Martin Meredith

I'm not sure how it's placed for you/how late you plan to observe, but I would point that huge FOV at NGC 1268 in Perseus and see how many galaxies you can count... Martin

Here's the brighter (by far) of two Abell clusters I observed a couple of nights ago. Replaying this now in Jocular as an animation, I can see light clouds passing through every sub, but the averaging effect meant I could get an image without realising (until now) that this was happening -- the power of EEA! The second cluster is less than a degree away but is distance class 6 and while I was able to spot about a dozen tiny galaxies, the cloud had thickened up by this time. In fact, there are 4 Abell clusters within1.5 degrees of each other with distance classes of 3, 5, 6 and 6, so a good hours could be spent here on a clearer night without really moving the scope. Abell 71 presents an interesting composition because it contains mag 4.3 eps And (164 light years away) and a triplet of constrasting NGC galaxies around 260 million light years distant, so well over a million times further out than eps And. I always find these conjunctions mind-boggling. The mag 13.8 elliptical is NGC 183 and above it are a pair of edge-on-ish spirals, mag 15.6 type Sab NGC 184 and the well-matched mag 15.7 So-a type NGC 181. Although it seems somehow unlikely, this triplet may well be part of the Abell cluster itself based on distance estimates. The two lines I've marked represent more or less the diameter of Abell 71 (in the long direction). What I find appealing is that this is an unusual quasi-linear grouping of the clusters brightest members. It takes a bit of scrutiny, but this is a chain of galaxies, mainly with magnitudes around 17.0, some fainter, a couple brighter. The unusual structure is clearer on the chart (after mental rotation). It is hard to see where such a group has a centre. I read in a very interesting 1985 article [1] entitled A POSSIBLE 300 MEGAPARSEC FILAMENT OF CLUSTERS OF GALAXIES IN PERSEUS-PEGASUS that Abell 71 might serve as a link between the Pisces-Cetus supercluster and Perseus-Pisces supercluster. Its distance and location is right for this. I imagine there has been more recent work to confirm or refute the idea [edit: yes, it is even mentioned in Wikipedia! https://en.wikipedia.org/wiki/Perseus–Pegasus_Filament -- a filament a billion light years long]. I have no idea whether the 'strung-out' ness of these galaxies is related to it being part of such a filament, or accidental. In either case, it is for me part of the charm of EEA to spot something potential interesting and then later find that it is indeed a fascinating part of our universe. cheers Martin [1] http://articles.adsabs.harvard.edu/pdf/1985ApJ...299....5B

I prepared a list of Arps for last night and working my way through them had to discard the first 4 or 5 as they were actually also Hicksons that I'd already observed... I managed a few before getting clouded out, and Arp 113 is the most appealing and perhaps the most interesting too. It is also known as VV 166 and I suppose this name should take precedence, although the NGC 70 group, as it is also called, has been known since at least the 1930s. This group belongs to the "Elliptical galaxies close to and perturbing spirals" section. In the labelled plot (N up) the numbers are NGC designations. NGC 68 and NGC 71 are type E-S0 (elliptical/impossible to tell if there is a bar), while NGC 70 and 72 are clearly spirals, types Sbc and Sab respectively. I have NGC 70 and 71 as having active galactic nuclei -- both are Seyfert type 2 (I'm not sure what the type 2 means). The distance estimate for this group is intriguing. Most of the members (including the outlier NGC 74) have distances in the range 325-345 MLyrs. This is also the case for the mag 15.7 galaxy on the extreme left hiding in the shdow of the bright star, so it is a group with a very dense core cohort and some further flung members. However, NGC 68 -- one of the main players, visually -- is estimated to be at 278 MLyrs. Looking around for any information about this group, I came across an article entitled Galaxy collisions in dense groups with Hickson as lead author which mentions that one galaxy in NGC 70 has a discrepant redshift. [1] There is an older paper that discusses the discrepancy in more detail [2], concluding that it is most likely not a member. Thus it appears we are left with a very pleasing chance lineup. cheers Martin [1] http://articles.adsabs.harvard.edu/pdf/1977ApJ...213..323H [2] http://articles.adsabs.harvard.edu/pdf/1974ApJ...193...19K

Thanks Mike. So this is the Taffy pair? In that case I viewed it some years ago -- doh! I will dig out my old capture if I can find it 😉 Martin

I was out last night until the clouds and moon simultaneously forced me back inside, mainly looking at Arps in Pegasus and Andromeda, but as usual I got distracted by other nearby objects on the charts and just as well I did as otherwise I might not have come across this beauty: VV 254 in Pegasus. Remarkably, these are not in the NGC or IC catalogues but are UGC 12914/5, clearly interacting at a distance of 213 MLys. The slightly brighter galaxy is mag 13.4, type SBc and has much interesting structure, with a very bright and condensed core, one strongly-defined spiral arm and a large ring-like halo. UGC 12915 is mag 14.0 and also of type SBc. Its two arm features look like a crab's pincers. I left this running for a while to tease out more of the fainter structure, better appreciated maybe in the negative view (N is up here). cheers Martin

http://astronomie-va.com/forum/viewtopic.php?f=8&t=435&sid=cdaa2295fee6680db177c60543263900 My French is quite pauvre, but this seems to be live-stacking using a Dob without tracking. Martin

Hi Brian The emphasis in EAA is on simplicity. Since most sessions tend to last for a few hours at most (and it is possible to get away with a short session between clouds), it is useful to streamline things as much as possible. So, for example, you don't need to guide for EAA (some do, most don't, as far as I can tell). The same goes for auto-focus. With a Bahtinov mask you can accomplish focusing in half a minute and it should stay in focus for the entire session (if not, then check the focuser before looking into autofocus). Alt-az is perfectly fine too. So I guess this agrees with what you're suggesting. I use alt-az, 2-star alignment (no plate solving) and can get up and running in 5 minutes on a good night. Its just as well because its amazing how often the clouds comes over while I'm framing the first object... I imagine you've already looked at https://astronomy.tools/calculators/ccd_suitability. I can't find the QHY5y but if the specs for the QHY5 are the same, then it looks like a very good option when used binned and with the 0.63 focal reducer. I would therefore use what you have got already before spending on a new camera. Most sensors can be cleaned easily unless something bizarre has happened. I use Baader Planetarium's Optical Wonder fluid with a cotton tip. Lightly wet one end, then start in the middle of the sensor and use a spiralling out motion to reach the edges, then immediately use the other (dry) end of the cotton tip to soak up excess fluid. Ensure it is dried off before replacing in the scope (matter of a few minutes). If you still have dirt issues, some of them might be calibrated out using flats, which are becoming a fairly normal part of the procedure even in EAA these days. I don't do planetary (except Uranus, Neptune and Pluto!) so maybe others will chime in, but I think it is quite hard to find a single setup that excels for planetary and deep sky. But having said that, the scope you've got is already very adaptable as you can use it at its native focal length for planetary work. All the best Martin

Hi Ken On the CMOS question you'll (I hope) get various opinions. Personally, I think CCD cameras without user-settable gain/bias are actually easier for beginners (and for experience observers for that matter). However, there is a much greater choice of reasonably-priced CMOS sensors and many EEVA observers seem to have moved to CMOS (though not so much on this forum). I've been using a small sensor CCD guide camera (the Lodestar X2 mono from Starlight Xpress) for EEVA for nearly 7 years and am very happy with it, even though in theory it lags behind some CMOS offerings in terms of things like read noise. A far more important issue than CCD/CMOS though is matching your sensor to whatever scope you end up using. This is going to have a much bigger effect on your experience. Check this out for some pointers: https://astronomy.tools/calculators/ccd_suitability Happy to discuss more! Martin

Hi Dan I'm not too familiar with your scope and camera (perhaps you could provide focal ratio for the scope and some details like pixel size for the camera), but it is certainly possible to do EEVA with a mid-sized frac and a well-matched sensor. I imagine you've already checked out https://astronomy.tools/calculators/ccd_suitability but if not, the key things to look for there are the 'native' arcsec/pixel of your scope/sensor combination, and then what happens to it when you use binning and/or focal reduction. In EEVA we like to build a bright image quite quickly compared to AP so a fast focal ratio is useful (f5 or below); that you can achieve with a focal reducer. Big pixels are also useful to improve SNR. If you already have a camera with smallish pixels then this can be achieved by binning so long as your arcsec/pixel doesn't become too much greater than 2. (I operate at 2.11) Also worth looking at is the field of view for your scope/sensor/focal reducer setup. A large FOV is good, of course, for some kinds of objects (bright nebulae, dark nebulae and the larger open clusters primarily), and I think perhaps a mid-sized frac is best for those types of objects in the timescale of EEVA exposures (e.g. total exposures of 2-10 mins typically). A bigger scope like an 8" Newt or SCT (the latter with focal reduction) is going to deliver better and in particular more detailed views of most galaxies and galaxy groups, of which there are many interesting examples, and if it is an astrograph (say f4 or so) even better I would say. I certainly wouldn't get a goto Dob for EEVA. You do need good tracking and its remarkable how effective (in my experience) a fast 8" scope is (which would be classed as small for a goto Dob I suppose). You didn't mention software but that makes all the difference too. Much AP software is designed for offline processing. Happy to discuss more Martin

Hi Flavio Thanks for spotting the equivalence of 2 and 3! I've now included the correct versions and reordered from 2 to 5 so the progression is clearer. I fully agree that these plots don't tell us the whole story about extended objects for the reasons you give. They're useful for detecting limiting magnitude, and for predicting the effects of seeing. I've often wondered whether it would be possible/feasible to simulate the kinds of effects we're discussing by taking a very high resolution Hubble image and treating it as an emitter of photons ie mapping each pixel intensity to the mean of a Poisson noise generator. I've too little time at the moment to pursue this unfortunately... cheers Martin

For what its worth, I applied the point source code to a range of scope/camera combinations and plotted SNR versus exposure for a single sub, for detecting a mag18 point source in a mag18 brightness sky and got this result: The Lodestar has 8.2um pixels while the ASI 178 has 2.4um pixels. The Borg has a focal length of 331mm versus 800mm for the Quattro 8" (I threw in the Quattro 10" to see what a near-doubling of mirror surface area would deliver). I applied a read noise of 7e for the Lodestar and 1e for the ASI 178 and appropriate central obstructions for the reflector and refractor. I'm a bit surprised by the Borg + Lodestar result but it looks like it is related to the FWHM. Here are results for FWHM=3, 4 and 5

Hi Flavio When talking about things like surface brightness, contrast and detail, we are still fundamentally talking about per-pixel SNR and resolution. So all the SNR machinery that applies to point sources essentially applies to diffuse sources too. I would go further, and say that for all but the fainter point sources, we typically have way too much SNR on bright sources (in the same way as when listening to speech in noise, beyond a certain level of noise it has no effect on intelligibility of the speech), so it is exactly in the diffuse regions where achieving an adequate SNR is critical. This concurs with my experience of e.g. awful colour noise in short exposures of anything nebulous that is anything but quite bright! For the sake of argument, if we were to remove all external sources of noise (e.g. read noise, thermal noise, sky noise) that can be handled in various ways, and just talk about the intrinsic noise due to uncertainty in arrival times of photons, then the only thing that matters is to collect as many photons as possible. In other words, getting as much target signal S per pixel in the timescales of a typical EEVA observation. Let's assume also that we want to keep resolution constant. How can we achieve this? There are at least 6 ways I can think of increasing S, but not all are permitted if we want to keep resolution constant, assuming all other factors are fixed. 1. Increase sensor quantum efficiency. This is a 'free' lunch (except that it costs), in the sense that we increase S without losing resolution. Most sensors have a highish QE these days so there is not much to gain here. 2. Use a sensor with larger pixels. This results in a loss of resolution. 3. Use binning. Same as 2. 4. Use focal reduction. This results in a loss of resolution too. 5. Increase exposure time. This increases S with no loss of resolution. 6. Increase aperture (all else being fixed). Now we get an increase in resolution but SNR-per-pixel stays the same. However, we don't want this increased resolution, so we combine this increase in aperture with focal reduction to get back to our original desired resolution. Then S (and hence SNR) increases. So it seems to me that in this idealised (but close to realistic scenario) where the only noise source is the uncertainty in photon arrival time, the only variables that can be traded to reach our target resolution at an adequate SNR are QE, exposure duration and aperture (as one would a priori expect, I guess!). Of course, I might have forgotten something! Happy to hear other opinions as always. Martin [Edit: one factor I didn't mention is field of view and how this affects the target; I've a horrible feeling this also need to be taken into account...]

