Fan-Cooled Xbox Live Camera for Planetary Imaging

The Xbox Live camera has found something of a following as a cheap planetary/lunar imaging camera since the SPC900 (which is undoubtedly a far better camera) started fetching silly prices. I’ve always found it very noisy however. The camera does get quite warm and it seems reasonable to assume therefore that the noise is partly due to heat. I’d seen someone else mod the camera to fit a fan, so I thought I’d have a go myself. I picked up a 30mm 5V fan from Ebay, cut a suitable hole in the back of the case, wired the fan to the USB 5V and ground lines and it seems to work nicely, at least as far as desktop testing goes. Proper testing will have to wait for a clear night I’ve not had one of those for a month 🙁 Here’s a photo of how it looks, anyhow:

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50mm Binocular Objective Finder

I wanted a 50mm right-angle finder, but didn’t fancy paying the £90 to £100 they seem to cost, so after someone mentioned it was possible I decided to make my own. I picked up a 50mm binocular objective, cheap diagonal and 25mm eyepiece from Astroboot for about £15 and rummaged through stuff I had lying around for the rest. The mount came from (I think) a dead red dot finder and most of the rest is lengths of various diameters of plastic pipe I had lying about.

This one is very much a “proof of concept” and was useful to make because it brought home just how much of the focal length could be taken up by the diagonal (as much as 60 or 70mm). I intend to make another (though straight through this time, so I can potentially use it as a finder-guider) and will cover the build step-by-step now I know what I’m doing. For the moment however, here are a couple of photos of my completed (but as yet unpainted) finder:

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Pathetic “10 Best Telescopes” Feature in The Independent

I’m not entirely sure why I find myself so incensed over this particular piece of trash journalism (and I use the word in the loosest possible sense). Perhaps because it aptly demonstrates the utter contempt for their readership endemic in the newspaper industry. Perhaps because if people are going to make the effort to spend time looking through a telescope I’d like them to get as much pleasure from it as I do. Or perhaps it’s just because on the basis of this rubbish, people might go out and spend their hard-earned on something totally unsuitable.

Yesterday the Independent newspaper published an article on the 10 Best Telescopes, clearly targeted towards astronomical use. If you read no further, take this one point away with you: ignore the article. It’s utter bottom-wash. If you are interested in buying a telescope for astronomy the best advice I can give is to decide on a budget and then either visit an observing session held by a local astronomy society, have a look at what they’re using and talk to other astronomers about what is available in your price range. If you can’t find a local society, join an on-line forum such as Stargazers Lounge where you’ll find more knowledgeable and friendly advice than you can shake a hairy stick at.

The Indie feature was cobbled together by Samuel Muston who claims on his twitter page that he “does something at the Independent”. Whatever that something is, it’s clearly not carefully-researched journalism. I don’t know how he managed to get the gig for writing this particular piece, but perhaps the only other person in the office at the time was the cleaner. The cleaner could not have turned in anything worse. Could it be that as a foodie, Mr. Muston spends much of his time staring at the world through glassware and was therefore considered experienced in judging the quality of a lens? When I used to visit Ludgate House, “home of the Daily Express”, many years ago it was clear that the hacks were more interested in an altogether different type of optic. Not that he should bear all the blame. Clearly the editor who allowed such drivel to be published was more interested in filling column inches than actually producing a useful article.

Before getting to the list of “best telescopes” itself, there are a couple of general points that should be made. To be a genuinely useful instrument for astronomical use a telescope must have good quality optics and they just don’t get produced on a budget for the limited size of the astronomy market. There are other components that need to work well too, otherwise you’ll end up wanting to throw the thing across the garden the first time you use it, but to some extent they can be improved with a little work. If you have a poor quality optical train then you might as well drop the telescope in the bin. Not everyone will share my opinion I’m sure, but I’d say that there are almost no telescopes costing less than £100 at the moment that are up to the job and a fair few more expensive ones that aren’t either. If you can’t afford £100 then a pair of binoculars somewhere around the 10×50 size is likely to give far more enjoyment. A cheap telescope may be ok for so-so views of the moon, but that’s about as far as you’ll get with it. The second point is that magnification claims made by manufacturers are irrelevant. What really influences the quality of the view achieved with a telescope is how much light it can capture and that is dependent on the aperture — the diameter or “width” of the telescope. The ability to have high magnification is useful (which is usually changed by swapping eyepieces), particularly for viewing objects in the solar system, but it’s not the be-all and end-all. There’s a general rule that a telescope will only be good for magnification up to twice its diameter in millimetres, but even then it’s rare for UK skies to be clear and still enough for greater than 250 times magnification.

