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Martin Meredith

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About Martin Meredith

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    Sub Dwarf

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  1. The connector on my Lodestar X2 came loose (after about 2.5 years) and the excellent Starlight Xpress fixed it for free and mailed it back to Spain at no cost. Impressive. Martin
  2. Thanks Rob. I've adjusted the mount and it seems to have helped to get more useable subs too. I should have added to my report that these were taken with a 60% moon in the same quadrant, so the automatic gradient removal really seems to have helped here. Yes, I favour the eyepiece view not just because it is actually what I am seeing/manipulating on the screen, but because it allows the appropriate level of zoom (and all are rotated with N up which helps me identify objects). Some of these objects occupy quite a small region of what is already a small sensor. Martin
  3. Continuing the hunt for interesting WBL groups, here are some from last night in Pegasus (which contains no fewer than 44 such groups). All are live stacks of 15s subs, no darks/flats. WBL 726. The lower left pair is the interacting pair VV2003 (NGC 7771 + NGC 7770), while the face on Sb is NGC 7769. Four fainter galaxies bisect these brighter members in a wavy N-S line. WBL 724. This is the central part of galaxy cluster Abell 2666. Main galaxy is NGC 7768, a mag 13.3 elliptical. Field full of delicious edge-ons. Exposure time is actually 10 x 15s = 2m30 (sub exposure length is estimated based on time of arrival differences in Jocular and it sometimes overestimated...). WBL 723. Understated group of 5 or more minor galaxies. Lovely member of the Flat Galaxy Catalogue (FGC 2527). The central (though strangely not the brightest) galaxy is NGC 7740, a mag 15.6 E-S0. Both galaxies at the extremes of the group are brighter, oddly missed in the NGC compilation/observation process. WBL 688. A group of 6 NGC galaxies, the brightest of which is NGC 7385, a mag 13.2 elliptical. Distance estimates range from 340-400 MLyrs for group members. Total exposure is 17 x 15s = 4m15. WBL 692. Main group is VV 84 and consists of NGC 7433, 7435, 7736, plus other gxs, interacting at around 350 MLyrs. This is the equal of many Hickson groups and why it didn't make that list I don't know. WBL 685. Tonight's star of the show for me, just the kind of jewel that WBLs sometimes throw up, with the benefit of a field rich in stars. The upper edge on is NGC 7345 and to its right is mag 15.2 type SBa NGC 7342. The group at the base have mags 14.7-15.6. One of the upper edge ones (the one to the right) appears to have a slight curve to it, or perhaps another gx. There are a bunch of fainter and/or more compact galaxies in this field too, unusually for such a star-rich area. Cheers Martin
  4. If you ever get the chance to visit the Natural History Museum in Vienna, it has (I believe) the world's largest collection of meteorites. I was fortunate enough to be passing through a few weeks back and came across it by chance. I don't recall whether it had samples of Sikhote Alin but it wouldn't surprise me. (The museum also has an amazing collection of rocks/minerals which is what drew me to it in the first place.)
  5. There are 195 Abell galaxy clusters in Aquarius alone. The richest (richness class 4 of 5, with more than 200 individual galaxies) is Abell 2645. It is also very distant (distance class 6 of 7), with a redshift of 0.25, corresponding to a distance of just under 3 billion light years. I was interested to see how many of these galaxies it would be possible to detect using the methods of EEVA i.e. short subs, live stacking. On the right is a shot taken with 48 x 15s subs, amounting to 12 minutes total exposure. The left shows the SDSS image of the same area. I had to apply an extreme stretch (of the form x / (x+small constant)) and invert the image to be able to see much at all and even then it wasn't obvious what were galaxies and what were clumps of statistical noise. But comparison with the DSS image shows quite a few member galaxies being picked up. There is a clear 'wishbone' or 'lambda' structure just NW of the cluster centre which shows up well, and a 'Cepheus' or 'monopoly house' shape just to the SE of centre that is clear on both images. It is hard to find photographic or visual magnitudes for these galaxies (the brightest galaxy listed by LEDA is mag 18.9) and they mainly have listed mags for the ugriz bands, but I estimate they are mainly in the range 19-21 (B), and I'm probably missing some at the top part of this range. These 'distant open clusters of the galaxy world' are amongst my favourite types of objects to observe. As I see the faint specks emerge in great numbers I imagine that each one may well be teeming with life in billions of individual systems, and this turns a barely-detectable signal in a few pixels into something else entirely. Details: Quattro 8" f/4 Newt on AZEq6 in alt-az mode, Lodestar X2 mono camera, SLL v3.3 for acquisition and Jocular for live stacking and processing. No darks nor flats. SQM 20.2. Martin
  6. Thanks Pete; me too! Just to confirm position and to check whether I could detect it in sub 1s, I was out last night again at around the same time as Pluto was transiting. Here's a comparison of positions showing movement from Monday to Thursday: And here are 1s, 0.5s and 0.25s captures: At 0.25s it was not visible on all subs -- maybe half of them. Martin
  7. Here's a 2m (15s subs) capture of this comet last night. Alignment was on the stars not the comet so the core is elongated. It sure is fast moving! Martin
