far laboratories - Astronomy Technology Today

My observatory
control scheme
is not slick or
powerful, and
it’s definitely
not suitable for
true remote
operation, but it
pleases me to
no end!
SIMPLE REMOTE
OBSERVATORY
OPERATION
By John Crilly
A quick search through the magazines
or on the Internet will reveal that there are
some very impressive amateur observatory
installations out there. Some incorporate a
very high degree of automation and system
integration involving not only mounts and
cameras, but also roofs, domes, weather stations,
rain detectors and other ancillary
equipment. Some such installations are sufficiently
automated to permit true remote
control, with no physical visit to the site
required for normal operation.
I’d like to describe some of the tools
and techniques that I have found useful in
my much less ambitious implementation of
remote observatory control. For my purposes,
I need to be able to operate the mount
and cameras from within my house, about
30 feet from the observatory. Because it’s so
near, I don’t mind going out and manually
operating the roof opening mechanism and
powering up and initializing the mount and
cameras to begin a session (and, of course, a
second visit to shut everything down and
close the roof when I’m finished). What I do
want is a way to sit inside, safe and warm,
and take images. To achieve this, I need to
be able to slew the mount to the desired target,
check and correct camera focus, and
capture a series of images using selected filters.
Finally, I need to be able to transfer the
resulting image files into my home computer
for processing. I need a setup which permits
frequent gear changes without having
to redo cables or software setups (I switch
things around frequently).
Step one was to install a telescope
mount capable of being controlled by a PC.
The first such mount installed here was a
CGE by Celestron. Like all subsequent
mounts I’ve used, its slews were controlled
by a serial connection to the PC and it was
autoguided either directly from an SBIG
camera or from the PC via a Shoestring
Astronomy GPUSB adaptor (more about
this and the other Shoestring products that
made this project possible will appear later).
I’ve also used Meade LX200 Classic and
LX200GPS mounts in this system, as well
as an RCX400 and an LXD750. The
LXD750 is in there now; I’m in the process
of updating to a Takahashi EM-200 mount.
Thanks to ASCOM, all of the various
mounts integrate painlessly with Software
Bisque’s TheSky software for telescope control.
I’ve also used Starry Night Pro and
Cartes du Ceil with no problems.
If the mount is a GEM, as I currently
use, I also install optical tubes. My
preference these days is two (or three) APO
refractors of differing focal lengths, mounted
side by side. I’ve also used a 7-inch
Maksutov-Cassegrain, a 6-inch Maksutov-
Newtonian, Schmidt-Cassegrains from 10
inches to 14 inches, and a 12-inch Meade
RCX – but always with an APO refractor.
The current setup is a TMB130SS and an
Astronomy TECHNOLOGY TODAY 59

SIMPLE REMOTE OBSERVATORY OPERATION
A&M 105/650 but there’s a Takahashi
FSQ-106 on the way and it’ll replace the
A&M for imaging.
Step two was to set up a PC in the
observatory and link it to my home computer.
I use a Dell desktop with a 2.0 Ghz
P4 chip and 1 GB of RAM and Windows
XP. I have never experienced any driver or
software incompatibility issues with this
setup. I’ve been meaning to update that PC
but I need to wait until I am sure that
everything I use is compatible with Vista. In
my case, the observatory is close enough to
my house that the wireless network I
already use easily reaches the observatory
computer. If that hadn’t been the case I’d
have installed a single Ethernet cable from
my network server to the observatory and
the link would probably be a little faster –
but the speed requirements for this system
are modest. The only other external cabling
required for my setup is a power feed to the
observatory. I use either VNC or www.logmein.com
to capture the observatory computer
from a PC in the house.
To avoid a mass of USB cables between
the PC and the mount, I use a pair of powered
USB hubs at the pier. I run two USB
cables from the PC to the pier. One goes to
a hub that is intended to have only USB2
devices attached; the other to the second
hub which is connected to USB devices.
This avoids the conflict that occurs when
connecting a mix of USB and USB2
devices to a single USB2 hub; when that is
done, all the communication slows down to
USB speeds. I’m not currently using any
USB2 devices so it’s not an issue for now,
but I do change gear frequently.
Step three was to install cameras and
integrate them. I have used a variety of
cameras by SBIG (currently an ST-10XEI),
a Canon 300D DSLR, and various guide
cameras (currently a Meade DSI Pro). All
the cameras use the PC USB port for control
and for download of image files. The
Canon requires an additional PC connection
for shutter control, and I use a
Shoestring Astronomy DSUSB for that
60 Astronomy TECHNOLOGY TODAY

