Zoom Eyepiece query

[F15Rules]

Hi Steve,

Some good stuff on here.

I've owned 3 Baader zooms and rate them highly for the money. If you are sticking to a budget around £150 that should get you a nice used one, or shop around and you might get a new one for around £170=£180. They are pretty well made.

I have also owned a Leica Vario (the one before the aspheric), and that was excellent. It was optically very good and had the usual c 40 deg to 60 deg view of the Baader and others. I have heard it said that it's as good optically as the Aspheric, just doesn't have the 60-80 deg fields of the latter. Not cheap though, I paid £265 for a used one, and the Aspherics are around £600 new I believe.

I now have a Pentax SMC 8-24mm, sometimes called the XL zoom. It's superb, although I have only had limited use of it so far. I was able to see the E and F stars in my Vixen ED103s recently, and other than field of view on some of my eyepieces, it compared well to them. I plan to post a review when I've had more chance to evaluate it properly. 

One thing I can review immediately though, is the build quality. It is superb, and a real step above both the Baader and Leica zooms: it oozes quality, is big, solid, waterproof (so a little stiff on the zoom to begin with when new), and has a lovely big eyelens. I should also say I also had the cheaper XF zoom, and for night time use (I don't do solar), it was dire, awful. Great globs of CA everywhere, I thought I had a faulty one, but others have said the same. Not remotely comparable with the XL one I have now.

I got mine when FLO had their offer on at £299 - they used to be selling at £405, so I am well pleased and feel that it is worth every penny just for the build - but the optics are great too. More of that when I do my review...

Dave

[Highburymark]

The prices of top quality zooms do seem to be coming down. As Dave points out, the Pentax 8-24mm is great value at £299 - it's absurd that the much inferior XF sells for just £4 less at the Widescreen Centre. The Leica ASPH - which I've seen for $1000 in the US, and £750 at Leica dealers in the UK - can be found for £400-£450 on a couple of European websites. 

[michael.h.f.wilkinson]

That Pentax zoom is very tempting, I must say.

Regarding the Hyperion Zoom, I always avoided it because its eye relief was too small. The Pentax should be fine on that front.

[Paul73]

The Baadar is fine on the eye relief if you don't wear glasses. I can't use shorter Plossls because of smearing eye lashes and an aversion to the whole "stabbed in the eye" experience.

£450 for the Leica?? Only if they have sorted out the inherent zoom issues around Fov (and a small lottery win - I'm running out of kidneys after dipping a toe into Ethos ownership).

Paul

[michael.h.f.wilkinson]

15 minutes ago, Paul73 said:

The Baadar is fine on the eye relief if you don't wear glasses. I can't use shorter Plossls because of smearing eye lashes and an aversion to the whole "stabbed in the eye" experience.

£450 for the Leica?? Only if they have sorted out the inherent zoom issues around Fov (and a small lottery win - I'm running out of kidneys after dipping a toe into Ethos ownership).

Paul

I do wear glasses when observing, hence the need for more eye relief. The Leica ASPH has an AFOV ranging from 60-80 degrees, so that is fine in my book. Expensive it certainly is. For solar I do not need more than the standard zooms offer, however, and for travel a good zoom like the Pentax, augmented with a MaxVision 24mm 68 deg would be very nice indeed

[F15Rules]

The Pentax specs show the eye relief as 20mm, which should be fine for glasses wearers, even allowing for the usual exaggeration to be found in marketing blurb! The eyecup rotates up and down too, I use mine in fully "closed" down position. 

I think Michael and Paul's previous post do illustrate the "marmite" effect that zooms have on different observers. Some (like me) are happy with the standard 40-60 deg range (once we get our heads around the fact that the lowest field of view is at the lowest magnification, while the biggest field is found at the highest magnifications - the exact reverse of the case with fixed length "normal" eyepieces), others prefer the 60-80 degree of the Leica Aspheric, and still others crave the 100deg of the Ethos et al.

Whilst I completely respect all 3 views, it does, to me that some of us almost miss the point of zooms, and in this respect I think the manufacturers don't really help themselves. What I mean by that is the following:

Apart from Tele Vue, whose high power zooms, at 2-4mm and 3-6mm can leave no one in any doubt for their intended use - high power observations, traditional zooms try to be all things to all men, hence the wide 8-24mm range. Now, many of these zooms including the Pentax, were originally designed for spotting scope use, so arguably they needed the wider range of focal lengths, partly to offer a "finder" low magnification to firstly identify the target - spotter scopes not having a finderscope. In my opinion, zooms intended for astro use for the mass market, should forget the 24mm end and just go for an 8mm to 18mm setting. Or 5mm-18mm would be even better if possible, with the 18mm having a minimum 50 degree field of view. 

For astronomical use, and as Michael just said, not many people are satisfied with only getting an "ortho" level of view (c40degrees) at the lowest operational focal length of the zoom (me included). So most of us use a fixed length eyepiece from around 20 or 24mm for those low power wide field views. I myself use ES 24mm 68 and 34mm 68s and the views they give are far more satisfying than normal zooms at low power...they are doing what they were designed to do.

The Leica type 60-80mm fov zooms are much more expensive, but then again one of those is giving you similar performance to 3 or 4 premium fixed length eyepieces, which would still cost a good deal more. And you are getting the convenience of the zoom. And I don't think we should underestimate the value of that convenience: I have noticed how much more time I spend actually looking through my scopes with the zoom, than with Fixed length eps. Far less faffing around in the dark searching for that "perfect magnification" point for the conditions on a given night. With the zoom, I just dial in the magnification that suits best - I often don't even know exactly what that magnfication is, just that the view looks the best on that night. 

