16
17
5. Click the
Expose
button. You should see the out of focus star in the image.
If you do not see anything, you need to increase the exposure time.
6. Check that the
Subframe
section at the bottom of the
Camera Control
window has both the
On
and
Mouse
boxes checked on.
7. Draw a small box around the unfocused star with your mouse (hold-click
and drag the mouse cursor around the star to draw the box, Figure 11).
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 12). The
FWHM
(Full-Width Half Maximum) indicates the
diameter of the star. The
Max Val
is the brightness value for the bright-
est 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 larg-
est
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 looking 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 13). Before proceeding to
take images, set the
Mode
box
back to
Single
.
Note: Due to atmospheric seeing
conditions, you may notice signifi-
cant fluctuation 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.
Caution: Once you have achieved focus, be sure to click the
Reset
button at
the bottom of the camera control window, otherwise the camera will crop all
your images into a small square!
Imaging Deep Sky Objects
Capturing impressive images of deep sky objects, such as galaxies, nebu-
lae, and star clusters, require long exposures. You will take several individual
images and stack them together to form one high-quality resultant image, just
as you would with planetary imaging. But while planetary images are formed
by stacking many exposures of less than 5 seconds, deep space images will
generally be comprised of individual images of a minute or longer!
Note that the StarShoot Pro is also capable of capturing planetary images. To
increase the image scale of the planets, a barlow lens is recommended. See
“Tips – Using Focal Reducers and Barlow Lenses”.
Figure 12.
The
FWHM
and
Max Pixel
in the
Camera Control Window
help
determine the best focus.
Figure 13.
Click
Reset
in the
Subframe
box after you have achieved
focus.
Figure 11.
Draw a
small box around the
star to focus on with
your mouse. The next
exposure will download
a “subframe”, using
only the small area
you selected which
greatly decreases the
download time.
