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View Full Version here: : Zoom EPs ???


Dazzler
16-10-2007, 12:10 PM
I am chipping away at upgrading to premium EPs over time and have just bought a near new Pentax XW10 (thanks Casstony :thumbsup:) which should see first light this weekend.

Just looking up the catalogue on the Pentax XW range I notice they make an 8-24mm zoom EP. On face value this would appear a very cost effective way of covering a wide magnification range on my f10 scope.

I am sure there must be some pitfall(s) to a zoom EP and was hoping someone may be able to cover them for me.

bojan
16-10-2007, 12:16 PM
I have 8-24mm Orthoscopic zoom from University Optics (I bought it 27 y ago) and I do not use it much due to small view angle (especially at 24mm, it is ~30deg or so.
Otherwise it is a decent eyepiece, eye relief is somewhat short, though.

Dazzler
16-10-2007, 12:51 PM
Thanks Bojan

The XW range have a 70deg fov so the above should not be a problem.

My question is really are there inherent issues in the zoom function of these EPs that you would not face with standard EPs that I should consider.

bojan
16-10-2007, 12:58 PM
This corresponds to 8mm FL. 24mm will have much smaller fov, 45 or less.

saberscorpx
17-10-2007, 12:23 AM
I Zoom. Then, when conditions allow, I barlow.

The convenience of a premium 24-8mm ZEP can spoil you fast.
Plenty of eye relief, excellent color correction, and sharp to the edges (I have the Orion clone).
Despite the spec AFOVs, the view does not appear overly restricted.
It ain't a Nagler, but it ain't bad.

As always, YMMV.


SJS

casstony
17-10-2007, 09:04 AM
You'll get better performance from discrete eyepieces, but more convenience from a zoom. I currently have a 35 mm Panoptic, 22mm Nagler, 14mm XW and a Vixen zoom. The zoom gets used when I want to cart minimal equipment outside, especially for quick looks, and its images are very respectable. It's main disadvantage for me is the narrow field at low power.

My suggestion would be to add two more quality widefield eyepieces (medium and low power) and one of the cheaper zooms if you want the convenience.

Dazzler
17-10-2007, 09:38 AM
Thanks all. :thumbsup:

Tony - your collection seems ideal for my setup. I envisage myself getting one more XW and a Nagler just to break things up. Not sure though whether the Nagler will be in the mid or low power range.

I'll see how I go with your XW on the weekend which is probably as high power as I need with my f10 Lx200r. I am sure there will be someone around in the local groups who will let me look through a Nagler.

I expect the zoom EP may be handy for PST use. Any thoughts on that from anyone? :shrug:

Cheers.

Miaplacidus
17-10-2007, 10:07 AM
I have an 8-24 zoom, one of the WO clones. I use it in the PST only, and even then changing the FL means an annoying change of focus.

In the end, all it has done is convince me that I change focal lengths too often and too needlessly. I'd be better off with TWO premium fixed focal length EPs and to stick to just looking through each of them for longer. I'd get better quality observing done that way, without so much fiddling.

The question for me is: Which two?

casstony
17-10-2007, 11:53 AM
If you can, take a look through a 20mm XW, 20mm Nagler and 22mm Nagler - these differ from each other significantly and the choice becomes a very personal one.

I use my zoom mostly in the pst and adjusting focus on the pst is fiddly, but I find I tend to figure out the appropriate setting for the conditions and then not adjust the zoom. The main reason I like the zoom is that I can carry the scope outside with one eyepiece and the mount lives on the back verandah - convenience. I also find that I can tolerate a bit of mucking around once I'm observing, and the easier it is to get set up the more likely I am to actually go out there.

MortonH
17-10-2007, 04:59 PM
My 8-24mm Televue zoom is mostly used for terrestrial vewing these days, but I have used it on comets with a small scope where I could subtly adjust the magnification to get the best contrast. It's also good for travelling.

However, due to the limited field of view (only an issue if you are used to good wide-field eyepieces, which I am!) it is very much an 'extra' in my bag, i.e. my prime eyepieces cover the same range.

I wouldn't pay megabucks for the Pentax version. As Casstony says above, a couple of decent eyepieces plus a standard zoom will probably serve you better.

Morton

Dazzler
17-10-2007, 05:19 PM
Good advice - thanks all! :thumbsup: