Martin Meredith

Its a fascinating field. I note from a capture I made in 2019 that UGC 12628 (Sc, bar, diffuse) is just outside your shot to the lower left, and at 223 MLyrs it isn't so far away from the other two and might have had some role in the interaction. There is a lot of 'fluff' in the environs of NGC 7679 potentially spread out in an arc between the two galaxies (there is a more diffuse patch in between NGC 7679 and the '21.9' object that is visible in my capture and in yours. The 21.9 is from the quasar catalog (I only use the two orthogonal short lines for quasars) but lacks a redshift. I suspect that it just happens to line up with one of the fuzzy patches though I note that it has only a 77% chance of being an actual quasar so it might be some falsae detection which happens to involve whatever is going on in that patch! I'm including my capture although it is (i) embarrasingly dusty and (ii) 28 mins exposure -- not sure why but perhaps I was trying to capture the mag 21.9 possible quasar Martin

I note the early evening observation times of these shots -- one of the advantages of late November in the UK I suppose! VV 1947 is suggestive of having an edge-on spiral to the upper right of the core. Must be fun trying to sort that one out. It is reminiscent of some of the overlapping galaxies -- I'll check to see if it is mentioned in that catalogue. The brighter member of VV 1977 seems to have a double core, but this might be an illusion. Its a good example of visiting one object but finding other interesting galaxies in the field. Martin

Agreed, what a wonderfully wide field you're getting with that setup. BTW I obviously need to take more account of the galaxy orientation when deciding on label placement (in case you're wondering why the NGC 891 label is so far off). Martin

I love the field of view you're getting with the Hyperstar for the Arp 113 field! Just checked my Arp 113 -- doesn't add much.

Glad you had a good club session. Some fascinating targets here. Aesthetically I particularly like NGC 1169 as I have a soft spot for galaxies in the midst of a rich star field. Martin

In case it helps, I use the colour_demosaicing module for debayering. It comes down to just 2 lines of code: from colour_demosaicing import demosaicing_CFA_Bayer_bilinear rgb = demosaicing_CFA_Bayer_bilinear(im, pattern='RGGB') where im is the 2D image to debayer, and pattern can be any of the usual colour pixel configurations. rgb is a N x M x 3 array. For binning/super-pixels as Tony describes you can use either rescale (for non-integer interpolation) or downscale_local_mean (for what we normally understand as binning i.e. downscaling by integer factors) from skimage.transform import rescale, downscale_local_mean rescale(im, 1 / binfac, anti_aliasing=True, mode='constant', preserve_range=True, multichannel=False) or downscale_local_mean(im, (binfac, binfac)) Martin

I use the remove from stack feature all the time and I believe others do too. Maybe you have excellent tracking and no wind gusts? Reshuffle is particularly useful to solve stack alignment 'failures'. It comes into its own with LRGB or narrowband+L where there are far fewer stars on e.g. the B subs. The 70-80-90-median are also useful to get rid of satellites etc The OSC thing was really just an add-on requested feature from one user to get things going quickly. Jocular wasn't really designed with this in mind. Handling OSC requires a rethink... cheers Martin

I believe there was a project ('windi') that attempted this some years ago, so your assumptions were half-right!

Hi Steve I looked into pyindi but it is very much Linux-oriented (last time I looked there was a library required that would need rebuilding for OSX). In fact, I looked at ASCOM, INDI and ALPACA over the summer (from a coding point of view). Personal opinions: I like INDI least. ASCOM was much more 'obvious' but not multi-platform. Both ASCOM and INDI are based on an outdated and verbose protocol (XML), for which reason I think JSON-based ALPACA is the way to go. But from an application programmer's perspective, what is actually required (in my opinion) is a 'simpleastro.py' that implements the most commonly-used 90% of functionality (move filter wheel, expose for N secs, set temperature, move mount to X, Y; sync mount, and little else) in a way that is cross-platform. This would be a wrapper around some of the above. Those applications that are cross-platform (there are not many of those!) either do this anyway, or transform everything into e.g. ALPACA. Martin Added in edit: you mention a win-based INDI server. I heard there was such a development some time ago but is it actually realised/maintained/working?

