Martin Meredith

I was out last night testing the new native live capture feature that will be released in the upcoming version of Jocular (initially supporting the Lodestar X2 mono, but with support for the Ultrastar planned shortly afterwards) and trying it out on a varied bunch of objects, mainly to ensure I was reading the sensor correctly (not a given -- quite a complex beast to program, for me at least!). I happened upon the only globular cluster in Bootes, NGC 5466, and noticed that the field contained a lot of quasars ranging in brightness from 18.7 down to 21.2. These provided a good test of the limiting magnitude that I could compare with earlier captures using StarlightLive. It is also a rather nice cluster! Here's a negative version where I've marked the locations of 5 quasars along with their (V) magnitudes and redshifts, as well as type Sc (though hardly recognisable as such) mag 17.4 galaxy at around three-quarters of a billion light years distant. Checking with Aladin I can confirm the presence of 4 quasars but the 5th, magnitude 21.2, eluded me. I'm never totally sure which is the preferred way to compute redshift to light years as it depends on the cosmological model, but using Ned Wright's calculator I get the following range of estimated distances in billions of light years z = 0.25: 2.77 - 2.97 z = 1.43: 7.75 - 9.26 z = 1.95: 8.59 - 10.3 z = 3.25: 9.7 - 11.7 (not seen) z = 3.89: 10.0 - 12.1 The lower value is from the 'open' model while the upper estimate is from the 'flat' model. I'd be interested in hearing from anyone who could explain the differences, and which is the better one to use based on current understanding! I also wonder if anyone fancies trying to catch the mag 21.2 quasar? This was quite a brief exposure with 10s subs and absolutely no calibration, so those with lower read noise cameras and a better process might conceivably stand a chance. cheers Martin

Amazing haul. These kind of comparisons are really interesting. Observing globular clusters as singletons they can seem a bit 'samey' but seeing them one after another or well laid out like you have done one can really appreciate their variety of features. Just a comparison of M9, 10 and 14 on your top 2 rows is quite revealing. There are few enough known galactic GCs (157 as far as I am aware) that observing all those visible from one's latitude over a season is a reasonable proposition (approximately 100 down to ~ -30deg 20' ). In fact, it would be an interesting activity to see what is the most southerly GC one can pick up with EEVA techniques. I once managed Omega Centauri but that was from the south of Spain. Rising above the sea it was an impressive sight in spite of intermittent near-horizontal light pollution from a nearby lighthouse. I will see if I can find the picture. Martin

Hi Mike I was testing the new version of Jocular last night and started with M13 to check alignment since it was close. Here's a 5-second sub with the Lodestar. It really is a wonderful cluster and longer stacks don't seem to add anything (at least in mono), perhaps because the display is so full of stars that one doesn't notice the slightly noisier background. This is with log stretch which I tend to use for the bright globs. Nothing gets close to the view in a large Dob though! I may reload this and look again with different stretches as I think log leaves it looking rather 'flat' whereas yours is closer to the visual appearance with the bright stars looking somehow punchier. Martin

That really is a spectacular pair Bill! Thanks for the links. NGC 4302 is an amazing 'bi-plane' of a galaxy. I'm trying to reorient it in my head to work out what is going on and failing. Must check out the Hubble link... Martin

Nice captures Mike! I never seem to have much success with PNs. Glad you're having fun with the stretch functions. We need more reports of which work well with different types of objects. I find log is great for globular clusters for instance. Bright PNs seem to work best with linear. Martin

From a fellow open-source Python EAA tool developer I fully applaud your efforts! I see we have gone down different lines with the main libraries we are using (I'm using scikit-image and Kivy for instance), but if there are any ways we can help each other out algorithmically then let's do so. I would absolutely love to see open-source Python-based platform-independent capture tools that can be used (but unfortunately lack the low-level skills to produce them myself). Maybe a topic for another thread? Martin

Hi Sara Some of the yellow ones are galaxies too. Take a look at this chart and you'll see quite a few marked. Perhaps the yellow are the fainter galaxies? cheers Martin BOO3989.pdf

I would contact SX to see if there is something like a firmware update that might solve this. I'm no expert though... And just to clarify, this is using binned mode in SLL? I wonder if you could download full resolution images and find a way to do the binning in software (I mean, as a check). We can discuss by PM if you like. I may add a binning option to Jocular at some point.

