March 29th on the South Downs - a mixed night under the stars

[Stu]

In many ways I should be, and am, grateful that the skies cleared all night for my club's dark sky trip this month to the South Downs. At best we saw mag 21.2 skies which is pretty impressive, but the transparency was poor and it stopped the galaxies from giving their best, and us from going as deep was we would have hoped. There was quite a glow from Bognor Regis to the South, worse than I had seen previously, presumably because of muck or moisture in the atmosphere. The faintest galaxy I reached was mag 12.5 I think and brighter ones lacked the contrast I would expect from these skies.

I work just outside Dartford and it takes 1.5 hours to get to the site from there. An extended (but good!) meeting with my boss made me about 35 mins later than expected and I ended up setting up in the dark rather than the leisurely daytime process I was hoping for. A bit of phaffing around with the laser and the 14" Sumerian was collimated. The various adjustments I've made to it recently have made life easier. The primary collimation had got very stiff, a simple tweak of a few nuts sorted that after contacting Sumerian for advice. I also rounded the secondary collimation bolts to stop it twisting the secondary when adjusting. Lastly, whilst still tight, attaching the alt bearings is now loosening up a bit.

We had a good turn out, 6 members and 4 scopes including Gavin's Skyvision 16" Goto dob, my 14" Sumerian Alkaid and John's 72mm TS on an AZGTi.

M42 was the obvious first target. Magnificent as usual, it had a clear green tint to it even when viewed unfiltered. Adding a UHC boosted the contrast nicely, really lovely structure visible with the arcing Bat wings. Whilst in the area I had a look to see if I could detect the Flame nebula but despite being well dark adapted there was nothing there.

I had a trawl around the normal brighter targets to see how they looked in the 14" ie DC, M36, 37, 38, 67, all looking good, but galaxies were looking fairly washed out due to the poor transparency. In fact, what I had intended to be as a purely visual outing turned into a visual followed by NV in order to see what it added and to allow us to see some of the fainter targets.

Visually M51 actually showed quite nicely,  two bright cores, one with a much larger halo around it and showing a darker zone within it representing the gap between spiral arms I assume. The bridge between the two galaxies was not visible.

M101 was a large, ghostly oval, brightening towards the centre but with no detail visible. A shadow of the galaxy I observed in my 16" at Lucksall some years ago.

M81 and 82, nice as ever. M82 showing a faint bit of structure to it in the central portion. The Leo triplet likewise were visible but not amazing, NGC3628 was very faint. Given that I can't see these chaps from home though, they were still great to get.

Moving on, I had really wanted to have a good look at Markarian's Chain, and having found M49 I began a fun galaxy hop via NGCs 4469, 4442, 4429, 4371 until I reached the triangle of galaxies including M84 and M86. I was able to follow the chain down to NGC4477 although I could not see 4458. Whilst in the area I caught M87, 88, 89 and 90.

Moving over to Coma Berenices, M53 was easily found, but try as I might, NGC5053 was nowhere to be seen. Must be a tough one, will try again on a better night. The Needle Galaxy showed some extention into the edge on spiral arms, although nothing like the intensity I've seen it before, whilst the whale was quite distinct, although not particularly whale-like - someone had a good imagination for that I think!

M1 looked surprisingly large, although featureless. I've not seen it that often and this was probably the best yet.

So, after about as much as I was going to get visually, what difference did adding the Photonis NV make?

Well, the answer varied alot depending upon the object type. Galaxies showed the smallest improvement, probably unsurprisingly, whilst globular and open clusters were significantly improved. Emission nebulae showed the most dramatic improvement, as expected, due to the heavy filtration used to observe them.

All comments from here on refer to observations made with the Photonis NV monocular fitted to the 14" Sumerian via 55mm Plossl and 6nm nebula filter or 642nm Galaxy filter.

Having tried and failed on the Flame earlier, it was now immediately obvious. The central lane plus other detail was there to be observed. Moving to IC434, this appeared as a relatively bright line with the Horsehead Nebula clearly visible, showing the difference the additional aperture and dark skies make vs the view in my Genesis from home the other night. The snout of the horse was not quite separated from the rest of IC434, but very nearly. A very nice view of an object otherwise impossible to view on the night.

M42 was dramatically enhanced, way more structure visible within the nebula and it was more extensive. M43 showed very distinctly, I often struggle to get a decent view of this one but it appeared like a comma, or even a circle with one quarter missing.

The Rosette was a little to large to fit comfortably in the field of view, so the overall was a little hard to observe, but there was some good petal-like structure visible. California was similar in that it would not fit in the fov, but at least was now visible and again, structure was visible in terms of the brighter outer edges.

The Globs viewed were all enhanced significantly as mentioned, much better resolution of stars, even if the stars themselves were not quite as nice to view. M13 was quite muted under these conditions without NV, but pop the magic device in and there was the Propeller, plain as day. Similarly M92, M3 and M5 all looked much better.

Finally galaxies. The structure in M82 was significantly improved, much better contrast in the central areas. M81 was brighter and larger but did not show any further detail.

