(Last updated on December 18, 2000)
The goal of this web site is to promote Video Astronomy to other amateur astronomers. For more information, e-mail [email protected]
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Click here to learn more about the basics of
video astronomy at VideoAstro.
This will also lead you to galleries of images and websites maintained by other
video astronomy enthusiasts.
I have been interested in astronomy and an amateur astronomer since the mid 1970's.
My first telescope was a Edmonds Scientific 3" Newtonian. This was soon followed by a
Criterion 6" Newtonian. I continued to use the 6" on a casual basis for many years.
Then, in the early 1990's, I was stunned by CCD images of the planets, particularly of Mars,
Jupiter, and Saturn, that were taken by Donald Parker using his 16" Newtonian from the steady
skies of southern Florida.. I became determined to achieve similar results by whatever means.
I assumed that I would require a large telescope, an expensive CCD camera, and exquisite seeing
conditions to even approach these fantastic images. I was wrong. In fact, I get pretty good
results with modest equipment (and expense).
After constructing an 8" Newtonian with superb optics I began experimenting with video Astronomy
in 1998. I started out using an old (1989 vintage) Panasonic videocamera to capture images of
the moon and planets. This showed promising results and prompted me to purchase (October, 2000)
a PC-23C video camera. Frames captured by the video camera are first recorded to a standard (cheap)
HQ VHS video recorder and later grabbed with a Snappy (v. 2.1) to a PC and stacked with Astrostack
(v. 0.9 beta), and manipulated with Adobe Photoshop 5.5) to achieve the final results. Some of these
results are shown below. The results I've obtained thus far have greatly exceed my expectations.
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EQUIPMENT: All the images on this page were captured through my 8" (203 mm) Newtonian. This scope has been "optimized" for high resolution, planetary work. First, it has some pretty good optics. I purchased the 8" f/7 primary of my scope from a chap in Toronto (Ric Rocosz) who ground it himself. Ric figured the mirror by way of the autocollmination test - against a 12 inch flat and using a a ronchi grating (80 lpi). The surface is very smooth and well-corrected. I also use a small secondary (1.3") giving a relatively small (16%) obstruction. I regularly collimate. The optics are mounted in a sonotube with a homemade low-profile helical focuser, a Protostar, 3-vane secondary support, and a homemade mirror mount. The mirror mount is well-ventilated and contains a small, 12 volt muffin fan that speeds cooling of the primary and helps reduce tube currents. It also maintains collimation remarkably well. The tube is roughened internally with crushed walnuts and painted ultra flat black (Krylon) to minimize light scattering. The scope is mounted on my old Criterion German Equatorial Mount. The mount has tracking but currently lacks slow-motion controls. Right now I consider the lack of slow-motion controls to be my greatest handicap. I'll probably rig some slow motion controls for my declination axis while I save money for a Losmandy GM-8 or similar mount.
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PROCESSING:
Most of what I've learned about Video Astronomy I've gleaned from magazines such as
Sky and Telescope, from books such as the newly published
Video Astronomy, and from various websites on the internet. I highly recommend
the website VideoAstro
and accompanying Video Astronomy discussion group, and the web pages
maintained by Thierry LeGault,
Gérard Therin, and
Antoniao Cidadao.
Image processing of the video images includes capturing the raw frames, stacking
numerous raw frames, and image processing of the resulting images.
The left image of Saturn (taken on November 26, 2000 @f/73) is a raw video frame (640 x 480)
after level adjustment in Adobe Photoshop. The middle frame is the result of stacking 160
raw frames. The right frame has had unsharp masking and gaussian blurring applied in
Astrostack and Adobe Photoshop.
These images of Jupiter, based on video footage taken on December 7, 2000, illustrate
the importance of processing to bring out subtle details of the original video frames.
The left image is the result of 80 frames average-combined in Astrostack. The middle image
has had a hard unsharp mask (level 16) applied in Astrostack followed by two passes of
gaussian blurring in Adobe Photoshop. The right image has had further unsharp masking
and gaussian blurring applied with Adobe Photoshop.
