In recent years, webcam imaging has become increasingly popular among amateur
astronomers. It is easy to see why: they are inexpensive (< $100) and it
is possible, with practice, to produce some truly amazing images. In my opinion,
there's no better alternative to those interested in taking "pretty pictures" without
spending a lot more $$$ for dedicated astro CCD cameras.
Keep in mind that webcams cannot be used "out of the box" for astro
imaging. You'll have to do some tinkering before you can use a webcam on your
telescope. Some modifications are simple, some are more complicated, but in
the end I'm sure you'll find a way to solve any problems you may encounter.
And there's always the satisfaction in getting results from something in whose
creation you actively participated in.
Why webcams? And which one?
Webcams' main purpose is visual communication over the Internet. But, some
models come with a CCD chip and are more expensive than their CMOS versions.
This is what you'll have to take into account when deciding if a certain webcam
is suitable for astro imaging: you'll need a webcam equipped with a CCD chip,
not CMOS. CCD's are much more sensitive to light and can be modified to take
long exposures for deep sky imaging, unlike the cheaper CMOS cameras. Don't
let the price difference tempt you!
Philips ToUcam Pro
I've only had experience with a Philips ToUcam Pro web camera but there are
other similar models out there and you will easily find details about specific
ones elsewhere on the internet, such as some older Philips Vesta models, QC
3000 and others. This review can easily be related to those webcams as well.
The heart of the system is a Sony CCD chip, with 5.6um pixel size, resolution
640x480, "one shot color" (well, it's a color web camera...). It
plugs into your computer via USB port.
Since this is a review of a completed modified webcam, I'm not going to go
into details about the various modifications. You can find those easily on
the net by following the links you'll see in this review. But here are some
To use a webcam with your telescope first you will have to remove (unscrew)
the camera's original lens. You'll also have to make an adapter to fit the
camera in your focuser or diagonal mirror. This can be done by attaching an
empty film canister in front as most of them fit correctly inside a 1.25" focuser
(some don't, make sure you "test" them first). The CCD should be
carefully centered or you'll have trouble finding objects on your monitor after
you center it in your eyepiece. Also, the plane of the CCD should be at a right
angle to the scope's optical path. This can sometimes be tricky, as all webcams
are not flat or perfectly round on their fronts (as the ToUCam Pro isn't).
The best solution would be to find a new housing or purchase a dedicated 1.25" adapter
for your webcam. The most popular are Stephen Mogg's adapters, availible for
a wide range of web cameras.
This is all you will need to do in order to take images of solar system objects
and bright stars. Because the original web camera is used for recording a video
stream, it's longest exposure time is 1/25s which is not enough for deep sky
use. You must have some knowledge in electronics to make the modification for
your webcam to take long exposures. This is also called a SC modification ("mod"),
by the initials of Steve Chambers, the gentleman who first made this breakthrough.
To see the details about the SC mod, please visit his homepage. From there
you will also find links to mods for many different webcams. If you think the
modification is too complicated for you, don't despair. My own camera was modified
by a friend from my astronomy club. There's another alternative: the SAC7 from
SAC Imaging, but it's price is higher.
GreenCam: my SC modified, air cooled ToUcam Pro
Oh, yes, I would like to personally thank mr. S.C. for his skills and making
his mod availible to the public :)
The learning curve
Because webcams are not desinged to take astronomical photos, you'll have
to learn a lot of tricks before your images start looking as good as the ones
taken by more experienced imagers. Don't get discouraged though; it's fun experimenting
with different software settings and seeing the results improve. And be patient,
take it step by step.
Yes, you'll definitely need to download some additional software. Although
you can record movies (AVI) with the provided Philips VRecord, it is a good
idea to capture AVIs with a more elaborate piece of software. If your webcam
is modified for long exposures, a different program is a must because it's
the only way to take long exposures. There are a few choices out there (like
Steve Chamber's own "Desire") but I prefer K3CCDTools by Peter Katreniak.
It is a great program with some neat features. It is not only a capture program
but it can also stack the resulting images in one final image. And it's free!
Check out the link for details.