SIMPLE REMOTE OBSERVATORY OPERATION
purpose. As mentioned above, when guiding
with the DSI Pro, another Shoestring
adaptor is required to interface the PC to
the mount’s autoguide port. Software used
is CCDSoft for the SBIG camera, PhD
Guiding for the DSI Pro, and Images Plus
for the Canon.
I have used a variety of remote DC
focus motors, controlled via the PC
through either the Meade mounts (which
all incorporate DC focus motor controllers)
or through yet another Shoestring
Astronomy device, the FCUSB. The
FCUSB connects to a USB port and drives
a DC focus motor under either the provided
manual focus software, or in autofocus
mode using Maxim/DL or CCDSoft and
provided ASCOM drivers. I have only fiddled
with autofocus to date but I intend to
use it more in the future. My next imaging
refractor will be an FSQ-106 with a
Robofocus controller and motor (they are
in transit but not yet here). I plan to use
autofocus with that setup most of the time,
as the Robofocus includes position
encoders and a temperature sensor, both of
which make it supremely suitable for autofocus.
Now is a good time to mention that
all the cables installed to this point must be
carefully dressed; if they tangle during
remote operation it will at best louse up an
image and at worst it will break something!
A typical session begins with the obligatory
trip out to the observatory. I open the
roof, power up the camera(s) and mount,
and initialize the mount. I install the guide
camera on the telescope I’ll be using for
guiding that night, and the imaging camera
(either the Canon or the SBIG) on the telescope
I’ll be using for imaging. I set the
focusers to their approximate positions
(from experience). I then go back inside to
wait for dark and for the temperature to
equalize. When I’m ready to begin I fire up
the home PC and link to the observatory
PC. I start TheSky software and link that to
the mount. I start my camera software
(either CCDSoft or Images Plus) and link
that to the camera I’ll use that night. I start
PhD Guiding and link that to the DSI Pro
and to the mount’s autoguide port.
I then slew the telescope to a fairly
bright star and take test images with both
cameras. I fine tune the focus of each, then
slew away from the bright star and, using
longer exposures, critically focus the imaging
camera on dimmer stars. So long as the
telescope is cooled down, I probably won’t
have to fiddle with either focus again – but
I keep an eye on images from both cameras
as the evening progresses.
Next, I slew the mount to the first target
for the night. I take a test shot with the
imaging camera to ensure that the object is
framed to my satisfaction and adjust the
mount if necessary. Then I start the guide
camera and ensure that there’s an appropriate
guide star available (with the DSI Pro at
reasonable focal lengths, there always has
been). I select a guide star and permit PhD
Guiding to self-calibrate. When using a selfguiding
SBIG camera it’s usually even easier
– but I found that guiding through narrowband
filters caused problems and I
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62 Astronomy TECHNOLOGY TODAY

