[sac-forum] video astronomy info

Hello, everyone,
 
Bill McDonald, president of the Prescott club, joined us at Cherry last
weekend with his Mallincam color video camera. Many of us took a look at
the results (essentially real-time color images on a 13" TV monitor) and
were impressed. Here's some additional info from Bill:
 
Some thoughts on video astronomy
 
The video approach to Astrophotography is about 8 or 10 years old. In
that time it has taken several giant morph steps. It started with a
group in Europe, QCUIAG, which specialized in the use of webcams to
observe/image bright celestial objects. This approach remains popular
for planetary and lunar imaging. The idea is to capture many (often
thousands) of short-frame video images, discard those most effected by
atmospheric disturbances, and stack the best frames to produce a final
image. Several sites provide free software which include quality
filtering, stacking, and a range of image processing tools (Registax).
A phenomenal example of this technique can be found at the website of
Christopher Go who images in Cebu in the Philippines. You can find the
site by googling Christopher Go. Check out his 1994 Jupiter images. I
think that that work was done with a C8 and a webcam. Several of his
Jupiter images have shown up in S&T. 
A lot of standard digital cameras have a video output which you can use
to drive a TV and produce nice live views of the moon and bright
planets.
A few years into this technology, a new approach developed, with
automatic integration of frames collected over two seconds.  That
allowed the collection of photons over an extended period, the effective
equivalent of increasing the scope aperture. Mintron was the generic
type. Adirondack Video Astronomy in upstate NY got into the game at this
point with their Stellacam.  
In February,2003 and January 2004 S&T reviewed the new technology,
suggesting that these 2 second integrating cameras were equivalent to
increasing aperture by a factor of three or four. Several new companies
got into the game at this point. SAC instruments in Florida started
producing a low cost version of the 2 second Mintron for $500 (SAC seems
to have collapsed since). That is the one that hooked me. Mallincam in
Canada began to produce cameras somewhere in this time frame. 
The next morph stage produced longer integration. The numbers continue
to go up. Stellacam III now offers unlimited integration and the latest
Mallincam version goes up to 56 seconds. Mallincam also introduced the
color version of their camera about a year ago. That is the one that I
am using, with a maximum integration time of 12 seconds. S&T published a
review of Stellacam III in the September, 2007 issue. 
Color vs B&W has been a bone of contention. Somehow Mallincam seems to
have gone to color without a significant loss of sensitivity (15%
according to Rock Mallin). My suspicion is that they must have lost
something, considering all the photons that are rejected. My guess is
that resolution is sacrificed, but I don't have any way to confirm that.

My conclusion is that while some information may have been lost in the
color version, the extra information that the color provides more than
compensates for whatever is lost. And the wow factor clearly favors
color. 
A few other issues. My original Mintron came with a hand control box
with a cable from the camera. That worked just fine. The Stellacam
family has always used a hand controller. The Mallincam is controlled
with a five button array on the end of the camera itself. Awful! Small
buttons. Adjustments are in braille. They are working on a wireless
control system. Apparently that will require a laptop. There are a lot
of settings to deal with. For example, you can convert to a negative
display like the old glass plate images. There are gain controls, color
balance controls,.......etc. I can normally set up for an observing
session and not touch anything. For imaging, you would want to adjust
for each object before you start collecting images. 
The Mallincam is long, causing some folks with Alt AZ mounts to limit
their overhead observing. I believe the Stellacam is much shorter.
I'm not sure about the Stellacam, but the Mallincam has dual outputs.
There is a standard Video output which I generally run into a
conventional TV and a S-video output which can be delivered to a frame
grabber in a laptop to capture images. The two can be used
simultaneously. 
For public observing, these systems are a marvel. For teaching they are
miles ahead of traditional approaches. 
I envision using these cameras for group observing. Half a dozen serious
observers sitting around a display ought to provide a powerful observing
experience. 
 
For now images run about 768X494 pixels. That limits how big a display
can be used. I use 13 and 19 inch Video displays. I will be testing
larger formats. 
 
The Mallincam cameras come with peltier coolers. They are an option with
Stellacam. The cooler kills warm pixels and diminishes hot pixels. I
think that you need to expect at least a few hot pixels in any of these
cameras....and a tendency for the number to increase with time/use.
 
I generally run with a 0.3 focal reducer. With the FR in place my
advanced series C8 (bottom of the line platform) almost always puts
targets near the center of the TV screen. I think that that is largely
because it is very easy to center alignment stars precisely. 
 
These systems are tolerant of bright sky conditions. The dark sky
adaptation that is so important in visual observing, is much less
critical in video observing, making these cameras very effective for
sidewalk observing.
 
A few web sites:
Mallincam:http://mallincam.tripod.com <http://mallincam.tripod.com/>  
Adirondack Video astronomy:www.astrovid.com <http://www.astrovid.com/>  
Yahoo groups:mallincam, stellacam, videoastro. Shootout between
Mallincam and Stellacam begins with post #24864 on the videoastro board.
 
I would be glad to add anything that is missing here.
 
Bill McDonald
skyhighaz@xxxxxxxxxxxx
 
 
 
Dan Gruber
 <mailto:dgruber@xxxxxxxxxxxx> dgruber@xxxxxxxxxxxx
home  (480) 951 - 6877

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