  8. The 732-member WBL catalogue of galaxy groupings tend to have relatively sparsely-distributed members and differ in this sense from the more compact groups such as the Hicksons (although some Hicksons are also members of the WBL catalogue, I think). Armed with nothing more than RA/Dec, I often like to dip in to the WBLs just to see what is there, as these are under-appreciated objects and don't appear on (m)any charts. The results can be quite varied, but typically consist of 3-7 galaxies that fit on my small sensor. Here are 4 from last night. WBL 676 is very close to the bright star o AQR and consists of 5 main galaxies, though a sixth mag 18.6 galaxy is also visible as a fuzzy blob just N of a star. The lowest galaxy is NGC 7182. I'd say this is a fairly typical (not particularly exciting) WBL object type, with the galaxies strung out across the field. Seeing was quite good through most of the session but seems to have deteriorated for this object. Nearby is Shakhbazian 81, a very challenging compact group of about 11 faint galaxies. Also in Aquarius is WBL 669, a 3-member group. Again, nothing particularly spectacular. Aquila contains just one WBL group, again a triplet. I enjoy looking for WBLs in star-rich constellations as the combination of a dense star field with galaxies in the distance is appealing and unusual. The 3 galaxies form a near equilateral triangle with the base composed of mag 14.2 Sc type UGC 11524 and mag 14.7 SBc UGC 11522 which are at a distance of around 250 M Lyrs and may well be interacting. Finally, back to Aquarius for WBL 666, one of the six WBLs in that constellation. This is a real beauty, with 7 individually-interesting galaxies in the field, and it is finding configurations like this that motivates me to explore the WBLs. I reckon this would make a good AP target. Interestingly, these galaxies are all at a similar distance of 180-200 M Lyrs so may be a physical grouping. On the inverted shot I've marked the 5 NGC galaxies and a couple of quasars. Q1 is mag 19.5 with a redshift of 2.06 (8-9 billion LYs?), while Q2 is mag 19.6 but much closer, with a redshift of 0.18 (around 2 billion). The non-inverted shot is an LRGB as I decided to add a little colour (although it is mainly luminosity so the effect is subtle). Thanks for looking Martin
  9. Thanks maw lod qan and Carbon Brush. Its worth adding that I am at around 43 degrees which helps a lot, and that Pluto was about 25 degrees above the horizon. Now is a good time to catch it though as it transits more or less when astronomical darkness is reached. Martin
  10. Very nice images. I like the large FOV this sensor provides, especially for objects like the double cluster.
  11. Thanks Rob. I think the main differences are that I'm using mono + filters, which I find produce better star colours than using a colour Lodestar, and that I'm using LRGB and LAB colour space, which provides good resolution (from the L) and an easy to manipulate saturation component. I should have added that I'm also using (fractional) colour binning, set to about 2x2, which helps reduce colour noise. These are the only manipulations. There is no messing around with the individual R, G and B channels (and still no histograms!). Martin
  12. I've always been fascinated by the M24 region after learning that it is a window thru a gap in the nearest spiral arm through to the next arm, in the direction of the centre of our galaxy. NGC 6603 is a distant star cluster within M24 and is thought to lie near to the galactic bulge. This is a live LRGB combination using 5s subs for a total of just over 2 minutes. I like the slightly curved line of stars running across the centre of the cluster. The cluster contains a population of around a dozen red giants. It has been considered to have globular cluster characteristics e.g. see http://articles.adsabs.harvard.edu/pdf/1993A%26A...270..117B The cluster is indeed very dense and has a diameter that fits the small Lodestar chip nicely. (I am always amazed at what can be done with a sub 800x600 pixel sensor). The peach and blue field stars add interest to this region. I have yet to dig out colour data for these but they appear useful for calibration. [edit: the B-V values for the three bright stars below the cluster are 1.02, 2.0 and -0.11 respectively, which looks about right] I'm continuing to experiment with live LRGB methods. I used SLL to capture through each of LRGB filters while Jocular did the rest. I simply adjusted the saturation and the degree of power stretch applied to the RGB data (the L is stretched independently in the normal way for mono). Thanks for looking Martin
  13. The most extensive collection of dark cloud designations that I know about is the Dutra & Bica catalogue from 2002 which contains just over 5000 named objects. I checked and the Jellyfish does not contain any of these. They do note that the catalogue is not complete. It might be worth seeing who has cited this work to check if there are more recent catalogues. Martin
  14. Following a discussion over the summer as to how short an exposure would be needed to capture Pluto with 'typical' kit, I had a recollection that I'd managed it some years ago in 1s but couldn't lay my hands on the evidence... Theoretically it should be possible with decent skies in sub-1s with an 8" f/4 scope and a sensitive mono guide camera with large pixels. So last night I had a go and sure enough, it is indeed possible to capture in 1s. I've marked the position by comparing with the DSS image at Aladin (see central region below). There does appear to be a star near to Pluto's position on the DSS but it is around mag 16 and not quite in the right place. The star to the right of Pluto has a GAIA g mag of 14.6, which is similar to the estimated 14.3 for Pluto. Details on image. No darks/flats. North up. Taken through Baader C filter. Looking at this sub, even with the relatively high read noise Lodestar X2 camera, I'm pretty sure it could be done in less, maybe as little as 0.25s. Why the rush? Well, I'm never going to be able to resolve surface details so the point source is about as good as it is going to get cheers Martin
  15. After a 3+ months break, I managed decent session last night, looking at a variety of objects, mainly in the cluster-rich regions of Sagittarius, but straying into Pegasus later. As I finished the Pleiades were already quite high. Surprising how quickly summer turns to winter... Here are a couple of Abell galaxy clusters. No darks nor flats, just hot pixel removal. North is up. Other details on images. Abell 2593 This cluster is relatively close at around 600 M Lys. The brightest galaxy is NGC 7649, a mag 15.4 elliptical. This cluster benefits from an extensive set of magnitude data down to mag 22 so is useful in working out magnitude reach. The bright star at the base is mag 7.5 triple star Burnham 719. Abell 2666 I'm including a screenshot with the details I wrote at the time. This is a really appealing cluster, containing a mix of different galaxy shapes, with a linear structure of variously-oriented edge-ons. Distance around 380 M Lyrs. The bright star near the centre is the variable GR Peg. This is 23 x 15s subs for a total of 5m 45s. Thanks for looking Martin
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