"Stacking" is another thing you'll do a lot. All your images (long
exposures or short ones) are recorded in one or more AVI movies. Again, this
is not a dedicated astro camera, so if you look at single frames, you'll see
a lot of noise that reduces visible detail. If you build a cooling system for
your webcam, the noise and hot pixels will be reduced, but still present. By
stacking frames one on top of another, you are increasing the signal to noise
ratio (SNR). The signal (planetary detail, or a faint part of a nebula for
instance) is present in all frames and gets stronger by stacking more frames,
but the noise is random and eventually gets "overwhelmed" by the
signal. This is best seen in the following example: on the left is a single
frame of Saturn and on the right is the result after stacking and processing
311 frames. This image was recorded on a night of very good seeing by my friend
Vid Nikolic and his C8, 2x barlow, and an air cooled ToUcam Pro.
Left: single frame, Right: 311 frames stacked and processed
The more frames you stack, the better the final image will be. This is a general
rule both for deep sky and planetary images but there are some specifics which
I'll explain later. Stacking can be done in K3CCDTools, but my favorite program
is Registax (also free!).
After stacking, the resulting image should be processed so finer details can
be made visible. Registax does that too, by using wavelets, a process somewhat
similar to unsharp masking. Here, experimenting is the key, and with practice
you'll soon be able to make your images sharper with a few clicks of your mouse.
Of course, you can export the resulting image and continue your experiments
in other programs like Photoshop or whatever you prefer.
Last but definitely not the least important: communication with other enthusiasts
over the net! Of course, I'm talking about QCUIAG (QuickCam and Unconventional
Imaging Astronomy Group – visit QCUIAG homepage, too!) Yahoogroup where
the "webcam revolution" started in the first place. There you can
seek help, share your images and discuss everything about unconventional and
webcam imaging. But please, before you ask a question, chances are the same
question has been answered before, so it's a good idea to search the archives
on Yahoogroups. Also, QCUIAG is a good source of information, so even if you
don't have any major problems, it's a good idea to subscribe and lurk for a
while before jumping in on the train. And please, if you post your images on
the group, make sure they are <50kb JPEGs. There are still a lot of modem
users out there... The QCUIAG guys are a great bunch, so try to behave yourself
or I'll get flamed (or worse) ;) OK, lets continue with the review ;)
Imaging the Solar System
Webcams work best in our own neighbourhood, the solar system. Even without
the SC mod, you can take extremely detailed pictures of the Moon, Sun and planets.
At first, my images weren't that great, but with practice they got better and
better (currently, my primary instrument is a 120mm chinese refractor). All
my imaging sessions are done through a window in my room (I do not have a laptop,
nor a balcony) and seeing is often awful. I record my AVIs by putting the webcam
directly into the focuser, with or without a barlow.
The webcams' main strength is their ability to record an AVI movie with short
exposures. This can, in effect, beat the seeing! Yes, the seeing may be bad,
but if you are patient and carefully focus your target, here and there you
can find some frames that will be much sharper than others. When stacking,
you will choose and stack only the sharpest frames and can come up with an
at least acceptable result! Yes, this is definitely true! And when the seeing
is excellent you can expect the results as the Saturn photo you've seen earlier
in this review. It will not be easy (sometimes even frustrating), but be patient
and you'll be rewarded. If you own a laptop you'll be definitely better off
than I am, and I must say I really enjoy taking images with my ToUcam Pro even
if my observing site is not that good. In planetary imaging the webcams have
the advantage on ordinary digital cameras, even astronomical CCD's whose images
may take a while to download. Your webcam will record ALL moments of good seeing,
something that other cameras are not able to do.
There are some other things to consider. If you own a refractor, it's a good
idea to use an IR blocking filter. Web cameras are sensitive to near IR, but
refractors are designed for visual obseriving and nearIR part of the spectrum
is not focused correctly. This results in a blurry image:
Also, when producing the final result you should try to use as many frames
as possible, to increase the SNR ratio. This can sometimes be counterproductive,
because if the seeing is bad, stacking those blurry frames will worsen the
image. This is especially true for big targets like the Sun and Moon where
one part of the frame is sharp, but the other is a blurry mess. Sometimes
less is more but you'll have to find that out by trial and error.