And so to the “10 best telescopes”:

  1. Skyliner 250PX
    Certainly a good telescope and by no means as expensive compared to others as Mr. Muston suggests, but it’s also big and heavy (between 30kg and 35kg, I believe). Telescopes of this size often come up second-hand because people find they’re too awkward to get out to use and to store and prices can be surprisingly low as a result. Not a good choice at all for a beginner.
  2. Olympus EXP SI Binoculars
    Many astronomers have a pair of binoculars as well as a telescope and they’re great to have. If you can’t justify the cost of a telescope then a good pair of binoculars is an excellent alternative. They don’t have to be as expensive as this pair. If you’re interested in going down this route, talk to an astronomer or dealer who is knowledgeable about using binoculars for astronomy. What’s good for terrestrial use may not work well on the night sky.
  3. National Geographic Land & Sky
    Fails the £100 test. A toy. And better as a rounders bat than a toy telescope at that. Avoid it.
  4. Bunkerbound.
    Same again. Even Amazon have it in their “Toys & Games” section.
  5. EVOSTAR-102 (EQ3-2) Refractor.
    A decent telescope on a fairly competent mount. It’s more biased towards viewing objects in the solar system rather than galaxies and nebulae. The mount will be awkward to get the hang of and perhaps even frustrating as a beginner. The advantage is that if it’s properly aligned it can easily track objects as they appear to move across the sky, and (at extra cost) it can be motorised.
  6. Vario-Finder 10×60 with Astro Lens
    Baader make some good quality astronomy kit, but this really isn’t designed to be an astronomical telescope and for the money you could get something much more satisfying. Avoid it.
  7. Celestron Astromaster
    There are a number of different models in the Astromaster range, but I’ll assume from the price that it’s the 130EQ that’s being discussed here. It’s nearer the budget end of the market to be honest, but it is still a perfectly acceptable beginner’s telescope and will give far better views of galaxies and nebulae than most of the telescopes Mr Muston recommends, although they’ll still mostly be fuzzy grey blobs. Not really ideal if your interest is with objects in the solar system however.
  8. Explorer-130p Supatrak Auto
    Another perfectly acceptable telescope. Once you’ve found an object it will track it across the sky. The same comments apply as for the Astromaster.
  9. The Celestron Travel Scope
    I assume from the brand that this will be optically ok. 70mm of aperture isn’t really going to satisfy anyone for very long though, and if the compelling reason to buy for Mr. Muston is that it comes with its own bag, well, I’m sure it’s not beyond the wit of most astronomers to find a suitable bag or case to transport a telescope in. Failing that, get some binoculars.
  10. Infinity 76P 3″ Reflector
    Cute, but I think it’s really just Skywatcher’s Heritage 76 model wrapped up to look like a toy. It is a proper reflecting telescope however, with a parabolic mirror. I think Mr Muston made up “aspherical technology”. It is a very small aperture though and going to be limited as a result. Some of the brighter nebulae and galaxies would be visible, as would some of the planets, but you’d not see any real detail. I’d buy the Heritage 76 in preference, but a pair of binoculars might be better than either.

So ignoring the binoculars, of the list of “10 Best” we end up with perhaps three that are “ok” for beginners but far from “the best” and one that an experienced astronomer might choose if their interest lay in that direction.

