Mar 2014: PEST has moved
PEST has moved to what should be its permanent location.
Same roll-off structure but much better access to the sky, especially the
western and northern horizons.
PEST has moved.
The observatory has now moved to a new location.
I now have a more unobstructed western horizon, but otherwise there has
been no major change. Here's a more detailed description of the observatory and photometry
October 2010: My backyard observatory is now running.
In 2010, I acquired a 12"
LX200GPS SCT, and built an observatory to house it. With the larger
telescope it is just not practical to set up, polar align for each night's
observation, and then stow away in the morning. In addition, for
high precision photometry, numerous flat frames must be taken, and to
avoid having to take flats for each night's observations, the camera needs
to be kept in place between nights.
I had thought that the solution
would be to build a trolley so that the scope and tripod could be wheeled
into and out of my shed. I did build a trolley (visible as the
wooded frame at the base of the tripod in the picture below), but my shed
would have needed modification and this turned out to be more difficult
than I expected. I then looked around for a kit shed which I could
modify so that the roof would roll off. This was another dead end as
all of the sheds I looked at were either not quite the right size, or
would be difficult to modify - most rely on a fixed roof for rigidity.
the end I designed and built a roll-off building out of wood sections and
plywood. It took two weeks to build and the result is very
satisfactory. The shelf inside serves as a desk, but is
also important structurally because it provides rigidity to the structure.
I recently added an Optec TCF-Si
focuser and together with observatory automation software
CCD Commander, plate solver
Pinpoint and focus
I have an almost completely automated set-up. The only exceptions
are that I have to open the observatory doors and roll the building off
A normal night's observation now
starts with the observatory being rolled back, power and computer switched
on and CCD Commander started. CCD Commander then runs a script that
starts CCDSoft, connects to the camera then starts camera cooling.
The script waits for the sun to be at a specified angle below the horizon
then starts an automatic sky flat sequence. Once this is finished
there is a further wait for darkness, then a slew to a specified arbitrary
location above the eastern horizon. An image is then taken, plate
solved, and the scope is synched to the coordinates thus obtained.
This step is probably not strictly necessary but since this takes place at
the start of the observation program for the night it gives me an
opportunity to confirm that scope pointing is accurate before leaving the
rest of the sequence to take place unattended. As the sky brightens
just before dawn (specified in terms of sun altitude), CCD Commander will
stop data acquisition, then wait for further light before starting to take
sky flats. When the sky is too bright for any further flats, CCD
Commander parks the scope. All I have to do when I wake up is copy
the night's data onto a USB stick, turn off the computer and close the
Exoplanet transit detections
A shallow transit of 6 mmag in a mag 11.7 star -
HAT-P-26b, on 1st March 2011, and the corresponding transit system
geometry compared to our Sun and Jupiter.
This is a good illustration of the effect of the
atmosphere on photometric precision. These observations were made at
airmass between 2.2 and 1.4. This is quite large - at my latitude
this star does not get very high. Despite the HAT-P-26 being
brighter than WASP-19 (mag 11.7 vs 12.3) precision is worse (2.9 mmag vs
An example of a transit observation made automatically
8th Feb 2011, of WASP-19b. Transit depth 25 mmags. Note that
with the 12" scope, a precision of 2 mmags was achieved for a star of mag
12.3, more than a magnitude dimmer than the C9.25 observation below.
For comparison, a transit
observation made with the C9.25 scope, on 3rd May 2010, of WASP-15b. Depth of transit is just
10 millimags. Precision of 2 mmags achieved.
These charts and transit model fitting
were done at the
Exoplanet Transit Database
(ETD) website. PEST stands for Perth Exoplanet Survey Telescope,
which is what I am calling my humble backyard setup!
My first exoplanet transit
detection. An important milestone towards what
I hope will be the discovery of new transiting exoplanets! The chart
below shows the 0.02 (2%) magnitude increase in brightness of the parent
star of the giant exoplanet WASP-17b as it exits from transit. The
end of transit was as predicted by the
Exoplanet Transit Database,
at HJD 2455265.27 (9th March 2010 UT). The camera was my new ST-8XME
and the scope the Celestron C9.25.
This was a relatively easy
detection. There were numerous problems with the observation run -
WASP-17 was just rising so that the start of the data set was obtained at
low elevation (high airmass), and guiding was lost just after end of
transit. Nevertheless the 0.02 mag transit is well within the
internal precision of the observations. Since then, I have been able
to achieve improved photometric precision such that a 3 millimag (0.3%)
transit of a magnitude 11 star should be detectable.