Very nice shot DragonAstro! I personally love the inverted images. Now, 5m subs are something I could only dream of.... (my mount is capable of being used in EQ mode but I never have, preferring altaz for convenience). Likewise, Mike, the bridge is definitely visible in your 10s subs version. Have you considered using darks to handle the odd hot/warm pixel? Martin

Nice shot. That's not one I've seen to date. Very irregular. I like the 'neck' of material curving out of the top. It would be interesting to find out more about what is going on here. And for a dwarf it must be quite bright to get such a detailed image in a short overall exposure. Worth a look in colour. Any idea whether the Ultrastar issue can be fixed? It looks like some kind of weird inverted bleeding of charge from the bright stars. I assume it is always horizontal, flowing along the rows. Does it also occur when you expose in unbinned mode for a sufficiently long time? Martin

Interesting objects Mike. VV223 looks vaguely like a pair of headphones upside down. I like the idea of a nest of galaxies in VV 678. From your blow-up there could be any number between 3 and 5. Looks pretty challenging. Coma is well-placed -- just need a clear spell. Martin

Whereas at the moment Spain (at least here in the north) looks like this 😭

Thanks Paul and Rob. Here's another one from a few weeks ago that I enjoyed at the time due to the complex spiral arm structure that we are seeing practically face-on. This is NGC 2835 in Hydra, close to the border with Pyxis, classified in the Arp-Madore catalogue as a 3-armed spiral, and a rather loose one (type Sc). It is quite close at 37 million LYs and bright (mag 11.1, although with a moderate surface brightness of 22.7) and I imagine would be quite spectacular for us in the north if it were not at -22 degrees. Also in the shot is the triple star B 1989. The closest component has a separation of 1" so no chance of me resolving it, but the other component is nicely-seen.

http://simbad.u-strasbg.fr/simbad/ is the best source I've found Martin

If you go to Aladin https://aladin.u-strasbg.fr/AladinLite/ and type hdf into the search box, it will bring up the field. Then select the SIMBAD checkbox on the right and you will be overwhelmed with dots. Click on any one to get galaxy data, including magnitudes. Hours of fun.... Martin

Nice work! There was a thread on this some time ago with a few people taking up the challenge using short exposures but I don't recall anyone getting more than a few galaxies. Martin

VV 1537 This is a field I came across completely by chance a couple of night ago while scanning the charts. I enjoy looking at odd/random groupings and this region of the sky has a distant (1.2 billion light year) galaxy group, Abell 1541, close to a couple of NGC galaxies, and a member of the VV catalogue. I operate a small sensor (field of view about 2/3 of degree on the long edge) but it is amazing what one can cram in! I had no idea what to expect and that made the observation all the more exciting. This is an image from that first encounter to give an idea of the overall configuration. It is an unusual field. In some ways from an aesthetic point of view it is arguably a bit of a mess! There is just too much going on and the objects are of such different types that it is more like three separate views. But in each case there are hints of something fascinating. Those two face on spirals, NGC 4411 and 4411B, type Sc and SABc respectively, are listed at 64 and 66 MLYs so must presumably be ripe for interaction. Likewise the foetus-like NGC 4410 with its very bright apparent double core. I also thought I caught a hint of some bridge between IC 790 and the 'next galaxy down'. When I read more about what I was seeing, I realised I would have to come back for a deeper look. I rarely observe for more than 15 minutes, but some objects merit much longer, and there is so much going on here that it certainly falls into that category for me. So here is a longer view from last night, oriented with N upwards (unfortunately I had to dispense with Abell 1541 on this occasion in the interests of bringing the main objects into the centre of the image). One accidental benefit is that a very low surface brightness galaxy has crept it at around 3 oclock (the faint smudge, more easily seen on the negative image). This is VC 869 (I imagine the VC designation corresponds to the Virgo Cluster Catalogue), also known as PGC (LEDA) 40640. The listed surface brightness is 24.4. It is a dwarf elliptical or irregular galaxy, first mentioned in this 1956 paper [1]. Ignoring the VV group for a moment, the additional observing time has brought out a host of detail in NGC 4411 and 4411B. The Sc type of NGC 4411 shows up in much looser, almost 'S'-like spiral arms, compared to the moderately-tight arms of NGC 4411B. The latter has a faint halo, lacking in NGC 4411. A great many knots are also apparent in the arms of both galaxies. I see a hint of a bar in NGC 4411. Now to VV 1537 (supposedly the purpose of this post!). According to [2] this is actually a group of four galaxies in obvious interaction as part of a larger group of 12 galaxies. It is worth taking a look at their Figure 1 as it makes the features I'm going to mention quite clear. The paper also mentions why this is not a member of the Hickson catalogue... Taking the line of 'three' galaxies from right to left: rightmost: the cashew-shaped entity is a very close pair of galaxies (NGC 4410A/B) that are locked in interaction middle: IC790 is a Sab type, also known as the C-member of the 4410 group left: this is PGC 40736, type Sa, known as the D-member As far as I can make out, there are two bridges of stars here, as well as two tails. The clearest bridge snakes between the C and D members, while a fainter bridge runs between A/B and C. Then each of the A and B members appear to have tail curving out in opposite directions from the centre of their interaction. These features are clearer on the negative image. They bring to mind the Antennae galaxies, but on a smaller scale. thanks for looking Martin [1] http://articles.adsabs.harvard.edu/pdf/1956AJ.....61...69R [2] https://www.aanda.org/articles/aa/pdf/2008/26/aa8119-07.pdf

