Martin Meredith

From the same session, this is NGC 6445, a mag 13.2 PN, also in Sagittarius, this time with a surface brightness of 22.0. This 'wide' field shot shows the object, just over half an arc-minute in diameter, sitting in a somewhat less crowded star field. (This is one minute in RGB (4 x 15s subs) plus a few minutes of 5s luminosity subs.) It is described in one abstract as "a non-symmetric type I bipolar nebula with a very bright central ring, opened lobes, and remarkable features." Some of the structure can be seen in a single 5s sub but the addition of colour shows further features. The right hand edge seems more diffuse/wispy than the left. I'm seeing this as a tilted hourglass, presumably the pair of lobes spreading out from a pinched central region. The central star has magnitude 19.0. Consulting the figures in this paper I see that in fact all I have caught is the 'very bright central ring'. The lobes are barely visible in broadband imaging. The lobes in the images from the article are visible to differing extents in H-alpha, O-III and S-II. This is definitely one to return to with narrowband to try to catch some of the butterfly-like wing structures (seen in H-alpha) that would be visible to the upper left and lower right. These extend more than 1 arc-minute to each side. The left panel is my shot inverted and heavily stretched, compared to the H-alpha panel from the above paper. Cheers Martin

I'm starting this thread to encourage posting of short-exposure images of planetary nebulae. Apart from the obvious suspects, M27, M57 etc, I generally haven't had a lot of success (and have therefore avoided) these objects. They have either been relatively large and faint (many of the Abell planetarles), or small and far too bright for my sensitive, large-pixel sensor, and end up lacking all detail. Recently I've started to pay more attention to the surface brightness and size characteristics, and it seems there is a sweet spot where it is possible to obtain some detail of the structure of these fascinating objects in short observation durations (say 4-10 mins, although I would definitely spend longer than this on the more interesting objects). I suppose it is logical that most of the planetaries reside in regions where there are lots of other so-far-unexploded stars, so they can be really difficult to find. My own charts are frankly totally useless for finding most planetaries as they don't show sufficient stars (the file size of the charts would be just too big if I included stars down to the magnitude in the image). The planetarium programs I have access to also don't seem to plot enough field stars to help either. Combine this with a very small sensor and it is a bit hit or miss as to whether they appear on the frame at all. On the other hand, it is great fun trying to track them down during (or more likely) after the session! One thing that definitely helps a lot is colour, not just to appreciate the beauty and variety of these objects, but also to find them in the first place. Take this image of the mag 13.0 planetary IC 4673 in Sagittarius (surface brightness 20.3). This is actually 1 minute each of L R G and B, but displayed as mono. Its a typically dense star field on the edge of what I think is Lynds dark nebula LDN 119 to the upper right. Spot the PN? It has an apparent diameter of 0.25' in case that helps (the wider dimension of the image is around 40') ....Actually, it isn't too hard in this case (for bonus points mag 16.something PN M 2-26 is also in the image but it took me an hour to track down). Here's the same thing in colour and the PN can 'immediately' (?) be seen standing out as a grey-blue tear-shaped object. Closer in, the shape looks more like a curved piece of chorizo Star colours may well look odd as I tend to turn the saturation up more than usual.... Turning the saturation up even more in a longer exposure (about 8 mins) suggests a greenish tinge to the upper half with maybe a hint of pink towards the top. However, there is a lot of interpolation going on here so these could well be artefacts. So far I've been unable to find out much specific information about this nebula except that the central star has magnitude 17.6 (and isn't visible here). I observed this one a couple of nights ago on an evening of exceptional seeing. I'll post a few more from that session later. Thanks for looking Martin

Thanks Bill. The problem with great seeing is that it spoils the next night when the seeing returns to its usual mediocrity (as happened last night...). Actually, I did (by mistake) visit the same object on both nights so when I've sorted through the planetary nebulae I've been looking at these past couple of nights I'll post a comparison.

Thanks for that link Bill. I'll take a look tomorrow. Meanwhile the scope is cooling... Thanks Mike. I'd like to pretend I was out seeking this cluster on purpose but it was purely accidental that I came across it near another object I was looking at and the name was sufficiently unusual to let it pass by. I'm fortunate to get a reasonable view of Sagittarius here. I spent much of the session observing planetary nebulae thereabouts of which there are 100s in Sagittarius, though mainly too faint for me, and those that are sufficiently bright are hard to find amongst the star fields -- fun though! Tonight I'm hoping to spot some PNs in Aquila instead. The moon is too close to Sagittarius for comfort.