M51 was a good one, enhanced halo and more defined structure within the halo. Similar type detail to the visual view, just brighter and better contrast.

Makarian's Chain was again just brighter and with more contrast between the background and galaxy, presumably from the filtering. I was able to spot a number of fainter galaxies which were not there without the NV such as NGCs 4402 and 4425. I think, if I recall correctly, that NGC 4461 also split from 4458.

I hope this has been a useful indication of the differences in what could be observed  visually vs NV under the same conditions. The benefit ranges from a small increment in detail visible and being able to spot slightly fainter galaxies, through much improved resolution of globular to showing you the virtually invisible with the likes of the Horsehead. There will have been some impact on my night vision from using the monocular, though I tried to make sure I looked at everything just through the eyepiece first to avoid that as much as possible.

A fun night out, great to get some clear skies for once and good confirmation that mag 21 plus skies are available within 1.5 hours of London. Shame about the transparency but still, some lovely targets seen.

[Littleguy80]

Very nice session, Stu. We were observing a lot of the same targets that night  Sounds like you’re enjoying having some decent aperture again with the 14”. 

[BGazing]

Nice one, sucks that it was humid. There are only so many moonless clear nights.

We were lucky this Saturday, completely clear at our fav dark star spot, 21.73 SQM and no moisture. 12 inch dob showed spiral structure of M51 and even M101, while C8 zoomed into Whale, Silver needle and Needle. M42 the obvious target, but a pleasant surprise was Thor's helmet in mere 8 inches and OIII. It really resembles pictures.

Last year we recorded 21.77 at the same site and I could swear it made a bit of difference on galaxies. One can compensate by going higher, improves transparency.

[Stu]

2 hours ago, Littleguy80 said:

Very nice session, Stu. We were observing a lot of the same targets that night  Sounds like you’re enjoying having some decent aperture again with the 14”. 

Thanks Neil, yes I had noticed that

The 14" is great, so compact and easy to take around. Such a shame the transparency didn't play ball.

[Stu]

47 minutes ago, BGazing said:

Nice one, sucks that it was humid. There are only so many moonless clear nights.

We were lucky this Saturday, completely clear at our fav dark star spot, 21.73 SQM and no moisture. 12 inch dob showed spiral structure of M51 and even M101, while C8 zoomed into Whale, Silver needle and Needle. M42 the obvious target, but a pleasant surprise was Thor's helmet in mere 8 inches and OIII. It really resembles pictures.

Last year we recorded 21.77 at the same site and I could swear it made a bit of difference on galaxies. One can compensate by going higher, improves transparency.

I reckon every little but makes a difference although it may have been a difference in transparency?

I do recall at SGL10 objects like the Needle and M101 were so much better in my 16", but that was as much sky conditions as a thing else. I really want to get a decent transparent night on these targets, it's been a long time since I saw them well.

Can I order a heavy downpour on a Thursday night, ahead of a clear Friday when I'm free and we have arranged a club night? That's not too much to ask is it???

 

[BGazing]

3 hours ago, Stu said:

I reckon every little but makes a difference although it may have been a difference in transparency?

I do recall at SGL10 objects like the Needle and M101 were so much better in my 16", but that was as much sky conditions as a thing else. I really want to get a decent transparent night on these targets, it's been a long time since I saw them well.

Can I order a heavy downpour on a Thursday night, ahead of a clear Friday when I'm free and we have arranged a club night? That's not too much to ask is it???

 

It could have been transparency, but my impression was that 21.77 night was more humid, and consequently less transparent.

Downpour on Thursday meens a lot of humidity on Friday, be careful what you wish for.

[Stu]

15 minutes ago, BGazing said:

It could have been transparency, but my impression was that 21.77 night was more humid, and consequently less transparent.

Downpour on Thursday meens a lot of humidity on Friday, be careful what you wish for.

Hard to get it all right at once. I've often noticed that the night after a downpour the skies are transparent because all the muck has been washed out of the atmosphere. Takes a few days to build up again.

[scarp15]

Good report Stu and for conveying the descriptions accounting for the conditions and Unihedron SQM-L ave reading. A devise I am aware that you have been using for a while, it is reassuring that there are steadily more users referencing (Unihedron) SQM-L (average) readings to acknowledge their deep sky session reportings - instead of random quotes from online maps. Great that you had a system for assembling and collimating the truss dob after dark. Interesting comparison between the two observing methodologies. The average at best transparency conditions are clearly defined in your report, the subsequent NV outcome such as based on globular's, expressing the image. Within improved transparency conditions as of course we know and 21.2 mag skies, good sized aperture dob, the Globs are sensational and much else is possible and engaging. It is alarming how much distant sky glow can impact a location, particularly in those moisture prone conditions, Green Belt zones do not have the necessary protection anymore. It is actually probably only us visual astronomers, aiming to become dark adapted, ecologists and perhaps a bunch of nightscape photographers / aurora hunters, that actually get to witness this - all in the name of 'progress'.