Martin Meredith

This is a new one to me (Arp 200). You did really well in challenging conditions to capture some good details, esp. with 3s exposures. The loop at the upper right is very evident. Here it was very windy (~125km/h) earlier in the week -- a litle too much even for EEVA! Martin

One of my favourite types of Arp galaxies are the ring structures. Unfortunately there are only three to savour: Arps 146, 147 and 148, the first two in Cetus and the latter in Ursa Major. (There will be more out there to find outside the Arp catalogue...) This is Arp 146. The full field shot shows how tiny this configuration appears. (There was a whole raft of satellites flying through here; choosing the outlier removal to retain 90% of pixels at each point got rid of most of them but I see that one managed to escape...). What we have to put up with! This is using mean stacking with no outlier rejection: Zoomed in a lot the ring becomes more apparent. The ring part is PGC 509 while the galaxy just below and to the left is PGC 510. It is thought that one galaxy passed through the other, leading to a bright ring of star formation. There is an excellent picture here: http://cseligman.com/text/atlas/pgc00a.htm showing how blue the ring is. One a good night I'd like to capture some colour for this pair. Apparently the pair is about a billion light years distant. The challenge for all 3 ring galaxies is to capture as much of the ring as possible. I'm missing some compared to deeper shots. I will have to be more patient and wait for this object to transit on a night of good seeing! Martin

Thanks for that link, Mike. They are indeed great descriptions and images. Indeed, it seems that the companion Arp had in mind for Arp 48 is the closest dot to the E of the core of the main galaxy. The companion of the main galaxy in Arp 88 is a real challenge (the galaxy itself is mag 17. I have something in the right place (to the W) but no obvious structure. I'm not sure if this has already been mentioned earlier in the thread but the original Atlas of Peculiar Galaxies can also be downloaded as a single pdf here: http://articles.adsabs.harvard.edu/pdf/1966ApJS...14....1A which is quite convenient except that the images need to be rotated. Martin

I was looking at the supernova in NGC 514 a couple of nights back and noticed not one but 3 Arps nearby. They fit comfortably into a single shot even with the Lodestar at 800mm focal length. Arp 48 is classed as a spiral with a low surface brightness companion on its arm. The negative shots are zooms with N up. The stellar-looking object to the SE of the spiral is a galaxy, as is the slightly fainter object to the W. It isn't clear which is the LSB companion noted by Arp. The other blobs in the image appear to be very faint galaxies in a cluster. The DSS image shows a tail starting at the W edge and curving tightly back on itself. I've a hint of it here, but no more. Arp 88 is very small and quite faint. It is (strangely?) classified as a spiral with a large high surface brightness companion on its arm (presumably the object to the W in this figure). One does wonder if Arp's descriptions for 48 and 88 are the wrong way round. Of the three Arps, the showpiece is Arp 119. This is a member of the class of ellipticals with close perturbing spirals. The lower galaxy (UGC 849) is of type Sd and contains an active galactic nucleus (Markarian 984). We can just see the hints of multiple arms to the lower part. It seems clear that it has undergone (or is undergoing) an interaction, with all the tails fanned out behind it. The DSS image is well worth a look! I may revisit this is colour as there is a clear contrast between the two galaxies. I also managed a look at the very fine ring galaxy Arp 146 in Cetus which I'll post separately. Thanks for looking Martin

Glad to hear that! Will send it in a moment. V0.3 supports native image capture for the Lodestar and I plan to add support for the Ultrastar very soon (days away but needs to be tested as I don't have access to that camera). It also controls the SX filterwheel (but no others). No, there is no OSC but it supports mono + filters (LRGB, manipulated in LAB space). Martin

Hi Wormix and I are (I hope) going to solve this via PM but in case anyone else is installing the earlier version of Jocular, please use a version of Python prior to 3.8 since Kivy (the GUI library I'm using) doesn't work with v3.8. Rather than use miniconda, I now recommend going to python.org for the download and choosing say python v3.7.9. This issue will be resolved at some point when Kivy releases v2.0 (it is fixed in the Kivy 2.0 release candidate). v0.3 of Jocular is also out for beta testing should anyone wish to try it out. Just send me a PM. Here's a manualv3.pdfdraft of the manual. The first page lists the features. It is reasonably stable for OSX (retina and non-retina screens) but there are still a few issues related to native capture on Windows to sort out. Martin manualv3.pdf

Hi Looking at my charts, there are a few reflection nebulae from the van den Bergh catalog that are marked as variable: a few in Cassiopeia: VdB 5, VdB 7, VdB 9 also VdB 24 in Perseus and VdB 34 in Auriga I haven't observed these myself but they might be worth checking out. cheers Martin http://articles.adsabs.harvard.edu/pdf/1966AJ.....71..990V

Just had a look at this SN a few minutes ago. It is indeed distinctly blue!

