8
9
Camera Controls
For best images, you can adjust the camera controls though Orion AmCap to
fine tune the image. You can see how the camera controls affect an image in
the
Live Video Window
.
From the Options menu choose
Video Capture Filter
and you can access the
camera controls. Here you will find the
Brightness
,
Contrast
,
Gamma
,
Hue
,
Saturation
(level of color),
Sharpness
(keep this low as it can add noise), and
Exposure
controls. The
Exposure
control is a gain adjustment that allows
additional flexibility in adjusting image brightness. You can manually adjust
this by moving the slider
.
To return the camera controls to their default set-
tings, click the
Default
button.
The other camera controls are available by selecting
Video Capture Pin
from
the Options menu. This accesses the Stream Format property sheet, which
allows you to set additional parameters. The
Frame Rate
, while generally
should be left at 15 frames/second for the sharpest planetary images, can
be toggled down to 7.5 frames/second for brightest exposures. This value
may be overridden If the use Frame Rate box Is checked in the Capture ->
Set Frame Rate menu. (You can also use the
Video Capture Filter
selection
described previously to adjust image brightness.) Check the
Flip Horizontal
box to change the orientation of the image display in the
Live Video Window
.
The Output Size can be used to shrink the image size if desired; the camera
defaults to 640x480, but you should raise this to the highest setting (1280 x
1024) for the maximum possible resolution.
Try several different settings to get a feel of how the camera controls work
and affect the resultant image on the computer screen. The
Brightness
and
Exposure
controls are the ones you will use the most. The telescope being
used, seeing conditions, and object being imaged will dictate how these cam-
era controls should be set. Usually Exposure will be set first, then Brightness
is adjusted as needed.
astronomical Imaging
Now that you’re familiar with basic camera and software operation, it’s time to
take the SSSSI-IV out at night under the stars to capture some astronomical
images. We recommend starting with the Moon, as it is easy to acquire into
the camera’s field of view, and typically does not require stacking of multiple
exposures as planetary images do.
Imaging the Moon
Imaging the Moon is much like imaging terrestrial objects during the day. Since
the exposure is very short, it is not critical that the telescope be precisely polar
aligned.
When the moon is past half full, it is
hard to get detail due to the tremendous
glare off of the lunar surface. Most detail,
even on a sliver of a moon, will be at the
terminator (that tiny thin line between
the shadow and light, see Figure 7). To
get more of the moon in the image, a
focal reducer will need to be used. For
close-ups of craters use a Barlow lens
(see “Using Focal Reducers and Barlow
Lenses”).
Imaging Planets
The best planetary images will be
obtained by stacking (combining) many
individual images in order to improve
image contrast, brightness, and detail.
A great way to obtain images for stack-
ing is to take several seconds of video
of the planet, then break the video into
individual frames for stacking. Since the
SSSSI-IV has a maximum frame rate of
15 frames per second at maximum reso-
lution, you can literally obtain hundreds
of images for stacking in seconds! You
save time by taking one video instead of
dozens of individual pictures!
Since you will be taking multiple images over a period of time, it is important
you have a decent polar alignment in order to keep the planet within the field of
view of the camera. To this end, having a motor drive (at least single-axis) will
also be helpful. Otherwise, you will periodically need to rotate the R.A. slow-
motion knob to keep the planet within the camera’s field.
tips
Focusing
One of the hardest things to do in planetary imaging is achieving good focus.
You can make this process easier by simply watching the
Live Video
window
to focus. Depending upon the viewing conditions you may notice that the
image goes in and out of focus, this is due to viewing conditions. This is to be
expected and one of the reasons why post processing software can bring out
the best in your captured images. Focus as best as possible with the average
frame being at best focus to ensure more in focus frames than out of focus.
Figure 7.
The moon’s surface detail
looks the best along the terminator.
Figure 8.
Jupiter with Ganymede
and shadow in transit. Left. Live
image Right. 500 frames Aligned,
stacked and enhanced using Registax
Image Processing Software. Image
taken with Orion 180mm Mak-Cass
telescope.
