As a result of the hardware and software modifications in the Willmann-Bell upgrade package, and recent improvements in image processing software, you may wish to revise your Standard Operating Procedure (S.O.P.) for the Cookbook CCD camera.
We now consider the optimum configuration for deep-sky imaging with the Cookbook 245 to be:
Before the LDC upgrade, it was possible to make a convincing case that the high sensitivity of 252-wide mode justified its use. With the reduced noise levels in LDC mode, however, the higher spatial resolution of 378-wide makes it the clear choice.
LDC mode should be ON when the subject is faint; for bright subjects such as the moon, planets, and daytime scenes, where the integration time is less than 1 second, LDC mode should be OFF because it reduces the dynamic range of the camera. In particular, flat fields and flat darks should be made with LDC OFF.
Drift subtract should be ON at all times. In 378-wide mode and all 252-wide modes except double sampling, the Reset value should be set to 100 approximately; this means that Ref will be 0. To reduce drift in the Reset value, the camera body should be wrapped so that the electronics come to equilibrium with the water-cooled camera body rather than the surrounding air temperature.
It is desirable to obtain dark frames at every observing session. S.O.P. is to shoot a set of darks after the camera has reached thermal equlibrium, usually near the end of the session. The total integration time for the darks should equal or exceed the longest total used for the images. Ten to twenty 300-second integrations is adequate. The darks should be averaged to make a master dark frame.
Dark frames are scaled automatically if you are using CB245, AIP245, or Multi245 software. Dark frames from the Cookbook CCD camera are sufficiently stable that darks taken days or weeks earlier can be scaled and used for calibration, however old dark frames should be treated as back-ups rather than S.O.P. Archive your master dark frames in case you need to re-use them some day.
Flat field images should be taken well into the session, with the same focus and camera orientation used for imaging. Shoot flats and flat darks with LDC mode OFF to prevent saturation of group 3 "hot" pixels.
For bright objects requiring integrations under 1 second, S.O.P. is to use the camera with LDC OFF. Note that dark frames taken with LDC ON cannot be used to calibrate images taken with LDC OFF, and vice versa. Dark frames made in these two modes are quite different.
Single integrations up to 1200 seconds can be used with deep-sky subjects,
but integrations over 600 seconds should be inspected to make sure that
the group 3 "hot" pixels are not saturating. Because of this,
use multiple imaging for making "ultra-deep" images. Multiple
mode can reach effective integration times of many hours.
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