ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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looking for some recommendations on 1.25 eps in the 24-26mm range with up to a 70 deg afov. I have tried the Hyperion (too big) and cannot afford the Panoptics. Prefer sharp field stop and sharp to the edge over a wider afov. Considering televue 25mm Plossl and meade 5000 26mm. Also heard the Burgess stellar eps might be an option.
Thanks
Patrick
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12588
Loc: Cumberland, R I , USA42N71.4W
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No 24-26mm eyepiece near 70° will have a sharp field stop in a standard binoviewer. The field stops will all be too wide for the standard binoviewers and will be vignetted.
Regardless of what anyone tries to argue, the widest available field stop in a 1.25" 26mm eyepiece will show only 63°. The widest available field stop in a 24mm eyepiece, the Panoptic, will only show you 64°.
The so-called 22mm clear aperture binoviewers all have a prism aperture stop of 20mm. The widest 24-26mm eyepiece field stops that will not show vignette, eyepieces in which you will clearly be able to see the field stop, would be 24-26mm plossls.
Even the widest clear aperture 1.25" binoviewer, the Denk, which has a true prism aperture of 25+mm, but less than 26mm, will slightly vignette the 24 Panoptic.
I've used all of these:
The 26mm Meade 5000 will vignette, and has at best mediocre outer edge sharpness. However it does exhibit good contrast. The older Meade 4000 SP 26mm plossl gives up a bit in contrast but has much better outer edge sharpness and does not vignette. The Stellervue 23mm eyepieces are mediocre and do not measure up near the TV plossls or the Meade SP4000. I'd rate these as low-mid quality plossls. The Televue 25mm or the older smooth sided TV 26mm plossls would both be better choices. So would the 24mm Tak LE.
edz
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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thanks Ed - so no pint in getting anything wider than 60 degrees unless I go to a 26mm bino like the Denk. So what would you recommend in the 60 deg range?
thanks
RP
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12588
Loc: Cumberland, R I , USA42N71.4W
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I have not found an eyepiece in the 60° range that I would recommend over the TV25pl, TV26pl or TakLE24pl.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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thanks Ed - I was leaning towards the TV 25mm plossl, even though it's not 60 deg - I really like the TV plossl line
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Nick Lloyd
Carpal Tunnel
Reged: 10/24/06
Posts: 1641
Loc: cincinnati
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The TV plossl is a great planetary/luna eyepiece for the $... which is where binoviewing comes into use most often.
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"The best scope is the one you use." -rcg
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ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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Yup - I agree. For whatever reason, I was not "blown away" by the view of dso's through the BV - however, the moon and the planets are a completely different story.
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Nick Lloyd
Carpal Tunnel
Reged: 10/24/06
Posts: 1641
Loc: cincinnati
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For DSO objects, my 28mm RKE pair sees a lot of use. High contrast, lightweight, comfortable eye relief. These seem to work better if the observer is seated, rather than standing. YMMV.
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"The best scope is the one you use." -rcg
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ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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Hi Ed -
if you don't mind, could you please help understand how to figure what is the lowest power plossl ep I can use in my 22mm BV without vignetting? and how about if I jump up to a 26mm denk or earthwin? I currently have 2 - 32mm TV plossls that I use in my 22mm BV, but the field stops are blurry in the BV - is that because of vignetting? My scopes are an 8" f/6 DOB and a 10" f/7 planetary DOB.
thanks for your help
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ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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thanks Nick - and by the way, what does YMMV stand for?
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12588
Loc: Cumberland, R I , USA42N71.4W
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See the resources link and read the posts on Clear Aperture. FWIW, there are no 22mm binoviewers. All of them have a prism aperture of 20mm. Some of them refer to that as 22mm clear aperture because the they are referring to it by the general size of an eyepiece field stop that it will illuminate.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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thanks again , Ed !
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ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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Hello Ed -
the ep chart is awesome - thank you for doing all that work for the rest of us.
I have a question about using an OCA in front of the binoviewer. If I use a 1.3x OCA with 32mm plossls, would I use the fov/vignetting data for the adjusted fl? for example, If I use a 32mm TV 1.25 Plossl with the 1.3x OCA, it comes out to about the same specs as a 24mm. Would I then look under the 24mm tab to see how much fov loss there would be?
thanks
RP
Edited by ruachsheavens (08/31/08 04:21 PM)
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CESDewar
GorillAstronomer
Reged: 01/16/05
Posts: 1812
Loc: Morganton, GA, USA
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Quote:
thanks Nick - and by the way, what does YMMV stand for?
YMMV = "Your Mileage My Vary" - in other words "this is my opinion, but I recognize that other people may have a differing opinion based upon their circumstances"
BTW (By The Way) - all you need to do with acronyms like this is go to google and enter:
#define YMMV
and you'll get your answer!
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David E
Carpal Tunnel
Reged: 05/25/06
Posts: 1756
Loc: North Carolina
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Quote:
Considering televue 25mm Plossl and meade 5000 26mm. Also heard the Burgess stellar eps might be an option.
Thanks
Patrick
My vote for those three would be the Televue Plossls. Also, a good "poor man's Panoptic" is the SmartAstronomy EF19. Not as sharp at the edge as a Pan but acceptable for its price range IMO and it has excellent on-axis performance. It is also very well protected against ghosts and off-axis flaring.
David E
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David E
So when at times the mob is swayed
To carry praise or blame too far,
We may choose something like a star
To stay our minds on and be staid.
-Robert Frost
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12588
Loc: Cumberland, R I , USA42N71.4W
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FOV and vignette is not controlled by focal length. Iit is controlled by the prism aperture in the binoviewer and the field stop aperture in the eyepiece, regardless what the power is.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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ruachsheavens
professor emeritus
Reged: 07/17/05
Posts: 530
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thank you
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