Supernova Search Program
In February 2007 I started a supernova search
program using my C9.25 telescope, Vixen GPD mount, ART 285 CCD camera and
several pieces of software which I wrote. These consist of;
1. GalaxyGen - a script to generate a list of
galaxy targets suitable for a night's observing run. This also
generates a list that can be used to download reference DSS images (see
below). The main issue the search algorithm has to account for is
that my polar alignment (non permanent mount) is not perfect, so that a
large excursion away from the initial alignment point in terms of azimuth
and altitude will lead to inaccurate pointing and failure to acquire the
target. This is overcome by picking targets within a narrow band of
declination, but with increasing RA through the observing run, such that
the telescope always points to approximately the same alt-az point.
2. TargetPoint - a script that controls the
mount and camera and successively points the telescope to each galaxy on
the list, acquiring a set number of images of each target.
3. Examiner - a script that enable quick
comparison of these images to reference images downloaded from the
Digitized Sky Survey (DSS).
Typically between 150 to 200 galaxies can be
observed in an automated overnight run. Using individual 20s
exposures, supernovae down to mag 17 should be detectable.
Proof of concept was achieved when a supernovae was
detected in PGC51820 (ESO385-32) on 14th March 2007. Subsequent
checking revealed that this SN had been discovered about a month
previously and is designated SN2007X. For more information on the
search program, see the Supernova Search page.
I recently acquired an SBIG ST-8XME
CCD camera with which I am doing mainly photometry.
The astrophotography on these pages
were taken with a
home-assembled CCD camera, the
This is a cooled 16-bit camera based on the 1.4 Megapixel Sony ICX285AL
chip, as well as with a Digital SLR (Canon
EOS300D), modified using a procedure
described by Terry
Gary Honis. The modification involves removing the internal IR-cut filter which severely reduces
the camera's sensitivity to the important
Some words of warning - making
this modification obviously invalidates your camera warranty. There
is also a fair bit of fine work involved and you run a real risk of
ruining your camera! I had to open up the camera and readjust some
connections 3 times, before the camera would work properly again. I
did not replace the original filter with a less aggressive IR cut filter,
nor another piece of glass, so the camera now does not auto-focus properly
and, because of it's response to IR, its colour rendition is severely
compromised for normal photographs. You have been warned...
A more complete set of images from the DSLR is at the
A summary of my equipment. I use an Orion 80ED
refractor, a Celestron C9.25 Schmidt-Cassegrain, usually
used with a x0.63 focal reducer, and a
Vixen GPD mount with
SkySensor 2000 PC. The Go To facility makes for very easy target
||The Trifid Nebula in
NGC 6726 with globular cluster NGC 6723
around NGC 6559 in Sagittarius.
||NGC 6334, the Cat's
Paw Nebula in Scorpius.
|NGC6164-5 in Norma
||NGC 6188 in Ara
||LRGB composite of the Eta Carinae
|IC 2944, LRGB - trying for a more
natural colour balance.
||NGC 3576 in Carina,
||NGC 3576 in Carina, with the
|The main part of the Eta Carinae
Nebula, H-alpha with the 80ED and ART285. Very good guiding
and conditions, so apologies as I've posted a large image here...
||The southern part of
the Eta Carinae Nebula.
|| Thor's Helmet
Nebula in H-alpha, with the Orion 80ED and ART285 camera.
|First light with an Orion 80ED.
A closer view of the optical performance of this scope.
||NGC 6888, The Crescent Nebula in
Looking through the Galactic bulge to the other side of our Galaxy.
|The Trifid Nebula
(M20) - RGB / H alpha composite.
||A colour/ H alpha composite of the
Omega Nebula, M17.
||A colour/ H alpha composite of the
Eagle Nebula, M16.
|The Dumbell Nebula, M27, a
planetary nebula in Vulpecula. Set in a very rich star field.
||First attempt at a composite H
alpha / RGB image of the Lagoon Nebula.
||Eagle Nebula, and open
cluster M16. Site of the "Pillars of Creation".
|The Omega (or Swan) Nebula, M17
in hydrogen alpha. Nearly 2 hours total exposure!
||The region around Eta
Carinae in hydrogen alpha. This is a mosaic of 4 frames that
extends about 2 deg of sky lengthwise.
||The Trifid Nebula (M20) in
hydrogen-alpha. Only the emission part of the nebula is visible,
the light of the reflection (blue) nebula being almost completely
blocked by the filter.