Night sky images?

[Gina]

Well... I got the lens assembly out of the mounting and took the IR filter off the end (had to cut through the plastic tube). Then I placed it carefully onto the image sensor - it was just slightly bigger - plugged the camera in and ran the software, with just diffused white light landing on the IR filter and sensor. It won't do! Only the centre of the filter disc is actually blocking IR. The centre of the image shows a slight greenish tinge but there's a strong pinkish area around the edge. Obviously the filter disc is OK on the camera lens as that's less than 2mm diameter but no good for my purpose. So I'll need to buy a filter.

I've ordered a light red 1.25" filter from Amazon and I may try to find an IR filter. On further investigation, I think I may be able to use the Celestron T-adaptor if I cut a bit off the webcam tube - the image sensor is something like 2cm in from the front.

[Gina]

As a temporary arrangement I have set up an "Astrophotography" page within my weather web site with a selection of moon images from yesterday and today. I cleaned the image sensor and set up this afternoon for more moon shots. (The image sensor collected a few dust particles again, unfortunately). The conditions were not as good today but I captured a few images and processed them with the GIMP.

Here's a direct link to this new page :- http://ginad.org.uk/weathergd/Astrophotography.html
It's also available from the Home Page of my weather site.

Later on I intend to create a separate web site for my astrophotography.

[Gina]

I've been unable to find a supply of IR blocking filters in 1.25" size (or smaller - I could use a smaller size inside the webcam tube).

[mcrossley]

Gina

I got mine from Baader in Germany, but I'm sure you can get them from the UK, probably cheaper too.

http://www.alpineastro.com/filters/filt ... #UV-IR-Cut Filter

I'll have a search...

Mark

[Gina]

Thanks Mark I've done a Google search and found a US site that does them for $32 plus $2.80 shipping to the UK. That's the cheapest I've found so far world-wide. I haven't found anyone in the UK selling 1.25" IR filters (or IR/UV). I'd have thought astrophotography would have been popular enough to make sales in this country viable.

[mcrossley]

For UK suppliers:
http://www.firstlightoptics.com/products.php?cat=144
http://www.rothervalleyoptics.co.uk/rev ... d3645.html (cheapest I found)

Found these in the US, the unmounted samples are cheap, not sure how much the shipping is though:
http://www.optics-online.com/irc.asp

[Gina]

Rother Valley Optics seem pretty good, I may well get one from them. I got a Celestron T-adaptor and my adapted MS Lifecam fits beautifully in it but to use 1.25" filters I'll need to adapt it to fit outside the T-adaptor. If I could get a threaded ring to screw into the outside of a 1.25" filter I could attach the webcam to that. Or I guess I could glue the webcam body to a cheap UV filter - no problem with keeping a UV filter, I don't think. Alternatively, something like 1" filters would fit inside.

Too much cloud for any moon gazing or anything else astronomical in the last few days. The only thing I've been able to test the telescope with is my anemometer about 15 or 20 metres away on it's pole! Watching plastic cups spin around on a slightly wobbly pole soon wanes in excitement!!

Apart from night sky objects I'm also interested in solar imaging though I fully realise the dangers. RVO sell Baader solar film in A4 size which looks very interesting - the proper stuff for the job. Link here :- http://www.rothervalleyoptics.co.uk/a4- ... _d502.html
I'd need either a larger image sensor or some means of reducing the magnification. Maybe use a digital camera.

[Gina]

The light red moon filter I ordered came this morning. It's labelled 1.25" but it doesn't fit my (so called) 1.25" adapter. In fact, I've just measured my 1.25" adapter and the thread measures just over 1.6". The filter thread is about 1.10" and it's outside diameter 1.22". The inside tube diameter of the adapter is 1.25" - so that's where the 1.25" comes from in that case, not the thread size, I guess.

