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This page explains how I modified a Logitech Quickcam Express webcam for
astrophotography. It should be general enough to apply to just about any
inexpensive webcam.
You know the kind, the little webcams mounted in a ball and sits on your
computer. Sorry, I no longer have the original housing, but hopefully you get
the idea.
To make a device like this, you need an inexpensive webcam, like the
Logitech Quickcam. You'll also need a T adapter like that often used to
mate a 35mm SLR camera to an astronomical telescope.
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You can use this convenient astro-customized search engine to locate
a suitable webcam, or even commercial astrocamera.
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Astrocam Assembly Diagram
At left is a diagram of the webcam modifications.
Inside the webcam housing is usually a single circuit card, hosting the CCD
array in the center of the card.
If you have machining equipment, you can make a really nifty astro-camera.
Not being a machinist, I had to find a simpler way.
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I had a simple T thread snout for mounting a 35mm SLR camera to a standard
1.25" focuser. This adaptor is just a 1.25" barrel that has a
T thread for a mounting.
With a T adaptor for one's particular 35mm camera, this snout allows easy
prime focus photography.
I was able to find an old soft-plastic pill bottle that was the right
diameter to snuggly fit over the T thread. I cut off the bottom inch or so of
the plastic bottle (discarding the top), cut a 1/2" hole in it to allow
light to reach the CCD array, and screwed the pill bottle end onto my T thread
adaptor.
I also fabricated a simple cover over the back of the circuit card, and
hurray, I had a CCD camera for astrophotography.
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Astrocam Parts
This image will help clarify my diagram and description.
On the left you see the modified webcam astro-camera. The white part
(blackened inside) is the plastic pill bottle end. You can see the hole cut in
the bottom to expose the CCD array (the square).
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The pill bottle is just the right diameter to tightly fit over the T-threads of the camera to focuser adaptor, shown on the right of the picture.
You can see that with electrical tape and some thin cardboard (like poster board), I fabricated a simple cover over the rear of the astro-camera.
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Assembled Astro-camera
At left you can see the assembled astro-camera. The snout slides exactly
into a 1.25" focuser.
The USB cable is plugged into a computer during use, and I run the vendor
supplied webcam software to make the exposures.
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My camera is only suitable for the moon and planets, in that it doesn't
have the capacity for long time exposures.
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Astro-camera on Telescope
This is a image of the webcam astro-camera mounted to my Meade ETX90. As you
can see, it simply slides into the focuser instead of an eyepiece.
If I need more magnification, I insert a barlow lens first, then the
webcam.
Individual pictures can be taken with the webcam, and is the technique I
used for most of the images displayed on my photography pages (I was still
learning).
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However, I've found that what works better is to use the astro-camera
to take movies (avi files). Small clips of 2 to 4 seconds.
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Since the camera takes about 10 images per second, a few seconds gives me
plenty of images to work with.
Then I use an image selection and averaging program to combine the frames
of a film clip into a single image. This technique helps reduce atmospheric
turbulence and pixel gain errors of the camera.
Note, this technique can't really overcome a bad seeing night, but can
certainly help reduce the residual turbulence on a good night.
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Webcam Astro-camera Result
At left is my best Mars image, taken during the 2003 opposition with
my Meade ETX90 and the modified webcam astro-camera.
I believe it to be a rather remarkable photo with such a modest instrument. It is a stack of 48 frames taken from an avi file. For this image I used
the Image Stacker program.
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I used to use the Image Stacker or the RegiStax program for stacking frames from an avi file. Now I use a perl script of my own design, and some ImageMagick tools in Linux.
I hope to take more of these kind of pictures in the future. Currently I don't have a functioning laptop, so dragging a desktop out to take photographs is a cumbersome ordeal.
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My little device has a small CCD, so the field of view it encompasses is also small. Getting moon images is easy. If I see the moon in the finder, some portion of the moon is also in the camera. I use my handy added slow motion control on the Meade ETX90 to move to the part of the moon I want.
Planets are tougher. I may have the planet in the finder, but I often can't find it in the camera. I've gotten around this with the Meade ETX90 by removing the rear plug and putting in another eyepiece. Using the flip mirror, I can look through the auxiliary eyepiece to center the planet, then flip back to the camera.
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Final Comments
If you are interested in constructing such a device, I suggest you try with an inexpensive webcam. I paid (a few years ago) about $30 for mine. I figured if it lasted long enough to give me a bout 3 rolls of film worth of pictures, it was worth the expenditure.
I've been lucky. My little webcam is still working.
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To get the most out of your photographs, it helps to keep track of
upcoming targets. The moon is one of my favorites. Best moon photos are
obtained when your targets of choice are near the terminator. A good
planning tool for lunar photography as well as lunar observing is the
software package Xephem, shown in some detail at my Xephem Review page.
Jupiter is one of the best targets for planetary photography.
It is bright enough (Saturn is kind of dim) and big enough (Mars is kind of
small) to make a good target. Some prior planning here is also helpful in
order to get a shot of the Great Red Spot, or some transiting Jovian
satellite. For my Jupiter observing and photographing guide, I again use
the Xephem software package.
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