Here is the NGC 80 group which contains Arp 65, as indicated (I have it as NGC 90 but I read that it is actually NGC 91). There are no fewer than 9 NGC galaxies in this shot, which incidentally lies just to the south of Shakhbazian 364 (the weird IC 1542 lies just at the middle-left edge in this shot). This is 16 x 20s = 5m 20s total exposure. Arp 65 is classified as 'spiral with small high surface brightness companion on arm'. Kanipe & Webb's The Arp Atlas of Peculiar Galaxies identifies 3 possible companions, all of which are some way from the galaxy core, and are identified on this close-up (North up): Companion 1 is magnitude 18.0 but the other two are quite a bit fainter (no data found so far). Article [1] goes into Arp 65 in some detail, and looks at the evidence for an interaction between NGC 90 and the type Sab NGC 93 seen at the top left. Their figure 1 gives a good detailed view of this system, and shows a clear tail reaching all the way to comp 3 (not seen in my image). A higher-resolution attempt at this might show up more features, including a better look at the fork in the southern tail. There is certainly a lot more going on here than in my image. Martin [1] https://arxiv.org/pdf/1509.02614.pdf

Good ideas, and in general there are all sorts of highly non-monotonic techniques that could be included to bring out faint detail. I included an implementation of CLAHE (contrast limited adaptive histogram equalisation) in a much earlier version (never released) but perhaps it is time to reinclude it. It is quite easy to add this via the adaptive_histogram method here: https://scikit-image.org/docs/0.15.x/api/skimage.exposure.html As for anti-stretch, changing the gamma function to include exponents > 1 is one way to go. Martin

Very good catch. I can see that it is still very bright. Would you believe I had this SN on my list for Friday and was so distracted by other interesting stuff I forgot all about it. Maybe tonight... Thanks for beta-testing the new version of Jocular. I'm more surprised than anyone that it can handle 70 x 12M images in such a way that you can operate on them more or less in real time... but as a result I'm happy to have removed the former limitation to 2M pixels. Its worth pointing out (to others) that the exposure info on the image is not going to be accurate in your use case, where the capture is performed by another program. The estimation process I use needs some refinement to better reflect the interval between subs arriving. Martin

Here's a link to my recent Shakhbazian 364 observation:

Thanks for that information Mike. I must use NED more often as Simbad and pals didn't deliver on this occasion. I will continue looking for the gen on IC 1542 when I get some spare time. I'm rather surprised Arp didn't include this one! Martin

During a briefish session last night I came across this field just to the north of the wonderful NGC 80 galaxy group (the two NGCs at the base of this shot belong to that NGC-rich group and since it also contains Arp 65 I'll post in the Arp thread). This screenshot shows the general field so that the tiny apparent size of some of the objects can be appreciated. My main target was Shakhbazian 364 which is a delicate chain of 5 very faint galaxies whose magnitudes have to be around 18 or lower (there is a 6th member some way off the line to the N). This chain is highly-reminiscent of Hickson 55 in Ursa Major, so much so that I had to check the designation. This is a poor shot of Hickson 55 from some time back: Perhaps the weirdest object in the shot is IC 1542: I haven't yet been able to dig out any information about what kind of galaxy (or galaxies) this might be but it looks pretty irregular (the only information that might be relevant is from a paper entitled The clustering of dwarf galaxies but there is no explicit mention of IC 1542). I can't help but see a terrier dog facing to the left with a ball at its feet. Just to the north of IC 1542 is another chain of three galaxies although these are not listed anywhere that I can find. All in all a fascinating part of the sky. Martin PS Perhaps we need a Shakhbazian thread to gather together observations of these fien objects?

