Introduction to the 85cm telescope
of NAOC
1. Scientific goals of the 85cm
telescope:
The 85-cm Cassegrain telescope is one of the NAOC facilities,
dedicating to the photometry of short-period pulsating variables,
eclipsing binaries, white dwarfs, cataclysmic variables and related
stars. This telescope is available to
professional astronomers from anywhere in China (in the world in the
near future) who wish to observe.
Since 1995, the telescope has been fully putting into photmetric
observations of Delta Scuti stars, Eclipsing binaries and White Dwarfs.
By now, this telescope has contributed a lots to the WET (Whole Earth
Telescope) campaigns on white dwarfs
and subdwarf B pulsating stars and the STEPHI (STEllar PHotmetry
International) on Delta Scuti stars. Normally, the WET was
organized once or twice per year by American astronomers at the
University of Texas (1991-1998), the Iowa State University (1998-2005)
or the University of Delware (2005-present), the headquarter of all WET
runs. The three-channel photoelectric photometer is especially designed
for the WET campaigns. Now the WET runs have upgraded to mainly use
CCDs (e.g. Apogee Alta U47+ camera-like). Initially, the STEPHI was
organized each year by French astronomers at Observatorie de Paris,
Meudon. STEPHI runs use a four-channel French photoelectric photometer.
Besides participating these two main cross-continent multisite
campaigns, Chinese astronomers also join or organize some small
international multisite observations on this telescope. In order to
increase scientific producitivities, astronomers in other field of
photometry are encouraged to make use this telescope in recent years.
Astronomers from Yunnan Observatory, Taiwan and other
universities also observe with this telescope each year.
2. Photometers in use
Currently there are 3 photometers available for observers to chose for
their specific missions.
(1) Three-channel WET high-speed photoelectric photometer(3-CH)
The 3-ch photometer equiped with standard Johnson UBV filters. With no
filter-wheel controller, observers need to select or switch them
manually. This photometer is controlled by a DOS program called Q9. The
output data of the photometer are in ASCII format, and they can be
processed with the program QED or its X-window version XQED. In use of
this photometer, observers can monitor the target, sky background and a
comparison star within about 15 arc minute from the target,
simultaneously. Q9 displays light curves of the three channels in a
real-time mode, so observers can monitor the light variations during
the observations. As for guiding, the photometer uses a part of the
comparison channel light and displays the comparison's image through an
ST6 CCD camera. The data file is small, after observations, observers
can transfer their data to their home institutions by our Internet
connection, or just save them onto a 1.44MB floppy disk.
(2) Four-channel Chevreton STEPHI photoelectric photometer(4-CH)
The 4-ch photometer has the colone of Stromgren uvby filters equiped.
Normally, one can use two filters at the same time. The integration
time using this photometer is commonly 1 second. So after a full night
run, the data file is big regarding to a floppy disk capacity. The
control and data-taking prgroam runs in MS-DOS mode, is also graphic --
observers can see the light curves on each channel.
(3) Apogee AP7P CCD Cassegrain direct imaging photometer
This CCD photometer served as our experimental photometer for the image
quality at this telescope. Observational results show that the data are
quite good. Astronomers have used it for some two years since the
winter of 2002. In a near future, a new liquid Nitrogen coolled
scientific CCD camera is expected to be installed in the place of this
Apogee AP7P CCD.
There are China-made stardand Johnson BV filters available for choice
-- automatic switch is not provided, use one filter each night is
suggested. The CCD sized 512x512 pixels with a full field of view of
about 15 arc minutes. The data are saved in standard FITS format. Zhou
Aiying has written IRAF scripts for automatic aperture photometry of
the images obtained
with this CCD at 85cm telescope. For use of the scripts, please contact
at <aiying@bao.ac.cn>. Observers' data will be burn onto CDs at
the end of their run, or they can transfer to their home institutions
by FTP or SFTP after observation each night.
3. Photometers used on 85cm telescope
Historically, we used three other photometric systems on this
telescope. Now they have been out of work for years for different
reasons.
(1) CCD lightcurve survey photometer(controlled by VAX)
This CCD lightcurve survey photometer was used originally at 2.16m. The
CCD photometer was controlled by a VAX computer. Because the VAX
machine was broken, and it cannot startup, it stopped its service since
the December of 2002. If the software used in VAX could be transplanted
to PC, this CCD would be useful for variables studies.
In fact, this CCD photometer is quite nice, its output is purely
ASCII-- each star's magnitude saved as a column as the results of
aperture photometry. Using this CCD photometer, astronomers have
collected good data, published papers and discovered three new
variables:
--- a new Delta Scuti variable star GSC 2683-3076:
REF: Du B.-T., Zhou A.-Y., Zhang X.-B., Liu Zong-Li,
Zhang R.-X.,
Li H.-B., Jiang Z.-J.,
Dong X.-Y., and Zhao L.-M.,
1999, IBVS,
No.4805
--- a new variable GSC 2038_1730
REF: Zhang X.B & Zhang R.X, 2002, IBVS No.5290
--- a new W UMa variable star GSC 2293-1021:
REF: Liu Z. L., Zhou A. Y., Xu D. W., and Lu Y.,
2000, IBVS, No.4981
(2) Single-channel photoelectric photometer(1-CH)(out of work)
This signle-channel photoelectric photometer was allowed to use at the
85cm telescope by its owner, Shanghai Observatory in 1998. Astronomers
and engineers in the group of "Variables and Unstable Stars" of the
previous Beijing Astronomical
Observatory, had put some times on this instrument. Finally, for
various reasons, it was dismissed for use on this telescope.
(3) Photoelectric Radial Velocity Spectrometer and Multi-color
Photometer
This instrument was the first one on the 85cm telescope. It was being
still in its testing stage from about 1992 to the mid of 1995. Due to
the optical fibre connection between the spectrometer and telescope is
very hard to work properly, it is difficult to observe and get useful
data. A double-lined spectroscopic binary was successfully observed
with this spectrometer in 1995 (Ref: ). However, being lack of
continue support of both manpower and fund, as well as the
administration adjustment of the Beijing Astronomical Observatory, this
instrument was then put aside in the dome since late 1995.
4. Applying for Observing Time at the 85-cm telescope)
If you are interested in using our telescope and instruments (or wish
to bring your own instrument), you should complete an application form
and e-mail it to <aiying@bao.ac.cn>. The telescope time
application form is a Microsoft Word document into which you enter
details of your application. Applications are welcome any time
before our deadlines.
The tables of observing times for the 85-cm telescope are arranged
every six months. Remember to check this schedule for possible changes
which may affect your observing run. If you want to make changes to
your observing request, contact <aiying@bao.ac.cn>.
Deadlines for Observing Applications
25 December for next January-June observing season
25 June for next July/December observing season
Application Form for Observing Time on the 85-cm telescope at NAOC
5. The 85cm telescope -- Basic parameters
Zhou Aiying
First draft on 2004.10.20