Fascinating image. The upward-going tail is quite extensive compared to the size of the galaxy, similar to the Antennae at first glance. i see what you mean about the possible tidal stream. I look forward to observing this one. Martin

Thanks Paul. I heard about the weather you've been having in the UK. Here we've been pretty lucky so far (not to say unseasonably warm and dry until a few days back). Wishing you a clear spell to seek out these objects. Visually, this one might fit into a widefield view along with theta Lyr. Martin

NGC 6791 was thought in the 1980s [1] to be the oldest known open cluster, with an age exceeding 8 billion years. With new discoveries and more accurate distance estimates, it is now considered to be only the 7th oldest, with Berkeley 17 hitting a round 10 billion, and 3 ESO clusters reaching back further still. But by any measurement, NGC 6791 is ancient. Situated in Lyra at a similar declination to that of Vega and around 6 degrees in the direction of Cygnus, NGC 6791 is a rich collection of mainly faint stars with a moderate amount of reddening, an obvious cluster that is clearly distinguishable from the foreground star field. This is a 2m40s total exposure consisting of 8 x 5s subs in each of LRGB, live combined, observed with an 8" f4 reflector and Lodestar X2 mono CCD camera on 27th October 2021. There are a range of stellar colours on display within the apparent radius of the cluster itself, with some peachy (presumably foreground) stars to the south, and a couple of almost blue stars forming a diagonal either side of the centre -- again, presumably foreground members. The B-V colour indices of these blue-ish stars are in the range 0.1-0.3. The lower of the two is a pulsating delta Scuti variable while the upper is a rotationally variable star. However, the reason I've made the annulus transparent is to bring the deep red star at the upper right into the picture. While it might appear that this is merely a side-effect of over-saturated colours, in fact I turned saturation down to near minimum for this shot. This is the carbon star U Lyr with a spectacular colour index of over 4.6! The star varies from mag 8.3 to 13.5 in 451 days. It is hard to say where it is in the cycle without doing some proper photometry, but given that the aforementioned peachy stars are mag 10.5 I'd say it must be closer to max than min (how's that for caution). U Lyr is also an optical double star -- designated ES 2489 after its discoverer, T. E. Espin in 1930 -- with a separation of just over 10", a magnitude difference to secondary of nearly 3, and a position angle of 190 degrees [2]. It is visible nestling in the artefactual halo just below the carbon star. Thanks for looking Martin [1] http://articles.adsabs.harvard.edu/pdf/1981AJ.....86.1332H [2] https://www.stelledoppie.it/index2.php?iddoppia=80236

Hi Pat I notice from your website that you used LodestarLive (as it then was) back in 2015. I believe it is still available (as StarlightLive) for Windows from the SX website. It is probably still one of the simplest ways to acquire images with a Lodestar for VA. I'm not a Windows user myself but iI know others are still using it. Martin

This is a very nice demonstration that matching a small pixel camera to a small aperture scope is perfectly workable solution for EAA -- nice round stars too. Great work! Martin

I'm afraid not. What OS are you running? It is most likely that I'll provide native support for Ultrastar for Macs in the next release if someone is willing to test it. Martin

That's a great capture. Aperture really helps when it comes to faint nebulosity. Now I can make out 3 strands. The back story is fascinating. I recalled that PNs are capable of multiple ejections but the idea of slower processes such as you describe is a new one to me. I wonder if the Helix is also the product of such a process. Martin

Hi Mike Thanks. With PNs you never really know what you're going to get if, like me, you avoid looking them up beforehand... Do you currently use an extender? I need to use one if I don't use the filterwheel, Replacing it with the filter wheel gives me a similar focal distance. Your Ultrastar will slide in until it almost touches the filters so the critical distance is to the back plane of the filters, plus a little extra. Martin

I can imagine how annoying this is. Is there an option in the platesolving software to alter the minimum number of stars extracted? Or a log option that indicates what part of the process platesolving has failed on? It might not even get to the matching stage if it is trying to find say 30 stars. Martin

BV 5-1 is more easily found as either ARO 199 or BV 1 BV stands for Böhm-Vitense whose 1956 discovery paper is available [1], although no real details of BV 5-1 are provided as far as I can see. A more recent article [2] suggests that what we're seeing in optical images is the equatorial line, perpendicular to the axis of symmetry of the PN (my understanding is that it is edge-on to our line of sight). There are some good optical images in the paper by James Kaler and colleagues [3] This view provides more idea of scale and context (and weirdness) .. and tracking errors maybe too. [1] http://articles.adsabs.harvard.edu/pdf/1956PASP...68..430B [2] https://www.aanda.org/articles/aa/pdf/2001/35/aah2956.pdf [3] http://articles.adsabs.harvard.edu/pdf/1988AJ.....96.1407K

