I found a set of “nets” for icosahedron models of planets and moons recently and made one each of Jupiter with my daughter. They’re quite tricky to make the final joins on — you really need delicate slim fingers, not short dumpy ones such as I am gifted with. Anyhow, here’s how mine turned out:
I downloaded the net as a PDF file from here, but found other paper models here and here. As yet we’ve not tried the last two.
Yesterday (22nd July) morning I received a phone call about a bee swarm in a local garden. The swarm was in a holly bush right next to the path to the front door of the house and the owners have young children so not collecting it wasn’t really an option, but I’m now left with a debate over what to do with it. It seems very late to allow them to try to consolidate a new colony in time for the winter, so perhaps I should just dispose of the queen and combine them with another colony, though it was quite a large swarm.
I’m genuinely surprised to see one this late in the year. I imagine they’ve been waiting for some time for an opportunity to leave the parent colony, unable to do so because of the poor weather.
I think I’ll give them a couple of weeks to see if the queen starts laying and then make a judgement about how to combine them.
Having had an excellent night two nights ago I had six Messier objects left to find and set myself the goal of finding M7 this week on the basis that whatever happens in August, between the Moon and the turning of the seasons it will be lost to me until next summer. According to Stellarium it was going to be a really tricky object to find anyhow as it wasn’t going to get much more than four degrees above the horizon at any point.
I had the ST120 out cooling early and took it up to my usual observing site at about 11pm. The sky was clear of cloud, but the seeing was very poor with light pollution from the local town particularly being scattered as much as fifteen degrees up from the horizon. Nonetheless I was on a mission. Clearly the trees have grown an awful lot or the configuration of Stellarium is not quite perfect as its idea of where M7 should be was clearly higher than it could actually be judging from the position Kaus Australis which was the initial point for my star hop and pretty much the same altitude. Kaus Australis was actually below the maximum height of the tree line though I could see it through a gap, so I was feeling fairly negative about my chances of finding M7, but as I panned westwards across the treetops it suddenly popped out in a small gap. I had to wait for the trees as they moved to be able to see it and I’m not actually sure I could see the entire cluster at any one point, but there was nothing else in Stellarium that it could be and based on the few stars and its alignment with the “tail” of Scorpius I’m certain I found it. I still feel somewhat cheated though. Short of taking a scope much further south or finding a hill with a completely clear southern horizon I don’t think there’s much else I can do though.
My “backup plan” for the evening was to find M30, but it was too early and Capriconus was lost in the haze of light to the east anyhow, so I left the scope out and returned to the house to grab some binoculars and spent an hour sitting on the patio watching the sky, looking for meteors and satellites (I saw at least half a dozen of each including what I believe was an Iridium flare, but it disappeared over the house before I could catch up with it). I’ve never had a “good” summer for observing, so I took some time to try to familiarise myself with the orientation of summer constellations and to revisit old friends such as M13. Away from the light pollution around the horizon the sky was much clearer and far more enjoyable to look around.
Around midnight the sky seemed to suddenly get much darker. I wouldn’t be entirely surprised if the local towns have some sort of “switch off” policy at midnight. There certainly seemed to be a marked and immediate change in the darkness of the sky. It was also getting a fair bit colder and when I returned to the scope it was running with dew. Capricornus was visible by this stage though still affected by the haze on the horizon. I found the semi-circle of stars around ζ Capricorni and just swung the scope around a little to the north to find M30 quite easily. In the haze it appeared very dense, somewhat like an unfocused star and no detail was visible, but I have at least found it and Capricornus will be higher in the sky later in the year for me to look at it again.
Although the evening had started off disappointing, spending time with the bins and finding M30 in a clearer sky more than made up for it so I decided to call it a night and returned to the house to dry off the scope. This takes my total of Messier objects found up to 106., leaving just M74, M77, M79 and M83 to find.