SIMPLE REMOTE OBSERVATORY OPERATION
sometimes like to shoot narrowband. The
use of a separate guide camera eliminates
these problems and I always have a second
telescope available for guiding, so these days
I just do it this way.
Now it’s time to set up the camera control
software to take a sequence of images.
When using the Canon I first take some
short dark frames and bias frames with the
telescope capped. I can use these later to
calibrate the images. I already have a library
of flat frames for each setup, but the darks
and bias shots must be taken at the same
camera temperature as the light frames so
it’s best to grab those now. Then I tell
Images Plus how to name the files, and how
many frames of what duration I want –
then off it goes. With the SBIG it’s somewhat
different. Because I always cool it to
the same temperature, I can tell CCDSoft to
calibrate each frame as it is taken, using
library darks, flats, and bias frames. That
way I don’t need to calibrate them later. I
tell it how to name the files, and how many
frames of what duration to take using
which filters. Either the CFW-8 filter wheel
I’ve been using or the Homeier filter wheel
I’m switching to is under CCDSoft control.
With either camera, I can relax now, just
checking the resulting images for focus and
cloud intrusion from time to time. When
that image is completed, I stop the autoguiding,
slew to the next target, and begin
again. After the last target is completed, I
shut down all the programs and head out to
the observatory to power everything down
and close the roof. Once in the house, I use
Images Plus and Photoshop to process the
resulting images. Many of the images I’ve
captured here may be seen at
www.urbanobservatory.com, along with
construction photos of the observatory
itself.
I have mentioned a number of devices
which make this operation possible, as well
as inexpensive and easy. I’ll now describe
some of them more fully, and tell you where
they can be obtained.
First, Shoestring Astronomy. They are
online, at www.shoestringastronomy.com
(surprise!). Their GPUSB autoguide port
device ($66) is widely used, and all the popular
autoguide software knows how to talk
to it. Connect it to a USB port and to a
mount’s autoguide port via the available,
inexpensive cable ($4), and it’s ready to use.
That cable is compatible with nearly every
mount out there. Two exceptions are the
Vixen SS2K, which uses the same connector
but with a strange pinout, and the
Takahashi Temma controller (used on all of
their PC-compatible mounts), which uses a
DIN connector. Shoestring offers inexpensive
adaptor cables ($15) for both. To use a
DSLR for long exposure images, a shutter
control interface is required. Shoestring’s
DSUSB ($66-$75) takes care of this. Again
connect this device to a USB port and to a
DSLR using the available interface cable
($4). A few DSLR cameras use an oddball
connector and for use with those,
Shoestring offers a cable modification serv-
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Astronomy TECHNOLOGY TODAY 63

SIMPLE REMOTE OBSERVATORY OPERATION
ice ($15). To remotely control a standard
DC focus motor you’ll want their FCUSB
interface ($70). A USB connection and an
available focus motor cable ($6-$8) plus
their driver software (free) will do the trick.
If you have autofocus software available,
their ASCOM driver (free) will connect to
that. I’m not affiliated with Shoestring
Astronomy (I paid normal retail for all of
these items), and I didn’t intend for this to
read like an SA ad – but I use their stuff a lot
and recommend it whenever I can. This project
would have been more difficult and/or
more expensive without these products.
The other required devices are more
generally available. Powered USB2 hubs are
everywhere for $20. SBIG’s motorized filter
wheel is $595 without filters from any dealer.
The DSLR and SBIG cameras are also
widely offered. The DSI Pro has been discontinued
but the DSI Pro II is still available
and it’s even better. Windows-compatible
PC desktops are all over the place. Both
VNC and www.logmein.com are free
(though if you need to transfer files you’ll
need the pay version of logmein). DC focus
motors are generally available for $50-$200
and the Robofocus is about $500. Images
Plus is around $200, TheSky is $150-$300,
and CCDSoft is $350, but can be downloaded
at no charge if you own an SBIG
camera. You can spend whatever you feel
like on the camera(s), mount and optical
tube(s) and except for autofocusing, there’s
free software available for every function
mentioned here.
The project may sound complicated,
but it wasn’t. It all went in gradually, one
piece at a time, as I found the need to
remotely control each function. My
observatory control scheme is not slick or
powerful, and it’s definitely not suitable for
true remote operation, but it pleases me to
no end!
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Astronomy TECHNOLOGY TODAY 65