Shame on you, Samuel Muston. You give your profession a bad name (as if it wasn’t already going to take a special dispensation to get it into the bottom-most pit of Hell) and do nothing but damage your limited credibility. Next time you get asked to write about something you have no experience of, have the balls to admit you can’t do it, or at least do some proper research rather than copying out a quick few hundred words from the brochures between courses of a boozy lunch.

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Lifecam Saturn Montage

I spent some time last weekend capturing images of Saturn with my modded Lifecam using different SharpCap settings. This is a very different camera to use compared with the SPC900. There’s no direct control of gain, and the pixel size is almost half that of the SPC900. That didn’t actually lead to more detail being captured as to get sufficient light onto the sensor to get the camera working well enough I had to do without a barlow of any kind. Here’s a montage of the results. The first image is one taken three weeks ago with the SPC900. The others are all taken with the Lifecam with different saturation and brightness settings.

I’m really not sure I can consider myself at all happy with the performance of the Lifecam as yet. I think I need to wait until Jupiter is back in the sky later this year to do a good comparative test of the two cameras side-by-side. Otherwise, I think I’m done with planetary imaging for a while. Time for a break to do some DSO hunting and catch up on other astro jobs.

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Observation Report 15 May 2012

I’ve been doing a lot of planetary imaging recently, so tonight decided that I’d have a dedicated observing session and at about 11:45 took my ST120 into the field in front of the house where I have as clear a view as possible of the southern horizon.

Given the state of the weather at the moment and the chance that I might not get the opportunity again for some time, my plan was to quickly visit as many of the Messier objects currently low in the southern sky as possible that I’d not already seen with a view to just finding them so I can repeat the process later at my leisure should the opportunity arise.

First off was M68, low between Hyades and Corvus. Took me five or ten minutes to get my head into star-hopping mode again, but soon found my way to it. At least, I was looking straight at it, but it wasn’t anywhere to be seen. Too much haze and a touch of LP in the damp air to the south west to be able to see it.

Keeping the theme going I moved over to M107 which I was unable to find last year for exactly the same reason. This time however it proved fairly straightforward and I moved on to M80.

My plan for M80 was to star-hop down from Acrab, but having struggled to pick out which of the multiplicity of stars in the finder was Acrab, I moved instead to Antares to work my way up. I’m pleased I did. What a stunning colour and brightness it has. And just as I was admiring it, what was that fuzzy object creeping into the corner of my view? Not M80, certainly, but M4, very clear and bright. Under decent skies I reckon it might give M13 a run for its money.

A fair bit of skipping back and forth later I eventually found M80 having hopped up from M4, very small and easily-overlooked.

Next on my list was M83, but it was clearly already going to be obscured by trees, so no chance there.

That was pretty much everything on my “try now” list, but as M4 was on my “try if you stay up late enough” (I have a “try if you don’t want to get up in the morning” list, too) I thought I’d have a go at a couple of others. M9 looked a fairly easy hop down from Sabik and indeed it provde so, as I realised I was looking straight at it even as I was picking stars out to hop by.

The same happened with M19, too. It looked like a reasonable hop from tau Scorpius, but there aren’t that many bright stars in that area and whilst I was casting about for candidates to find in Stellarium, there it was…

I was on the point of calling it a night there when I realised that Sagitta was fairly high in the East and M71 which I’d failed to find last summer is bang in the middle of it so I had to try that again. Actually locating the constellation in the finder was something of a challenge given the number of stars, but eventually I found something that looked like the western end of the constellation and decided I’d work from there. The asterism is much wider than I intuitively felt and it took me some time to gauge the distances, but just as the clouds started to drift in I managed to find a faint fuzzy blob alongside the constellation.

I’ve done a little observing over the last few months between imaging runs, to find comet Garradd and so on, but it’s been a real pleasure to get back to spending a night just looking and hunting for DSOs. Though I’d liked to have spent more time on each, they’re much easier to find second time around so it’s all useful. If summer holidays take us further south this year hopefully I’ll get to see them under better conditions. I can’t complain about my view of the southern horizon, but looking for anything that’s barely ten degrees above it is always going to be a bit of a struggle with the 120.

