Astrophotography with a webcam

Looking at the night sky is very pleasing, but after a while I itched to take some photos of what I see. After all, a telescope is just a big lens, so it should not be too difficult right?

A good options is to use an SLR camera. Basically you only need an adapter to fit the camera into the eyepiece socket. Unfortunately, I don't have one and a good digital SLR camera costs quite a few bucks.

Another good, and only somewhat less expensive solution is to buy one of the commercially available astrophotography cameras. Very nice colour and black-and-white products are available. The advantage of these cameras are that they are smaller, lighter, post processing software is included and they typically don't have aggressive IR filters that filters out too much into the red spectrum.

For me however, the modified webcam option sounds much more attractive. The biggest advantage is that webcams are much cheaper than SLR or specialised astrophotography cameras. It also offers the opportunity for some hardware hacking. Good stuff!

The webcam that I used is the Logitech Quickcam Pro 4000 (QC4K). Its a more high-end webcam that allows you to capture video at 640x480, while most lower priced offerings only do 320x240. You can also take still pictures at 1.3 Mega Pixels. Furthermore, the camera drivers makes it possible to modify the exposure time, CCD gain and some other useful parameters.

I did a bit of research on the web to prepare for the operation. Most sites mostly say the same things. You start by removing the webcam's own lens. For some webcams its easier than others, in the case of the QC4K you need to open the camera to unscrew the lens. Next you need to find a way to attached the camera to the telescope's eyepiece socket. The most popular method is to attach a film canister onto the front of the webcam's body. The film canister fits perfectly into a 1.25 inch (approx. 32 mm) eyepiece socket. Add a computer and you are ready for action!

I first tested the modified webcam with the telescope during the day. Initially I couldn't get a focused image, the CCD was too far away from the telescope's focal point. The CCD is in the center of the webcam's body, so in order to get the CCD closer to the eyepiece I had to remove the PCB and attach it directly onto the film canister. This works nicely, but it is definitely not a good long-term solution. Another solution is to use a Barlow lens, but then of course you may magnify the subject too much.

Focusing the webcam image is quite difficult due to the short focal length of the camera. It is generally recommended to adjust the focus using some distant land mark. However, the Moon was visible during the day so I used it instead and it worked quite well. Having used the Moon to focus the camera it was an obvious subject for my first photo shoot!

If you want to take pictures of celestial objects you have one fairly big problem to deal with, the rotation of the Earth. This movement is very prominent and even short exposures show a visible streak of the object across the image. A good solution to this problem is to move your telescope in synchronisation with the movement of the earth. Unfortunately this capability comes at a stiff price, so not all telescope mounts has this capability. In the digital age we have another alternative. Record a video of the object as it moves, then use software to align and stack the individual frames. The resulting image has a better signal-to-noise ratio than the individual frames. Using this method, one can also simulate long exposure shots. I used the free Registax stacking program for post-processing. There is a number of commercial packages available. One of the most popular products is AstroStack.

I took a couple of videos of the Moon during the day. A big problem for me is the almost persistent wind here in the Strand. As you can imagine, it induces vibration of the telescope tube in turn causes causes motion blur. Not very pleasing. Fortunately the wind was fairly quite for a change. Allowing me to play in peace.

Here are two processed images I extracted from the video steams. Click to enlarge.








Later the night I record some video of Saturn, but by that time the wind situation was back to normal. The video was very erratic and there was too much motion blur to do anything useful with the stream. I manage to get one still shot where you can vaguely see the rings of Saturn, but the quality is not very good. Here goes ..





Compared to the other pictures available on the net these pictures are not very awe inspiring, but they are my own pictures. The experience was great fun and very educational. There is still many questions that I need to figure out for myself, such as what is the field-of-view/magnification of the webcam-telescope together and how do you calculate it. Sadly, just after taking these pictures, one of the axle's of my telescope mount broke (cheap ass plastic component inside!). So I'll have to wait until the supplier can fix it before I can play some more :(

Here is some links to astrophotography with webcames:

• AstroCam
  
• Logitech Quickcam 4000
  
• Older Logitech Quickcam page