Both images, 50 frames stacked and processed identically in RegiStax and PhotoShop
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of Mintron based frame integrating video cameras utilizing Sony ICX248AL HAD EXview CCD & Sony ICX038DLA HAD CCD |
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by Jim Ferreira BakerSt@comcast.net Video Capture Astrophotography: http://www.lafterhall.com/astro.html |
| There has been a need for side by side comparison,
on actual astronomical deep sky objects, through a telescope, of the frame
integrating low light video cameras that utilize the Sony ICX248AL HAD
EXview video chip and those that use a standard Sony ICX038DLA HAD video
chip. Much of past discussion regarding the sensitivity of these
two systems have been based upon informed speculation utilizing the available
technical data and on some optical bench testing. As the following
suggests, there are some differences in conclusions reached regarding the
usefulness of the extra sensitivity of the EXview video chip:
Terry Platt, Starlight Xpress Ltd., compared
the ICX248AL EXview video chip with a standard ICX038DLA chip and concluded
that the EXview chip possessed twice the sensitivity of the standard chip
with essentially the same thermal and readout noise. His conclusions
appear to be based upon comparison of the technical data available from
Sony for the two video chips.
Conversely, Mike Palermiti, optical designer,
Jupiter FL, has commented that “the "Ex" chip does not offer any significant
improvements for astronomical work unless filtered at specific longer wavelengths.”
His conclusions were reach based upon optical bench testing of the two
video chips.
To conduct side by comparison two deep sky objects were chosen, M13 and M57, one being a stellar object, the other containing reasonably bright nebulosity. Both objects are easily recorded by both cameras with a 15cm Mak-Cass @ f/10 and were well placed near the zenith during late evening. Cameras utilized for this test are the StellaCam EX from Adirondack Video Astronomy and the DeepSky Pro, standard model, from Internet Telescope Exchange. Both cameras are based upon the same camera technology utilizing the same frame integrating electronics, and the same means of manual camera adjustment, meaning, for test purposes, they are essentially the same system except for the video CCDs which are being compared here. |
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(StellaCam EX) negative image of 50 frames . |
(Standard DeepSky Pro) negative image of 50 frames . |
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negative image of 50 frames . |
negative image of 50 frames . |
| The series of photos for both objects clearly
demonstrate that the EXview camera is notably more sensitive than the standard
HAD chip camera on these two deep sky objects. A conservative estimate
is that the EXview camera records at least 1 magnitude deeper than the
non-EX system.
Included below are images where image brightness has been increased by 2x, 4x and 8x, relative, using identical brightness settings on the unprocessed stacked images. The brighter images better display the extent of the video chip thermal glow and the presence of warm pixels, and suggest how much could be gained in image processing. Note that the EXview images do show noticeably more thermal glow than the non-EX camera images, however the number of warm pixels visible for both video chips is quite comparable. |
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| The next step will likely be a side by side
comparison using a color sequence of stars.
Stay tuned! |
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| Equipment & Procedures:
Scope:
Cameras:
Utilized the same well regulated 12VDC power supply No IR-blocking filtration was used Camera Settings: >Frame Integration: x128
Direct capture to computer, BMP format, with PixelSmart 512-8 EIA frame grabber 50 frames captured for each image displayed Frames stacked with RegiStax software, including video frame de-interlace Image brightness was adjusted identically for each image with the PixelSmart 512-8 frame grabber software with relative intensity levels at 0, 2x, 4x and 8x Frame captures for M57 and M13 were done one half hour either side of crossing the meridian Seeing Conditions: fair, with good transparency and mild turbulence Temperature: high 60s 7 September 2003, Livermore CA
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