skysurfer
13-08-2014, 03:21 AM
There is a discussion on CloudyNights in the subforum 'Binoculars' about Vixen SG 2.1x42 Widefield Binoculars (http://www.cloudynights.com/topic/463676-vixen-sg-21x42-widefield-binoculars/) which is more a 'binocular wide field observing device'. It shows a large FOV (28 degrees I believe) it is not an 'ordinary' bino and just enhances naked eye views peering about 1.5 magnitude deeper into the sky. But I consider the price of $300 somewhat too steep.
I selected the Panoptic 24 which has one of the largest possible TFOV for a small sized (1.25") eyepiece.
So I experimented with my 85mm f/1.8 Canon lens which I use for widefield astrophotography and a Panoptic 24 eyepiece. Due to the weather not under the stars yet, but the image quality looks promising. OK, just single eye as a telescope and upside down image but I don't mind. The FOV is 18 degrees, allowing most of Cygnus or Orion constellation, or the Southern Cross and the Pointers in one field.
Really crisp, contrasty and razor sharp nearly to the edges despite the steep f/1.8 light cone.
When you already have such lenses and don't mind upside down views (a 50mm lens with a 20...25mm eyepiece will get close to the Vixen SG 2.1x42 28º FOV) the investment is only a few dollars for a rear lens cap and an 1.25" PVC plumbing tube socket.
A Nagler 13 gives a really amazing field with this lens: 6.5x47 with a FOV of 12 degrees.
Unlike the mini binos or opera glasses. it allows exchangeable eyepieces and use of filters such as UHC or OIII. And taking less gear with me on holiday as I already take the lens(es) with me for astrophotography and the eyepieces as well for the telescope.
So for me, these advantages outweigh the disadvantages of single eyed upside-down image viewing.
Test under the stars
11 August at night, but not dark because of Full (Super-)Moon, and crystal clear transparent sky after weeks of hazyness of Dutch skies.
I tested the same two Canon lenses: EF 50mm f/2.5 macro and EF 85mm f/1.8, both with Televue Panoptic 24mm (2.1x20 resp. 3.5x47).
2.1x20: Not really much gain compared to naked eye, M13 was barely visible. FOV 29 degrees, Comparing the same star with one eye naked and the other eye through the scopelet showed barely difference. But sharp to the edges. Cygnus fitted in one field. So I am lucky I did not waste $300 for the Vixen SG 2.1x42 which should have about equal performance, only a little boost (< 0.4 mag) because of 2 eyes viewing.
3,5x47: This is a real 'naked eye light pollution fighter' for such nights. FOV 18 degrees, stars to beyond mag 7 while the NELM was 4.5-5. Comparing the same star with one eye naked and the other eye through the scopelet showed a great difference, not as much as my 10x50, but close. M13 and M92 were visible, nice view of Lyra (no M57 of course) lots of stars in Cygnus, I got Deneb, gamma, delta and epsilon Cygni easily in one field. Same as the other lens: sharp till the edges and no color errors. GlennleDrew : yes with my 5mm night pupil (dark nights : 6mm) it still is sharp despite f/3.
Comparable in FOV and magnitude gain to Libra 4x22 but with MUCH better IQ. Recently somebody tested that mini bino but the edge sharpness was disgusting ....
To be tested yet under a really dark sky and also with filters.
Conclusion: the 50mm is so-so (but I'll test it under dark sky) but the 85mm looks promising. Very good image quality, which I already know from the (astro)photos made with it, so it not only an excellent photographic but also an excellent visual performer.
Of course a Canon 85 (or 50) + Panoptic 24 cost over $500 together but if you already have that stuff you can better take the single eyed upside down image for granted (but sharp to the edges) than spending another $300 for the Vixen SG 2.1x42.
Australians having such lenses and eyepieces can get even more fun with such devices as the skies in 99% of AU are really dark when the Moon is absent. Think about the Coal Sack, the center of our Galaxy and possible Barnards Loop (with a filter) ?
I'll try that on my upcoming South Africa trip.
I selected the Panoptic 24 which has one of the largest possible TFOV for a small sized (1.25") eyepiece.
So I experimented with my 85mm f/1.8 Canon lens which I use for widefield astrophotography and a Panoptic 24 eyepiece. Due to the weather not under the stars yet, but the image quality looks promising. OK, just single eye as a telescope and upside down image but I don't mind. The FOV is 18 degrees, allowing most of Cygnus or Orion constellation, or the Southern Cross and the Pointers in one field.
Really crisp, contrasty and razor sharp nearly to the edges despite the steep f/1.8 light cone.
When you already have such lenses and don't mind upside down views (a 50mm lens with a 20...25mm eyepiece will get close to the Vixen SG 2.1x42 28º FOV) the investment is only a few dollars for a rear lens cap and an 1.25" PVC plumbing tube socket.
A Nagler 13 gives a really amazing field with this lens: 6.5x47 with a FOV of 12 degrees.
Unlike the mini binos or opera glasses. it allows exchangeable eyepieces and use of filters such as UHC or OIII. And taking less gear with me on holiday as I already take the lens(es) with me for astrophotography and the eyepieces as well for the telescope.
So for me, these advantages outweigh the disadvantages of single eyed upside-down image viewing.
Test under the stars
11 August at night, but not dark because of Full (Super-)Moon, and crystal clear transparent sky after weeks of hazyness of Dutch skies.
I tested the same two Canon lenses: EF 50mm f/2.5 macro and EF 85mm f/1.8, both with Televue Panoptic 24mm (2.1x20 resp. 3.5x47).
2.1x20: Not really much gain compared to naked eye, M13 was barely visible. FOV 29 degrees, Comparing the same star with one eye naked and the other eye through the scopelet showed barely difference. But sharp to the edges. Cygnus fitted in one field. So I am lucky I did not waste $300 for the Vixen SG 2.1x42 which should have about equal performance, only a little boost (< 0.4 mag) because of 2 eyes viewing.
3,5x47: This is a real 'naked eye light pollution fighter' for such nights. FOV 18 degrees, stars to beyond mag 7 while the NELM was 4.5-5. Comparing the same star with one eye naked and the other eye through the scopelet showed a great difference, not as much as my 10x50, but close. M13 and M92 were visible, nice view of Lyra (no M57 of course) lots of stars in Cygnus, I got Deneb, gamma, delta and epsilon Cygni easily in one field. Same as the other lens: sharp till the edges and no color errors. GlennleDrew : yes with my 5mm night pupil (dark nights : 6mm) it still is sharp despite f/3.
Comparable in FOV and magnitude gain to Libra 4x22 but with MUCH better IQ. Recently somebody tested that mini bino but the edge sharpness was disgusting ....
To be tested yet under a really dark sky and also with filters.
Conclusion: the 50mm is so-so (but I'll test it under dark sky) but the 85mm looks promising. Very good image quality, which I already know from the (astro)photos made with it, so it not only an excellent photographic but also an excellent visual performer.
Of course a Canon 85 (or 50) + Panoptic 24 cost over $500 together but if you already have that stuff you can better take the single eyed upside down image for granted (but sharp to the edges) than spending another $300 for the Vixen SG 2.1x42.
Australians having such lenses and eyepieces can get even more fun with such devices as the skies in 99% of AU are really dark when the Moon is absent. Think about the Coal Sack, the center of our Galaxy and possible Barnards Loop (with a filter) ?
I'll try that on my upcoming South Africa trip.