The merits of 3x vs 1x night vision observing

[GavStar]

I attended my local astro meeting last night which unfortunately despite a promising weather forecast earlier in the week turned out to be clouded out. But it was nice to catch up in the pub for a beer anyway and we had a good turn out. @Stu‘s efforts with the club website are clearly paying dividends.

Nevertheless, I was frustrated that I wasn’t able to do any observing and decided to get up at 4.30am when the forecast looked very good. Luckily I was greeted by completely clear skies but with the sky going to start brightening within an hour I only had time for some quick 1x and 3x night vision viewing.

I started with my 1x NV binocular setup as per below.

At this time, Cygnus was at a decent height so I focused on this area as I hadn’t observed it for a while.

Despite being in my light polluted London garden, I got some really nice views with a decent amount of fluffy nebulae above the North America and gamma Cygni nebulae. Comparing one eye vs two eyes again confirmed the material benefits of binocular viewing. Ic1396 was also visible but I couldn’t see the Veil.

Overall though I got the best views widefield I’ve had of this region from London - beginning to show some of the extended nebulosity in the region that previously I’ve only seen from dark sites.

I then switched to my 3x mono NV setup as per this second image.

I have to say this setup has been a bit disappointing for me in the past and I haven’t used it much. I’ve found the significant vignetting offputting. But this time I had a pleasant surprise. The vignetting was still there of course but after a minute or so I didn’t really notice it since I was concentrating on the excellent views I was getting.

Despite being in mono mode I could see a lot more detail compared to the 1x bino. The pelican nebula was much clearer and really stood out together with ic5068 and sh2-119. The added magnification made a remarkable difference on these objects. IC1396 had more contrast and I began to see hints of a couple of dark lanes in it.

Gamma Cygni (ic1318a, b and c) was bright and clear. Then moving down the eastern veil nebula really stood out and after a bit of concentrating I could pick out the western veil and pickering’s triangle. 

So only a very quick session but it was a nice one! And it’s caused my to reassess the merits of my 3x setup, I can see this being used much more often in the future.

[Merlin]

How much did the mono-scope cost?

[GavStar]

8 hours ago, Merlin said:

How much did the mono-scope cost?

They range from €4K to €10k

https://actinblack.lu/product/pvs14/

[GavStar]

@alanjgreen asked for details (including suppliers etc) of my 3x night vision setup so I thought it may also be useful to reproduce the info here as follows:

You can’t use 2inch filters with the 3x setup. So I’ve got a 1.25 chroma ha filter as well as my 2 inch one.

The 3x monocular I got from actinblack as normal - it costs €630.

https://actinblack.lu/product/3x-mag/

Then you need two further bits from www.rafcamera.com - the small metal pvs-14 to 1.25 adapter to add the filter into the pvs -14 night vision monocular and then an adapter to attach the 3x lens to put over the pvs-14 monocukar

https://www.rafcamera.com/adapter-envis-to-astro-1-25

https://www.rafcamera.com/adapter-envis-3x-to-pvs-14

Just to stress again there is a lot of vignetting with this setup which can’t be avoided due to the 3x adapter sitting further away from the pvs-14 due to the filter width. At first I found it very distracting but by concentrating on the centre of the fov I have learnt to really like it. It runs at f1.2 like the 1x monocular. I’d say the vignetting reduces the fov from 13 degrees to around 9.

[GavStar]

This is a photo I took last August but it gives a good indication of the views of the North America and pelican nebulae  I was getting with my 3x lens the other night.

 

Whereas I don’t think this video gives a good indication of the live eyepiece views

I’m guessing that the live video camera shows up the scintillation much more than our eyes do. In any case, I adjust the gain to reduce the scintillation such that it isn’t noticeable. Also the contrast appears noticeably lower in the video compared to what I saw in my london back garden. And at a dark site the nebulae would pop even more...

[Highburymark]

Yep - while faithfully showing the brightness of objects with night vision I think some of those YouTube videos actually put people off because of the scintillation. Fortunately it's easy to reduce that to minimal levels with a modern monocular, even if that means a dimmer image.

Nice result with the 3x Gavin. 

[PeterW]

I mount a 2” in front of the 3x, nearly fits, though I need a better adapter ring. You can sometimes find the 3x secondhand for a fraction of that price. Took me a while though.

@Highburymark exactly, with gain control and white phosphor you’d be hard pressed to tell you weren’t looking through a plain glass eyepiece.. apart from maybe the narrow field of view...

 

Peter

[mark81]

I have never paid much attention to these NV instruments before - I've never really come across them... Interesting to hear how they perform too.  

Nice report...

[PeterW]

@GavStar will be expecting this sort of view from you soon... https://youtu.be/HMVx6vLR6kI

Peter

[GavStar]

16 hours ago, PeterW said:

@GavStar will be expecting this sort of view from you soon... https://youtu.be/HMVx6vLR6kI

Peter

@PeterW that’s a very interesting video. There is very little scintillation on this one. A key difference is that he was running unfiltered here (since he was looking at starfields rather than emission nebulae) compared with using a narrowband ha filter in the previous one. Maybe this is the reason for the lack of scintillation?

Interesting discussion about tube specs in the comments as well - he was using a good tube with a signal to noise of 34. I still find the green colour offputting compared to the white ones I use. Also I would have preferred it if he took his gain down since the sky background is pretty bright even though he’s at a quite dark site.

In summary I’m pretty optimistic that my monocukars with the 3x lens will produce similar views - looking forward to trying this out in late summer! Another positive is that given I would be running unfiltered I can use the 3x lens with its standard push on adapter so the vignetting will be minimal (unlike when I’m using a Ha filter for nebulae)

[PeterW]

Yes, the scintillation would probably be lower with the brighter image, can get very strange when you kill all the input light with max gain.

Peter