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MortonH
30-04-2007, 06:08 PM
The ad on myastroshop says (for the 13mm) "Sharp pinpoint stars right across the field of view, even with an f/4.9 telescope".

On the assumption that an f/4.9 scope would be a Newtonian, wouldn't coma prevent pinpoint-sharp stars at the edge no matter how good the eyepiece is?

Morton

matt
30-04-2007, 06:13 PM
You might have something there, Morton:)

Never let the truth get in the way of a convincing ad spiel, eh!:lol:

Starkler
30-04-2007, 08:15 PM
Not if you use a coma corrector eg. televue paracorr.

matt
30-04-2007, 08:21 PM
The ad doesn't mention using a coma corrector to achieve pinpoint stars to the edge of the FOV:whistle:

MortonH
30-04-2007, 08:21 PM
Yes, but you don't get a free Paracorr with the eyepiece!!!

Morton

janoskiss
01-05-2007, 01:26 PM
the ad does not mention newtonian. All it says to me is that the EP can cope with a fast light cone. Aberrations of the telescope itself, including any coma, as well as field curvature of the mirror or objective lens, are a separate issue.

MortonH
01-05-2007, 05:25 PM
Thanks, Steve. Knew there would be a good explanation.

Morton

Dave47tuc
01-05-2007, 06:59 PM
Morton,:)

Many things get stated on eyepieces. I mean cloudy nights is full of this eyepiece is great but this one is better or no what I have is the best, so on and so on.
Can make for amusing reading.

I have owned many eyepieces, but for me who is very short sighted and find it hard to see colours against a black background. I find the Vixen LVWs very nice eyepieces indeed. I have the 22, 13 and 8 mm and hope to get the other 3 in time.

As I get older Im finding it harder to see much if any difference in high end eyepieces. Like LVWs Pentaxs XW and Naglers etc.
They all work fantastically well.

Saying that I find the LVWs really easy to use. No blackout or trying to get your eye in the right spot to see the whole field. Great eye relief, and look in my F5 DOB I do not see too much wrong with them. They give a very nice clean image. If there is any false colour I dont see it (but thats me) all stars seem tight across the field.
They are just nice to use for me any ways.

The LVWs can be a little under rated, but those who have used them know they are right up there in the high end market place.

If you can get hold of the 13 mm LVW I know you will like it very much, no matter the scope and f ratio, to a point!
:D

MortonH
01-05-2007, 07:08 PM
Thanks, Dave. It's always good to hear from someone that actually uses the item being discussed.

Morton

Miaplacidus
01-05-2007, 07:20 PM
Hi Morton,

I have a 5 mm LVW and now a 8 mm LVW (took delivery today). I find the 5 mm superior to my 5 mm Radian in terms of crispness and colour.

I notice that you and I have similar scopes. All these eyepieces perform very well in them.

No one ever seems to mention it, but ever since I upgraded the Megrez to the fluorite doublet, I get a bit annoyed by the extra weight. William Optics make great scopes, no question, but they are heavy for their aperture. My Megrez now requires an extender, and now it is especially back heavy. Balancing is an issue, and so I have to use a sturdier/heavier tripod as well, which all goes to counteract the "grab-and-go-ness" of the thing. Sometimes I wish I still had the old F6.25 lens. I actually removed the two speed focuser to try and reduce the weight, and now I'm wondering if I should change to lighter EPs, like the Pentax XFs. The Naglers are heavier again. (The radian is lighter than the LVW.)

Just food for thought.

Cheers,

Brian.

MortonH
01-05-2007, 08:10 PM
Eyepiece weight isn't too much of an issue, although fitting them all in my bag is! Interesting what you say about the LVW compared to the Radian. I thought Radians were the bee's knees when I got mine a few years back. Seems like the competition has fought back. There's a great choice out there and plenty of people seem to prefer something else to the Radians. That's why I'm tempted to give another brand a try around 11-13mm.

Interesting comments on the Megrez. I love mine. I've taken it as carry-on luggage several times and it only needs a fairly average camera tripod for casual viewing.