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Installing Grub on MD Disk Partitions

I rarely have to do this, so I can never recall exactly how on those odd occasions when it does come up. Usually it’s when one of the boot disks in a server has been replaced. Anyhow, as much to remind myself as for any other reason, here’s what I do on my CentOS servers which have /boot partitions as the primary partition on both /dev/sda and /dev/sdb.

# /sbin/grub
grub> device (hd0) /dev/sda
grub> root (hd0,0) 
grub> setup (hd0)
grub> device (hd0) /dev/sdb
grub> root (hd0,0) 
grub> setup (hd0)

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Microsoft Lifecam Cinema Planetary Camera Mod

Thanks to the cloud rolling in rather early last night I decided to do the conversion of my Lifecam Cinema for astro use. I was intended to fit it into a Billetparts adapter, but they’re out of stock and I decided I couldn’t wait, so instead I’ve used one of the 25mm eyepieces that Skywatcher ship with so many of their scopes. Pulling off the eyecup and unscrewing the inner lens retainer was easy enough, all the lenses and spacers dropped out and I was left with a neat little package to fit the modded camera into.

For doing the mod I followed Gary Honis’s instructions, though with a few changes:

  1. Once the retaining circlip for the USB cable has been removed, it makes life easier if the entire cable is removed at this point. The ground clip is easy to ease off the casing using a small screwdriver and the USB plug can be gently levered out of the socket the same way. It has a lip on the side, so just put a small screwdriver under the lip and gently ease it out of the socket
  2. Once the microphone button has been removed, ignore the instructions to remove the two screws deep inside the casing. They’re a real pain to reach, almost invisible (mine were even painted black) and in fact they don’t actually hold the mount to the casing at all. I did the entire mod without touching them. Once you’ve removed the button and USB cable, skip straight to working on the front end of the camera.
  3. When you get to the stage of removing the long screw deep inside the camera, the entire mount will drop off in one piece.
  4. When it comes to removing the lens assembly, undo the two screws that hold it on first. Then apply the soldering iron to the solder pads. The lens is only surface-mounted and will just drop off.
  5. There’s an oval retaining clip around the hole for the microphone. I removed that when reassembling the camera as it was bound to fall out and or get broken at some point.

Once reassembled, I refitted the backplate to my camera and an O-ring over the front end of the camera body and slid it back into the eyepiece housing. The backplate fixes the rear of the camera body in place and the O-ring holds the front, so it can’t move about at all. To keep the sensor free of dust I fitted an IR filter into the original threads in the end of the eyepiece.

Thanks to Gary for doing the hard work in the first place. I’ve tested the camera and it responds to light, so I now look forward to using it as soon as the sky clears.

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Chrooted SFTP for Linux

I had a few problems recently when I was trying to set up chrooted SFTP for a single user on a CentOS6 server. Whichever set of instructions I followed, I couldn’t get it to work for me. Eventually, combining information from a number of sources, I got it to work. Here’s how.

First create the user account. You can use /sbin/nologin for their shell as they’re never actually going to log in. Install the ssh keys and check that everything works as normal. I’ll assume that the user in this instance is called import and their group is named the same.

Edit /etc/ssh/sshd_config. I added to the end:

Match User import
    ChrootDirectory /srv/chroot/%u
    AllowTCPForwarding no
    X11Forwarding no
    ForceCommand internal-sftp

You can match more than one user, or a group if need more than one SFTP account. The %u here is replaced by the username. If you want to restrict people to their home directories use %h. I also had to change this line in the same
file:

Subsystem  sftp  /usr/libexec/openssh/sftp-server

to read:

Subsystem sftp  internal-sftp

Restart ssh using service sshd restart.

