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Benefits of two eye night vision observing on nebulae

binoculars NV
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#1 Gavster

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Posted 26 October 2020 - 06:52 AM

I've previously written about how much I enjoy night vision observing with my Williams Optics 103mm pegasus binoscope:

https://www.cloudyni...sion-binoscope/

 

However, recently I've either been using my grab and go refractors for quick and easy observing or my C11 or 16 inch dob for more serious sessions. Since the WO binoscope is not grab and go (requiring my Panther TTS-160 mount) and also has relatively small aperture, I haven't had a proper outing with it since April. Weather conditions have been poor in the UK for the last month or so, but the forecast last night was for clear skies from 2am, and with Orion nicely visible at that time from my London back garden, I decided it was about time to dust off the binoscope for a proper large nebulae session.

 

I've also acquired 2x 67mm televue nv plossl adapters so it was a good opportunity to test these out for binoscope usage. With the 67mm, the setup has a nice fast f2.6 effective speed, 11x mag and 3.5 degrees fov, perfect for those famous large nebulae that grace the sky at this time of year. Due to the severe light pollution in my back garden (sqm 18.6 as measured last night), I use a very narrow 3nm chroma ha filter with each monocular.

 

According to specialist nv binocular users I commit a cardinal sin by using very mismatched monoculars, in the left I use a Photonis 4G PVS-14 (actually gen 2 tech but top end) and in the right a Harder gen 3 PVS-14. The harder tube has nearly double the luminance gain of the photonis (the key drawback of gen 2 tech) but also has a materially higher sn. Having the monoculars side by side its extremely easy to do direct comparisons of the different tubes by switching from one to the other in mono mode. The lower gain coupled with the narrow 3nm ha filter resulted in the photonis being obviously visibly less good, the nebulae fine detail was noticeably less clear and distinct compared to the Harder. However, the brain is a fantastic thing and in bino mode even with the drawbacks of the Photonis tube, the views were a big jump better than the Harder mono mode (again easy to see, just by switching the photonis tube off and on!). I mentioned in my previous thread a number of advantages of bino nv observing, but the key one apparent to me last night was just how clear fine detail was in the nebulae compared to the mono mode. The brain really does some awesome stuff. I've decided that the next time I visit a dark site, I will be taking my binoscope with me - I've only used it in LP London and am itching to see the results at a dark site.

 

The nebulae views I was getting last night were the best I've had from London (the 67mm televue eyepieces making a difference here also, working really well albeit with some vignetting due to the ~38mm image circle of the binoscope. The vignetting wasn't a particular issue for me as the vast majority of the fov wasn't impacted visually and I won't be using this system for taking phone photos!).

 

M42 was the obvious first port of call given Orion was blazing bright in the southern sky and the full extent of the extended nebulosity was clearly visible. Then onto the horsehead and flame which were bright and the horsehead had a nice shape even at this low magnification. But the first wow moment really was the Rosette in which lots of intricate detail was visible which isn't the case usually from London. The bino mode really "smoothed" out the nebulosity and the fainter bits became much clearer, but it was the sheer fine detail shown that blew me away given the observing conditions. The fox fur nebula and cone were easy to see, something that hasn't happened for me from London before. The wide band of Barnard's Loop was very contrasty.

 

Then I scanned around enjoying all the other nebulae highlights including seagull, monkeyhead, lowers (very nice when often it disappoints me at a LP site), monkeyhead (that's a bright one!), jellyfish, sharpless 254/255/257 (a bit small but all three clearly visible, first time I've observed these from home, I stumbled upon these by accident in Gran Canaria in a 16 inch dob in February), spider and fly nebula, and flaming star.

 

To finish off a very enjoyable session, I scanned over to the California which provided another "wow" moment, the top and bottom bands were very distinct but also the fine nebulae detail within was fantastic. I did a quick comparison with mono mode and this object unambiguously showed how much of a difference two eyes makes on nv nebulae observing. A similar thing happened on the final objects of the night, the heart and soul, looking much like the views and phone images I have taken from dark (21+ sqm) sites, wonderful.

 

Now I must getting planning that dark sky trip for the next new moon....

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Edited by Gavster, 26 October 2020 - 08:08 AM.

  • GeezerGazer, Starman27, REC and 4 others like this

#2 PEterW

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Posted 26 October 2020 - 08:00 AM

Epic stuff, who needs dark skies?!

Peter

#3 gatorengineer

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Posted 26 October 2020 - 10:24 AM

Get a siebert 2" Binoviewer...... nice setup.....



#4 Gavster

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Posted 26 October 2020 - 10:49 AM

Get a siebert 2" Binoviewer...... nice setup.....

A few people have tried nv with binoviewers but been disappointed with the results due to the split light beam eg

https://www.cloudyni...nv-binoviewing/



#5 gatorengineer

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Posted 26 October 2020 - 06:01 PM

Throw enough aperature at it, (36") and it would only be like monoviewing 24's....LOL.  Interesting thread.



#6 GeezerGazer

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Posted 26 October 2020 - 09:45 PM

Thanks for the lovely report.  Sounds like a great session! 

Ray


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