Meade Image Processing Specifications download pdf (Page 18)

8 AUTOSTAR CCD PHOTOMETRY

You now have a set of Master Dark Frames for the desired

exposure times. These are stored in a folder called Darks located

in the Meade Images folder (unless you designated a different

folder).

2.5 Taking Star Images

When taking stellar images for photometry, one of the great

features of CCD imaging with the Autostar Suite software is the

ability to automatically take multiple short exposure images and

stack them. The images can also be automatically aligned with the

software. While a single, long-exposure (say, 60 seconds) might be

considered to be better than 10 each 6-second exposures, the

shorter exposures have advantages. One big advantage of stacking

multiple images is that the signal-to-noise (S/N) ratio is improved,

while also minimizing any tracking errors.

2.5.1 Imaging Procedure

1. Find the star field to be imaged and center the telescope on the

first star. Position the B filter in the optical path. If you are using

an SCT telescope equipped with a mirror lock and an external

electric focuser, set the fine electric focus so that the range of

movement is about midway between the extremes. Now do a

(normal) coarse focus with the telescope manual focuser (the knob

that moves the primary mirror). Turn (or drive) the knob CCW

past the focus and then CW back to the focus. (Always finish by

moving the focus in the same direction.)

Now Lock the mirror (if the telescope has a Mirror Lock). Final

focus using the fine motion electric focuser for the sharpest images

with the CCD camera.

Figure 2-7 shows a screen shot with the DSI Pro CCD camera

connected and working. Check the focus in each of the filters. At

HPO, we have found that imaging with the I filter seems to be the

most critical. If that is focused well, the other filters are usually

acceptable also.

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Meade Image Processing Specifications Page 18