Tell me about your zooms

[Miaplacidus (Brian)]

OK, ok. I have an ETX 105 (FL 1470), a 200 mm dob (F6) and a FD 80mm refractor (FL 555, F6.9). I already have some premium eyepieces (LVW and Radian 5 mm; Naglers; Pentax XW 10 mm). But I'm thinking of getting a general purpose, grab-and-go zoom eye piece, somewhere in the 8-20mm range, that would be suitable for all these scopes. I like decent eye relief and hate kidney beaning. I like a wider field of view, but not at the expense of sharpness on axis, and preferably something that doesn't weigh a kilo. I would use it in daytime on the refractor if I could. I don't want to have to remove it to change focus, either, but rather something that moves smoothly.
Time was all zooms were rubbish, but I've heard times have changed. I've heard that Leica and Pentaxes are among the best, but I see that WO have one now, and then there is the generic Televue/Meade/Vixen zoom. (I've already discounted the heavy Speer-Waler.)

So tell me, which one should I buy?

(And don't say "profigliano"!)

Brian.

[ausastronomer (John Bambury)]

How much are you prepared to spend

CS-John B

[Miaplacidus (Brian)]

Originally Posted by ausastronomer

How much are you prepared to spend

CS-John B

Yes, I should have said, shouldn't I? Well, I was sort of leaving that open. Seriously, if someone could persuade me that $700 was actually worth it (the more expensive of the two Pentax?), then I guess I would actually even give that a lot of consideration. (My problem, being in Hobart, is the extreme difficulty of trying before buying.) It isn't that hard to justify a good zoom, I figure, if it can replace two or three other EPs. Otherwise, a sensible restriction would be sub-$500. Really, if you could graph such a thing, I'd be looking for where the value line crosses the quality line.

Just so you know, I'm pretty set at 5 (LVW), 10 (XW). I'm planning to swap my 12mm Nagler for a 17 at some point. And I'm happy enough with my cheaper long FL EPs.

Cheers,

Brian.

[Miaplacidus (Brian)]

Is this a silence that speaks volumes? Are zooms still unpopular? Could it be that nobody uses one?

BTW, I am just as interested in any user's negative experiences. Criticism is probably more useful than simple praise.

Cheers,

Brian.

[casstony]

I've been holding back waiting for a more skilled/critical observer to comment but since none has here's my opinion; the modern zooms are good enough that I wouldn't be without one for the convenience. I've used a william optics/proxima 8-24mm and a vixen 8-24mm and they both looked about as sharp as a plossl to me. The vixen may be a little soft at 8mm. Before accumulating the Nagler, Panoptic and LVW I have now, I used the zoom for most of my observing though now it mainly gets used in my PST.

The new Hyperion zoom is getting good reports and may be worth looking at, though I don't like the look of the eyecup (personal preference - I like a narrow eyecup rather than a wide one).

[janoskiss (Steve H)]

Originally Posted by Miaplacidus

Is this a silence that speaks volumes? Are zooms still unpopular? Could it be that nobody uses one?

All the zooms incl the pricey ones go very narrow in the AFOV at the low power end which kind of defeats their purpose for general use. The only use I see for zoom eps is at high powers, for observing planets in a tracking scope, where magnification is important but FOV is not.

[astropolak (Joe)]

I have the Vixen 8-24.
Surprisingly good quality optics, good enough to see a lot of detail in planetary observing. Little ghosting, no light scatter.
The FOV is nowhere near good enough for DSO's 50 deg at 8mm focal length, 40 deg at 24 deg.
It is not as enjoyable to use as for example Pentax XF or XW but its light, relatively cheap and it has 20mm eye relief.
I use it as calibration eyepiece in my LX200.
Funny only a year ago or so I thought it was all I'll ever need. This is before I've discovered Pentax eyepieces - with the help of John (Ausastronomer)....mostly.

RGDS Joe

[Miaplacidus (Brian)]

Thanks for the tip about the Hyperions, Tony. I will look into that (pun intended). I doubt anything could beat a 10 mm Pentax XW in the PST.

Thanks for reminding me about the narrow FOV, Steve. I hear that the expensive Pentaxes have quite respectable fields (42-60 degrees, supposedly), as too did a Leica I looked through in the daytime once. But most of the 8-20 mm range really isn't "planetary" magnification in my scopes, so the purpose becomes a bit vague, doesn't it?