Here's a dozen PNs I observed in the northern skies over the last two nights, mainly but not always before the moon came up (I was blaming Bilbao's light pollution halo until I realised what was the actual culprit...) The sizes are quite varied, randing from 5 arcsecs to 5.7 arcmin. These all taken using the 8" f4 Quattro, Lodestar X2 mono and Baader LRGB filters, live combined, with roughly equal numbers of subs in each filter. More details below. No calibration frames used. Saturation has been turned up high for most of these. IC 5217 6.6" Lac 2m40 (32x5s) -- tiny but intense HU 1-1 5.0" Cas 2m40 (32x5s) -- mnauve/grey, featureless but then again, occupies only 2.5 of my pixels BV 5-1 18" Cas 3m45 (45x5s) -- what a strange object! Simeiz 22 5.67' Cas 9m45 (39x15s) -- brighter than I imagined; beautiful crescent NGC 7139 1.28' Cep 5m25s (65x5s) -- blood orange slice NGC 6058 23" Her 5m20 (64x5s) -- electric NGC 7354 23" Cep 5m20 (64x5s) -- lots of structure/colour NGC 40 48" Cep 4m25 (53x5s) -- had to turn saturation *down* M76 1.12' Per 4m10 (50x5s) -- red apple core with electric blue IC 1747 13" Cas 4m30 (54x5s) -- incomplete doughnut IC 289 35" Cas 7m15 (29x15s) -- subtle, interesting structure EGB 1 4.5' Cas 7m45 (31x15s) -- there is something there (pale red) but not obvious, although a blue star is visible which is likely to be the central star Simeiz 22 is well worth a look in mono too. It needs a huge stretch but the double stranded structure is clear. Now I'm off to see what I can find out about BV 5-1.... Cheers Martin

Hi Mike I think it is more a function of distance (reddening with all the intermediate dust). As a bit of fun I turned saturation up to try to match the SDSS view. Its always interesting to match the star colours to an external reference (though I do find the SDSS a bit over-the-top). Martin

IC 166 is a relatively faint open cluster set amongst a rich star field in Cassiopeia, a couple of degrees almost due south of Segin. At times the dense foreground can make such clusters hard to spot, but on this occasion the profusion of fainter stars makes the cluster stand out even in mono. But what makes this cluster interesting for me is the uniform reddening of its members in contrast to the range of stellar colours on offer in the foreground. This is reminiscent of the best of the Berkeley clusters which often have a similar configuration -- lots of faint red stars tightly clustered, giving it a kind of 'gritty' texture. With a diameter of just over 7 arcmin it fits nicely in a small FOV. IC 166 is about 1 billion years old (give or take 200 million years) and while this makes it quite a lot older than most, it is classified as an 'intermediate' age cluster. Due to disruption to members as the cluster orbits the galaxy, not many clusters reach the grand old age of a billion. However, IC 166 sits beyond the Perseus arm of the galaxy at a distance of 4.3 kpc from us, or 12.7 kpc from the centre of the galaxy, and it is hypothesised that disruptive effects are lower in the outer disc so chances of survival are higher. The dense 'nearby' star field set against the more distant cluster I think adds some depth to the shot. Ref [1] gives some optically-derived information while [2] contains a spectrographic study, complete with the slightly deflating conclusion that IC 166 is an unremarkable cluster. For me it was probably the highlight of the night... This is a live LRGB combination with manipulations in LAB colour space. The camera is not mentioned on the image -- it was my usual Lodestar X2 mono. cheers Martin [1] https://arxiv.org/pdf/astro-ph/0703075.pdf [2] https://arxiv.org/pdf/1806.09575.pdf

Like Stu, I've never used my Az-EQ6 in EQ mode. I use it almost exclusively for short subs (EEVA-style). I keeping telling myself I will try out EQ one day but its been nearly 7 years in Alt-az. Martin

Really interesting to read about this southern galaxy. I see that LEDA provides an estimate of 12.0' whereas Simbad gives 10.72'. Perhaps different sources uses different criteria for deciding where the arms end? Whichever it is, it would fit very nicely on my sensor! In principle I could observe this at 11 degrees above the horizon but it is in the direction where I suffer most light pollution. I have observed a few galaxies in Fornax and it is one of those constellations (Grus being another one) that I'm aware of having some great DSOs having pored through the Night Sky Observer's Guide. One day... Martin

Agreed. And not just kids -- I wouldn't mind seeing it myself! For the same reason we ought to have at least one day a year where all the lights are switched off for an hour or two, just so everyone can see the wonder of nature that is over our heads night after night (clouds permitting). Martin