Lunar data mining and “Alexander’s beaded rim”

October’s “Sky at Night” magazine has quite a few lunar images. The regular “Moonwatch” article is about the crater “Alexander” and its environs. Alexander is a difficult to identify eroded crater. In particular it talks about “Alexander’s beaded rim” about which it says “The peaks that define Alexander’s western rim appear like tiny stars arranged in a beautiful arc”. I have to confess that from the images in the magazine, this clair-obscur effect totally eluded me.

So, as I now have quite an extensive set of window-sill based images (of varying quality!) of the Moon in a variety of phases a bit of data mining was indicated. I found the following image which I cropped and labelled the features to be approximately the same as that in the magazine;

Then, after a bit of contrast stretching in GIMP, we get this:

NOW I can see an effect, although whether it is the one they were talking about, I don’t know! It is pretty though.

While looking at this image set, nearby there was also a pretty good manifestation of the Lunar “V”.

Weekend Opportunism

Between a busy work week, family commitments and some so-so forecasts it wasn’t looking good for astronomy this weekend, but it turned out pretty well.

Friday Night:
Didn’t get out until about 10:30 but tried to make up for lost time by setting both the main scope going and trying out my 50mm lens on the Star Adventurer. I had high hopes for the 50mm lens- it’s another oldie (I’ve had it about 15 years), but online quite a few people are getting great results with them. Well- I’m not in that club (yet). The diaphragm only has five blades and although I stopped it down to f2.8 (it’ll open up to f1.8) all of my stars are pentagons and DSS is refusing to recognise them as stars- so no results from that. Fortunately, the main rig saved the day: I went for NGC6946 – The Fireworks Galaxy with my 200p. Throughout the session low clouds were interrupting the view, and around half the subs were lost, but the ones I did hang onto gave the result below. Over the summer I’ve picked up a second hand Canon 550d that has been home modified with a Peltier cooler and put into a metal case- it’s not pretty, but it seems to be effective. This is 13×4 minute subs and throughout this session it held the temperature down to around 7-8 degrees which I’m pleased with (a couple of degrees below ambient, my 600d usually runs about 10 degrees above ambient and is consequently much noisier). The target itself is quite a bit smaller than I’d anticipated- this is a crop of about 20% of the frame. Despite the small size- I think this is a lovely target- both for its colours and the asymmetry in the arms.


Whilst the cameras were doing their stuff I had the Dob out on the following objects:

The Double-Double- I used Vega to get the finders lined up then dropped down to Epsilon Lyra to check out the seeing. It was a straightforward split, but I could see that the transparency was not great.

M13 & M92 – I often start with these and never get tired of them. In Binoviewers at about 260x they fill the field of view and appear 3 dimensional. For me these are the only types of objects that actually look better in the eyepiece than in a photo; I love the difference in their appearance- M13’s great with lots of features, but a bit of a mess with arms everywhere, whereas M92 is compact and very neat. Just wonderful.

The Veil – I was reading a thread on SGL recently which referenced a Sky and Telescope article on The Veil (https://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/explore-veil-nebula/) . Using this as a guide, and with an Oiii filter a 30mm eyepiece (55x) and a coat over my head I managed to explore just about the whole thing. I’m a bit prone to hopping from object to object whilst observing, so it was great to really take my time in the tranquillity of the small hours and drink it all in with nothing but the odd clunk of a shutter release and that American woman with the nice voice who commentates on APT saying “Dithering started…” softly in the background. Ahhh… a very nice dither contemplating the remnants of a supernova.

I was on the Veil for over half an hour and loved every minute of it, but decided with to move on with the Oiii filter and go check out M27. This is normally not a problem, but by this point the transparency had deteriorated so much I was unable to hop to it. Altair was the only nearby star that was naked eye visible and despite several attempts I just couldn’t find the stars in the finder to hop up to M27. Reluctant to retire I switched up to the North East to check out M31 as the skies looked better in that direction. Before I could get to it a bank of cloud blotted it out. Time for bed…


I managed to pop out briefly whilst doing other things on Saturday evening and set the imaging rig running on M13. This was a bit of an experiment: I’ve imaged M13 before, but with my guide camera on a smaller scope using the short exposure method. Whilst I was quite pleased with those outcomes (see https://roslistonastronomy.uk/catching-up-on-images) , I wanted to see how it would look with more integration time and a DSLR chip. This is 22x 4 min subs plus calibration frames and I am really pleased with it. As a bonus for the last half-hour it was running I sat outside with Sam observing the sky primarily with Mark 1 eyeballs. After a while we were both able to pick out the Milky Way running up through Cassiopeia and Cygnus despite the local light pollution. A real pleasure!

Local project?