And thanx, Joe, for reminding me about how good the premium EPs are.

So that's settled then. I'll buy either a Hyperion or a WO or a Vixen zoom just for fun, and get myself a 17mm Nagler and a 7mm XW and an 8mm LV for more serious viewing. Excellent!

Now, who can I kill?

[tegea]

Hello,

Very interresting subject ! I'm also currently looking for a zoom eyepiece. I would like to have the best possible optical quality and the less "tunnel effect" as possible in wide FOV.

There are quite a lot of 8-24mm zooms (TV, Vixen, Meade...) but those are almost all the same and they are not satisfying. I Tried the TV 8-24 on my tak FS60 and I found that the image sharpness was not very good, and that there was a yellow color in the image.

During my searches on the net, I found that the best zoom eyepiece were not the astronomical ones, but the eyepieces for quality spotting-scopes. People who tried them for astronomy all agree that they are far better than the astronomical classical 8-24mm.
Here you can find :
- the NIKON 7-21mm "SpottingScope" zoom eyepiece (not the "FieldScope" one). FoV is 38-60°. You will need to find a 1.25" adaptator to use it. It is described to be the sharpest, and to have the better light transmission abd therefore the best contrast. No image distortion. Tunnel effect exists, but less than in the classical 8-24mm. This one is quite cheap : around $300.
- the LEICA 7.3-22mm zoom. FoV is 38-68°. A 1.25" adaptor is available. Sharpness is just a little bit lower than the Nikon. Curiously, it is described as having no noticable "tunnel effect" at 22mm. Around $750.
- the ZEISS 8.4-21.5mm zoom. FoV is the best of all : 49-68°, "No tunnel effect" ! It is as sharp as the Nikon but has a small amount of image distortion at 21.5mm. It can be purchased with a Zeiss 1.25" barrel. Around $600.
- There is also a SWAROVSKI zoom eyepiece which should also be a good one, but I found nobody who tried it for astronomy. Around $650.

I will probably purchase the NIKON one as it is excellent optically and quite cheap. My second choice would be the Zeiss because of it's amazing 49-68° FoV.

[MikeyB (Michael)]

I've got the Nikon Fieldscope MCII zoom eyepiece, which I believe is 7 - 21mm, although Nippon Kogaku seem to release remarkably few specs for their gear, even top of the range stuff like this. Nikon eyepieces use a non-standard screw mount for which Tomy make an adaptor to 1.25" in their Borg series of astronomical fittings (available through the excellent Hutech: http://sciencecenter.net/hutech/borg.../html/7162.htm).

The zoom is primarily used in my PST, where its high contrast and very flexible focal length work brilliantly and the somewhat narrow field of view at lower magnification is not an issue. It is also a splendid planetary/lunar viewing eyepiece - if it wasn't for its dedicated PST usage, it could easily replace my fixed eyepieces for those applications.

In a previous life as an amateur photographer, I always understood that zooms suffered from low contrast and indifferent resolution - seems nobody told the wizards at Nikon!

[MortonH]

I have a Tele Vue 8-24mm zoom, bought about 6 years ago. on an 80mm or 100mm wide-field refractor they are quite versatile, although I find that at the 10-8mm range the image gets a bit soft. The most annoying thing is that it is not parfocal, but it's nice to adjust the magnification to improve the contrast (as you go to higher mag). The field of view is also very narrow. Doesn't bother me too much for atsronomy unless I want to see large objects, but try it in the day time and you really notice how restricted the view is.

Quality is reasonably good for the price, but if you have premium eyepieces (I have a couple of Radians/Naglers) you will notice the difference.

Morton

[tegea]

MickeyB > Do you know the difference between the 2 Nikon zooms :
- the spottingscope MC
- the fieldscope MCII
I do not have any technical specs of the second one. The only thing I know is that it is more expensive than the first one.

And thanks for the Hutech link ! It solves the problem.

[MikeyB (Michael)]

I'm glad if I've helped a little, Tegea.

The main difference between the two eyepieces is that the MC has a 2.25x zoom range, while the MCII covers 3x (sorry for such low tech data, but Nikon don't reveal much!)