Hi jcj380 A few people have experimented with this approach and managed to get some results with brighter objects, but I've not heard of anyone who has moved from experiment to habitual use. The late Nytecam (Maurice Gavin) demonstrated the approach either here or on CloudyNights though if memory serves I don't think this was using alt-az. It is certainly possible for a certain class of DSOs (I believe Maurice used the Ring Nebula as an example). You might be able to find those posts. You don't say what scope you would be considering but this question does get raised from time to time and often from people who have dobs with reasonably large apertures. Although such scopes are capable of capturing enough photons in short exposures to reduce the effect of blur as the object moves during the sub-exposure, the bigger issues with these scopes are finding the object in the first place and keeping it on the sensor between exposures in order to build up a stack. I did try it myself on my big dob many years back just for the hell of it but with a focal length of over 2000mm and a tiny sensor it was an absolute nightmare! With shorter focal lengths and bigger sensors you might have some luck. But there are always going to be more relaxing ways to observe. cheers Martin

That's interesting practical experience Mike. Excellent seeing is rare for me too. And I can confirm that I never use binning. A paltry 752 x 580 pixels is already few enough, thank you... Having said that, from an aesthetic viewpoint it would be good to have rounder stars on occasion. Martin

Hi Flavio Interesting questions. You might find some useful pointers (or not) in the thread below where I implement Raab's algorithm for determing how faint a source you can detect given aperture/focal length/QE/pixel size (admittedly it concerns point sources, but the principle of how many photons falls on a given pixel still applies). The (Python) code is also there in case it helps for simulations of the effect of pixel size while holding the rest constant (or I am happy to run such simulations given a bit of free time). So this is my understanding of the effect of pixel size: If you hold aperture, focal length and sensor QE constant, then the number of photons that are converted to electrons indeed should be the same regardless of pixel size. But this is across the entire sensor. To be meaningful you need to distinguish between global and local (spatial) SNR. At the level of individual pixels the SNR will vary with pixel size. You can have a huge pixel-wise SNR if you consider the sensor as a single pixel, or a terrible pixel-wise SNR if you have infinitely small pixels. As I see it, when doing EEVA we are explictly or implictly trading off 3 variables: pixel size (i.e. spatial resolution when focal ratio is fixed), SNR and total exposure time. SNR, at least for EEVA purposes, needs to be 'good enough' to see the faint details in DSOs, faint quasars, etc (this is probably the main thing distinguishing EEVA and AP) Exposure time is the thing we have most control over, but total exposure tends to be relatively short in EEVA (~10-15 mins max, often shorter) Pixel size needs to be small enough to achieve the spatial resolution we are seeking, at least up to the limit imposed by seeing (unless we are using lucky imaging) What you really want is a good SNR all the way down to the seeing limit on any one night. But the only guaranteed way to achieve this at the chosen resolution is to increase exposure time (everything else being equal ie aperture/focal ratio/sensor QE). Looked at like this, small pixel sizes (at least down to the best seeing we expect) are advantageous IMO mainly because they give us a second way to increase SNR (via binning) instead of having to use longer total exposure i.e. more flexibility. I say this as the owner of a camera with huge pixels! Martin

Fantastic image Bill. You could spend a good hour exploring the different galaxy types in that cluster. I didn't spot the reducer until Mike pointed it out. That's a great idea and seems to have no noticeable distortions. You must have it well collimated! Thanks for the additional info Mike. Abell 2937 is indeed confusing position-wise. The article I link to shows two great clumps of galaxies. I've rotated one of their north-down plates to match mine (which is on the left in case not obvious!) centred where my solid circle is. It is hard to know how far out the cluster extends -- and I suppose at these distances incorporating the other ellipses I've marked might mean this has a too-large extent. On the other hand, many Abell clusters are part of much larger structures. See https://cdsarc.u-strasbg.fr/viz-bin/Cat?J/MNRAS/445/4073 for a catalogue of these (Bill, you'd need a 0.1 reducer to fit some of these on the Lodestar 🙂

I've been checking some of my earlier ACO captures and found this one from a year ago. ACO 2666 in Pegasus is at the other distance extreme -- distance class I, with 34 members within 2 mags of the 3rd brightest. It provides a nice illustration of the wide variety within this catalogue. This group is at about 390 million LYs. The brightest galaxy is the (inevitable) elliptical (mag 13.3 NGC 7768), but it is surrounded by some gorgeous edge-ons (from top to bottom, mag 16.8 type Sc, mag 15.5 type Sbc, mag 16.3 NGC 7766, ending at the bright NGC 7767, mag 14.5 type S0-a. The edges of the field contain some further edge-ons, all at a similar distance. Perhaps the most interesting galaxy here is the near face-on Sc type at about 1 o'clock. This alone might be worth a closer look. The 'ring' appears quite knotty. The bright star to the L of the central elliptical is GR Peg which varies from mag 10.4-11 about 5 times a year.

