April 18, 2014

Planetary Imaging with an Off-the-Shelf Web Cam.

Jupiter via Webcam

Jupiter via the Webcam Method. Photo by Author.

A few years ago, I came across an article in Sky & Telescope about an emerging technology. Apparently, some intrepid sky enthusiasts (I hate the word amateur… to me it denotes bottlecap collecting or trainspotting and other space filling activities) were creating their own planetary webcams. Always a minimalist, I generally skip the high tech gizmo sections of magazines. But the inner-techno geek in me loves the homemade stuff. Reading on, I discovered that only four ingredients were required; a webcam, a laptop, some freeware, and a telescope. I soon realized our house possessed three, and could easily add the fourth. All that remained was to piece these together and I could be imaging that very night! The first step was to modify the web cam to fit my telescope. Standard telescope eyepiece holders are 1 1/4″ barrels; these are the most common, although 0.965″ and 2″ do exist. I simply unscrewed the lens of the webcam (a logitech 4000pro), and attached 1″ diameter piece of copper tubing to the exposed aperture. I then mated it to a 1 1/4″ eyepiece tube and shimmed up the 1/4″ difference with duct tape (every good project has some duct tape in it somewhere!) A word about web cams; there has been some pretty lively banter out there about what models to use; I know that TwoYouCams and VestaPros are the most prevalent for astro imaging. Ironically, the Vestas were originally discontinued until their popularity as astrocams brought them back; Celestron, Orion, and Meade have also taken notice of this market and introduced their own models. I only make note that my off the shelf, 60$ after rebate Logitech with its CMOS chip was acceptable for planetary imaging. Try that old web cam kicking around the desk; it may surpass what’s out there.
Next is the software; I use K3CCD tools for the capture, and Registax for the fine processing and Adobe Photoshop for the final touch ups. K3CCD Tools was free when I initially downloaded it a few years ago; I believe there is a nominal fee involved now. I won’t go into the nuts and bolts details about running the software as each has its own tutorial. Suffice to say, the more you play with them the more proficient you get.
I cobbled this setup together with my C8 Celestron 8″ Schmitt-Cassegrain telescope. It has a focal ratio of f/10 which is decent for planetary imaging. I even created a cardboard stop to reduce the aperture down to about 70mm giving me a focal ratio of about f/28, but I usually found this to be unnecessary. Incidentally, I love this tendency among astronomers; we go bankrupt to get the largest aperture possible, then promptly stop it down to a pin hole!
Quickly, I found that acquiring the target could be a difficult task. The field of view on the computer screen is at most, a few dozen arc minutes across. A few tricks I’ve learned; make sure your finderscope is perfectly aligned; then center the object using the highest magnification possible. Then switch out the eyepiece for the web cam. If the object still doesn’t present itself, a final trick is to throw it way out of focus and begin a gentle sweep with the fine tuners of the region. the object should look like a silver, out of focus donut. I’ve found that the out-of-focus trick works because it makes my prey appear larger and hence more likely to be spotted. Make sure the camera is set on auto when you do it so that the image can handle the dispersion.
Once the image is centered, two things will determine the final image; seeing and focus. To achieve a razor fine focus, make sure your optics are fully collimated. The most common problem I’ve seen is a planet will appear fuzzy on one side and sharp on the other. I quick adjustment of the secondary mirror might be in order. Also, focusing at a high zoom and then backing off helps. Finally, focus in tiny increments, as you’ll have to wait a few seconds for vibrations to dampen. A remote electronic focuser would fix this. As for seeing, you’ll always get your steadiest skies at your zenith. Try to image objects as they transit the local meridian. Heavens-Above has an excellent site with precise transit times.
Stacking and aligning images has become an art form all its own; some astronomers will painstakingly examine thousands of images to select only a handful were the seeing was perfect, often with amazing results. Registax and K3CDD also provide algorithmic tools that do this automatically, with reasonable results. I like to use Photoshop to do final contrast, sharpening and cropping adjustments.
What can you image with a planetary web cam? You are pretty much confined to brighter, compact objects; I’ve done decent images of Jupiter, Saturn, Mars, and Venus. I’ve done lunar photography, too; I once captured a blurry (the moon was at a very low elevation) transit of the International Space Station in front of the moon. Some brighter variables work, as well. Some enthusiasts have taken the game a step further, making homemade deep sky imagers. What ever the outcome, I always have a fondness for the homemade stuff. Look for a few of my pics taken with the above set up (including the blurry ISS pic), here soon!
And here it is…

Transit.

A Web Cam Transit of the ISS in front of the Moon! (Photo by Author).

Comments

  1. Daniel says:

    I couldn’t understand some parts of this article Planetary Imaging with an Off-the-Shelf Web Cam, but I guess I just need to check some more resources regarding this, because it sounds interesting.

  2. Hi, my name wiki. I’m 16 and I like your site very much. Ill be back soon. :)

Trackbacks

  1. [...] detail on the ISS as well. Some years back, we constructed just such a device from an off the shelf webcam. If you own a laptop (you’re reading this, right?) a telescope, and a webcam, you can be imaging [...]

  2. [...] Fewer still are well positioned for a given longitude. Both were shot with our infamous ad-hoc webcam setup. The ISS pass ended up being a no-go for technical reasons; ya win some, ya lose some… but [...]

  3. [...] detail and serves as a fun diary. In addition to visual observation, many backyard observers use modified webcams to take images that would have been the envy of many observatories only decades ago. Another fun [...]

Speak Your Mind

*