The Automated Patrol Telescope

APT

The Automated Patrol Telescope (APT) is a wide-field CCD imaging telescope, which is operated by the University of New South Wales at Siding Spring Observatory, Australia. Here are one, two, and three photos of the APT and the nearby ROTSE-III telescope.

Specifications

The optical design employed resembles that of a Schmidt camera, but uses a 3-element lens to achieve a wide, corrected field of view. Telescope motion and operation of the CCD have been placed under computer control, allowing automated observations for long-term survey and monitoring projects. The APT has 0.5m aperture f/1 optics which produce a 5 degree flat field, of which a 2X3 degree field is utilised by the CCD currently installed. Imaging can be done either unfiltered or through B, V R and I broad-band filters.

Current computing projects involving the APT

During 2003 eight Computing Science & Engineering students are working on the APT software. Here is a link to a list of projects. And here and here are what typical students look like.

PMAC device driver for Linux

The APT RA/Dec motors are driven by a PMAC-Ultra-Lite with a PMAC macro station for fibre-optic isolation. PMAC is made by Delta Tau. Here is the device driver we use to interface to the PMAC from a PC running Linux (kernel 2.4). If you use the driver, please e-mail Michael Ashley (m.ashley@unsw.edu.au) with any comments/bugs/features. Here is the code that we download to the PMAC to run the telescope. Note that we use the m4 macro-preprocessor to make it easier to maintain the PMAC code.

Wright Instruments CCD camera for Linux

The APT uses a Wright Instruments CCD camera, that has given excellent service for many years. Here is a gzipped tarball containing the device driver (for kernel version 2.4; if you need an earlier version, try this) and other support files. If you use the driver, please e-mail Michael Ashley (m.ashley@unsw.edu.au) with any comments/bugs/features.

Eta Carina

An image of Eta Carina, showing the ability of the Wright Instruments CCD device driver to read out rectangular and circular areas. This image is raw (i.e., no flat-fielding).

Observer's Guide

The APT Observer's Guide provides technical information for observers who wish to use the telescope. If you have APT data, you might be interested in AptReduce.cl, a script for reducing a night's data and AptProc.cl, a script for reducing individual images. Alternatively, pick up the entire APT IRAF reduction suite, which includes both programs, and more, in an IRAF external package; note: you will need the SAO header file to compile the astrometry routines.

Photographs of the Telescope

Here are a bunch of high-resolution photographs of the APT and the observatory. Each slide set is about 2 MBytes in size. Slide set 1. Slide set 2. Slide set 3. Slide set 4.

History

The APT was developed by extensively modifying the optical, mechanical and electronic systems of a Baker-Nunn satellite tracking camera. The Baker-Nunn had been located at Woomera in South Australia during the 1960's, and thereafter was stationed at Orroral Valley near Canberra. The camera was donated by the Smithsonian Institution to the University of New South Wales in 1992. Most of the mechanical, electrical and electronic modifications to the camera were performed in-house at the University, and the telescope was then taken to its present site at Siding Spring, and housed in a "roll-off" roof building which allows rapid access of any part of the sky. The CCD camera used in the APT was purchased from Wright Instruments, Enfield, U.K., and features an EEV CCD with 1152 x 770 pixels. The optics were redesigned at UNSW to allow the use of standard 5-mm thick astronomical filters in front of the CCD, and also to produce a flat-field. The optics were refigured by James Optics Ltd, Melbourne, Australia. In 1993, final installation was done of the telescope's modified optics, and observations for research with the completed telescope started in early 1994.

Scientific Highlights (as of 1995)

Orion

Much to our embarrassment, this section is out of date!

In reverse chronological order. Note: MCBA is Michael Ashley, CSB is Colin Bembrick, BDC is Brad Carter, JBWC is Jack Cochrane, PM is Peter Mitchell:

* 23-Aug-1995 Bruce Grossan, MCBA---Work commences on using the APT for a gamma ray burst detection experiment, in a collaboration between the Lawrence Berkeley Laboratory (Grossan, Perlmutter), and UNSW (Ashley, Storey). Supernovae observations continue. An image was taken of Comet Hale-Bopp, currently at about 10th magnitude.

* 1995 Andrew Jacob---An experimental program to test a new H alpha filter concept.

* 20-Apr-1995 Brian Schmidt, MCBA---Observations commence for a supernova search. Over 800 galaxies can be observed in two nights (40 fields per night, each field is observed for two consecutive 300 second exposures, each field contains on average 10 galaxies).