The other comparative specs are on this page: http://nikon.topica.ne.jp/bi_e/products/nature_a.htm

[Miaplacidus (Brian)]

Thanks for your comments everybody. I ended up buying a 8-24mm zoom for $110, figuring I could hardly go wrong and that it would be suitable for star parties. As expected, it suffers like all the rest from a restricted FOV, but it foots the bill for quick looks with the refractor. I'll save my money for some prime non-zoom EPs.

[astroturf (Bryan)]

Hello everybody

I am/was about to purchase a teleview 8-24 zoom lens
this nikon zoom sounds like it's the business

does anyone know where one could be purchased in sydney or anywhere in australia?
thanks
Bryan

[MikeyB (Michael)]

Sirius Optics (http://www.sirius-optics.com.au/nikon%20sscope.htm)

and

NVT (http://www.nvt.com.au/Spotting-Scope...e-Accessories/)

both list the Nikon zooms on their websites, but you could also try BinTel in Sydney (https://www.bintelshop.com.au/welcome.htm), who list the Nikon spotting scopes if not the eyepieces.

There may be others too - spotting scope buyers are a different mob from the astro crowd!

[astroturf (Bryan)]

Hi guys
this might seem like a dumb question
would an eyepiece like this pentax model
http://televue.telescopes.com/produc...pes-34438.html
be suitable for sky observing, If it would be how would you all rate it?
I'd heard someone mention a pentax zoom earlier & wondered if it was this one
Thanks
Bryan

[tegea]

I never looked through the Pentax zoom but read that it was sharp on all the FoV at 19.5 but not so sharp at the center at the short focal length. The center "quite" sharp area at the long focal length is approx. 30°. The rest of the FoV is less sharp. So this pentax SMC XF zoom might be good but not excellent.

I found the following very interresting test report about zooms here : http://www.birdforum.net/showthread.php?t=73582 It says that the Baader Hyperion zoom eyepiece is a really good one. In Addition, it is quite cheap !

I recently acquired a new Baader Hyperion zoom eyepiece (24mm-8mm). This eyepiece comes with a 1.25" barrel and can also be attached directly to the Zeiss Diascope and Celestron/Synta spotting scopes. What is most interesting about the Baader is that it has, for a zoom, an unusually wide field at the low end of its magnification range, comparable to the Zeiss Diascope zoom. In the US it is available from Alpine Astronomical at a cost of $189. This is less than half the price of the Zeiss zoom eyepiece which could make it interesting to those thinking of purchasing a Diascope. I already own the Zeiss zoom (25.1mm-8.4mm), current Swarovski zoom (23.1mm-7.7mm) and Nikon 20x-60x MC zoom, NOT the MC II (21mm-7mm). All of these are adapted for use on astronomical telescopes. I tested all the eyepieces on an Astro-Physics 92mm f/6.6 APO refractor.

First let me dispense with the question of sharpness at the center of the field. On my AP refractor all of the eyepieces here are perfectly sharp in the center throughout their zoom ranges, just as sharp as fixed magnification eyepieces of very high quality. The birding scopes these eyepieces are used on will virtually always be the limiting factor for center sharpness.

There are performance differences, but they are in the areas of light transmission, contrast, color accuracy, eye relief, field width and off-axis field curvature, astigmatism, distortion and lateral color.

I measured the eye relief and apparent field of each eyepiece at four magnifications on the eyepiece barrel; 20x, 30x, 40x and 60x. I measured the Baader at 24mm, 8mm and two settings in between that would correspond to about 30x and 40x if it were mounted on the Zeiss Diascope. The Baader has “clickstops” which are supposed to correspond to 20mm, 16mm and 12mm. These are ridiculously inaccurate. The 20mm setting actually corresponds to about 13mm, the 16mm corresponds to 10-11mm and the 12mm corresponds to about 9mm. The end stops do seem to be close to 24mm and 8mm.

First the figures for eye relief. These are measured from the eyecup rim set at its lowest position. Distance to the glass of the eyelens would be longer by 4-5mm and with most of these eyepieces (except the Nikon) the eyecups are so wide that the center of a curved eyeglass lens will probably get closer to the eyelens than the rim of the eyecup, adding a couple of mm’s to the effective eye relief. These figures may look short, but I find I can see the entire field at every magnification with all the eyepieces while wearing reading glasses. Only the Nikon’s eye relief “feels” a bit short to me without glasses. All of the eyepieces show the usual dip in the middle of the zoom range.