As it turned out, I wasn’t done there. I woke up at 3:30am and went to get a drink, passing a window facing north-east. As I looked out of the window I could see Venus chasing Jupiter away from the oncoming dawn. If I’d been a little more aware of what was going on I could also have seen the Pleiades and an ISS pass, but even so I don’t think I have reason to be too unhappy with my nights viewing.
With almost horizon-to-horizon blue skies yesterday evening I gambled on putting out both the 127 Mak on the EQ3-2 so I could polar align it for any solar imaging that I can find time for, and the ST120 with its new-to-me dual-speed Crayford. As twilight fell the occasional cloud popped up, but nothing that bothered me too much. Things were still looking good. Sadly the story was not the same by 11pm as a fair bit of cloud had built up and was speeding its way across the sky, greatly enlarging the light dome of Taunton and blotting out much from the north round to the south-east. Nonetheless, my last night out was 19th June, and 15th May before that. I’d probably sit outside under a blanket with holes poked it in by now, so I was determined to make the best of it.
M72 and M73 were my first two targets, but Capricornus was completely covered by cloud so I went back to look for M24. I just couldn’t find M24 last time I was out, but I’ve since seen photographic images showing it quite clearly which gave me a much better idea of what I was looking for. Having spent a little time on a detour to M22 and the Omega and Eagle nebulae I found what is clearly a much more dense area of blue-white stars in the right place for M24. Now i’ve seen it and understand what it is I’m not in the least surprised I couldn’t find it last time. My expectations were all wrong and I probably looked straight at it without realising what I was looking at.
The main Sagittarius asterism was scooting along the tree tops, so I decided to try to find the three Messier objects along the bottom edge. All three were fairly simple star hops from Kaus Australis, but being so low on the horizon they were also fairly unrewarding to view. More aperture and a more southerly latitude is required for these one day I think. M54 was a landmark for me though, being my 100th Messier object.
Around half past midnight I looked up at Ursa Minor to get an estimate of NELM for the night (getting up towards 5.5) and as I was counting stars a beautiful meteor shot southwards straight through both Ursa Minor and Major leaving a trail of sparkling debris behind it covering about thirty to forty degrees of sky (measured using my hands) before winking out. It must be the prettiest meteor I’ve ever seen. Such a shame it lasted no more than a heartbeat.
By this time the cloud over Capricornus was clearing and I could see the “tail” stars, so I moved on to find M75. Another that needs more aperture, I think, but hopefully it should benefit from being a little higher in the sky later in the year. I’m not at all sure the remaining cloud wasn’t washing out the view a little too, as M72 and M73 were very much the same. I fancy I did at one point glimpse the Saturn Nebula using averted vision, but I really can’t be sure.
My final “new” Messier for the night was M55, still low on the horizon and not the most straightforward of hops from τ Sagittarii as few stars were visible at such low altitude. I identified where I thought it ought to be and was greeted with a mushy grey view of, well, nothing, really. For just a fleeting few seconds the sky cleared and I saw what might well be a fairly impressive globular cluster under better conditions, but obviously last night was not to be the night. Another for the “more aperture, less latitude” list.
As I packed up I spent a bit of time just looking at the sky as a whole. Much of the cloud had cleared and the view of the Milky Way was outstanding, clearly running all the way from Scorpius over to the northern side of Cassiopeia. As I walked down the garden path I was so distracted by the fact that I could see M31 with the naked eye that I almost impaled myself on the washing line.
Clearly this was too good to miss, so I packed up the scope, found the bins and a beer and sat outside just scooting around the sky picking out stars, watching satellites and chasing meteors with the 10x50s. At one point I saw an astonishingly bright flash in the Milky Way near Sagitta which travelled north as it dimmed. I assume it was an Iridium flare, but I’ve not yet checked. Having never seen it before I also found the Coathanger entirely by chance, and whilst looking away and finding it again just to prove I could realised that it is also a naked eye object here.
By 2am I decided that If I didn’t want to be a complete waste of space this morning I’d better call it a night and did so very contentedly.