Create the chroot directory. In this case /srv/chroot/import. Make sure this and all parent directories are owned by root and not writeable by “group” or “other”. For example:

# mkdir -p /srv/chroot/import
# chown root:root /srv
# chown root:root /srv/chroot
# chown root:root /srv/chroot/import
# chmod 755 /srv
# chmod 755 /srv/chroot
# chmod 755 /srv/chroot/import

If you see an error in the logs relating to the permissions on the chroot directory later when you’re testing, it’s probably because you’ve gone wrong here. The ssh server checks the ownership and access rights for all the components of the chroot path.

Obviously there’s going to be a bit of trouble when our import user tries to upload their files here, because their chroot directory is only writeable by root. sshd won’t let you get away with changing this though, so create a subdirectory for uploads and allow the import user to write to it:

# mkdir /srv/chroot/import/upload
# chown import:import /srv/chroot/import/upload
# chmod 700 /srv/chroot/import/upload

At this point it should all work. SELinux can interfere with things, but that’s a whole different bag of oysters:

$ sftp import@10.20.30.40
Connected to 10.20.30.40.
sftp> ls
upload  
sftp> cd upload
sftp> pwd
Remote working directory: /upload
sftp> put testfile 
Uploading testfile to /upload/testfile
testfile                                  100% 2180     2.1KB/s   00:00    
sftp> ls
testfile
sftp> quit
$ 

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Xbox Skycam Falls at the Final Hurdle

I’ve been experimenting this evening with different lenses in the Xbox webcam. It looks like with a wide-angle lens with a field of view of 160 to 170 degrees the stars just don’t put enough light onto the sensor to be visible above the dark noise, if at all. In fact, whilst I could easily focus on Venus using the stock lens, with a 170 degree lens I couldn’t even find it at all.

I think that means that for a sky camera, unless it’s for somewhere with a particularly limited field of view, this camera is a non-starter. With the wide-angle lens in however it looks like it should work nicely as an analemma camera and that’s what I now plan to do with it.

For the sky camera I think I’m back to my original plan of using an LX modded SPC900.

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qastrocam-g2 — Astro Image Capture for Linux

Today, pretty much by accident, I stumbled over qastrocam-g2. It’s an astro-imaging capture application for Linux. Thus far I’ve been muddling through with SharpCap, which is absolutely no criticism of that application at all. I just really can’t get on with Windows. I’ve used UNIX, Linux and other UNIX-like operating systems for over twenty-five years and Windows is just completely alien to my thinking.

The application claims to support QHY5 and QHY6 cameras natively as well as the SPC900, and to support cameras via the V4L2 interface (the PWC driver for the SPC900 kind of claims to be V4L2, but it’s exceptionally non-standard).

Anyhow, whilst qtastrocam-g2 gives the impression of being potentially moribund, source for the beta of the latest release is available from SourceForge, so I downloaded it and tried to build it on one of my Ubuntu 11.04 machines. I needed to install quite a few packages to get through the configuration steps. I started with these and they pulled in a whole heap of others:

  • libv4l-dev
  • libqwtplot3d-qt3-dev
  • libusb-dev
  • libcfitsio3-dev
  • libavifile-0.7-dev

After that I needed to patch all those files including the linux/videodev.h header to instead include linux/videodev2.h and libv4l1-videodev.h. I have a patch file for this, but I need to tweak wordpress to allow me to display it without mangling all the ‘<‘ and ‘>’ symbols. That done, everything went pretty smoothly.

First impressions are that it’s competent and fairly well done, though I couldn’t get the debayering to work. That is a bit strange on the SPC900 anyhow, so I may just have been doing things wrong. I’ll be using a different SPC900 for testing though, so I shan’t worry about that just yet. It does appear to support the SPC900 well, but newer cameras such as the Xbox Live and Lifecam Cinema are missing the V4L2 extended controls. I may well look at integrating those myself later.

Clear sky is forecast for this evening though the way the rain is presently hurling itself against my window does make me doubt the word of the Met Office. If it does turn out nice again however, I shall be giving the application a field test on Mars and Saturn tonight.

Posted in Astroimaging, Astronomy, Computing, Linux | 8 Comments