I don't think we yet have a dedicated Abell galaxy clusters thread, so please feel free to contribute observations here. In total, there are 5250 such clusters, including some 1174 that are the 'Southern Abells' with declinations lower than -16, so more than enough for a single observing season 😉 These clusters were catalogued by Abell, Corwin and Olowin (and are nowadays often referred to with the designation ACO) and have a wide spectrum of visual appearances. They are mainly very faint -- about 90% have nearly all of their member galaxies fainter than mag 16, but that for me is part of the challenge and excitement of observing them with EEVA techniques. There is something very special about a very rich galaxy group which occupies a compact region of the view and is teeming with faint objects. Add to that the uncertainty of the group's appearance, and indeed whether it will appear at all, and I think a good evening's viewing can be had with these groups. Most ACOs are, if not exactly uncharted territory, barely make it on to the deepest charts, and I imagine very rarely observed at all. I used to pass quickly by when scanning the charts for interesting objects, but now when I see a completely empty circle enclosing a supposed ACO group, I often stop to take a look (though only if I have at least 10-15 minutes to spare). I'm going to start this thread with an observation from last night. It was meant to be clear but the promised clear skies were actually plagued with scudding low clouds throughout the brief session (I also had a plane fly right through one sub). In the end there were more frames that were completely clouded than clear (my darks library benefited from the initial waiting around...). In a moonlit night under such conditions I would normally have called it a day, but I perservered as I was interested in testing some aspects of calibration in Jocular. Surprisingly, even though the overall captures took longer than usual, it was (just about) feasible to do some observing under such conditions, and I think speaks to the value of the EEVA approach. I observed 4 ACOs in all but I'm just posting one, and I think at first glance it will appear like the winner of the under-whelming object of the year. This is ACO 2397 in Aquarius, a few arcminutes away from NGC 7164. This is the result of nearly 9 minutes observation with the clouded out subs ruthlessly culled from the stack. In this annotated view the cluster is represented by the solid ring, but I wonder whether the galaxies marked at the right also belong to the cluster? How many galaxies are present in the cluster? The listed member count is 146 but this number needs to be interpreted with care as it corresponds to the count of cluster members with magnitudes up to 2 magnitudes fainter that of the third brightest member (so in this case roughly in the range 18-20). Hence the actual member count is higher (potentially much higher). Abell et al also report the magnitude of the tenth brightest galaxy. In this case it is 17.9. The group has a redshift of 0.224, a richness of 3 (scale 0-5, where 5 is the richest) and a distance class of 6 (scale 0-7, where 7 is the most distant). I calculate that the distance is somewhere between 2 and 2.7 billion light years. An image of this cluster (N down) appears as plate 27 of article [1], where some of these galaxies can be ID'd (so are not just patches of noise!), and table 13 of that article provides galaxy photometry for the cluster. This shows that the brightest galaxy is a dizzingly intense m17.68 (marked on my shot) and there appear to be over 530 members down to around mag 23. Individual subs show nothing at all, and it takes quite a few subs before the first members can be confidently identified. But that is part of the pleasure of observing faint ACOs. [1] http://articles.adsabs.harvard.edu/pdf/1983ApJS...52..183B Of course, there are much brighter ACOs out there such as 539 in Orion, 2151 in Hercules and 426 in Perseus, which are much closer and spectacular in a different way. cheers Martin

Hi Ted A 10" f4.7 would be a great scope for EAA in my opinion, paired with the right sensor, so long as your tracking is up to it at that focal length. The ASI 294 looks like an excellent fit but looking at the arcsec/pixel I imagine you'd mainly be using it binned 2x2 except on nights of great seeing. Everything else looks significantly smaller in terms of FOV. I quite like the newish 533 with the square sensor which isn't too bad FOV-wise, but I've no idea how it compares cost-wise. Martin

I too like diffraction spikes, but not when something is twisted, generating secondary spikes (if you excuse the pun). What is it that causes them? (I will try to fix now that the weather has closed in again..) I too was inspired by Macavity's post a couple of weeks back:

For lack of replies I'll make a few comments although I have no experience with the ZWO cameras mentioned. The key things to aim for for EEVA-style observing are sensitive cameras and fast focal ratios (under f6, preferably under f5). Both help to get bright images on to the screen quickly, ie in the near-live timescale (say 5-15s for the initial image, then subsequently improving as more are stacked). Sensors with quite large pixels and high quantum efficiency (75% or above) work well, or cameras with smaller pixels that can be used in binned mode (to effectively create larger pixels). Many users of SCTs employ focal reduction. Newt users seems to have success with native focal ratios so long as they are f5 or under. It is worth visiting https://astronomy.tools to check not only the apparent field of view of your scope and proposed camera combination (with or without focal reducers), but also the CCD suitability calculator at the same site, to determine whether you will be over or under sampling. I operate at just over 2"/pixel which is under sampled on the nights of best seeing, but I find it adequate most of the time. You also need to decide whether you want a single setup for 'everything' ie all the way from large bright nebulae to planets, or whether you'd be happy with a compromise that works well for most objects. It is actually quite hard to find a setup that is good for large bright nebulae and planets since they are at opposite ends of the apparent diameter scale. I myself find there is plenty of mileage in smaller sensors and continue to use a 0.4 Mpixel camera with large pixels as my only camera, paired with a fast Newt (8" f4). This is a compromise in the sense that it isn't good for the bright planets (though it is good for Uranus, Neptune and Pluto and their respective moons), and it isn't good for larger objects like many bright nebulae (they don't fit). But it works well for the remaining 99.9% of DSOs... Colour cameras are good for the immediate wow factor for bright objects but are actually a little harder to use than mono cameras in an EEVA-setting (more controls to get the colour balance right). Mono cameras provide better spatial detail of galaxies and other faint objects in near-live viewing. It comes down to what kind of objects you envisage spending most time looking at. There is no question that open clusters and planetary nebulae benefit from colour, as do globular clusters and bright/reflection nebulae. As you look at the kind of images that have been posted on EEVA forums, it is worth checking how many are colour images of fainter objects -- not so many. You'll see a lot of M27, M57, M8, M4 and the like, but these are really pretty bright. Its something that is worth bearing in mind in near-live viewing. That said, most open clusters (of which we see very few on the forums) respond well to colour. Toadeh, I'm a Mac user and can say that EEVA software for Mac is very limited -- but does exist. I believe ASIlive works on Macs for instance if you end up with a ZWO camera. StarlightLive works on Macs for certain Starlight Xpress cameras such as the Lodestar and Ultrastar but isn't being maintained as much as a few years back (I've had problems running it on the latest OSX, Catalina). Mainly for this reason I've written software that works on a Mac (Jocular) but that doesn't support OSC cameras (it does support mono + filters for colour though) nor cameras with large pixel counts. So the situation on Macs is not ideal, but it is workable, though there may only be one option for any given camera that actually works! Tteedd, you don't say what your scope and mount are so it is a little hard to comment in more detail on your proposed choice of camera. cheers Martin

That's a tough one (typical of the Abell PNs!). Interesting to read about the central star. Apparently it has a period of just under 12 hours and varies in the brightness by 1.5 mags in that time if I've read it correctly. Depending on the shape of the light curve you might be able to catch some of this variation in a typical EAA session. My eye is also drawn to that lovely curved 'thing' just to the right in the eyepiece view. Looking it up it appears to be a chance alignment of some stars with a mag 17.8 galaxy (PGC 1793463... the longer the number, the more recently catalogued I imagine). This is estimated to be 999 million light years away, so quite a range of distance in this image. Martin

Nice capture, Mike. Very smooth against the background. Looking more into Jones 1, there's a good shot of it here: http://helixgate.net/jones1.html Apparently, the blue central star is mag 16.0 (GAIA green filter) and has a B-V (or rather GAIA b - GAIA g) of -0.25, making it very blue indeed (other estimates give a B-V of -0.1). Jn 1 or Jones 1 doesn't turn up anything on Simbad but PK104-29.1 does the trick. Martin

HI Tony Aiming to release Jocular for testing in a week or two and more widely in October.... (looking at your sig line) with native support for the mono Ultrastar (mono Lodestar is already there). For that FOV I think some of the larger Abell galaxy clusters would look superb. I'm thinking Abell 426 in Perseus which covers just under a degree, and 2147 and 2199 in Hercules. From a distance, NGC 185 looks like the view of Centaurus A through a small refractor. Very interesting to see it in colour with that clear dust lane. I don't find 20 mins excessive for EAA for an interesting object like this, but I myself would be using shorter subs in a live context (not least because I'm using alt-az!) cheers Martin

Very nice shots. NGC 891 is wonderful. I've never heard of Barbon's galaxy -- thanks for that. Sounds like a task for LRGB indeed. cheers Martin