I thought filter sizes were their thread diameter - I'm sure that used to be the case many years ago when I used a 35mm film SLR. I have a 27mm UV filter I bought to provide an optical window for a sealed box for an all-sky camera when I've got one sorted out. The thread on that measures 27mm on the outside of the thread - that makes sense. So what's it with these imperial sized objects? Confused??? I certainly am!!

I'm thinking that for my modified webcam sensor I may get 27mm filters and glue a UV one to the webcam tube. Then I can attach other 27mm ones to it and slide the whole unit into either the adaptor or the focussing tube - both of which are 1.25" (31.7mm).

Seems I've got a lot more thinking, research and planning to do.

[Gina]

Here's another moon image taken with my MS Lifecam sensor and levels adjusted in GIMP.

2011-03-18-185430b.jpg

Next is an image of Saturn again taken with my MS Lifecam sensor. It's vastly overexposed and this is about the best I could do with GIMP. Obviously I need to set the sensitivity on manual using the Lifecam driver. I'll try that another time - I've been using Cheese in Linux to capture the images and the driver only works with Windows.

2011-03-18-212743.jpg

[Gina]

I've sussed out the T-adapter. The thread is not for filters but specially for adapter rings to match the body of particular makes of DSLR cameras. I've accepted an offer of a secondhand Sony A200K camera with 18-70mm zoom lens, so I've ordered a connecting ring for that. It fits the bayonet fitting on the camera body. This arrangement is specifically to allow the CCD camera sensor to be used with a telescope with the camera body solidly attached. The large CCD should give better coverage for moon shots and wide star clusters etc. Long exposures for deep sky objects should be no problem using "bulb" setting and remote release.

The Sony will be an upgrade from my point-n-shoot Canon Powershot S40 digital camera. It's a fraction of the normal price for a DSLR so I can just about afford it. I used to use a film SLR (Pentax Spotmatic) and miss the features of an SLR.

[Gina]

Back on topic which, if I remember correctly, was a full-sky (fish-eye) view of the night sky...

I have now received my CCTV camera with a 0.001 lux light sensitivity and have it looking out of a window at a moonlit scene, a dozen or more distant street lights (only some of which I can see with the naked eye) and a couple of points of light in the sky. There is patchy, thin cloud and no stars are visible due to that and the moonlight. So it seems the camera is more sensitive than the human eye and I'm hopeful of using it as a whole sky (or a good part of it) night camera. I need to sort out TV video input to computer. I think I have a card but also a computer that I rarely use that I know has TV video input. Using Registax should remove the noise and make plenty of stars visible. With a frame rate of 25 per sec (50 fields) it should be possible the collect lots of frames for each image upload to my web site. This is assuming I have enough processing power.

The 15" CCTV monitor needs viewing at a distance to reduce the effect of nose and see behind it.

[Super-T]

Does this mean that the bigger the nose the more the effect?

[Gordon-Loomberah]

[Gina]

That "nose" in the last line should read "noise" as I expect you know. I've got quite a nice little nose really (Well. I'm happy enough with it.)

[Gina]

The image sensor isn't perfect. The white spec I thought was a star wasn't, it was a hot pixel. There's also a pixel wide white stripe down the RHS. Neither of these defects would be a problem for it's intended purpose of a CCTV surveillance/security camera. Nor would it be much of a problem as a sky camera. Registax can remove hot pixels etc. (EDIT - this only shows up at low light levels - not visible in daylight.)

I've yet to take it apart but I think it uses a "board camera" lens and if so, I could replace the current 3.6mm lens with a 2.1mm I have, to increase it's current coverage of 90-100 degrees to more like 140. But I'm not sure the fish-eye lens will cover a 1/3" CCD.

Anyway, I'm sufficiently impressed that I might buy another. They're still on sale at just under £25 from DinoDirect. Don't expect fast delivery though, allow 2-3 weeks. If you use either courier delivery or insurance, you get parcel tracking - worth a couple of quid extra I think.
http://www.dinodirect.com/1-3-SONY-B-W- ... y-GBP.html