My EQ3-2 is one of the older models that has fittings for scope rings, but doesn’t have any form of dovetail clamp. The new models have both. I prefer to use dovetails as it makes swapping scopes around between mounts easier, so I decided to modify my mount to add a suitable saddle. I’ve seen this done by mounting a saddle on a section of dovetail that is then bolted to the mount using the holes for the rings, but I wanted something with a little more lateral stability.
I bought a new saddle from Sky’s the Limit and after some hunting around discovered that it’s possible to buy small sheets of aluminium on ebay for very little money. I bought some 5mm sheet and cut out a piece that would support the entire base of the saddle as well as resting on the sides of the mount head. The plate extends out far enough to reach the holes for mounting scope rings. I drilled out matching holes in the plate and tapped them to accept an M6 thread. When fitted to the mount the bolts then hold the plate tight to the top of the mount without it being able to rock or twist.
Four more holes tapped to M6 take the screws that hold the saddle to the plate. Tapping M6 holes squarely in 5mm plate is tricky. I discovered the way to do it is to put the tap into the chuck of a pillar drill with the plate clamped to the table and then turn the chuck by hand. This keeps the tap square to the face of the plate. Doubtless there’s some clever way to do this, but it worked for me.
Here’s what it looks like when assembled:
I’ve not had a chance to try it out properly yet as it’s rained for the last three months. Hopefully things will change some time soon. If they don’t change soon though I’ll be making a similar adaptor for my AZ3 to take a dovetail.
Unless you have some strange rain fetish, June has been an awful month weather-wise. There’s been hardly a single day here when it didn’t rain and even when rain wasn’t falling the sky has been mostly cloudy. According to the Met Office June was the wettest month on record (for more than 100 years) with rainfall across the UK averaging perhaps 10% more than the previous worst year. There’s little sign of a let-up in July either thanks to the northern polar jet stream just sitting stationary across the UK for the foreseeable future.
So, the numbers. Generation for June was 327kWh, worse than any other month since February. That brings our total generation to 2507kWh since installation, bringing in about £1130 in FIT payments and saving us up to £375 in electricity not purchased from the grid.
Such poor performance has pushed our predicted output for the year even further back to around 3370kWh for the year. Unless the sun goes out I can’t see how July can really be that much worse.
My second right-angle finder based on a binocular objective is now built (if not yet cosmetically finished) and this time I’ve taken photos so I can now document the construction process.
My aim was to make a functioning right-angle finder pretty much as cheaply as possible using whatever I had lying about. To that ends I started with one lens and its housing from a broken pair of binoculars. This doesn’t actually get assembled until the end, but there’s one thing it must be used for first: working out the focal length to enable the size of the rest of the pieces to be calculated. From a few scraps of wood I built this little stand:
The idea is to rest the lens housing in the hole and the top and adjust that block of wood up or down until an image is focused on the paper at the bottom (or it can be used sideways on). It’s possible to measure off the focal length directly if the image is focused at “infinity”, but I decided it would be easier to get something nearby in focus and use the formula 1/f = 1/a + 1/b, where f is the focal length, a is the distance from the lens to an object and b is the distance from the lens to the focused image. The filament in an incandescent light bulb seemed like a good choice, so I set up on the floor underneath one and brought the filament into focus. I measured the distance from the lens to the filament at 1800mm and lens to image at 200mm, giving a focal length of 180mm. As a check I repeated the test on another object and obtained the same result. I intend to use a Skywatcher kit 25mm eyepiece with this finder, so that would give 7.2x magnification which seems fine to me. If I want a little more magnification I can always drop down a few millimetres on the eyepiece focal length.
The length of the objective housing I measured at 58mm. A bit of research suggested that all mirror-based 1.25″ diagonals have an optical path length of 75mm. The focal plane of the 25mm eyepiece appears to be at about the same place as the chrome barrel starts and so I wanted the focal plane of the finder to be at the top of the diagonal, leaving me 47mm of optical path (180 – 58 – 75) to make up. I decided to knock 4mm off that to give a bit of play in case I’d not measured something correctly, giving a final length of 43mm.
