Prepare observing sheets and finding charts BEFORE YOU ARRIVE
AT LAB. TA's can refuse you access to lab is you haven't prepared.
Telescope properly mounted; polar axis oriented to North; RA
and DEC circles properly zeroed (if using); telescope unclamped
Lens caps removed
Finder focused
Finder and main scope co-aligned. Check on terrestrial
targets, moon, or bright star. Objects in the center of main
scope under high power should be on cross hairs of finder. If
not, realign the finder and main telescope (ask TA's for help
the first time).
Lowest power eyepiece (i.e. longest focal length) in
main scope. Tighten set screw so that eyepiece cannot
slip.
Main scope focused (check on terrestrial target or bright star
field)
Telescope unclamped
Have finding chart/sky map identifying target or RA and DEC coordinates
available. Know what the target should look like when you locate it.
Target finding methods:
Boresighting:
Use binoculars to locate general field (optional)
Move telescope to vicinity of target
Take care to minimize parallax between your
eyeline and finder
Double check position against sky map and/or
binoculars
Star-hopping:
Boresight to an easy reference object
With telescope unclamped, move in a series of small steps through
intermediate reference objects (located in the finder or main
eyepiece) to the target
You need a good star chart to use this method
One-axis slewing:
Look up another object which lies at the same RA or DEC as your
target. Set on that by boresighting or star-hopping.
Clamp the axis for the coordinate in common
Carefully offset the other axis while looking through the finder
or main eyepiece to locate the target
You do not have to zero the coordinate dials to use this method.
RA, DEC coordinates:
Look up target coordinates. If your telescope does not read
directly in RA, you will need to compute the HA (for the time you
estimate you will have the telescope set) from the ST and the
target's RA.
Move the telescope (one coordinate at a time) until proper
coordinates are read on dials. (The dials must have been properly
zeroed beforehand by setting on a bright reference star.)
Instead of setting both coordinates, you can set just one (DEC
is best), then do a one-axis slew to the target while looking through
the eyepiece.
Be sure the telescope is clamped
Check for the target in the main telescope; if not there, unclamp
and systematically repeat the steps for finding the target.
If using RA,DEC and the target is not in telescope, check
calibration of both coordinate dials using a relatively
nearby bright star. If you can't find the target after a second
try, check that the coordinates you are using are correct.
Go to higher power eyepiece only after confirming target in
low power and centering carefully. Be sure to loosen and
tighten set screw for eyepiece appropriately.
Lecture Index