Web camera photography

Making an adapter
Making high resolution images with web cameras
Some tips
IR-sensitivity of the Toucam
Web cameras with microscopes
Collimation links
Resources for video and webcam astronomy
Software

Web cameras are great for high-resolution imaging of the Sun, Moon and planets. In fact, they are probably better than very expensive cooled astronomy CCD cameras, mainly because you can take hundreds or thousand of pictures in a few minutes.

The following is not meant as a comprehensive guide for webcam astrophotography, but a short introduction and a few tips you may not find elsewhere.

Making an adapter
The most common way to use a web camera with a telescope is to remove the web camera lens and use an adapter to attach the camera to the telescope focuser. You can make an adapter from a film cannister, which happens to have the correct diameter for a 1.25" focuser. Just cut off the bottom. Or, you can buy a more professional one from Steven Mogg or from Perseu.

My homemade telescope adapter. Like most of my homemade stuff, it involves a lot of duct tape. My web camera is the Philips Toucam Pro, which is among the best for astronomy use.

Making high resolution images with web cameras
The single most important factor in obtaining high resolution is good seeing. There is not much you can do about high-altitude turbulence, but see my tips on avoiding low altitude turbulence.

1. Make absolutely sure the telescope is in thermal equilibrium, well collimated (collimation links), and precisely focused. Your mirror may take a LOT longer to cool down than you realize; see for yourself with the DOS program Cool.exe by Alan Adler. Precise, vibration-free tracking will of course be a great benefit. Get a UV/IR-blocking filter, it will result in far better colors in the image. See this page for a good overview of atmospheric dispersion and other atmospheric effects on astronomical observations. See also this IR-FAQ.

2. Capture a video in uncompressed format. K3CCDTools is an excellent capture program. The lowest frame rate produces the sharpest pictures. Higher frame rates cause compression of the frames with loss of information. 5 or 10 frames per second will usually give the best results. One of the secrets is to capture a huge number of frames; several gigabytes if you have room on the hard drive. Note that some file systems have 2 gb limit on the file size. Some of the frames will be from moments with much better than average seeing.

What is the correct magnification to use? Forget about the airy disk size of your telescope; you will be able to capture far smaller details provided they are high-contrast. I have seen images from a 7 inch telescope showing a hint of the Encke division in Saturns's rings. That's a 0.05" (arc second) feature imaged with a telescope whose airy disk radius is 0.7"! To capture very small details (in good seeing) you thus have to use a really high magnification. To increase the power, use a barlow lens. However, a high magnification also requires a steady mounting and precise tracking, and finding and focusing the object may be very difficult. Start with something easy, e.g. the Moon, at low or moderate magnification. With precise tracking and excellent seeing, use around f/30 to f/40.

3. Select the best frames, and align and stack them. A few hundred frames are usually combined. Jupiter presents a special situation; its rapid rotation means you should not combine frames captured more than up to a minute or two apart, otherwise its rotation will start to smear the details. There are several programs available for selecting, aligning and stacking frames. In my opinion, one of the best at this moment is Registax.

Single frame	50 frames stacked and unsharp masked

4. Post-processing. Unsharp masking, histogram adjustment, color balance etc. By using unsharp masking you can bring out details. But be careful, you may bring out false details from noise by using too agressive processing. Use unsharp masking with a small radius to bring out small details, and a large radius to enhance larger features.

Deep sky photography
Many web cameras can be modified to enable long exposures for deep sky objects. I have not tried this. Links to the modifications can be found here.

IR-sensitivity of the Toucam Pro web camera
After I saw the very detailed images of Mars obtained in IR (infrared) by Plinio Camaiti, I decided to try imaging in the IR myself. I bought two filters from Edmund optics, the 695nm and the 850nm (see their webpages for specifications). I did not expect the Toucam to be able to see much through the latter - I can't see a thing through it with my eyes. As it turns out the camera is sensitive enough to such long wavelengths to see a variety of objects. The camera can easily see the Moon, stars, and Mars at f/25 through the filter. Saturn is visible too at f/25, as the below images show. The decreased light throughput with the IR-filters causes the raw frames to have a lot more noise. This problem might be overcome by capturing and stacking more frames.

Saturn captured at f/25 with and without the 850 nm filter, on Jan 17, 2004. Seeing was 2/10. About 60 frames were stacked.

Saturn captured at f/25 with and without the 695 nm filter, on Feb 18, 2004. Seeing was 4/10. About 140 frames were stacked and processed (unsharp masking, histogram adjustments, colour balance).

Web cameras with microscopes
I have used my web camera in prime focus with stereoscopes and microscopes at work. The quality is not as good as with a digital video camera, but good enough for many applications. After searching the lab I found some bottles with just the right diameter for the phototubes of the stereoscope and microscope. Note that when you want to use this particular web camera in daylight or a lit room, you may have to shield the white plastic body from light, since a moderate light level will penetrate the body and reduce the contrast.

In prime focus the field of view of the camera is very small, and at high magnifications the image is oversampled a bit (about 0.05μm/pixel for a 100x oil objective, which has a resolution of about 0.2 μm at best).

My stereoscope and microscope adapters. Not very beautiful, but cheap and simple.

The camera in place on the stereoscope (left, covered with aluminum foil to shield it from the light in the room), and the microscope (right).

Left: Anchovy otolith through the stereoscope. Right: Herring otolith through the microscope (lots of dust inside). Each ring represents one day's growth. Click on the images for full size.

Collimation links
FAQ about collimating a newtonian telescope by Nils Olof Carlin
A treatise on Newtonian Collimation by Scott McCluney
Collimating Newtonian optics by Mel Bartels
Adventures in collimation by Bryan Greer
Collimation by Thierry Legault

Resources for video and webcam astronomy
QCUIAG group at Yahoo
AstroCam
Videoastro
Imaging cookbook by Jan Timmermans
Carsten Arnholm's astronomy page

Software (a small selection)
Astrostack
Registax
AVI2BMP
K3CCDTools
Software link page and more