* 04-Mar-1995 to 20-Apr-1995 MCBA, Oliver Prouton, and CSB---Observations of the Delta Scuti variable star FG Vir were made as partof an international campaign coordinated by Michel Breger in Austria. 8000 images were taken over 163 hours of observations over 44 nights, using 60 second integrations separated by 15 seconds. An rms accuracy of 0.003 magnitudes was reached during each 60 second V-band observation of the 6.5 magnitude star. This accuracy was achieved by defocussing the APT so that images were 15 pixels across, thereby reducing the effect of intrapixel sensitivity variations. The advantage of the APT for this observation is that bright standard stars could be measured on the same exposure. A subset of the images is being used for an undergraduate experiment in image analysis by Michel Breger in Austria.

* Nov-1994, Joe Liske, MCBA, BDC, CSB, PM---Observations of geostationary objects for a Lockheed contract.

* 1994, BDC, MCBA, CSB---Time-resolved photometry of a flare star---part of an international multi-observatory campaign.

* 1994, MCBA, BDC---High-speed imaging of Jupiter during the Shoemaker-Levy 9 collision. Nothing detected, but 40,000 blurry images obtained!

* 1994, Takehiko Wada, Ohno, Munetaka Ueno, MCBA, BDC, CSB--A 20cm infrared (JHK) camera was strapped to the side of the APT and used for 2.5 months to take images of the Galactic centre and LMC for a MACHO experiment.

* 1994, BDC, MCBA---Observations of stars in open clusters for variability.

During 1994, the telescope was employed mainly for the following astronomical research activities:

Stellar activity in open clusters and associations

Stellar activity describes the analogue of solar activity that is observed in many low-mass stars. Studies of stellar activity are useful for understanding the structure and heating of stellar atmospheres, and can help us learn more about stellar rotation, evolution, and angular momentum loss. Young stars possess the most intense activity. The most energetic stellar flares observed occur on pre-main sequence stars, and flare activity is prevalent in many open clusters. Pre-main sequence stars show relatively large photometric variations indicative of starspots covering significant fractions of their surfaces, and chromospheric plages similar to those in solar active regions have been identified.

With its wide field of view, and facility for long-term photometric monitoring of cluster stars in B, V, R and I colours, the APT is well suited to photometric studies of activity in star clusters. In addition, its observations can complement spectroscopic investigations done with other telescopes. The APT is being used to observe stars in Galactic open clusters and regions of star formation, with research focussed on the following topics:

Photometric and colour variability in pre-main sequence and young main sequence stars, and the role of starspots and accretion processes.

Obtaining flares light curves, energies and statistics, to resolve present ambiguities, and provide data for studies of the relationship between flare activity and the evolution of low-mass stars.

Surveying and explaining the systematic sequence in blue excesses observed among some very late-type, pre-main sequence stars.

Investigation of the dichotomy in rotation rates that develops when stars evolve from the pre-main sequence to the main sequence.

Photometry of galaxies

Imaging of relatively evolved and nearby clusters of galaxies are used to obtain integrated galaxy magnitudes in different colours, for comparison with similar surveys of very distant and hence young clusters obtained with large telescopes. Comparison of the two datasets will provide a direct measurement of the observational effects of galaxy evolution.

APT Details

LOCATION
Siding Spring Observatory, near Coonabarabran, NSW, Australia
Latitude.........................31d 16' 30'' South
Longitude........................149d 03' 40'' East
Altitude.........................1140 metres above sea level

MOUNTING
Declination South limit.........-75 degrees (software limit)
Declination North limit.........+29d 55' (software limit)
RA West and East limits.........Approx 4h from meridian (software limit)

OPTICS
Baker-Nunn, with modification by UNSW for use with a CCD
Optical design..................modified Baker-Nunn
Clear aperture..................0.5m
Focal ratio.....................f/1
Mirror diameter.................0.78m
Optically corrected flat field..5 degrees diameter
Filters.........................B, V, R, I, Clear; 5mm thick 80mm dia.

CCD (Old)
CCD sensor used.................EEV (GEC)
Precise plate scale.............9.41 arcsec/pixel
Pixel format....................770 columns x 1152 rows
Field of view covered by CCD....3 degrees (E-W) x 2 degrees (N-S)
Image format with overscan......800 columns x 1152 rows
Pixel size......................22.5 microns square
Readout speed settings..........slow fast
Readout noise...................4.7 e- 8.9 e-
Low gain........................20.4 e-/ADU 21.6 e-/ADU
High gain.......................5.1 e-/ADU 5.4 e-/ADU
Pixel read cycle time...........35 microsec 5.5 microsec
Vertical transfer cycle time....3.0 3.0
Typical frame readout time......50s 15s
Cooling.........................Thermoelectric stable at 200K after 15.5 minutes
Dark current....................<0.8 e/pix/s (0.73 e-/pix/s 300s exp)
A->D converter..................16 bits from 0 to +65535 counts
Bits per pixel..................-16 bits/pixel in FITS header (unsigned 16-bit integer)
Pixel electron well depth.......420,000 e-

Correspondence to Michael Ashley (mcba @ phys.unsw.edu.au)