is the amplitude spectrum of 1.5 hours of SAAO 1-m data on a star which gave a
count rate of 230,000 per second. It is corrected only for mean extinction in B
which was kappaB = 0.29 on that night. This is not great data; it is typical
data. So this is about what we are looking for from the other
observatories.
is the amplitude spectrum of the 0.5-hr of data from BAO with two low frequency
peaks prewhitened. This was necessary because of a large change in the
extinction during the 0.5 hr -- probably because of the approaching cloudy
conditions. Given that the run was only 0.5 hr and cloud was coming, I would
say that the amplitude spectrum is promising. It would be useful, if there is
time, to have 1 hr under photometric conditions.
The frequencies in HR 1217 are at 2.6 mHz. The SAAO noise level there is 0.5
mmag; the BAO noise level is nearly 1 mmag. I believe this is probably only
because of the short run and non-optimal conditions. I suspect that a longer
run at BAO will give good results, and I wouldn't hesitate to include them in
an roAp star campaign.
This 1.5-hr run on HD219831 by Mike Reed is excellent. The amplitude
spectrum is
attached as a ps file. The data have only been corrected for extinction;
the
extinction coefficient was about 0.3. The low frequency peak with an
amplitude
of 1 mmag is typical of even good nights -- it is caused by small changes
in
transparency. A peak of this size can be caused by just a change in
humidity.
It is not important. The amplitude spectrum drops to the noise level of
only
0.25 mmag at the frequency of HR1217. This is a good example of how a
larger
telescope reduces scintillation noise. This is the quality to which all
should
aspire.
Don Kurtz