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Nagler Typr 6 vs. Pentax XW

Started by ryderc1, 10/10/2006 10:46AM
Posted 10/10/2006 10:46AM Opening Post
I've generally been a TeleVue eyepiece addict for several years but recently decided to try the Pentax XW line. I've been very happy with my Type 6 Naglers but my worsening asigmatism is increasingly forcing me to either wear eyeglasses or use a TeleVue Dioptrx while observing. At
anything more than about a 1mm exit pupil I benefit from viewing through a corrective lens. Since the Type 6 Naglers won't accept Dioptrx I revcently took advantage of an opportunity to buy 5 and 7 XW's due to their generous eye relief, 70-degree FOV and generally very positive comments I'd read from other observers.

For those rare nights of great seeing I have some TMB SuperMono's and Pentax SMC Orthos. But those nights are few and far between in my area and, since I'm almost exclusively an alt/az mount user, the wider fields available with the Naglers and XW's are more practical most of the time.

I spent almost two hours this past Sunday night doing a head-to-head comparison of the 5 and 7 XW's to my 5 and 7 Type 6 Naglers using the Moon as my target. I chose my TMB 100/800 as the "test scope" because it has exceedingly good optics and I wanted to minimize any adverse effects caused by the scope's optics as opposed to eyepiece produced
effects. The two major lunar features observed were Petavius and Langrenus, both of which offer a nice range of crater wall and floor features as well as central peaks which produce small shadows and enhance the ability to make sharpness and contrast comparisons.

I limited my comparison to optical performance and not ergonomics but I find both eyepieces easy and comfortable to use. I've read comments about eyelash oils getting on the Nagler optics but I've never found that to be an issue with me. The XW's, of course, are widely touted for their "comfort" and I'd concur.

Despite both the Naglers and XW's having relatively large FOV's (82 degrees and 70 degrees, respecively)I tend to view objects at higher powers on axis or at least within the central 50% of the FOV. As a result, differences in performance beyond the central 50% of the FOV were not studied.

Without going into excessive detail, I found that fine details plainly visible in the Nagler were seen with more difficulty in the XW's, if at all. Contrast differences on lunar features were similar but the surrounding sky through the Naglers was definitley darker. I'm not sure whether this was due to the Nagler having superior contrast or whethet it was due to some form of ghosting effect
produced by the Pentax. I'd heard reports of slighly warmish tones imparted by the XW's but I found no appreciable tonal differences in lunar views between the eyepieces.

There's no doubt that both eyepieces are great performers and I'd be happy with either one. If my vision were such that glasses or Dioptrx weren't needed, I'd choose the Nagler over the XW based on my comparisons. Of course, I'd want to cmpare performace on other targets and in my other scopes before drawing final conclusions.

My next move will be to try some Radians, since Dioptrx will fit all of them and they are reputed to be very good lunar/planetary performers.

Of course, these are my personal, subjective findings only and "your mileage may vary".

Charlie
Posted 10/10/2006 12:01PM #1
Charles,

Thanks for the comparison! How did you find the focus snap for each EP? Either one easier to reach optimum focus than the other?

Also, would be interesting to also hear a quick compare (if you have time) on a glob for light grasp and contrast and point size comparison. M15 is up and about and a good test target.

Thx.
-Bill
Posted 10/10/2006 01:10PM #2
I found the Radian to slightly out perform the XL Pentax 5.2mm. Just a bit better in contrast and detail. The Nagler Type 6 5mm was not as good as the Radian for my test, but I was using a fast f/4.3 reflector and doing planetary testing.
I think it would be a nice test to compare the XW, Nagler and Radian. Let us know if you do this.
Thanks for the comparison! grin

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