Night sky images?

Gina · **Posted:** Sat Mar 12, 2011 9:25 am

I think the first thing I'll try is my second MS Lifecam Cinema webcam. It should fit nicely in the eyepiece holder. It's the right shape.

mcrossley · **Posted:** Sat Mar 12, 2011 10:30 am

Gina, you can buy cheap eyepiece adapters for webcams, they have the standard 12.5mm lens thread one end, and 1.25" eyepiece push fit the other, they only cost a few quid, often made of Delrin.

Gina · **Posted:** Sat Mar 12, 2011 10:53 am

mcrossley wrote:

Gina, you can buy cheap eyepiece adapters for webcams, they have the standard 12.5mm lens thread one end, and 1.25" eyepiece push fit the other, they only cost a few quid, often made of Delrin.

Thanks for the info

But none of the webcams I've got have a 12.5mm thread. Anyway, I'll bear it in mind.

Gina · **Posted:** Sat Mar 12, 2011 9:41 pm

Found info on modifying a Microsoft Lifecam Cinema for telescope use :- http://ghonis2.ho8.com/lifecam/lifecam1.html

I found this very useful and have successfully completed all the steps mentioned (except mounting in the extension tubes)

It's a very clear article. I made up my own mounting - just a matter of increasing the 1" webcam tube to 1.25" for the telescope eyepiece mounting. Can't try it on the night sky tonight due to complete cloud cover. I did try it with a terrestrial view though this afternoon. That wasn't too good either due to mist. Removing the webcam's lens also removed an IR cut filter and this resulted in a pinkish cast on the image. I'm not sure yet if I'll remove it from the lens and mount it in front of the sensor. It might be useful to collect infra-red for night sky objects to increase the sensitivity. OTOH IR will focus at a different point from visible light and might cause blurring.

One thing I noticed in removing the webcam lens was that it's quite a small aperture. Using a 1.2mm "board lens" instead should increase the sensitivity as well as increase the angle of view to something like 120 degrees. This might make the modified webcam suitable as an almost whole sky night cam. Testing indoors at night with the 1.2 mm board lens, showed a significant increase in sensitivity and an estimated 120 degrees coverage as compared with the unmodified camera coverage of about 45 degrees. A webcam is easier to connect to a computer but unfortunately, nobody as yet seems to have found any way of increasing the exposure time.

Gina · **Posted:** Mon Mar 14, 2011 7:39 pm

I now have my modified MS Lifecam webcam reasonably securely mounted on my telescope (Celestron Astromaster EQ130-MD) and have been trying it out using Cheese as the webcam software. Today the visibility was alright and in a break in the clouds I was able to see the moon. It was daylight so the contrast is a bit lacking but it gives an idea of what can be achieved. With the IR filter removed from the camera (it's attached to the webcam lens which I removed) there was a strong pinkish cast to the image. This can't be totally removed by colour balance correction. I've applied some correction in the magenta-green balance in the following images. I think for moon photos it really wants an IR filter. This image sensor is quite small though runs at 1280x800 resolution and with a 3 micron pixel size, gives a large magnification - I think a 1/3 inch CCD sensor would probably be better. (I also need to clear some debris off the image sensor before I capture any more pics :lol:

) These images have been reduced to 640x400 for posting here.

Attachment:

2011-03-14-174145.jpg

Attachment:

2011-03-14-174229.jpg

Attachment:

2011-03-14-174300.jpg

Attachment:

2011-03-14-174334.jpg

Gina · **Posted:** Mon Mar 14, 2011 8:15 pm

One of the images above after "enhancement" using GIMP to change to monochrome and increase contrast by changing the gamma curve.

Attachment:

2011-03-14-174300a.jpg

Or a different gamma curve to bring out the craters on the terminator :- And I've left this image full size.

Attachment:

2011-03-14-174300b.jpg

Gina · **Posted:** Mon Mar 14, 2011 8:32 pm

Another GIMP doctored image - full resolution but cropped to remove uninteresting bits :-

Attachment:

2011-03-14-174334a.jpg

fractonimbus · **Posted:** Mon Mar 14, 2011 8:36 pm

Excellent start :-)

The SLR camera people seem to prefer a manual blower ball to clean stuff off the sensor. Can't remember the brand but it looks like a rocket (appropriate in this context!!)

DN

(added: the brand is "Giottos")
and Jessops seems to have one that's nearly identical:

mcrossley · **Posted:** Mon Mar 14, 2011 8:47 pm

Gina, a small IR blocking filter would be a good idea - you can get them in 1.25" eyepiece screw mounts for just this purpose. As an alternative for the Moon you may want to try a red filter. This has the advantage of 'calming' the seeing too (longer wavelengths are less affected by atmospheric turbulence than short).

Also you want to try Registax on your captured videos, it will bring out tons more detail.

As for sensor cleaning, I use Scotch Magic Tape - the opaque stuff that is semi-sticky - much to the horror of many folks, on all my sensors, even my expensive APS sized sensor astro cam. :shock:

I got the tip from a camera manufacturer and it works a treat, far cheaper than all the expensive cleaning kits you can buy

At your own risk of course! :lol:

Gina · **Posted:** Mon Mar 14, 2011 9:20 pm

Thanks very much for the tips Mark

I've found the MS Lifecam body needs to be beyond the end of the focus tube so I could put a filter between the focus tube and the webcam body. I want to make up an improved mounting anyway. The Celestron T-Adapter, Universal 1-1/4" would be too long unfortunately so it's Blue Peter time again

Oh, and yes, I'll be try Registrax shortly.

Gina · **Posted:** Tue Mar 15, 2011 11:12 am

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 · **Posted:** Tue Mar 15, 2011 7:33 pm

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 · **Posted:** Tue Mar 15, 2011 8:52 pm

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 · **Posted:** Tue Mar 15, 2011 9:24 pm

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 · **Posted:** Tue Mar 15, 2011 10:40 pm

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.

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Night sky images?

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