One of the most important processing functions is making a level adjustment to increase the dynamic range of an image. This adjustment is referred to as "the histogram-stretch function" of Photoshop in the book "Video Astronomy" by Massey, Dobbins, and Douglass (p. 78). After first setting the low and and high tonal ranges to "stretch" the image, I find that setting the midtone adjustment level can make a big difference in the final image of objects that show relatively low surface contrast.
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Saturn, November 26, 2000 This image was made with my 203 mm f/7 newtonian @ f/73
using eyepiece projection (a Sirius 7.5 mm Plossl projecting 86 mm) and a PC-23C
B&W CCD video camera (unfiltered). This is the result of 169 stacked frames.
The frames were combined using Astrostack. Unsharp masking was applied in
Astrostack and gaussian blurring was applied in Adobe Photoshop.
This image illustrates the sensitivity of the PC-23C video camera. The left image
is the result of 11 stacked frames. the right image has been enhanced to show four
of Saturn's satellites. This image was obtained on October 26, 2000 at about 7:30 UT
with an eyepiece projection yielding f/40. The fainter satellites are readily are
readily visible on the videotape, but a little difficult to see on this image.
Jupiter and Io (through a Wratten #80A Medium Blue filter) image obtained on November 14, 2000 at about 8:20 UT and is
an average of 57 frames.
Jupiter and Ganymede (through a Wratten #25 Red filter) image obtained on November 26, 2000 at about 8:20 UT and is
an average of 57 frames.
This animation was created using a series of 16 images of Jupiter obtained
between 4:43 and 6:30 on December 7, 2000 UT (1 hour, 47 minutes). Each image
is the result of 80 stacked video frames made with my 203 mm f/7 newtonian
@ f/73 using eyepiece projection (a Sirius 7.5 mm Plossl projecting 86 mm) and
a PC-23C B&W CCD video camera (with a Wratten #25 Red filter). The moon that
appears from the left is Io.
Jupiter and the Gallilean sattelites. This is a composite image based on video
taken on December 7, 2000 at about 6:00 UT. Jupiter and Io were captured
together (combined 80 frames). Europa and Callisto were also captured together
(45 frames), and Ganymede was captured alone (53 frames). Seeing that night was about 5-7
and video frames of Ganymede were carefully selected. At the time, Jupiter was 48.4"
in diameter (at the equator), Io was 1.23", Europa was 1.06", Ganymede was 1.78",
and Callisto was 1.63". The brightness contrast between Europa and Callisto is real.
The relative brightnesses of the other moons is approximate. At 6:05 UT (the time
that the Jupiter and Io image was captured) CM1=147, CM2=44.
A closeup of Ganymede from December 7, 2000 at about 6:00 UT based on 53 frames showing
some surface markings.
Uranus @ f/70.
A composite of a portion of Jupiter (with Ganymede), Saturn, and Uranus at
the same scale. All images were captured @ f/73 on the evening of
November 26, 2000.
Plato on December 5, 2000 UT.
Plato on December 7, 2000 UT.
Clavius and Tycho on December 7, 2000 UT. Unfortunately, I have yet to image
the moon under anything better than fair seeing conditions.
One frame of Rigel and its 6.7 magnitude companion (separated by about 9") @ about f/70 on October 26, 2000.
71 stacked frames of M42 @ about f/8 on November 26, 2000.
The Trapezium. On the left is a full 640 x 480 frame including the Trapezium at f/73 (20 stacked frames)on
October 26, 2000. On the right is the same frame processed to bring out the faint (about 11th magnitude)
"E" and "F" components.
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RESULTS:What do I do with these images? Besides getting real satisfaction out of obtaining and sharing these images (I can usually see details at the monitor that are not visible to me at the eyepiece), I also send some of them to the Association of Lunar and Planetary Observers (ALPO) and International Jupiter Watch (IJW). These images are important for study of atmospheric circulation and seasonal changes on various planets. I'm also looking at the potential for using CCD video cameras to document short-term brightness fluctuations of variable stars.
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