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Martin Meredith

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About Martin Meredith

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  1. The other thing to add regarding refocusing is the importance of acquiring a set of parfocal filters which include a clear (C) or a luminosity (L) filter. This way, there is no need to refocus when adding narrowband, at least for EEVA purposes. I have the Baader LRGBC set which includes both L and C. The difference is one of passband: L covers pretty much the same as RGB combined, while C is much wider and therefore better for making use of the near-IR sensitivity of modern cameras. The 3 members of the Baader narrowband set are parfocal with these too, so I just pack my 9-slot filterwheel with the lot of them, plus a piece of flocking for a dark filter, and a spectral grating (which almost certainly isn't parfocal!). https://www.baader-planetarium.com/en/blog/the-baader-l-rgb-c-ccd-filters/ In fact, all of my luminosity captures are taken through a C filter (so I guess I lose a tiny fraction of transmission). I do this so that if I'm observing something in mono that turns out to be potentially interesting enough to add a quick colorisation, I can simply add some RGB to the end. Or vice versa, if I'm doing an LRGB capture and want to improve spatial resolution and depth, I can add more L (actually C) without refocusing. Martin
  2. Agreed, wonderful image and FOV in short exposures. I've used Ha in an EEVA setting, but not for a while. There are some objects with plenty of signal, but the best time I had was adding it to luminosity data 'live' (using SLL). This animation shows the effect of adding Ha to a L base can be quite informative. I'm planning to add a L+Ha mode to Jocular in addition to the LRGB and mono, using the saturation slider to modulate the effect of Ha. It helps of course to have an electronic filter wheel for multispectral work during a live session. Martin
  3. That's a great image. This is my LRGB version stretched as far as I can go, oriented almost like Rick's. Seems a case where we need AP amounts of data to see this plume! There are several quite bright globs in here according to his image, inlcuding the pinky-red object at the upper-right.
  4. By coincidence, I was also looking at Arp 168 a few nights back, wondering about its inclusion in the Arp catalogue. What I found striking were what I imagine must be dusty regions of M31 -- only visible when stretched a lot. There is something that could be described as a plume (on the NE side of the galaxy in this shot), but equally it could be part of the outer envelope of M31. Thanks for pointing out the globs of M31 (I now plan to add them as a catalogue). I can imagine how much fun it would be to track them all down. Martin
  5. 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
  6. 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
  7. 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
  8. 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
  9. 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
  10. 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
  11. 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
  12. Just had a look at this SN a few minutes ago. It is indeed distinctly blue!
  13. 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
  14. 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
  15. 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
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