Martin Meredith

What with all the focus on faint tiny stuff we don't see many Messier galaxies in these threads. I've been going thru some of my recent captures and discovered a few. I sometimes forget how beautiful these can be -- especially M88 which is just hanging there in space. So here's a collage of 6 Messier galaxies live-combined in LRGB, 6-11min exposures. N is up in all cases except for M106 where I adjusted it for purely aesthetic reasons. top row: M108 type Sc, inclination 68 degrees, looking like an angry turbulent rotating bed of clouds M88 type Sb 63 degrees -- surely the perfect inclination? M105 (type E -- what more is there to say?) bottom row: M91 type Sc, appears face on but inclination is listed at 37 degrees, which I suppose explains the asymmetric halo M106 type Sbc, looks like the Corryvreckan whirlpool, inclination 68 degrees (can this be right?); almost too large for the Lodestar with its extensive outer gas M64 type SABa, inclination 64 degrees, fascinating inner 'eye' with tons of structure

Me too -- I want to know what colour those stars are! Nice catch. Virgo is so full of interesting galaxies. Martin

Welcome from your neighbour in Alava 🙂 Martin

Arp 5 is 'well weird'. I looked at both of these last year but my images don't add anything new to yours -- my Arp 87 has less definition. Here's one of my own from the other night that has something of a family resemblance to Arp 87. This is Arp 240 which consists of NGC 5257 (SABb) & 5258 (SBb) involved in a graceful exchange of gases. I've stretched this quite a bit to bring out the linking structures that are really quite faint for my setup.

Thanks Paul. The second one seemed to be closer (brighter flash) but who knows? Their apparent speed was more or less identical though, which is interesting (close and slow versus less close and faster...).

Thanks Bill. Here's part of one sub. It looks like something with a light flashing every 3 or 4 seconds since its a 15s sub. Distant plane? (ignore the two stars -- just a coincidence) also on the *same* series is this one which looks like a closer version of the same thing except that the 'flash' only occurred on one sub as it passed through. Both needed the same amount of time (~2mins) to cross the field (approx 0.44 degrees). Perhaps a fllght path towards Madrid or something but strange that I've not seen it before as the scope is quite often pointed that way at a similar altitude. I often get things crossing the field but these were atypical... Martin

15s subs

Hi MIke By a strange coincidence I was also observing one of these PCGs earlier in the week, except it was called SHK 204! It has 13 listed members of which what looks to me like the faintest (near the centre) is mag 20.4 (B filter). Most of the group is listed at just over 2 billion LYs away but that faint member is given at nearly 6 (I'm never sure how accurate the measures are but if so this is an interesting interloper). I generally start off in monochrome but if there are several brightish stars my curiosity as to their spectral class gets the better of me and I add a few RGB subs at the end. From L to R we have G8V (mag 12.8)+G2 (mag 10.4) (this is double star COU 594 with a sep of 2.8"), F2 (mag 10), K01V (mag 8.6) and K4III (mag 9.7). This is a linear 'stretch' with saturation turned right up. SHK 204 is completely invisible with the linear stretch. Its like having 2 images in one, part of the fun of interactive observing! I did wonder whether these 4 stars which forms such a perfect curve are part of a grouping. They really are gorgeous and must be impressive visually. Now digging a bit deeper I see that (at least some of them) are part of the huge Melotte 111 grouping that dominates Coma (and which is large enough to contains several other SHK groups). The distance ratios in these fields always gets me. Martin

Excellent report. I like the Herschel(?) style of abbrevations too -- I wonder what he'd have made of this device? Talking of which, I've never looked through one myself yet but would love to one day. Martin

Its great that in the 15" + Ultrastar you can preserve detail in galaxy as well as seeing the tidal stream. I was hoping to look at this again last night by combining L and OIII but the clouds rolled in shortly after setting up the scope (grrrrr). I note from that article that the PNs and GCs that are being used as tracers for the stream are incredibly faint and probably beyond EEVA techniques short of investing in a very large aperture scope... Martin