Here's a globular that is not so much dim as a little hard to spot (not helped that I didn't centre it as I was not sure whether I had it in the field or not...). I also had trouble finding it in the catalogues as I have it by its previous name. This is nowadays known as AL3 after Andrews and Lindsay who discovered it in 1967, although it was initially believed to be an open cluster. It was only confirmed as a globular cluster in 2006 as described in this paper: https://arxiv.org/pdf/astro-ph/0606718.pdf. In fact, I needed to check their Figure 1 to ensure I had the right spot. This is located in the inner bulge of our galaxy and was only identified/discriminated from the stellar field due to metallicity differences. Here's a zoomed and oriented version to match their figure. The resolution I'm getting is so much poorer than the 1.54m scope they used.... But seriously, what look like individual stars in my image are often amalgams of several. Martin

Indeed! I believe the timing is not great (happens in the late afternoon?). However, the following year there will be a longer total eclipse visible in the south of Spain. None at all since since 1905 and then 2 at once (plus an annular eclipse the following year, I believe)! Martin [edit: the 2027 eclipse is about 4m 30s in the Cadiz region: https://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2027Aug02Tgoogle.html]

This is the same pair with the same kit..... What a difference 6 degrees of altitude (and a night of better seeing) makes! Even so, this was at 17 degrees and the quarter moon was not very far away at the time. Admittedly it is a longer exposure but that isn't the point -- the stars are crisp on the individual subs. This is a glorious region of the galaxy. This is 4 x 15s in each of LRGB together with about 14 x 5s of luminosity data (this is becoming part of my live approach: lay down some colour then add in short exposure L if I want to capture spatial detail, or longer exposure L for more depth). Ignore the temp/SQM details. Temp was around 20C and SQM I guess around 19 at this point.

Very interesting post, Mike. There is a whole world of compact groups out there that I imagine are barely observed yet fascinating to look at. There is something in particular that is appealing about chains of galaxies too. You're right about that super-thin galaxy -- a wonderful object! Part of the enjoyment with EEA with these faint objects for me at least is the process of star-hopping (and occasionally galaxy-hopping too), which is just as much fun as visually. That's partly why I'm resisting the (academic) temptation to incorporate some kind of plate solving in the tool. Where would be the fun in having the object of interest appear bang in the middle of the sensor every time! There's also the serendipity of coming across other interesting things en route. Martin

We seemed to be having issues with some Palomar GCs in this thread but the other night I came across one that is far from faint. This is Pal 8 in Sagittarius. The left is a single 10s sub while the right is an LRGB combination (about 40s in each filter). This one is set in a wonderfully starry field and I imagine it is easier to spot than some of the other Palomars as it is both compact and relatively bright (though not the most compact nor the brightest of the Palomars). Reading more about them it seems they do cover a wide range of visibility. Indeed, 3 of them are among the 6 most distant 'halo' clusters in our galaxy. Spotting all of them I think would be an interesting challenge and fortunately for northern observers the lowest declination is -26 (Pal 6 in Ophiuchus) [the Palomar sky survey only went to -27 dec]. Pal 8 was discovered by George Abell The paper contains the remark: "Six of the new clusters, Nos. 1, 3, 4, 5, 12, and 13, are inconspicuous and barely recognizable because of their great distance. However, plates obtained with the 200-inch telescope by Sandage reveal that they are bona fide globular clusters." Pal 8 is regarded as a highly-reddened cluster. Here's a longer stack (I added a lot of luminosity subs; the colour is still 1 minute of each apart from blue which seems to have sneaked in an extra minute) zoomed into the central region with the colour saturation turned up a little. Presumably the whitish star at the top is a much closer foreground star. cheers Martin

