Orion 52084 - Manual (Page 16)

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8. In the Camera Control Window, in the box below the Mode box, select
Focus. Click Expose. The camera will only download the area you previ-
ously selected, which makes each image download significantly faster than
the whole frame.
Note: If the StarShoot Pro is grossly out of focus, no object will appear in the
image, not even a blur. Increase the exposure time if needed and patiently
move through the focus range of your telescope until you see the centered
star come into view.
9. Gradually adjust the telescope’s focuser inward until the star visually
comes to a small point on your computer screen. You have achieved a
rough focus. Some small adjustments remain to get a perfect focus.
10. Click the Stop button.
11. Set Seconds somewhere between 0.002 and 0.1 seconds (or longer for
fainter stars).
12. Click Expose.
13. Carefully watch the FWHM and Max Pixel values in the Camera Control
Window (Figure 11). The FWHM (Full-Width Half Maximum) indicates the
diameter of the star. The Max Val is the brightness value for the brightest
pixel in the star. The smaller the FWHM, and the larger the Max Pixel, the
closer you are to focused.
14. Adjust the focus as needed to get the smallest FWHM and largest Max
Pixel possible. The Max Pixel should stay well below 65535, as this is the
saturation level for the camera. If the Max Pixel approaches 65535, reduce
the exposure time or try selecting a fainter star. Paying attention to these
values will help you get a very accurate focus, far better than simply look-
ing at the star image on your screen.
15. Click Stop once you reach the best focus and click Reset in the Subframe
section at the bottom of the Camera Control window (Figure 12). Before
proceeding to take images, set the Mode box back to Single.
Note: Due to atmospheric seeing conditions, you may notice significant fluc-
tuation in the
FWHM and Max Pixel values while focusing. You typically have
to take multiple exposures each time you adjust the focuser to determine the
quality of your focus.
Figure 11. The FWHM and Max Pixel
in the Camera Control Window help
determine the best focus.