This article is worth reading for more on Arp 189/NGC 4651, apparently known as the Umbrella Galaxy (due to the extended halo around the galaxy and the 'bent stick' of the tidal stream -- remind me to reorient my image next time...). https://arxiv.org/pdf/1406.5511.pdf Fig 1 provides a wonderful view of the tidal stream whle Fig 2 gives plenty of material for anyone interested in seeking out globular clusters and planetary nebulae in this galaxy. These relatively bright objects are being used as stream tracers. Martin

Looking at it right now. Seems to be similar in brightness to the star at its 4 o'clock which is Gaia G mag 12.8 (not sure how that translates into visual). Its certainly very bright. Martin

Here's one I ended last night's Coma session with and it turned out to be quite a surprise. This is Arp 189, aka NGC 4651, a type SA(rs)bc ie a late-ish non-barred spiral with an inner ring. The details revealed are pretty interesting in themselves, with a kind of bright heart-shaped split ring on its side and much fainter outer arms. I was observing this for a few minutes before wondering what the peculiarity was. It took quite a while longer for me to notice an exceedingly faint and perfectly linear structure heading off to the East (left in this image). I continued observing for quite a while, hence the 10m length of the total exposure, to see if this was real or an artefact. Eventually it became 'clear' (to some extent!) that this was a real feature. Sure enough, reading about it now it comes under the class 'narrow filaments'. Forgive the overexposed core but this was the only way I could produce a visible image of the filament, which is most unusual, having as it appears to a near-90 degree left turn at the end of it. I have no idea how this came about (more reading later). This is perhaps the most challenging Arp I've encountered to date. cheers Martin

Added to my (EEVA) observing list! This is a beautiful example of its type with some interesting stellar contrasts in the surrounding field. Martin

I've made up a list of 1989 overlapping galaxies here. The object type is OG for ease of search... You will need to refer to the paper for what the type codes mean. Just drop it into your catalogues folder. (This means they will also get picked up when annotating) Enjoy! Talking of which, we have a clear night but the sky is full of supended sand -- again! It never seems to coincide with the moon. Martin overlapping_j.csv

Some beautiful examples of overlapping galaxies (including Arp 198) found by Galaxy Zoo volunteers and described here: https://arxiv.org/pdf/1211.6723.pdf Yes, the edge-on is behind the face-on (type Q in the paper) Martin

When I observed this I noted "like a microphone or an ice-cream cornet..." A close in view shows a really interesting pair -- an edge-on plus a face-on spiral! Nice. I see the face-on in front of the edge-on. What do you reckon? Just out of shot I spotted this little chain -- no details available:

Great capture Roel and not really very blown out. This thread got me looking back over my most recent capture and playing around with different stretches, and this is the best I can do. I should say that this is post-hoc as in not what I observed at the scope (probably), but it is possible to have observed this at the scope in the sense that it uses exactly the same tools as are available during a live session and no other processing! In this case an arcsinh stretch gave the greatest amount of nebulosity while retaining the Trapezium stars. More saturated views are of course possible but they don't alter the nebulosity/Trapezium question. Martin

I voted for the Coathanger because there is so much going on in the background, giving the image a real feeling of depth and mystery. Even without the Coathanger I think I would choose it! The colours are great and perhaps its their overall warmth in contrast to the diamond sharp double cluster that is winning me over. best of luck Martin

Not sure it is exposed anywhere. I will add a version option to command line for the next release. However, if you track down the location of the module on your system it is the only line of code in __init__.py The version will also appear in the title bar. Martin

I added an extra check a few days back which I'm pretty sure in is the latest PyPi release (0.4.2) so if you do an update without mentioning the version name it should be ok. Haven't had a lot of time to work thru any other ramifications, but I think it will at least not try to debayer calibration frames! [Edit] Just updated to v0.4.3 which fixes a bug which occurs if you try to load an OSC image in mono mode, and an option to choose binning by averaging (as on the camera) rather than by interpolation (which is more accurate as it handles antialiasing). Martin