I hesitate to post this one, but in the spirit of showing what is possible with EEVA techniques, here is a messy but I think interesting field containing two globular clusters that must be less than half a degree apart. There are few (if any) places where two globulars fit on to my tiny sensor. I observed this at 11 degrees and used 1s exposures to try to at least capture vaguely small stars; this is the best I could manage -- a grand total of 18s exposure before it disappeared below the roof of the church (not before producing some horrible artefacts). This is close to the galactic centre and is apparently one of the brightest regions of the Milky Way due to a relatively small amount of obscuring dust, and as such is part of an observational 'opportunity' known as Baade's Window.https://en.wikipedia.org/wiki/Baade's_Window (where there is a wonderful photo showing just how star-dense this region is). Both are estimated to be at around 25000 light-years distance. I wonder what the view is like from these globulars to one another. Ignore the time of 9.21 am; this was still on my laptop and unsaved until I came back to it this morning having abandoned any thought of saving it last night... Martin

In Mike's spirit of let's look at because we can... here's a first foray into Microscopium for me. This pair, VV 1895, transits at a dizzying 18 degrees (I observed them at about 16 degrees). South for me is right into the village streetlamps and general murk (leading to diffuse star shapes) so is never ideal for capturing low-lying objects but even so they are recognisable as spirals. The northern member is IC 5007, a mag 13.1 type Scd galaxy, while the lower galaxy is IC 5039, mag 13.2 type Sbc. There is a mag 17.4 galaxy at the N tip of IC 5039 that is just about visible. They are also listed in the Arp Madore catalogue with the description 'wide pair of bright spirals and companions' (the latter referring to a scattering of mag 16-18 galaxies in the vicinity).

Thanks Rob. I agree, the Trumpler looks like the top of a castle wall. its quite unusual to see rectangular stellar patterns though the eye-brain is a wonderful thing. Yes, the LRGB is now working to my satisfaction and remains histogram-free so there is no need to spend observing time fiddling around. It isn't that that is holding up the next release of the software, more the fact that I can't stop myself tinkering/refactoring. I really must try to get it finalised. This version supports the Lodestar natively as well as the SX filter wheel, so LRGB is just a single keypress, giving plenty of time to watch the image building up. I need to make the support for the filter wheel more robust though, and the aim is to support the Ultrastar too. Martin

Here are a few shots from last night at quite low declinations in star-rich regions. The first is Barnard 104, a dark nebula in Scutum that looks like the number 7 or a tick depending on the orientation. I set it off to one side as I like the contrast with the bright, warm star off to one side. I might be wrong but I think that is a type G0 mag 4.2 Beta Scuti. The filter details are given on the shot. I find that the white control has to be quite close to the black point for dark nebulae. Next, at Dec -27, and with an altitude at the time of about 15 degrees, is Barnard 86, the so-called Ink Spot (although to me it is an upturned hat like the cover of the Blue Nile album of the same name). This is actually the same object I have for my avatar picture, but updated for colour. The cluster of blue-ish stars is NGC 6420. I've always like the practically uncountable number of stars in this image. Finally (the scope is calling), here is what I think is Trumpler 31 in Sagittarius, even lower at a Dec of -28 and around 13 degrees when I observed it. I really don't know if this is the right spot or whether the cluster refers to the brighter foreground stars or the dense cloud behind it, but I really enjoyed finding this (it was a random end the evening's observing being just a short hop from Barnard 86. cheers Martin

Believe it or not, I have a shot of this one, but it doesn't add anything to yours. The Shakhbazians always manage to throw up interesting shapes -- as you say, very attractive. There is something about these 'miniatures' that is compelling when doing this style of observing -- one of the many reasons I like the Berkeley clusters.

That's a great comparison. If I get a chance I will give this one a go tonight, probably using longer exposures now we have the Hubble image to check against...

Its remarkable how low an altitude you can go and still get decent views. You never know what you're going to turn up with these barely visited galaxies.

BTW hot pixel removal in Jocular is based on co-occurence in multiple subs (three at present, but configurable). So if you do see the occasional hot pixel it is quite possibly a cosmic ray... which I think we can get away with as astrophysically-interesting event rather than an artefact. (Still annoying when using colour filters though!) Martin

Hi Mike Good to see some galaxies in Capricorn, not a constellation I have visited much myself. Glad you had transparent skies -- I was out last night with the opposite... but since I was mainly looking at open clusters it wasn't so bad. I will post a few later. Regarding cooling, I may be missing a whole world of high fidelity captures but I have never found its absence a big problem for this style of observing (tonight it is predicted to be 27 C at 9pm so maybe I will eat my words). The key seems to me to be automatic hot pixel removal rather than darks. Any failures in that department are easily noticeable when using colour! Here's an example from part of M16 last night with and without hot pixel removal: I don't see many/any hot pixels in your captures so I imagine it is working correctly. I do notice that at this time of year the number of bad pixels reported is somewhat higher (a quick check showed about 70 in a January capture versus about 130 last night). Martin