Another instance where less is more: the FPS (Frames Per Second) setting.
The higher the FPS setting, the more compression is used by webcams firmware
on single frames which results in poorer quality images. It is reccomended
that you do not use more than 15 FPS. When the seeing is good, 5 FPS is probably
the best choice.
After you've done everything right, the rewards can be amazing...you can capture
very fine details on planets, occultations, transits, make an animation of
a planet's rotation or even a 3D photo! Here are some examples. Bear in mind
these images are not the best I've seen on QCUIAG!
Sunspot 9608, 120mm achromat, 2x barlow,
Clavius, C8, 2x barlow, 81 frames (by Vid Nikolic)
Jupiter, C8, 2x barlow, 78 frames (by Vid Nikolic)
Deep Sky Images
As I mentioned before, to take deep sky pictures, you'll need to modify your
webcam so it can take long exposures. After the modification the webcam will
need to be plugged in to your computer's parallel port in addition to the USB
connection. Keep this in mind if your laptop doesn't have a parallel port so
you can make a version for the serial port (see links on Steve Chambers' homapege).
I recommend you build some kind of cooling for your modified webcam, to minimize
thermal noise, hot pixels, etc. My ToUcam (GreenCam ;) ) is air cooled and
it seems quite sufficient for now. You can try and build a peltier cooled version
for even longer exposures before noise starts to become a problem.
Now, I must say my experience with deep sky imaging is somewhat limited since
my mount isn't motorized. But I've made some experiments with my GreenCam coupled
to old photo lenses and I've been on few imaging sessions with my friend Vid
Nikolic. Deep sky imaging takes (obviously) more time – you have to focus
on dim stars and find your target that can sometimes be overlooked if the exposure
is set too low. Once the target is found, I must say it's a real pleasure to
see your faint fuzzy appear on the screen! Your maximum exposure times will
be limited by the tracking of your mount, light pollution, and the amount of
noise your webcam produces. Good news is, you will be able to capture good
images of bright targets (Messiers, bright NGCs) even in light polluted skies,
as you will se from the examples below.
As with recording solar system objects, the more frames you stack, the better
detail you will be able to capture. You'll cut down the noise and bring out
subtler details in "big stacks" (say, 50 or more frames) than in
smaller stacks (~10 frames). Of course, you should first start with small stacks
and build up from there. The big stacks will take time to capture and process
but when you see the result it will be worth it.
Although the pixel size may seem small for deep sky imaging, the CCD is pretty
sensitive. Surprising for just an ordinary webcam. Telescopes with long focal
lenghts (SCTs for example) will benefit from focal reducers. IR blocking filters
are useful for deep sky imaging too, so you won't get "bloated" stars
when capturing images with a refractor or photo lens.
As you can see in the image below, the webcam can capture stars of magnitude
16 in just 15 seconds exposure time. And this from a light polluted city with
almost a million souls (Zagreb, Croatia)... (image has been processed to bring
out faint stars)
Here are some other images, all courtesy by Vid Nikolic (Thanks Vid ;) ).
All of them were captured with his C8 @ f/3.3 (focal reducer). Frames were
registered and stacked in Registax with some additional processing in Photoshop.
Dark frames were also used. You can see more images on his homepage. All images
were done from zagreb, except NGC 4565 which was taken from Japetic (our dark
sky site, limiting mag 6.2 on best nights).
M13, 35x10s frames
M27, 14x15s frames
M42 core, 3x12s frames
Imaging with a webcam is great fun! Webcams excell on planetary imaging but
are also good on deep sky. Considering the price, it's performance is surprisingly
good! There's really no reason why you shouldn't give it a try! The only quirk
with webcam imaging is that it requires a lot of patience and a good deal of
experimenting both with hardware and software. Mind you, his is not necessarily
a bad thing! The only real downside is that the camera must be used with a
computer. So if you have to travel to your dark sky site and take images from
there, you must have a laptop. Still, as you've seen, good results can be had
from light polluted skies, too.