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sawacs
super member
Reged: 03/15/06
Posts: 131
Loc: KOKC Area
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Gents, I spent the evening comparing a few eyepieces on various objects.
The scope used was the Zhumell 10" and the eyepieces used were the Pentax 12mm XF, 12mm Nagler, Pentax 10mm XF, and the TV 11mm Plossl.
To my eye, the differences were easily seen.
For example, looking at the double cluster, certain stars could be seen using direct vision through both Pentax eyepieces where averted vision was required to see the same stars with the 12mm Nagler.
I spent an hour or so studying the double cluster comparing the four eyepieces and came to the following conclusion.
The 12mm XF and the 10mm XW are tack sharp with amazing light throughput. The 12mm Nagler really doesnt stand a chance between the two Pentax eyepieces unless your goal is very wide fields. The TV 11mm Possl was very close but the difference would boil down to eye relief giving an edge up to the Pentax's.
If I were rich, I would keep the 12mm and 17mm Naglers but I am not so they have to go.... 
Btw, I have nothing against the TV eyepieces. All I can say is most observers would never noticed a difference and would be happy either way. I will never get rid of my TV Plossls as they are wonderful and have their purposes.
Respectfully,
Sawacs
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"Face Piles of Trials With Smiles"
Zhumell 10" Deluxe
Discovery PDHQ 12.5" F/6
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BillP
Post Laureate
Reged: 11/26/06
Posts: 3954
Loc: Vienna, VA
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Ahhh...an hour+ observing the Double Cluster! I envy you. It's been raining or overcast in my area for almost a month it seems  Anyway...what you just did is without a doubt the best approach to determine what works best ... do your own shootout and "see" for yourself 
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Bill Paolini
XT10i Dob---TSA-102 S-APO---APM80/480 S-APO--- P.S.T.
TMB Supermonos---Meade UWAs---TV Panoptic---AT Titan II ED
To your own eyes be true...
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sawacs
super member
Reged: 03/15/06
Posts: 131
Loc: KOKC Area
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Bill, this summer has been the worst summer that I can remember for cloudy skies and rain. My yard has never one dried out! I have a small back porch that allows me some observing time but I have to be picky:
Sawacs)
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"Face Piles of Trials With Smiles"
Zhumell 10" Deluxe
Discovery PDHQ 12.5" F/6
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Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1987
Loc: Prescott, AZ
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Pentax eyepieces have always intrigued me. If they were available without the #!*& safety undercut, I think my 10 or so TeleVue eyepieces would be listed for sale tomorrow morning.
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Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
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Lane
Carpal Tunnel
Reged: 11/19/07
Posts: 1515
Loc: Frisco, Texas
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I would not be to hasty to jump off the televue ship. The 10mm XW is a really fine eyepiece and one of my favorites. The 7mm may be just as good, but those two are definitely the best of the line. I am not sure the others would do as well in a side by side comparison. I have compared my 40 to the 41 Pan and there is virtually no difference except the pan is seriously ugly.
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Mounts: CGEM, ORION SIRIUS, AT Voyager/motorized
SCTs: C6, C8, C9.25, C11,
Refractors: TV Pronto, Orion ED80
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RAKing
Carpal Tunnel
Reged: 12/28/07
Posts: 2092
Loc: West of the D.C. Nebula
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Quote:
I have compared my 40 to the 41 Pan and there is virtually no difference except the pan is seriously ugly.
These things are hard to see in the dark, so it shouldn't matter. But I agree that nobody should feel embarrassed when they open their eyepiece box in public. 
So it wasn't just the great optics and the twist up eye guard that steered me to the Pentax 40XW. I guess looks did have something to do with it.
Ron
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Time spent looking at the stars is added to your life.
Tak FS-128, C925-CF, C6SE, other stray cats and refractors.
A-P Mach1 GTO
Zeiss orthos to Ethos - and some stuff in between.
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ausastronomer
scholastic sledgehammer
Reged: 06/30/03
Posts: 937
Loc: NSW Central Coast (Australia)
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Quote:
The 7mm may be just as good, but those two are definitely the best of the line. I am not sure the others would do as well in a side by side comparison.
I can tell you from experience that isn't quite the case. I have compared the XW's with Televue equivalents in most focal lengths. The 5mm XW is one of the best and IMO a better eyepiece than the 5mm Nagler T6. The 14mm XW without question outperforms the 13mm Nagler T6 in its ability to go deep and resolve dim threshhold targets. This is due to a combination of better light throughput and contrast IMO. The 13mm Nagler does have a flatter field than the 14mm XW. Put both eyepieces in a paracorr and I would take the 14mm XW each and every time because I am looking for performance criteria outside of a maximum FOV and the paracorr flattens the field in the 14mm XW (and the 20) very nicely. Similarly, the 30mm XW outperforms the 31mm Nagler in many criteria, including contrast and throughput. Ultimately, it comes back to what you are looking for in an eyepiece and what are the most important performance criteria to you.
To say that the 7mm and 10mm XW's are the only two which compete with their Nagler equivalents is grossly inaccurate.
Cheers,
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John Bambury
AS of NSW
AS of Hunter Valley
18"/F4.5 Obsession fully loaded with OMI optics
14"/F4.5 SDM fully loaded with Zambuto Optics
10"/F5 Newtonian with Argo Navis
Lots of Pentax XW's. 12mm & 17mm Nagler T4's, 31mm Nagler T5 & 13mm ETHOS. TV Paracorr and 1.8X TV Barlow and 2.5X TV Powermate
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chuckscap
sage
Reged: 07/18/09
Posts: 229
Loc: Colorado Springs, CO USA
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Things may be hard to see in the dark, but the appropriate response when you open something in the dark for a speical young lady should be: "Oh My God!"
chuck
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Rob S
professor emeritus
Reged: 03/16/07
Posts: 502
Loc: NZ
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Quote:
Pentax eyepieces have always intrigued me. If they were available without the #!*& safety undercut, I think my 10 or so TeleVue eyepieces would be listed for sale tomorrow morning.
Jeff,
Are the TV EP's you have, ones with no undercut?
If they do have them, you will be no worse off going to Pentax - but either way it would craw in my throat to have to move to an EP that had an undercut - and paying good coin for a mechanically defective piece of gear.
Regards,
Rob.
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8" f5 Dob with Feathertouch
Brandon: 16
Pentax: 7, 10 & 20XW
TMB: 30 Paragon
TV: 8 & 13 Ethos;
5 & 13 NaglerT6;
24 Panoptic
Leica Trinovid 8x50 BN
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