The 8" Quattro with the carbon fibre tube is my main scope and has been for 6 years. I collimate with the CatsEye autocollimator tools using the hotspot symbol. This is not too onerous. The most frustrating aspect is secondary adjustment. Even though I replaced the adjustment screws with Bob's Knobs and added some home-made plastic washers, it is not as smooth as I would like. The flip side is that -- once adjusted -- the secondary holds collimation well and it is usually just the primary that needs a quick 30s adjustment. As for wind, the 8" at f4 is quite short at 75 cm so not too bad I find. I only notice wind effects when I add the dew/light shield, which adds another 30cm to the length. This is mounted on an Eq6 class mount (Az-EQ6 to be precise). Caveat: I use my scope solely for EEA with a small sensor. If I were to use it for AP I would definitely use a coma corrector. cheers Martin

And I obviously had the same idea as I also have this one of VV 476, stretched relentlessly with about 6m of exposure in 10s subs. The companion is very faint. `

Fascinating shot of VV 508. It shows that the VV catalogue is full of surprises. So is the offset star in the ST4 shot? Martin [Edit: dug into my archives and found this shot of VV 508 -- I thought the configuration looked familiar! I see my stars are not as round as they ought to be... ]

Hi Callum These are looking good. That's a nice combination you have and should pull out plenty of resolution on the best nights. Speaking as a frequent poster myself of faint and barely visible stuff the Palomar clusters I've observed tend to be hard to make out but with extreme stretching can be rendered visible even if the rest of the frame suffers from noise -- not a problem in EEVA style observing! Martin

A lovely shot of these galaxies. NGC 6928 looks like an integral sign' galaxy. Looking at this group on the charts it struck me that it is likely to be in the WBL catalogue of weak groups (many tend to be groups sitting amidst quite a dense star field) and indeed it is, designated WBL 663. Off-topic, but Sky Tools 4 looks like a very competent piece of software. It would be easy to miss the little galaxy at the tip of NGC 6930. I notice it provides star colours. Do you know how deep does it go in terms of stellar magnitude? Martin

Thanks Mike. I hope to continue tonight since the moon will hold off for a little longer. It is predicted to be 31C at 10pm though so I might invest in some darks... For identification I use charts that I've constructed from the GAIA data (happy to share if anyone wants them) which make things a little easier, but alignment needs to be quite close for a small sensor like the Lodestar. In constructing these charts I've seen that the official RA/Dec for the Berkeleys are not accurate in quite a few cases. Once I complete the journey (I'm currently about 2/3 through) I'll put together some resources and try to estimate better coordinates. I must admit that I really like these faint clusters and when I occasionally happen upon say a Messier cluster it somehow appears bright and vulgar in comparison 😉. Not sure what OCs to look at next but perhaps the Ruprecht catalogue, although a great many are not visible here. Having said that, I've still not observed most of the NGC/IC clusters... so many interesting objects, so little time... Martin

Its been a while since I had the scope out and what with a near dead battery and software teething problems I was very lucky to be able to view 7 further Berkeley clusters in a 45 minute session between dusk and the rising of the near-full moon. I'm making a few changes to the code so the annotation isn't perfect (ignore the SQM reading) and I seem to have omitted the constellation codes -- Be 52 is in Vul, Be 44 in Sagitta and the remaining 5 are in Aquila. Most of the Berkeley clusters I've observed so far can best be described as faint but with a certain shimmering density of stars -- rather like Messier 41 appears in 10x50s, or perhaps Messier 46 rather than its neighbour M47. Most of the clusters from last night fit that description, but Be 82 is a real exception (assuming I've got the correct location!) -- sparse and bright (and beautiful, I think). Possibly the most challenging was Be 52 which needed a bit more of a stretch than I would normally use for clusters. These are all live-combined LRGB captures using 15s subs; generally with 1 minute's worth in each but sometimes with added L. No calibration (just hot pixel removal). Colour manipulations (at the scope) limited to saturation and colour stretch, but generally these were left at default settings. North is at the top. Thanks for looking! Martin