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- Who’s Afraid of a Phantom: Istar Phantom 140mm F/6.5, that is?
- SHARPSTAR 94EDPH APOCHROMATIC REFRACTOR
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- FIELD TEST: THE NOH CT-20 ALT-AZ MOUNT
- SkyTee-2 Alt/Az Mount Review
- SharpStar Askar ACL200 200-mm f/4 astrographic telephoto lens
- A review of the Unistellar EVscope
- Astrotrac 360 tracking platform – first impression
- FIELD TEST: CARL ZEISS APOCHROMATIC & SHARPEST (CZAS) BINOVIEWER
- Omegon 32mm 70º SWA eyepiece review
- Review of iPolar hardware and software for polar alignment
- Review of the Hubble Optics 14 inch, f/4.6 Premium Ultra Light Dobsonian Tele...
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Philips ToUcam Pro (and similar webcams)
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 general instructions.
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, 28 frames
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.