| 1) Set up the mount and level it. (6 minutes)
2) Install the telescope, guidescope, camera, and ST-4. Balance the
scope.(8 minutes)
3) Polar align using the polarscope. (2 minutes)
4) Drift align ( 1 hour ). This is where I can improve things quite
a bit. I use a barlow and 12 mm reticle eyepiece giving around 156x.
The hard part is finding a star at the meridian and at 0 declination. If I
have no drift after 5 minutes, in each position, then I can take photos of
45 minutes with 8x10 blowups with no noticeable field rotation.
5) Compose photo in camera viewfinder. This is another area where I
need improvement. If there are no bright starts (at least 3rd or 4th
magnitude) I cannot focus effectively. I then need to position the
scope on another star, focus and then try to get back to the same position
where I was. Perhaps digital setting circles would help here?
6) Locate star for autoguider. This usually takes about 5 minutes.
7) Adjust the ST-4 for a signal around 15-40 and exposure time around 2
seconds.
8) Take dark frame, calibrate at 2X speed and enter track mode.
9) I usually see errors of +/- 5 ST4 units in the worst case, with an
average of 2 or 3. This corresponds to an error of +/- 2 arc seconds
in terms of absolute errors or 0.8 to 1.2 arc seconds average.
Given that the seeing I have had in the past is around 3-4 arc seconds,
this seems reasonable.
10) The Nikon F3 has a manual setting at T but to use it you must flick a
very inconvenient lever instead of the usual shutter release.
However there is a trick: If you turn on the camera and engage the self
timer, you can then press the shutter release in the conventional
way. The beauty is that the timer flicks the shutter, but then does
not require any power after the usual 15 seconds that the camera stays in
power on mode.
11) At the end of the exposure, I put the lens cap on the main scope and
then manually end the exposure.
12) It seems easy, but something always goes wrong. Like last
Monday, when I went through all of the above after a 1 hour drive and had
the shutter open for 5 minutes. and then the clouds rolled in....or the
time I tripped over the power cord, ripping it out of the connector.
|