Here's my very first EAA capture, back in March 2014. Now that's what I call blown out! (also poorly focused). I have mixed feeling about M42. We see so many images that some groan 'oh no, not another M42', but it is actually our closest major star-forming region and hence supremely interesting from an astrophysical point of view. I think a lot of people get their first scope around xmas time and start off on this most obvious object, then move on (in my case it was shortly after buying a second hand 80mm achromat at Astrofest). I recently came back to M42 and found it absolutely fascinating to see the brown obscuring dust and the halo of pink around what looks like an oyster shell with the Trapezium stars in the middle. Way more interesting that the Horsehead 😉 In terms of keeping the Trapezium stars and the nebulosity, I've found it crucial to use anything except linear stretch (arcsinh is good), and to either keep exposures short (5s say) or if doing live LRGB imaging, to take advantage of the fact that the B in particular, and to some extent the R and G are going to deliver quite tight Trapezium stars due to their reduced transmissivity relative to L. cheers Martin

Hi Brainebula Fellow Mac user here. Have you tried connecting through Kstars/EKOS (free) or AstroTelescope (free for 13 days...), the latter from Cloudmakers? Both worked for me (as in discovered the correct ports etc without me having to do anything). AstroTelescope was much easier to figure out and worked immediately after selecting 'SynScan mount' under the 'INDIGO drivers' tab in the preferences panel. Clicking on the 4th icon from the right (4 arrows) brings up a manual control which allows you to move the mount. At least this way you might be able to check that the cabling etc is working. Mine is an AZEQ6 mount, 2014 vintage, without the USB connection, so I'm using the Lynx Astro cable from my MacBook direct to the mount. cheers Martin

When you think about it it makes sense because the abrupt edge of a rectangular window cannot ever be approximated as the sum of only low frequency components (deconstructing what the Fourier theorem). Try generating a sinusoid at some frequency f, then add in the first harmonic ie f + 2f, then add in also the next harmonic, etc and see what you get. Eventually, with high enough harmonics, you start to approximate a hard edge. (This assumes you add them all in zero phase, otherwise all bets are off but you won't get a hard edge either). Of course, the amplitude of the harmonic matters too and the above demonstration should be done with equal amplitudes to see the effect. Here's a nice discussion of the spectral effect of various window functions: https://en.wikipedia.org/wiki/Window_function#Windowing I forget where I heard it, but it was once remarked that practically any function that rises to a peak and then falls again has someone's name on it as a window function... Martin

Thanks Mike and Michael! Now for the King clusters. I happened upon one, unplanned, and enjoyed it so much that I went for another. Then I felt it would be good to have three Kings (very important here in Spain as the bringers of xmas presents...). I ended up with a rather untidy 4. I've just been reading about the history of these clusters. They were discovered by Ivan King in 1949 by inspection of plates from the 16" "Metcalf" refractor which I think was at the Harvard Observatory as the paper (which you can read here -- http://articles.adsabs.harvard.edu//full/1949bharo.919...41k/0000042.000.html will only take 1 minute!) was the Harvard College Observatory Bulletin. He listed 21 candidates of which he regarded 1-12 as definites. The list must have been extended slightly as there are 26 now listed, but 3 of them (including the 'definite' King 3) are missing (perhaps it coincides with another prior cluster). King is famous for his 1966 theory of the dynamic evolution of clusters which I had a quick glance at (a bit too late at night for equations) and see that it has been pretty influential, cited more than 2000 times. There's a brief note and a photo here: https://www.stellar-journeys.org/cluster-king-info.htm So to the objects themselves. Unlike Stock 24, King 5 is rather old ~ 1 billion years and highly-reddened. I love the zigzags of stars in this one. It resembles some of the Berkeleys in this sense but has more oomph -- brighter, larger. As for Stock 24, I think the diameter is something of an overestimate. King 7 estimated to be 700 million years, again highly-reddened King 8 is most likely the oldest of these 4 at around 1.1 billion years and rather compact. The visual double in the foreground provides a lovely colour contrast. Finally, King 17, which was first studied in detail as recently as 2008 and found to be of intermediate age. Unfortunately for the cluster the field is dominated by another carbon star, TX Aur, pretty bright with a range of 8.5 to 9.2. Working backwards thru the various mentions on Simbad, the earliest seems to be in a charming paper from 1899 under the designation BD.+ 38°i035. The paper, "ON THE SPECTRA OF STARS OF CLASS III b." is well worth a look at, if only to read about the observing conditions in Upsala. http://articles.adsabs.harvard.edu/pdf/1899ApJ.....9..119D. The star is now classified as a LB ('slow irregular') variable. thanks for looking Martin