3-6 Nagler

[ferret]

Hello everyone,

I am looking at a nagler 3-6 zoom for my 102 f6.6 refractor for planetary observing.

It's a fairly hefty purchase for me - more than 60% of the cost of my scope!

Has anyone got any experience with these that they'd like to share? Would I be better off with fixed focal length eyepieces (say a 3mm and a 6mm radian) instead?

[Dennis]

Hi ferret

Not a direct answer, but here is my experience with a zoom lens on my wife’s spotting ‘scope, a 77mm Leica apo.

Using the Leica 32mm standard eyepiece gives a very pleasing and satisfyingly wide field of view.

Using the Leica x20 to x60 zoom eyepiece gives me the feeling of looking down a tunnel, not as bad a looking down a straw, but certainly nowhere near as pleasing as the standard 32mm eyepiece. Therefore, the zoom gets little use in the field.

It might be that to achieve the focal length range for a zoom eyepiece, other characteristics such as field of view may suffer? Historically, prime focal length eyepieces have tended to out perform zooms across most of the important parameters. I’m not certain if modern zoom eyepieces have overcome these deficiencies, in much the same way that modern camera zooms have almost equaled the performance of prime photo lenses.

Cheers

Dennis

[MortonH]

I have the 3-6mm Nagler zoom. It's a handy eyepiece, very small and light, and I am very happy with the quality of the views. However, it has a relatively narrow apparent field of view (50 degrees) and relatively short eye relief. Depending on which eyepieces you already own or have used in the past, you may or may not find these factors to be an issue. All of my other eyepieces have at least a 60-degree field and more eye relief. So when I use the zoom, I feel a bit 'restricted'. Bear in mind that I do not own an equatorial mount, so the extra field of view is important for me as planets quickly drift across and out.

In terms of quality, I like it a lot. I use it on my 8" GSO Dob for planetary viewing. Occasionally, I push the magnification up to 300x (with the zoom set at 4mm), but normally the seeing won't allow such a high power. It's more common for me to max out at 240x with my 5mm Radian, which has a 60-degree apparent field and 20mm of eye relief.

If I was buying eyepieces again in this focal length range, I would be tempted to go for the Burgess/TMB 'planetary' eyepieces. They are $149 each from Frontier Optics, which means you can get three of them for less than the price of the 3-6mm zoom.

Morton

[ferret]

Thanks Morton.

At the moment, I use a 4 and 6 GSO for planetary as this was all I could afford when I got my scope.

From what I read, the shorter length GSO eyepieces are supposed to be pretty ordinary in fast focal lengths, so hopefully I'll see a big difference.

The Burgess eyepieces look interesting, though. Hmmm...

Pondering what to get is always more fun than the having for me.

[DougAdams]

Originally Posted by ferret

Has anyone got any experience with these that they'd like to share? Would I be better off with fixed focal length eyepieces (say a 3mm and a 6mm radian) instead?

I've been using one for about 3 months (around 20 sessions) in a couple of 4" refractors, one F8 and the other F5. Both on an alt-az mount.

Good points - the ability to zoom in and out without changing the eyepiece is very handy. The views through it are very good, particularly at 5mm.

Bad points - gets rather cruddy fast, due to the short eye relief (although I have worked out the eyepiece guide folds down, so that's improved things a lot). I've not had the seeing to get a worthwhile view with the 3mm setting (Jupiter, Moon... I see tons more detail on the 4 and 5mm settings). The field of view is very tight, compared to my other eyepieces (couple of Naglers and a Panoptic).

I'm starting to wonder if I'd be better off with something like a 3.5 mm Nag for my high power (around 150x and wider FOV), as the 3mm isn't cutting it.

[MortonH]

I have wondered about the 3mm setting, i.e. I'm never quite sure if the drop in image quality between 4mm and 3mm is due to the seeing or the eyepiece itself (or both). I also find with my TV 8-24mm zoom (not the same quality of optics, admittedly) it also seems to get a bit muddy at the 8mm setting. Maybe this is true of most zooms?

I think its greatest advantage is its tiny size and weight, compared to Radians, for example. But for extended viewing of the planets, particularly with an undriven scope, the extra field of view and eye relief from other eyepieces makes observing a whole lot more comfortable.

Morton