QSI 520c Betriebsanweisung PDF herunterladen (Seite 52)

QSI 500 SERIES USER GUIDE

taken with the CCD at the same temperature as your light frames. If you’re taking LRGB or

other filtered images, ideally you should take a set of flat fields through each filter.

Setup your telescope and possibly your light box to take your preferred style of flats. Adjust

the exposure so the average pixel is filled to approximately half its full well depth. With QSI

500 Series cameras you should strive for pixel values of roughly 30,000 ADUs. As with

dark frames, you should take at least as many flat frames as the light frames you took

through each filter. Taking additional flat fields will produce a master flat with less noise,

yielding higher quality images. Do not change your focus. To get correct flat fields, it is

important that the focus be identical to the focus used for the light frames.

Flat Darks

As with any exposure using a CCD camera, dark current builds up while taking a flat field

image therefore the dark current must be subtracted with a dark frame taken at the same

exposure as the flat field. Taking flat-darks is easier and less time consuming than regular

dark frames because the exposure time of flat field images is typically much shorter than

your light frames. If you take flat field images, it is critical that you also take a series of flat-

darks. They’re easy to take with the shorter exposure, so take at least 15 flat-darks.

Manual Image Calibration

MaxIm LE supports both automatic and manual image calibration. This section describes

basic manual image calibration in MaxIm LE. For complete instructions on calibrating

images, please see the online help in MaxIm LE.

Subtract Dark Frames

Begin by creating a master Dark Frame for each exposure length. A master dark frame is

created by combining all the individual dark frames using an average or median combine.

See the section below Combine Frames in MaxIm LE for detailed instructions on

combining multiple images.

Tip: In general, an average combine of multiple images will yield a combined

image with slightly less noise than a median combine, but this requires that none

of the frames being combined have any anomalous groups of light or dark pixels

caused by, for instance, cosmic rays.

Other programs, such as MaxIm DL, include additional combine methods that

attempt to provide the low noise of an average combine with the anomalous pixel

rejection of a median combine. You will need to experiment to achieve the best

results.

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QSI 520c Betriebsanweisung Seite 52