This thread is dedicated to observations from The catalogue of interacting galaxies by Vorontsov-Velyaminov Brief bio: https://en.wikipedia.org/wiki/Boris_Vorontsov-Velyaminov Many of these are fascinating systems to observe. There are plenty to go round, some 2014 in all! There is some overlap with other catalogues, notably Arp. Here is a CSV file listing them that I have put together (with some pain it must be said) from the original catalogue available at Vizier. If anyone has any further resources, please share them and I will post them here, or feel free to add them below. VV_reduced.csv Other resources can be found here: http://www.sai.msu.su/sn/vv/

Thanks for these images. Also looking 50% likely for here for tonight. I came across a very interesting field last night around NGC 4410 that I want to revisit. Very challenging VV group with multiple stellar bridges! I think we may need a VV thread...

I'm going to set the ball rolling with Hickson 40 from last night. This is a tight grouping of 5 galaxies around 310 million light years away. What's more, there are 5 distinct type of galaxy on display, some of which I think can be appreciated in this zoomed in shot (from top to bottom): Mag Type 15.1 S0-a 13.8 E 17.4 SABa 15.7 SBab 15.0 E-S0 North is up, East to the left I must say that that mag 17.4 galaxy appears brighter to me Here's a shot giving some idea of scale and the isolated nature of this group:

Arp 104 is a great place to start this thread. Yes, I can see a hint of the bridge in your shot. I managed to capture the bridge a few years back but only with a lot of stretching... (and 12.5 minutes of exposure). Mike, perhaps you need to go longer than 5s with a CCD due to read noise? There appears to be some kind of z-shaped galaxy cluster to the R too but I it isn't an Abell cluster as far as I can see. Here's a nice paper describing Arp 104 https://arxiv.org/abs/1009.0219v1 with some great photos from the 0.9m and 3.5m scopes at Kitt Peak, Arizona.

Fascinating to see these images -- thanks! There appear to be fragments behind the core too. I took the liberty to compare the two images in order to see what elements are in common. What do you reckon to these? Background stars? Mike's (left) is about 30 minutes before Bill's. There's a great animation here: Martin

Great collection of Arps there, many of them new to me. I have one of Arp 84 (looks like a stork or flamingo when oriented vertically). Arp 104 is another favourite and a real challenge to get the stellar bridge. Once we have the Arp thread I'll post an image but I recall it took a long sequence to get any sign of it, and it needs a horrendous dust-shadow inducing stretch. I'd be very impressed if you can get it from London! Talking of dust, those artefacts look like hot pixels to me, but hot pixels that have been image processed somehow. Were you using some kind of noise reduction in Sharpcap or other similar process? One might get those shapes by processing pixels with some kind of weird convolution. It would be interesting to find out. Are they point-like on the individual fits files? Martin

Very impressive! What sub length were you using? Seems like it is zipping along quite rapidly. Martin

I haven't had time yet to pay these great images all the attention they deserve -- later! But just to say it would be great to have an Arp thread (same goes for Hicksons too). I have a data table for the Arps that I'm happy to share too in such a thread (might take me until later tomorrow to bash it into shape). David, I'm planning to upgrade my Mac soon so I'd be interested to know what problems you're having with Jocular/Catalina at some point as I may run into them too! You might have noticed I posted a simpler installation procedure in case you decide to reinstall from scratch. In fact, I did a complete reinstall of Python myself this week and it turned out be quite painless using the miniconda approach that I'm now recommending. Martin