How about this for a project?

Observe/sketch/image as many of the Local Group of galaxies as possible.

Meet the Shy Side of the Local Group

They are well placed at the moment. There is the obvious M31, M32, M110 and M33. There is also the rather less obvious NGC147 and NGC185 (C17 and C18). There are also others.

Here are images of M32 and M110 I have extracted (not too successfully!) from existing images of M31,

and here is a reprocessed image I obtained last year of NGC185. So far I have never managed NGC147.

Anyone up for a challenge?


Observing report 31/8/19 Andrew Thornett. Rob Leonard, Neil Wyatt

Rob, Neil and I are at Brankley pastures conservation area near Hoar cross hall tonight observing in field. Currently lot of cloud but earlier on great view if Milky Way with kit of structure especially around Cygnus. M101 was very large occupying 60% field of view in 30mm OVL Aero eyepiece in Rob’s 14 inch Don with bright core. M57 big and bright with Baader Zoom 8-24mm set to 12mm and with UHC filter. Showed internal structure that demonstrated that, although centre cleared relative to ring, it isn’t empty but has network like internal filling. Central star not seen. Both cores of M51 seen with 14 inch Dob with Baader Zoom at 24mm, and we also saw Owl Nebula through light cloud using Baader Zoom with UHC filter in same eyepiece. I think I was able to faintly just see Witch’s Broom without UHC but before I could add UHC cloud came in and prevented further observation. Great reasonably dark observing siteonly minutes from home but you probably want to do with others as feels a bit isolated.

With quite a lot of cloud we resorted to unconventional means of observing. With 30mm finderscope we could all see M31. We could also see it in Vixen 2.1x binoculars. I was able to just make out M33 in the 30mm finderscope, and also the brightest portion of NGC7000 in the Vixen 2.1x binoculars.

M13 seen in Dob and 2.1x binoculars and Neil got a picture of Eastern Veil Nebula.

Started at 2100 and finished 0004.


Summer triangle and (almost!) Milky Way

Having been quite impressed with the view of the Milky Way from darkest Wales:

Milky Way in Wales

I thought I would see what I could do from the light-infested Midlands.

Answer – not much!

Here is a single 30-second (un-driven) exposure with my Sony DSC HX-90 snapshot camera. (The same as in Wales). You can just see a bit of the Milky Way.

As a bonus extra, here is Pegasus and its environs. You can just make out M31

A depressing thought is that I can remember as a kid in the 1960s admiring the Milky Way from industrial Rotherham. There were just 2 gaslamps on the street where we lived.

You just can’t beat proper dark skies! Look at this: https://spaceweathergallery.com/indiv_upload.php?upload_id=155226

Aperture Mask: Yes. Pluto: Not so much.

Got home from the trustees meeting last night to a glorious clear sky. On a Monday? Really?

I made an aperture mask for my dob over the weekend and was itching to try it out. The idea behind the mask is that on bright targets cutting out a bit of light and diffraction from the secondary struts should improve clarity, even though the aperture is reduced (350 to 160 in this instance).

And so after failing to resist temptation I was setup by 11:20:

Jupiter: Disappeared behind neighbors house. Need to catch it in the gap between house and apple tree 1.

Saturn: Seeing dreadful without mask: boiling away with no clarity at all. With the mask: same but dimmer. Hmmm.

Pluto: Spent ages looking for this. Definitely in the right place. Pluto formed a triangle asterism with two other faint stars. I upped the magnification to dim the sky glow and there was definitely something there. Wobbled the scope – that helped. Averted vision- didn’t make much difference. So- I’ve looked at Pluto but not seen it! Beginning to regret doing this on a work night…

Jupiter again. Behind apple tree 1. That moved quick! Damn!

Izar: At last- some success. Successively improved views moving from Baader zoom to binoviewers to adding aperture mask. In the final view the stars were pinpoint sharp and well separated with the companion showing a lovely blue.

Double double: the same experience. The 2 pairs were easily separated in all 3 configurations, but the binoviewers plus aperture mask gave the best view.

M13: Too dim for the mask, the best view was in the binoviewers- resolving all the way to the core and seemingly spherical, even though at that distance you don’t really have depth perception!

Jupiter again: Gotcha! Just before it snuck behind apple tree 2… Definitely a better view with the aperture mask- slightly dimmer but with much more clarity. 6 bands plus the GRS were clearly visible, with some detailing on the bands, plus the moons spread out as clear disks 3 to one side and one on the other.

Well worth the fatigue today!

Very pleased with the aperture mask- it’s not often an astro upgrade is almost free. It’s only really good for bright objects and with the binoviewers I had to velcro 4kgs onto the bottom of the tube to balance it- bit well worth the hassle!