Photos
and Drawings of 38° Classical Spectrograph
This is an actual photo of the
spectrograph (without its protective aluminum housing). The collimation lens
can slide (theoretically) on the brass rails. It is fitted inside machined
aluminum blocks. The grating tilts in a machined aluminum cup. There is a
switch on the grating so that it can flip from 0th order (adjustable
with a screw) and –1st order (adjustable with a micrometer). The
camera lens (normally attached to the camera), which appears to be floating in
midair, is normally attached to the spectrograph via a beam of aluminum.
This is Sarah Howell’s drawing of
our spectrograph, drawn with the telescope attached.
This is a
diagram of how the grating must be at just the correct angle for the spectrum
to enter the camera lens as desired.
This is a
photo of the slit assembly we constructed for the spectrograph. The slit is
composed of razor blades which are adjustable. One razor blade is epoxied to
the machined aluminum circlet that houses the slit. The other razor blade is
held down via a magnet and attached to the other slit with nuts. Springs keep
it held in place; it is adjustable with a screwdriver.
When the grating
is in 0th order, the entire spectrograph acts as a sort of
focal-reducer and the camera can simply take images when the slit is removed.
We were having so much trouble centering stars and other objects that we wanted
in the slit that we decided to alter the slit, so that one would not have to
remove it to take such an image (the act of removing the spectrograph tends to
totally knock our telescope out of alignment). Thus, we cut a slit in the
middle of it, so that you can find your object in the middle opening and then
move it down using the telescope’s controls so that it is just inside the slit.
This technique works very well.
Above the
ring nebula is shown, just peeking above the slit, and below is the spectrum we
took.
Please send
questions or comments to marymast@gmail.com
last
updated June 15, 2006