Thread: Discussion Moon Video
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Old Nov 26, 2012, 04:00 PM
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United States, MA, Walpole
Joined Dec 2003
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Originally Posted by sparklet View Post
I am impressed with the moon video.

I am itching to have a go, first clear night looks to be Wednesday here.

I have converted a No11 HD keychain camera to fit on my 8.5 inch reflector.

I removed the lens, easy as it just unscrewed on mine but some are fastened with glue and might be harder to remove. I had some thin brass tube that just fitted into the eyepiece holder on the scope. I cut a piece just long enough to fit into the eyepiece socket and then epoxied it onto the front of the No11 camera.

The tube is bigger in diameter than the No11 camera is thick. I just epoxied 2 thin pieces of wood onto the camera body to fill up the gap. You have to be careful not to cause a problem in getting to the buttons to work the camera. Pretty it isn't - functional it is.

The camera fits into place like a normal eyepiece. There is plenty of adjustment available on my focuser but it only needs a small amount of focus adjustment to bring the camera into focus. It's not a big amount and is fairly close to the position where a 40mm eyepiece is in focus.

I use the No11 in webcam mode. I also have a converted Logitech quickcam webcam.... modified nearly the same way as the No11.

I have only had chance to try the 2 cams on a small (and not very good) telescope but anticipate good results off my bigger reflector.

The No11 keychain camera is capable of giving a sharper image compared to the Logitech webcam. However, the image is pink tinged ! This is not a problem for still photos as they can easily be altered but could be a problem with video.

I use a couple of "normal" webcam programmes that are available in Linux. There are no proprietary drivers used for the 2 cameras, just what is provided by the Linux kernel.

I had some of the "dreaded" dust on the CMOS chip. Being a gentle soul who approaches everything very cautiously..... I just bunged the nozzle of an industrial vacuum cleaner over the tube that fits the camera into the eyepiece and give it a damned good going over !

My delicate approach seems to have got the sensor clean of dust.

Perhaps Tom will know if the pink colour can be got rid of ?
The pink tint is because you no longer have the camera's infrared filter to block those wavelengths from reaching the CMOS array. The keychain cameras have the IR filter mounted on the lens elements. All are on the back of the last element (inside the CMOS module) except for the #16 B lens which has that filter on the front surface (which is why it has a distinct red appearance at certain light angles). You could try to get an IR filter for larger lens optics and place it on the front of the CMOS module. That would also keep out dust and debris. Finding one which has the same wavelength filter properties to match the original would be the trickiest part perhaps. I've never tried it.

I've used lens cleaning air brushes and cleaning solution to clean my CMOS arrays on a couple of my 808 HD key cams, with good results. Never tried a vacuum... I'd probably end up sucking it into the dust bag!

I think a critical part is to get the CMOS array exactly perpendicular to the axis of the eyepiece holder. This is necessary to have the entire array in sharp focus across the entire frame. I had forgotten about the IR filter, but would try to find a suitable larger lens filter that works, then cement it flat across the front of the plastic lens module. Then arrange to make a cut across the eyepiece tube that is exactly perpendicular to the axis, perhaps with an appropriate blade on my radial arm saw. That should get it pretty close.
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Last edited by Tom Frank; Nov 26, 2012 at 04:07 PM.
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