As always, too many choices and not enough cash!

Morton

Fox
01-05-2007, 08:29 PM
G'day Morton, I have the LVW 13mm, so I'll put my 2 cents in.

IMHO there are not that many 'higher end' brand EP's to choose from in the 13-15mm 65-70 deg FOV range. The TV Panoptic 15 did not appeal to me (a bit dated now), so I tried the Pentax XW 14mm for a short while; the edge field curvature just didn't gel in my Genesis, so I sold it on.

On the other hand the LVW is much more to my liking, so I guess it's really a matter of try and see in your own scope. Edge of field performance is not as good as on-axis - but then tell me an EP where this isn't the norm. I find eye positioning to be just a bit touchy, but not overly bothersome.

LVW quality and construction are top notch, although I am surprised to hear on the adjacent 'Buy & Sell' forum that the white side writing/labelling on a Vixen LVW 5mm appeared to have worn-off; has any one (Miaplacidus?) come across this on other Vixen LVW's? I had assumed that the white writing/labelling would be higly durable, ie. essentially last forever with normal but gentle handling. I've never seen labeling loss on any of my other EP's - although the text/labeling is not 'inscribed' in the LVW.

Indeed, I am very tempted to explore the 5mm LVW to replace my 6mm Radian for planets - I am finding the Radian 6 can ghost quite a lot with the planets. In critical testing when the Genesis is well cooled and seeing is good, my Clave 6mm outperforms the Radian 6mm - the image in the Clave seems a bit brighter, tighter, and really snaps to focus better than the Radian. Subtle planetary detail is more readily evident in the Clave than Radian. I never really thought I would come to notice these things, they are subtle but real when you concentrate at the EP under good seeing conditions.

Miaplacidus, I am very interested to hear of your LVW-5/Radian-5 direct comparison - is this what you found with planets + refractor?

Cheers, Fox

MortonH
01-05-2007, 09:28 PM
Thanks, Fox. Ideally I want a focal length in the 11-13mm range, so the 14mm Pentax and 15mm Panoptic are out. Don't need the 82-degree field of a Nagler.

The Pentax XF 12mm sounds decent, but again has field curvature from 60% from centre. The other option might be a Baader Hyperion 13mm. And William Optics have just introduced their SPL line, which has a 12.5mm with 55-degree app FOV. Price is at the budget end so don't know about quality yet.

Vixen is probably top of the list if I decide to buy something. Until then, I'll keep using my 32mm Meade Plossl with my 2.5x Powermate!

Morton

Miaplacidus
01-05-2007, 10:08 PM
Hi Fox,

Yes, both my LVWs are second hand. Both came with worn labelling on the side. The one I got today was supposedly used only once, or at least minimally prior to me getting it, but it still has some of the writing missing. The oversized focal length number is still intact, though.



I posted something about this some time ago. Yes, I tried both EPs in several scopes. Last year there was a perfect night where I could even use them at the rather insane magnification (for an ETX) of 294x. On Jupiter back then the GRS was just disappearing from view, but was more obvious in the Vixen.

Apart from my own scopes, I compared these EPs in a C5, a Televue 101, and a C8(!). I doesn't really matter. In all these scopes the results were consistent: although close, the radian had slightly more chromatic aberration and the Vixen delivered a crisper image. The Radian has a "warmer" or yellow cast, compared to the Vixen, but in itself this doesn't worry me. One thing favours the radian, though: the Vixen has noticably more annoying fireflies (eyeball reflections) on bright objects, but it still provides a bit more detail/contrast. Anyway, given that a 5 mm EP is most likely lunar or planetary, and detail is paramount, I gave the guernsey to the Vixen. Now, as I say, I also want to take weight into consideration, and wouldn't mind trying a Pentax XF. (I have a Pentax XW 10 mm, which is nigh perfect but still relatively heavy.)

Cheers,

Brian.

Miaplacidus
01-05-2007, 10:13 PM
Having said all this, if I dropped one, I'd be pretty content just to keep the other. I don't mean to suggest that the differences are huge, just noticeable when doing the direct comparison.