Swaro 20x-16mm, 30x-12mm, 40x-10mm, 60x-14mm

Nikon 20x-12mm, 30x-8mm, 40x-8mm, 60x-12mm

Zeiss 20x-12mm, 30x-10mm, 40x-8mm, 60x-12mm

Baader 20x-11mm, 30x-9mm, 40x-9mm, 60x-12mm

Now the apparent field widths in degrees:

Swaro 20x-40, 30x-52, 40x-58, 60x-68

Nikon 20x-40, 30x-45, 40x-52, 60x-59

Zeiss 20x-50, 30x-57, 40x-62, 60x-71

Baader 24mm-49, 30x(16.8mm)-56, 40x(12.6mm)-60, 8mm-72

The Baader does have approximately the same apparent field as the Zeiss over its range. Both have wider fields than the the Swaro at low magnifications, but the gap narrows as magnification increases. The Nikon is just not very competitive when it comes to field width.

The clear loser in this group when it comes to light transmission, contrast and color accuracy is the Zeiss, which, compared to the others, is obviously dimmer and lower contrast with a yellow color cast. The Nikon, Baader and Swaro all have very high light transmission and contrast. About as good as it gets for complex eyepieces. The Baader is quite outstanding, possibly the brightest by a hair. It’s easily as bright or brighter than my Pentax 14mm XW and 13mm Nagler, and it gives up almost nothing in brightness and contrast compared to my 16mm Zeiss A-16 Ortho. Color transmission is also very accurate. The Baader and Nikon are nearly indistinguishable with very slight red casts and the Swaro is a tiny bit yellow, not blue like many people report for the complete Swaro scope optics.

There are some interesting differences in off-axis behaviour. Some of this, like distortion, will be exactly the same in other scopes, but field curvature and lateral color in other scopes may be different from my experience.

None of the eyepieces show significant off-axis astigmatism on the AP scope. Edge softness is almost entirely field curvature. At the lowest magnification the Baader has slightly less field curvature than the Zeiss. As magnification is increased field curvature decreases for both until they are about equal with very little curvature at 40x (12-13mm) and beyond. For comparison purposes this is an easy thing to measure by focusing an object at the edge, then moving it to the center and refocus, noting how much the focuser has to be rotated for different eyepieces. I’ve followed the recent discussion about how the Zeiss edge performance compares the the Swaro at low magnification so I also checked the field curvature of the Zeiss and Baader set at their lowest magnification at about 20 degrees off-axis and compared that to the Swaro set at 20x. The Swaro has a very flat field with very little astigmatism or field curvature all the way to the edge of its 40 degree field. Neither the Zeiss nor the Baader is quite as good at the edge of a 40 degree field circle. Their comparable “sweet spot” is about 30 degrees wide. The Nikon is close to the Swaro at low magnification but with a little more astigmatism. At short focal lengths the Baader and Swaro become excellent wide field, long eye relief eyepieces. The Zeiss is nearly as good except for the lower light transmission and contrast.

Distortion varies. There is mild barrel distortion at all focal lengths in the Swaro. The Nikon has very mild pincushion distortion at all focal lengths. There is moderate pincushion in the wider fields of the Zeiss and Baader which increases with magnification as the apparent fields get wider.The Baader has a bit more than the Zeiss, but neither has as much as, for instance, the TeleVue Panoptics at the same apparent field width.

I didn’t see any significant differences in lateral color in my telescope. It’s similar in all the eyepieces at the same distance from the center of the field. There is, of course, more at the field edges at high magnification as the apparent fields widen. I didn’t consider it to be a problem, but it could be worse in faster telescopes.

I haven’t had a chance to try the Baader on the Diascope yet, but it certainly looks like a real alternative. I prefer it to the Zeiss on my AP scope. On the Diascope it would produce a little more magnification than the Zeiss zoom (21x-63x on the 85mm), but would not be waterproof. Optically, I think the Baader is the best zoom eyepiece I’ve tried so far. It manages to combine the wide field width of the Zeiss with the high light transmission, contrast and color accuracy of the Swaro and Nikon, and at a bargain price. I can’t find much to complain about.

Too bad there isn't a Nikon adapter. I think the Baader would probably fit and the Fieldscopes would really benefit from this eyepece.