Rummaging around the workshop I came up with a number of sections of upvc piping in various diameters. The smallest was 32.5mm inside diameter and 36.5mm outside diameter. It fitted very snugly over the barrel of the 25mm eyepiece, but was a little slack on my cheap £4.50 diagonal. Close enough though. I cut a 25mm length of this to match the length of the barrel on the diagonal. Next was a piece 37mm internal diameter, 41mm external. That was a neat fit over the first piece and an exceptionally tight fit over the threads on the objective housing. I tested I could make it fit by putting the end of the pipe in boiling water and then inserting the housing, which went in easily and the pipe shrank to fit. I cut a section of this to my required length of 43mm. I think the first may have been 32mm nominal solvent-weld waste water pipe, and the second 40mm nominal push-fit waste water pipe.
I cut the same length from a pipe of 49mm internal diameter to use as the mounting ring. I think this was left-over ducting supplied by BT for running phone lines. Finally I found one more piece that was pretty much an interference fit inside the 49mm pipe and about 1mm larger internal diameter than my second piece. Glued in place with araldite this would do the same job as the O-ring in the normal Skywatcher finders. An O-ring might have worked better for me, too, but I didn’t have any of the right size. Here are all the pieces:
I glued the first section of pipe inside one end of the second to make the body of the finder and once that was dry set to marking and drilling out all the holes for the fittings and adjustment screws. I put a single hole in the body to hold a screw to lock the diagonal in place and tapped it out to 4mm. The (grey) adjustment ring needed much more work. I wanted three equally-spaced adjustment screws and two holes for the screws to fix the ring to the foot. As there was no way to reach those screws inside the adjustment ring, I also had to make two holes for screwdriver access in the top. I started by making a template to mark the positions of all the holes:
It’s actually quite easy to inscribe an equilateral triangle inside the circle. Start by folding the paper in half. Then open it out and fold in half at right angles to the first fold, so the ends of the first fold meet. Open it out again, and fold one edge up so the end of one of the existing folds meets the centre. The triangle is then the end-points of the last fold and the end of the diagonal opposite it. I used this to mark the positions of all the screws and drilled and tapped them out:
The locking screw for the diagonal is a stainless steel M4 12mm thumbscrew and the adjustment screws are M4 12mm allen bolts, also stainless. I actually decided in the end that I wasn’t happy with this adjustment ring (I was having a few niggles with the pillar drill at the time) and made a second to replace it later.
The foot for the finder is actually the mount from an old 8×20 finder with most of the ring sawn off:
I cleaned this up, drilled two more pilot holes to match those in the adjustment ring and screwed them together with a couple of 2.5mm self-tapping screws:
Finally I glued my O-ring substitute to the end of the diagonal body that would take the objective housing and when it was dry, removed a small piece to allow it to pass over the screws inside the adjustment ring:
Assembly was then just a case of shrink-fitting the objective:
and then sliding the body through the adjustment rings and fitting the diagonal at the other end:
First tests suggest I should have no problem reaching focus by sliding the diagonal in and out a little before locking it in place.
The only jobs remaining are to clean it up a little and give it a splash of paint. I may also use some fuse wire to add cross-hairs to the eyepiece, but it does need to be very fine wire.
Back in March I tried checking stars in Usra Major to get an idea of the naked eye limiting magnitude (NELM) for my home. The seeing wasn’t great that night, but I obtained a figure of 5.55 for NELM. Earlier this week I was out and whilst there is no true astronomical darkness at the moment the seeing was pretty good so at the end of the evening (about 2am) I repeated the test.
This time “star 11” between ηUMi and ζUMi was visible with direct vision suggesting an NELM figure for that night of 5.70 which I think is quite exceptional under the circumstances.
I look forward to the opportunity to try the test again when the seeing is good and the sky is genuinely dark.
If you’re modding the Xbox Live camera for astro imaging then the base is just one more thing to get in the way. Here’s how to remove it. I’ll assume you’ve already got the front shell off to start with.
