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Steve Napier
Carpal Tunnel
Reged: 05/10/04
Posts: 1559
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Hi everyone My name is Steve Napier and this is my first post on the Cloudynights Forum. Im 37 and have been using Binoculars for 30 years now.
I have a pair of Carl Zeiss Jena 10*50 Dekarems.I bought these before the Berlin Wall came down when Jena Binoculars were still at a reasonable price.I paid about £90 for them.
They have a FOV of 7.3 degrees,and here lies the problem.
I feel these binoculars would be far superior for Astronomical use if the field was about 5 degrees.
About three quaters of the way to the edge the stars look like seagulls!
The quality at the centre is excellent,very sharp and very bright.
I used to own a VERY cheap pair of Japanese binoculars whos optics were nowhere near as good as the Zeiss model but I enjoyed using them better as whole of the FOV could be seen with my eye giving a wonderful impression of total blackness surrounding the field of view.
I dont get this with the Zeiss binoculars.
Does anyone else feel they would benefit from binoculars giving a smaller FOV without the Seagull stars?
Thankyou
Steve.
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Anonymous
Unregistered
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In general, large FOV (like 7.3 degrees) invites increased edge distortions. There are special lens materials that can mitigate the distortions. But to answer your question, ideally I would like binos with no edge distortions, never mind the FOV! I'll take a reduction in the FOV to reduce the distortions.
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wilash
Fairy Godmother
Reged: 09/30/03
Posts: 5746
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Steve, have you tried an aperture mask to improve the images. Just slightly smaller like 45mm might reduce the abberations to an acceptable level. You could make them out of slip-on caps. Experiment with some paper masks to find the best aperture first. That way you can keep the large FOV. Just an idea.
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wilash
Fairy Godmother
Reged: 09/30/03
Posts: 5746
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By the way, welcome to Cloudy Nights.
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brocknroller
Pooh-Bah
Reged: 10/16/03
Posts: 1435
Loc: Cloudy Valley, PA
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Steve,
You can have your cake and eat it too, if you're willing to pay the price. Here's a review of three top brand wide field 10X50s, the Fujinon has the best edge performance (~ £370).
http://de.geocities.com/holger_merlitz/fujinon10x50.html
The Nikon 10X42 Superior E also has very good edges, and a relatively wide 6* FOV. It can be had for the same price as the Fujinon from US resellers. While 50mm is often considered the minimum aperture for stargazing, the SEs are extraordinarily bright, equal to and even beating many 10X50s. They also have a good close focus for birding.
If you can't afford a premium bin, and those fuzzy edges on your Dekarems bother you, you could make field stops for the EPs to reduce the FOV. John Cota, a CN bino forum member, has done this with his wide field bins and could probably tell you how to make the stops.
OTOH, wide FOV bins with mediocre edges work well for birding and even have their applications for astronomy. Last night, when I was looking for Comet NEAT, I wished I had my old Orion 10X50 Ultraview (6.5*). The edges on the Ultraview start falling off at about 60% out, but the distortion beyond the "sweet spot" wasn't that bad so I could easily make out what I was looking for, then center it.
The Celestron/EO 10X50 ED I used last night only has 5* FOV, but much better edges than the Ultraview. While 5* is sufficient for most binocular astronomy applications (how many binocular sky objects extend beyond 5*?), finding Comet NEAT took more time than it would have in the Ultraviews, particularly since looking for the comet in Monoceros was preposterous -- haze, swollen light dome, and skyglow from sheet lightening from the north. It actually didn't take that long to find because the comet was fairly bright and large, but with smaller objects, a wider FOV would have helped.
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Brock, the human tripod
****************************************
Every time I try to define a perfectly stable
person,
I am appalled by the dullness of that person.
-- J. D. Griffin
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Steve Napier
Carpal Tunnel
Reged: 05/10/04
Posts: 1559
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Thankyou for all your replies.
I will try stopping down the objectives,I never thought of this although I have done this with my old Oracle 3 when the seeing was bad.
Thanks for the welcome too.
Steve.
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KennyJ
Reged: 04/27/03
Posts: 9977
Loc: Lancashire UK
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Hello Steve and welcome to the forum from a fellow northern Englishman !
I suffer a very similar problem with my Swift Audubon Kestrels , which are 10 x 50s with a 7 degree TFOV.
They are great for daytime use though.
I've tried masking down all my binoculars for various reasons , but have not enjoyed much improvement with edge performance as a result.
Improved CONRAST - - yes -- Reduced Astigmatism -- yes
Reduced curviture - NO.
I think Brock's suggestion of following John Cota's idea of making field -stops for the eyepieces is far more likely to work , but it's the first I've heard of it so cannot advise you on how to do it .
Pretty simple I would have thought though.
Do let us know how you go on Steve.
Regards , Kenny.
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Two eyes and a preference to use both
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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Steve Napier
Carpal Tunnel
Reged: 05/10/04
Posts: 1559
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Hi Kenny and thanks for the welcome.I will try to stop down.Its been wonderful reading everyone"s posts reviews and articles,really pleased I have come across this wonderful site.
Ive also got a cheap pair of Tento 20*60s which are good value for money.An excellent lunar binocular for the money.
Steve.
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