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with the Adirondack Video Astronomy's Astrovid StellaCam II Jim Ferreira BakerSt@comcast.net |
The Astrovid StellaCam II from Adirondack
Video Astronomy is their variation on the Watec 120N, a video frame
integrating system capable of effective time exposures of up to 8.5 seconds.
The StellaCam II is roughly 2.5x more sensitive than the StellaCam EX  with
superior image quality both on the monitor and in the frame captured images.
The camera is amazingly small, roughly a 2 inch cube and far lighter than most wide field eyepieces. Its light weight makes it considerably easier to exchange out the camera for an eyepiece without having to readjust scope balance. The camera also seems to operate much cooler than other video camera heads. The back of the camera has receptacles for the control remote box, male BNC video line out and 12VDC power. Camera controls; frame integration, gain, iris control and gamma, are all on a separate control box which is also quite small and lightweight. The camera uses a standard Sony HAD CCD chip.
The chip does contain some "hot pixels," but far fewer than the Sony EXview
CCD and those present are much less intrusive. Curiously, there is
little evidence of "warm pixels" even at relatively warmer ambient operating
temperatures. Best of all, there is absolutely no amp glow which
is the primary shortcoming of the venerable StellaCam EX.
Viewing live images on the monitor, even extremely faint objects like the Horsehead nebula, is an amazing experience. The image has the rich quality of a photo that has been image processed. The monitor image is very smooth with minimal noise when the camera gain and gamma are set mid-range. Stars are quite small and round with very little disproportionate bloating of brighter stars. The camera appears to have an excellent dynamic range, evident both on the monitor and in the computer frame captures. Because the video frame captures contain smoother, less noisy images, far fewer frames need be stacked to produce high quality photos. Also, dark frames typically are not needed except when pushing image processing to extreme to bring up faint features. Even then, the hot pixels are noticable as only mid range gray points concentrated in a small area, depending on how much image drift is present in the stacked frames. In most cases the hot pixels are easily removed in image processing. With extended objects like the Orion Nebula or the Horsehead, faint dark donuts may be detected in the lighter regions. These small, dark regions are typically caused by dust on the CCD window and can be removed by recording and subtracting flat frames from the captured frames. So is there a down side to camera? Yes, well, no.....OK, sort of. As the camera integrates frames over 8.5 seconds,
there is a greater demand for accurate polar alignment than with the 2.5
second integration of the StellaCam EX. Drive periodic error is going
to be more noticeable over 8.5 seconds as will mount vibrations.
And since the camera is considerably more sensitive to light, greater attention
will have to be given to preventing stray light from entering the optical
system.
New -- the most recent images at the top
of the page were made with a Orion120mm
f/5 refractor @ f/3, capturing video frames to the computer by way of an
Imperx
video capture board, stacked in RegiStax and image processed in Adobe Photo
Shop.
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