Hi Vlaiv I look forward to seeing a prototype 🙂 As for stacking software, surely thall that is needed for it to work with INDILIB/GO is to have the FITs dumped to some directory which the stacking software knows about. I have some open source Python stacking software that could be adapted to this scenario (it would need some work but in principle it is all there so long as the RPi can handle the required Python dependencies). As well as stacking it is useful to be able to perform automatic background level estimation and gradient removal for this type of application, to give users a limited but still useful palette of adjustments. Best Martin

Very nice shot of the supernova! I didn't realise it was so bright. Regardless of any other issues, the imaging part of your setup looks to be doing really well -- great star shapes and a lovely flat field. Martin

Hi PCW I doubt it is Mayall II because you would expect to see the two neighbouring stars, but I am intrigued as to what you have spotted. It certainly looks like a glob but it could just be a star with bad seeing/poor focus. What is surprising is that the are no other objects present -- very rare to see a field with only one object. If you can, could you adjust the black and white points (esp. bringing the white point down towards the black) to see what else is in your image? This is especially important when you are applying a linear stretch. Could you say a bit more about what software you are using? Cheers Martin

I'm potentially interested in ALPACA but still trying to understand what components are needed to make this work on a completely Windows-free setup. Let's say I want to control a filterwheel. I write a client program, look up the JSON semantics for this device, and send the necessary JSON to an ALPACA server. So far so good. But then what? In the Windows case it is pretty clear that it converts the JSON into something ASCOM-compliant and sends the request to the device. End of story. I can see how this would work easily enough, and I can see that controlling ASCOM-compliant devices hooked up to a Windows box from any other device is pretty trivial. And it is trivial because all the drivers already exist, as does the ALPACA-ASCOM server. But this isn't my case. As I see it, for a non-Windows setup much of what is needed to get this to work (ALPACA server + drivers) isn't currently available and I'm not even clear whether it is being developed. It would be wonderful to have a truly OS-independent way to access devices, but is it going to happen? Am I missing something? Martin

Thanks for detailing your experiences Callum. Looking at the properties in Preview under Security it tells me I have full permissions for this PDF. But then I have the same issue as you when I try to open a cross-document hyperlink, so it even ignores the real owner of the files! All the charts were assembled in Latex with hyperlinks added via the hyperref package. This was back in 2015. Things might have moved on a bit in the PDF generation arena since then. Martin

Must be others somewhat deeper. I can see PGC 2027644 (mag 17.8) due south of NGC 507 and it is quite bright...

Good! Did you need to change any of the default settings? It might be useful for others. I've always used Preview but the latest Acrobat Reader seems to have pruned back its menus preventing them from taking over the entire viewing area. Minimalism is something that has taken the big software developers a long time to appreciate... Martin

Hi Tony I hope others who use the maps will chime in with what works for them. Yes, they all need to go into one directory (no subdirectories). This is the easiest way for me to be sure that every pdf can see every other pdf as there are 100s of hyperlinks on each chart, and all of them different). I use a 2020 Mac OS Catalina with Adobe Acrobat Reader DC. Over the years I've tried non-Adobe PDF readers but none seem to work well (either they don't allow cross-document hyperlinks or they are too slow; when set up, Acrobat is very fast and perfect I would say for these maps ~1s max page load per chart). The screenshots show the settings that seem most relevant. These result in only the current pdf being shown (rather than having a new tab for each) which is what you want. Let's see if this works! Martin

Good question.... since these charts are not just for EEA it could go in various places, but I suppose they could be regarded as EEVA Equipment?

Good catch! Arp 295 is a fascinating pairing with the bridge and counter-tail. It is definitely worth 11m 40s of anyone's time! I observed this some years ago when I appear to have been already experimenting with a circular orifice (this predates Jocular so would have been processed in GIMP to do the inversion). I will definitely we revisiting this soon if it clears up before Aquarius is lost for the year. You're getting better resolution of the lower galaxy than I can manage. Here's a short article from 1974 by Alan Stockton discussing the tidal origin of the bridge. 1974ApJ___190L__47S.pdf cheers Martin

Thanks for pointing at the Perseus Cluster. The single sub is very impressive for 20s. The wide field really helps put the size of this cluster into perspective. If I were to invest in a wide(r) field setup it would be for these types of objects. I'd be intererested to know what problem you're having with the charts because a few people have had issues with permissions/hyperlinks and it would be good to perhaps have a separate thread on sharing experiences in order to resolve any issues. Martin