Section 8 – Glossary
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the image. Maximum resolution is determined by the size of the individual CCD pixel.
The Research Series cameras can run in High, Medium, Low and Auto resolution
modes.
Response Factor
- Response Factor is a multiplier used by CCDOPS to calibrate CCDOPS to a
given telescope for photometric calculations. The Response Factor multiplied by 6700 is
the number of photoelectrons generated in the CCD for a 0th magnitude star per second
per square inch of aperture.
Saturation
- Saturation refers to the full well capacity of a CCD pixel as well as the maximum
counts available in the A/D converter. The pixel is saturated when the number of
electrons accumulated in the pixel reaches its full well capacity. The A/D is saturated
when the input voltage exceeds the maximum.
Sky Background
- The sky background illumination or brightness is the number of counts in
the image in areas free of stars or nebulosity and is due to city lights and sky glow.
High levels of sky background can increase the noise in images just like dark current.
For some objects deep sky filters can be used to reduce the sky background level.
Seeing
- Seeing refers to the steadiness and the clarity of the atmosphere during an observing
session.
TE Cooler
- The TE Cooler is a Thermal Electric cooling device used to cool the CCD down to
operating temperature. The CCD is mounted to the TE Cooler which is mounted to a
heat sink, usually the camera head housing.
TIFF Image File Format
- The TIFF image file format (which stands for Tagged Interchange File
Format) was developed jointly by Microsoft and Aldus Corporations to allow easy
interchange of graphics images between programs in areas such as presentation and
desktop publishing. CCDOPS can save image files in this format but it can not read
them.
Track and Accumulate
- The Track and Accumulate function is a SBIG patented feature of
CCDOPS that allows the user to automatically co-register and co-add (including dark
frame subtraction) a series of images of an object. These exposures can be taken
unguided as long as the "Snapshot time" does not exceed the length of time before
tracking errors of your clock drive become apparent. This allows you to image and track
without guiding or the need to connect the CCD Relay port to your drive motors.
Track List
- The Track List is an ASCII file generated by CCDOPS during a Track and
Accumulate session. The Track List logs all the corrections made by CCDOPS for each of
the images. Track lists are required when flat fielding Track and Accumulate images.
Tri-Color
- Tri-Color refers to color images created using three different colors mixed into a
balanced color image using red, green and blue filters. An object is imaged three times,
once with each color filter. The three images are then co-added and color balanced with
the appropriate software.
Vignetting
- Vignetting is obstruction of the light paths by parts of the instrument. It results in
an uneven illumination of the image plane. The effects of vignetting can be corrected
using flat field images.