First, remove the four screws (two holding in the PCB, two in the retaining clip). Pay attention to the orientation of the post carrying the USB cable up through the foot as the camera won’t go back together properly if you replace it the wrong way around.
Remove the USB connector from the back of the PCB. It can be gently wiggled out with a small screwdriver. Just don’t slip and gouge a huge hole in the PCB. Now turn the foot upside down and remove the non-slip ring with a knife or screwdriver to reveal two screws that must be removed:
There are four more screws hidden by the label that also need to be removed. Just feel for them through the label with a screwdriver and pierce the label when you find the holes to unscrew the screws:
It should now be possible to split the top and bottom halves of the foot to reveal some weights and another bracket holding the bottom end of the post:
Unscrew the bracket and the cable will pull through:
The camera can then be reassembled.
I modded a second Xbox Live camera to add a fan today and this time took photos, so here’s how it’s done. This one is slightly different from the first in that I’ve not chopped down the lens housing to fit a nosepiece yet. I also routed the cables for the fan slightly differently because I had problems with a screw head fouling the PCB USB connector. The fan is a 30mm 5VDC fan that I picked up from ebay for very little beer money.
Anyhow, I’ve assumed you can get the front shell off the camera. I’d write instructions on how to do that if I could remember how myself. I think you have to unscrew the lens as far as possible, pry off the front shell and then unscrew the lens completely as there’s a retaining lug inside the lens housing that stops the lens coming out first.
That sorted, you first need to remove all four screws visible here. Pay attention to the orientation of the post that carries the USB cable up from the camera foot. The camera won’t go back together properly if it’s replaced the wrong way around:
That allows the rear shell to be removed completely. Here are both front and rear views of the removed PCB:
It’s a convenient time to remove the USB plug. You can probably get by without removing this at all if you want, but it just makes life easier not to have the cable trailing about all of the time. The plug can be gently wiggled out of the socket with a small screwdriver. Just be careful not to slip and gouge a big piece out of the PCB:
The next step is to cut the hole in the back for the vent. Lots of small holes would probably work here, but I preferred to make one large one. The important thing is not to damage either the posts that hold the screws retaining the PCB or the posts that support the PCB at the corners without screws. Because it allowed me to place the hole much more predictably, I used a 25mm Forstner bit to cut the hole:
With the main hole done, the holes for the screws to retain the fan need to be cut. The fan has holes in three corners, the wires all meeting at the fourth. I held the fan against the back of the shell, marked the three holes and then rotated the fan ninety degrees, re-aligning the holes to mark the fourth for the cables. Again, care needs to be taken to position the holes where the posts will not be damaged. It doesn’t show too well in any of the photos, but there’s also a slight indentation inside the shell in the top right corner to give a bit more room for the USB socket. You don’t want to be bringing cables through there either.
I cut the connector off the fan wires, opened up the heatshrink sleeving a little and trimmed the yellow cable (the fan speed speed sensor on this fan) back, then fed the wires through and screwed the fan housing down. You can just see that I had to trim back the post on the top left a little to make room for the screw head. Don’t do the screws up so tight that the fan blades foul the shell. You can check at this point by just blowing through the fan.
Now strip back and tin the fan leads and solder them to the USB socket pins. This image doesn’t show it too well, but the red 5V fan lead is connected to the rightmost (or top) pin on the camera sensor side of the PCB, and the black ground lead is soldered to the fourth pin (there are five altogether):
At this point I decided I might as well remove the base, but I’ll cover that separately. Before reassembling everything it makes sense to plug the USB connector back in and test everything. Of course it will work first time and it’s just a matter of routing the leads where they’re out of the way, re-seating the PCB (make sure you get it sitting square on the pins supporting the corners without screws) and screwing everything back together before replacing the front half of the shell. I routed the fan leads around the corner of the PCB and looped across the top of the front of the PCB. Unfortunately the “spring” in the leads meant I couldn’t really get a useful shot of that.
But, in true Blue Peter fashion, here’s one I made earlier:
