Specifications

SBIG STF-8300 Manual

4. At the Telescope

Connect the camera to the computer and start CCDOps. Establish a link to

the camera and run the Camera Setup command. Enable the cooling to ~30

degrees below ambient and then watch the Link Status field to see the

temperature come down. Once the temperature reaches the Setpoint it will

jump back and forth by about 0.5 degrees. This is normal. The STF-8300

regulates the CCD temperature by dithering back and forth across the

Setpoint and while the readout of the temperature has a half-degree

resolution, the actual temperature is regulated to 0.1 degree. At this point

we’re ready to hook up to the telescope.

Focusing a CCD camera at the telescope can be a tedious operation, so

a few hints should be followed. Before using the software to focus the

camera the first time you should place a diffuser (such as scotch tape or

ground glass) at the approximate location of the CCD's sensitive surface

behind the eyepiece tube and focus the telescope on the moon, a bright

planet or a distant street lamp. This preliminary step will save you much

time in initially finding focus. The distance behind the eyepiece tube for

the STF-8300 is approximately 0.7 inches (backfocus).

To achieve fine focus, first center a bright star then insert the CCD head

into the eyepiece tube, taking care to seat it, and then enter the CCDOps

Focus Mode. Do not initially try to focus on the moon or planet – they are

harder. As we learned in the tutorial, the Focus Mode automatically

displays successive images on the screen as well as the peak brightness

value of the brightest object in the field of view. Using the telescope

controls, center the star image in the CCD, and adjust the focus until the star

image is a small as can be discerned. Next, shift the telescope to fainter

stars so the CCD is not saturated. Further adjust the focus to maximize the

displayed star brightness in counts and minimize the star diameter. This can

be tedious. It helps considerably if a pointer or marker is affixed to the

focus knob so you can rapidly return to the best focus once you've gone

through it.

An exposure of 1 to 3 seconds is recommended to smooth out some of

the atmospheric effects. While you can use the Full frame mode to focus,