How to - Work with a sub-frame of the image sensor.
The Starfish camera has a native resolution of 1280 x 1024 pixels. A single image from
the camera will have a total of 1.3 Mpixels. However, the camera can be operated in a
sub-frame mode where an arbitrary rectangular region of the image is captured by the
camera.
This can be useful when you are imaging a small object that does not take up the entire
field of view in the full frame mode. The advantage here is that the image file size is a
lot smaller thus saving disk space on your computer.
There is another advantage in that image capture and upload to the computer can be
much faster since a smaller number of pixels have to be transfered over the USB inter-
face and handled by the computer. This is especially useful during auto-guiding with the
camera or focusing the camera. You can define a small sub-frame around a particular
star being used for focusing or guiding and then operate the camera in sub-frame mode.
Frame rates can be greater than 60 frames/sec for small sub-frames.
To select a sub-frame region of interest on the Starfish camera:
1) Make sure you have
‘
Full Frame
’
mode set in the image window. It is also
helpful to have the zoom scale set so that you can see the entire image.
2) Click the
‘
Take Light
’
button to take a picture with the camera. The image win-
dow will display the picture just taken.
3) Using the mouse, draw a rectangle around the desired region in the image
window. The region will be displayed with a yellow rectangle overlay on the
image.
4) Click the
‘
Sub Frame
’
button at the top of the image window. This will switch
the camera
’
s mode of operation.
5) Click the
‘
Take Light
’
button to take a picture. The image window will display
the picture just taken but the image will be smaller as defined by the region of
interest just entered.
fishcamp engineering
Starfish
Guide Camera