Night sky images?

[fractonimbus]

One thing I'd like to do, but - at reasonable cost at least - the technology doesn't permit yet - is to set up a webcam that can also look at the stars at night. Somewhat along the lines of the various all sky cameras at observatories, eg the one I regularly use at Siding Spring, New South Wales: http://150.203.153.131/~hatuser/wth/cam_d.html (lower image).

The commercial solution is to use an instrument from SBIG - http://www.sbig.com/sbwhtmls/announce_allsky-340.htm but at >$2K, that's not a realistic choice!

So I'll probably have to wait until inexpensive high sensitivity low noise CCDs or CMOS become available integrated into webcams or budget security cameras.

I could do the job using my Canon 5DII but I don't want to bolt it onto the roof!

The other option is to integrate over several seconds, but that requires a low noise sensor. Again, probably expensive.

Does anyone know of any work going on in this area? Or promising hardware?

DN

[Gordon-Loomberah]

The all-sky (well almost, it misses most of the horizon) camera is operated by the Uni of NSW next to their Automated Patrol Telescope (which is rarely used these days), but there is no one on site much of the time, so it can be down for several days at a time. That is likely to get worse as the person who looked after it has just left, and I dont know if anyone will be taking care of it on a regular basis from now. I work at the Uppsala Schmidt Telescope, about 10 or 15m to the N of the camera.

The good news is that Steve Lee at the AAT is setting up a similar camera, but some mods should exclude the moisture build up after rain and fog. There are cameras and software around that cost way less than $2K that work well. Do a search for meteor cameras and software.
<vague recollection> I think the UNSW camera is integrating 128 frames to produce each image </vague recollection>

If only CCD/CMOS could match film

http://members.ozemail.com.au/~loombera ... Allsky.JPG

[fractonimbus]

G'day Gordon,

I think I missed you last time I was up at the 2.3 at SSO. Your fisheye image is superb. I think Dan Bayliss is about to commission a much better camera at HAT, which should improve on the UNSW camera! Brian Schmit was also talking about one for SkyMapper but I don't know where that's got to. I see that the AAT site also has its own all sky camera now, so Steve must have got it working.

For others on this list, the HAT weather station is set up to report on the meteorological conditions at the HAT telescopes up at Siding Spring Mountain: http://150.203.153.131/~hatuser/wth/ The AAT (Australian Astronomical Telescope) weather site is at http://site.aao.gov.au/AATdatabase/met.html

In the meantime I was thinking vaguely about how to make a cheap gadget to build to put up on my roof. It doesn't need brilliant performance because most nights in Canberra the limiting magnitude is about 4-4.5 due to streetlights.

I was wondering if a CCTV camera that works at low light level might work. Something like the Sony EXview chip based ones might be worth a look. ragecams.com sell that sort of stuff, along with fitting wide-angle lenses.

David Nicholls

[Gina]

I too would love an all sky night-view camera/webcam but my budget is very limited. We are in a rural area and don't suffer much light pollution so if I had access to affordable hardware, it would be practical.

[mcrossley]

Not quite up to this quality, but I have some images taken with a Philips webcam and a £12 wide angle lens somewhere. The web cam was modified to take long exposures (the default maximum exposure time is 1/5 sec), the exposure being controlled from the PC serial port. There are lots of pages on the web about modifying various webcams and software to control them. The key is getting a CCD based camera (most are CMOS) and one that has the 'standard' control chip - I forget the spec. It helps if you cool the camera too (amateur astro cameras are usually cooled to -20C or more below ambient) but not essential for exposures of less than 30s/1m. My webcam did have a TEC cooler too a one point! http://www.wilmslowastro.com/tips/webcam.htm

[Gina]

Interesting Matter of sourcing a suitable image sensor and fisheye lens. Maplin do a 2.9mm focal length lens - guess coverage depends on size of CCD but I don't think this will give anything like 180 degrees coverage.

[mcrossley]

I have a 1.9mm lens iirc that gives 140 degrees across the diagonal of a typical 1/4" webcam chip.

[Gina]

That seems reasonable 2.9mm would be wide angle but certainly not fisheye as I suspected. Any idea where a lens under 2mm focal length might be obtained?

The MS Lifecam HD webcam is reckoned to be about the most sensitive webcam around and has been modified to use with a telescope for astrophotography. I have one of these and found it very good. However, it seems nobody has found a way of making it take time exposures. I guess you could integrate a number of frames in software to improve S/N ratio.

[mcrossley]

Gina for all things webcam modified the QCUIAG group used to be the place to hang out - it may still be I haven't kept up with it.
http://www.qcuiag.org.uk/

Edmund Optics usually do a good selection of lenses, but they aren't the cheapest around.

[Gina]

From the data sheet, Lifecam :- image area: 3888 μm x 2430 μm, with pixel resolution of 1280 x 800.

If I used a 2.9mm FL lens, I work out that would give a view of about 70x45 degrees which is less than twice that with the Lifecam's own lens! And a long long way from 180 degrees or even 140 diagonal.

Going telephoto is easy - just use a 35mm film camera lens but wide angle is another matter! For a whole sky view you really do need a proper fisheye lens for a 1/4 inch sensor. A pipe-dream it would seem.

[Gina]

Gina for all things webcam modified the QCUIAG group used to be the place to hang out - it may still be I haven't kept up with it.
http://www.qcuiag.org.uk/

Thanks That looks an interesting site - I'll investigate.

Edmund Optics usually do a good selection of lenses, but they aren't the cheapest around.

I'll check them out too

[mcrossley]

The orginal mods were done by Steve Chambers
http://www.pmdo.com/wintro.htm

You can also modify the in-camera firmware for better results using long exposures
http://www.astrosurf.com/astrobond/ebrawe.htm

The lenses at Edmunds, you should be able to get them cheaper on the 'net though
http://www.edmundoptics.com/onlinecatal ... uctID=2196

[Gina]

Thanks for the links 1.68 mm FL lens and a 0.003-lux B/W camera with 1/3 inch CCD sensor would give 90 degrees coverage by my calculation though not sure the usual calculation applies at very short focal lengths. If you get 140 degrees with 1.9 mm, it looks like my calcs are wrong Price is getting a bit on the high side. OTOH the camera in question can be modified for long exposures as seen in one of the links.

I'll be giving this some thought - I'd really love to be able to record images of the night sky. I've spent hours at times watching the sky for comets or meteor showers without much luck.

I guess it would need a shutter to avoid sun damage in the daytime.

[Gordon-Loomberah]

David, do you have Rob McNaught's email address? let me know if not. He may well have a spare camera for sale, as he operates a network of meteor cameras full time, and would certainly be able to advise you of the best options.

[fractonimbus]

David, do you have Rob McNaught's email address? let me know if not. He may well have a spare camera for sale, as he operates a network of meteor cameras full time, and would certainly be able to advise you of the best options.

Yes, Gordon I do. Thanks for the suggestion. I'll email him and see what he has. Though I might delay that for a little while until I finish writing the paper I'm supposed to be writing for Astronomical Journal! I'm having much more fun with Cumulus and the weather station, but my thesis supervisor is breathing down my neck

DN