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gaz-in
sage
Reged: 12/17/07
Posts: 443
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Post deleted by gaz-in
Edited by gaz-in (11/02/09 06:50 PM)
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gaz-in
sage
Reged: 12/17/07
Posts: 443
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Post deleted by gaz-in
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gaz-in
sage
Reged: 12/17/07
Posts: 443
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Post deleted by gaz-in
Edited by gaz-in (11/02/09 07:07 PM)
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skyward_eyes
Carpal Tunnel
Reged: 12/12/06
Posts: 2105
Loc: Arizona
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TMB has the exact same eyepieces.
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star drop
Guilty as Charged
Reged: 02/02/08
Posts: 16395
Loc: Snow Plop, WNY
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From what you have found the eyepieces sound like a good deal for moderate focal length telescopes, Dan.
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Ted
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gaz-in
sage
Reged: 12/17/07
Posts: 443
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Post deleted by gaz-in
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hfjacinto
Almost got me
Reged: 01/12/09
Posts: 2096
Loc: Union,NJ
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Dan,
Thanks for the review. Sounds like a bargain. 90% of the performance for 50% of the cost.
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C9.25 ASGT 9*50 MM Finder,FT Focuser & 2" Diagonal
Meade LXD 75 6 Inch SNT w 9*50 MM Finder
5,6,9,14.5 MM Zhummel Planetary EPs
13,17,21,24,31,36 MM Baader Hyperion
6.7,8.8 MM Meade UWA & 11 MM Nagler T6
Planetary, OIII and Narrowband Filters
Thousand Oaks Dew Control w Kendrick Heaters
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Scott Watson
sage
Reged: 05/26/06
Posts: 282
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For most telescopes, 30ft is hardly "infinity" - the value the telescopes are optimized for. Frankly, I'm surprised you could even rack your focus enough to make them work. Next time you try this test, use little dots and put them much farther away. It will provide a more strict and more realistic test.
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gaz-in
sage
Reged: 12/17/07
Posts: 443
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Post deleted by gaz-in
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starrancher
professor emeritus
Reged: 06/09/09
Posts: 620
Loc: Northern Arizona
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Quote:
Yeah Ted, I concur it does seem good for moderate FL scopes....next I will try it outside in my 8" F6 DOB... my larger F5 DOB is being built by Rob Teeter and will not be ready till around the first of the year...so tests in it will have to wait...although the eyepieces seems like a good deal for $212 per eyepiece shipped...
Hey Dan ! after you're done testin' on the f6 , while you're waitin' on the f5 , I'll be more than happy to check 'em out on my f4 ! 
Just PM me for the address . 
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LXD75 AR5
LXD75 SN8
Series 4000 Plossls
Misc. other stuff
Fort Rock , Az .
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1304
Loc: Ottawa, Ontario, Canada
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Gaz-in,
Scott wasn't being cheeky; he highlighted 'infinity' simply to draw attention to the fact that a telescope is optimized to work best when the target lies at optical infinity. In such case all light rays enter the objective parallel.
Your 30 foot target distance is rather on the short side, and so spherical aberration will be present, no matter how perfect the objective. Setting the target more like a couple hundred feet away would be better.
Regarding field curvature... Any 'simple' objective lens or mirror (i.e., not employing additional optics 'down stream' to specifically flatten the field) suffers from this. In general, the field's radius of curvature is roughly 1/3 the objective focal length. As you can see, a short focal length 'scope will have a more strongly curved field than will one of long focal length. Add to this the fact that an eyepiece (or CCD chip, etc.) which covers a larger field will suffer a greater degree of curvature of field. That's why your 16mm seems worse than the 9mm.
If an optical designer chooses to, he can make an eyepiece's inherent field curvature whatever he wants, within limits. But which value to settle on? Because telescopes are available with a huge range of focal length--and hence degree of field curvature--no one value will work in all cases. So a compromise is made which is believed should cover the most common cases.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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star drop
Guilty as Charged
Reged: 02/02/08
Posts: 16395
Loc: Snow Plop, WNY
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Quote:
For most telescopes, 30ft is hardly "infinity" - the value the telescopes are optimized for. Frankly, I'm surprised you could even rack your focus enough to make them work. Next time you try this test, use little dots and put them much farther away. It will provide a more strict and more realistic test.
I have a modified Tuthill 50mm f/4 finder that accepts 2" barrel diameter eyepieces. All of my Naglers and a Meade UWA provide images with noticeable straight line distortions when used to look at kitchen cabinets at a distance of fifteen feet. If I used that setup to decide to accept or reject an eyepiece I would not own any eyepieces. In my humble opinion the fact that Dan was getting good results with a near focus indicates that the results will be better under normal use.
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Ted
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jack45
Carpal Tunnel
Reged: 07/07/03
Posts: 2475
Loc: Lacey WA
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I'd like to see Celestron and Meade come out with a 100 deg ep. If I were a betting man, I'd say Meade will be next.
Clear Skies!
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16"f/4.5 Discovery Split Tube/TV Paracorr
12.5"f/5 Discovery PDHQ
Orion f/4.9 XT12"Intelliscope
BV's/Bugress Model 24/Stellarvue Model BV3A
TV Smooth Side Plossls,7.4mm,10.5mm,17mm,21mm,26mm
Nagler EPs 9mm T/2,13mm T/1,16mm T/2,20mm T/2,26mm T/5
Axiom EPs 23mm,31mm LX,22mm Panoptic
UO EPs 5MM,6MM,7MM,12.5MM
Baader Hyp 8mm-24mm Zoom
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csa/montana
Den Mother
Reged: 05/14/05
Posts: 40316
Loc: montana
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Since the OP has deleted all his posts, making the thread ineffective; it will now be locked.
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Pentaxes; 5XW, 7XL, 10XW.
14mm Meade 4000 UWA
TV Panoptics; 22, 35
DreamCatcher Dobservatory, #2
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