gladly forgive a cheap Hyperion but not a much more expensive eyepiece ;-). And since you don't have that 21E to compare with, the AFOV feels nicely wide.

I guess the problems you hear about the (undoubtedly present) edge of field astigmatism are partly due to the self-selecting sample of observers. Not many people part with that money for an eyepiece, and you can bet they're a critical lot.

#21 btom

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Posted 31 January 2013 - 07:50 AM

Sixela, Do you still see the astig with paracorr? I would guess you do since the paracorr corrects for coma not astig but I'd appreciate an answer anyway. So perhaps I should ask do you see significant improvement in the eyepiece using the paracorr in your F/5?

#22 sixela

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Posted 01 February 2013 - 10:01 AM

The astigmatism is lessened with a Paracorr because the effective f/ratio behind the Paracorr is longer, but I'm at f/5.1 _with_ a Paracorr. It's an f/4.5 scope.

So I see astigmatism _with_ a Paracorr. As I said, I don't mind because I was really wanting to cover the 11-5mm range with the zoom, so it's always used with barlow.

The f/5 is a travel scope and I never use a Paracorr in there (and I can't these days since my only Paracorr left is a SIPS). I suspect that the Paracorr would not be enough to clean up all of the astigmatism. But with the travel scope it's still an excellent eyepiece and (with plus without the barlow) covers an _enormous_ range.






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