Finally, if you crave 100 degree fields, forget zooms. Unless and until they develop one that can go to that size of field of view, you won't be satisified, so don't bother. And if they do develop one, be prepared to take out a second mortgage on your house! :-).

I've heard a few views that the Pentax zoom isn't as good as the Pentax XF fixed range. But it is a different beast! If the zoom had the exact same fov as the XFs ie 70 degrees, I doubt very much that many, if any, would say it wasn't as good. If I am right, it's not the sharpness, or contrast, it is the field of view that they don't like. And the compromise with any zoom will be in field of view. I have put my Pentax up against my 14mm Meade 4000 UWA - a true, world class grenade of an eyepiece with 84 degree fov (for me, it bested my 13mm T6 Nagler, so I sold it). Within it's field limitations, the Pentax matches the Meade, no question. But the Meade offers 24deg more fov than the maximum the Pentax does - in fact matching 14mm for 14mm focal lengths, it's probably a difference of around 30 degrees, and if you really want 84 degree fields, you probably won't want the zoom.

But for convenience, flexibility, contrast, and sharpness, I never see the Pentax as second rate - just different. 

If I ever end up having to sell all my other eyepieces, I know I can be happy with the Pentax zoom and my ES 24mm 68 to satisfy the vast majority of my needs. Oh, and my APM x2.7 barlow. But that's a different story :-)..

 

Dave

[John]

I'd thought the Hyperion 8-24 zoom was quite closely comparing with decent fixed focal length eyepieces until I viewed the supernova in M82 with it - you might recall this excellent SN was pretty bright and hung around for quite some time.

Each time I studied M82 at high power (199x with my 12" dob) at the 8mm zoom setting I enjoyed the view but when I switched to a similar focal length fixed focal length eyepiece (ie: the Ethos, the 7mm Vixen SSW, or the Myriad 9mm which I had available at the time) the increase in brightness and contrast variation of M82 was immediately noticeable to the extent that I assume that it must have been at least a 10% difference, which is apparently the minimum difference that our eyes can detect.

I was surprised at this result to be honest but it was repeated on other similar target objects.

My problem is that when I've seen a difference as noticable as that, it rather puts me off the eyepiece

As an outreach tool or for holiday observing though the Hyperion zoom would be good I guess.

 

 

[Stu]

Great post Dave.

To pick up on one particular point, I rarely use my Leica zoom on its own, it is mainly used as a high power eyepiece with either an AP Barcon or Zeiss Abbé Barlow depending on which scope I'm using it with. It barlows very well, and gives me the flexibility I want at high powers, whilst not giving away any quality to the other fixed eyepieces. Perhaps the edges are not quite as neat in native mode, but they tighten up when barlowed and on-axis they rival or beat my BGOs particularly for solar and planetary. Strangely though I think the Orthos are better for doubles, just a cleaner image.

[F15Rules]

3 hours ago, Stu said:

Great post Dave.

To pick up on one particular point, I rarely use my Leica zoom on its own, it is mainly used as a high power eyepiece with either an AP Barcon or Zeiss Abbé Barlow depending on which scope I'm using it with. It barlows very well, and gives me the flexibility I want at high powers, whilst not giving away any quality to the other fixed eyepieces. Perhaps the edges are not quite as neat in native mode, but they tighten up when barlowed and on-axis they rival or beat my BGOs particularly for solar and planetary. Strangely though I think the Orthos are better for doubles, just a cleaner image.

Agreed, Stu.

I find it depends on the scope. With my ED103s, which is fast (for me) at F7.7, it only has a FL of 795mm, so at 8mm maximum the Pentax only gives about x100 magnification. Using my APM 2.7x barlow whacks this up to x268, great for the Moon or on good seeing nights, but a big jump. But I can use just the barlow element on it's own, threaded straight into the bottom of the Pentax zoom and in that configuration it gives x 150 - a really nice power on most nights, with good detail visible on Jupiter for example.

On my Moonraker 80mm F15 (which will take up to x300 on good nights routinely), the above values change, with the Pentax, to x150 at 8mm, x405 with the full APM barlow in place (far too high), and x 225 using just the Barlow element for x1.5 - just perfect for double star splitting, which is what this scope excels at :-)

A good barlow plus a zoom plus a decent wide field low power eyepiece = observing heaven :-)

Dave

[YKSE]

4 hours ago, F15Rules said:

.

But for convenience, flexibility, contrast, and sharpness, I never see the Pentax as second rate - just different. 

If I ever end up having to sell all my other eyepieces, I know I can be happy with the Pentax zoom and my ES 24mm 68 to satisfy the vast majority of my needs. Oh, and my APM x2.7 barlow. But that's a different story :-)..

 

Dave

Very well put, Dave. exactly my thought about good zooms

[bomberbaz]

Some very interesting points of view there, glad I asked this question as it has raised many more and helping me make amore balanced decision. Or it will when i eventuallyreach one ??

[Dave In Vermont]

Yes Dave - an excellent post! Very good optical history on these critters.

What you stated is why I usually generalize it as: "It 'tis the nature of the beast." If you understand their ++'s and --'s - you'll understand what you're buying and what it does and what it doesn't do.  If you do your homework on these before you drop your money for one, you'll get what you pay for. A fine example of "Caveat Emptor" exemplified. They shouldn't be considered a replacement for a good fixed-FL eyepiece. A convienence? Sure!

Clear skies and away!

Dave

[Highburymark]

Agree Dave - it's great to have the choice of either a zoom or fixed EPs. Nothing beats a fixed f/l EP, but I find zooms are particularly useful when the seeing is less than perfect (around 364 nights a year in the UK then) to achieve the best balance between magnification and sharpness, or for lightweight travel, when they are essential.