Starlight Xpress CoStar User Manual

CoStar handbook Issue 1 May 2011

Handbook for the SX ‘CoStar’ guide camera

Thank you for purchasing a Starlight Xpress ‘CoStar’ guide camera. We hope that you will be very
pleased with the performance of this product.

The CoStar is a very compact guider which is powered and operated via a single USB2.0 computer
connection. It also provides an opto-isolated output connection for direct control of most mounts, via
their ‘Autoguider’ sockets. This output is compatible with the ‘ST4’ style of RJ12 connection and
supplies 4 ‘pull down’ direction lines and a common return. Alternatively, you may send the mount
control signals via a serial connection from the guider control computer.

The CoStar utilises a sensitive Aptina MT9M001 mono Cmos imager with an array of 1304 x 1024
pixels in a ‘half-inch’ format. Although the chip is not cooled, it has a low dark signal and readout
noise, so it can be used to guide on faint stars that are beyond the reach of webcams and older CMOS
chip based guide cameras.

The CoStar specification:

Sensor - Aptina MT9M001 Cmos monochrome imager
Pixel count - 1304(H) x 1024(V)
Pixel size - 8.2 x 8.4uM
Barrel size - 32mm dia. x 60mm long (1.25 inch eyepiece push fit size)
Barrel thread - 1 inch x 32TPI ‘CS’ mount lens thread
Input connection - ‘Mini B’ USB socket for USB2.0
Output connection - 5 way JST ‘ZH’ style 1.5mm pitch plug to RJ12 autoguider plug
Output type - Opto-isolated 4 lines (N,S,E & W) pull down with common return line
Download rate - Approx. 10 frames per second in subframe mode

Installing the CoStar:

A new installation will require the driver files SXVIO.sys and Generic.sys, plus the SXVIO_CoStar.inf
file. If you run the ‘Setup.exe’ file on the supplied CD, it will install the drivers and operating software
automatically. If you are installing manually, copy these files into a convenient folder on drive C and
then connect the USB cable to the CoStar. Point the installer at this folder when it asks for the location
of the drivers and you should see it set up the hardware as a ‘BlockIOClass’ device in Device Manager.

CoStar handbook Issue 1 May 2011

The CoStar control software is CoStar.exe and the latest version may be downloaded from the Starlight
Xpress web site (http://www.starlight-xpress.co.uk), if necessary. Copy the exe file and dlls into a
folder on drive C and run the exe file to start the software. Alternatively, both ‘PHD’ and ‘Nebulosity2’
support the CoStar and may be preferred. An ‘ASCOM’ driver is available for use with the CoStar (and
other SX cameras). This allows you to use Maxim DL and other ASCOM compatible software, if you
wish. Please visit http://www.daddog.com/ascom/sx/index.html to download the latest version.

The USB and guider output connectors

Using the CoStar:

The CoStar is generally used with a separate guide telescope, or via an off-axis guider. It is designed to
be inserted into a standard 1.25” focuser assembly, but also has a 25mm ‘C’ type camera lens thread in
the front to allow standard CCTV lenses to be attached. Please note that the chip to lens distance is
only 12.5mm and so a ‘CS’ to ‘C’ extension will be needed to permit a standard C lens to reach focus.
Lenses designed for ‘CS’ mount cameras will focus without an extension tube, but many of these
lenses cannot fully illuminate a half-inch format chip, so take care when selecting a lens for this
purpose.

A typical set up might consist of an inexpensive 80mm F5 refractor ‘piggybacked’ onto an SCT, with
the CoStar fitted directly into its focus barrel. Many such telescopes are designed to be used with an
inverting prism ahead of the eyepiece and so the focuser may be too short when the CoStar is inserted
directly. In this case, an extension tube may often be made from a cheap Barlow lens assembly with the
lens removed. This configuration can be seen in the picture below.

CoStar handbook Issue 1 May 2011

The CoStar attached to an 80mm F5 guide ‘scope

The focal length of your guide telescope is not especially critical for good guiding, as the guiding
software searches for the ‘centroid’ of the guide star image and can resolve shifts of far less than 1
pixel. Using a guide scope with a relatively short focal length (between 300 and 500mm) makes guide
star finding very easy and this is a recommended setup for general purpose guiding.

The control of your telescope mount will depend on what inputs are provided. The CoStar output
connector supplies 4 pull-down lines and a common return line to simulate an ‘ST4’ style autoguider
output. The lines are isolated from the CoStar electronics by opto-isolator chips and so there is no risk
of damage when connecting the outputs to mounts with unprotected electronics. A standard ‘RJ12’
style output lead is supplied with the CoStar and this may be connected to any ST4 compatible
autoguider input socket on the mount. It is also possible to guide by using serial data from the computer
to an RS232 input on the mount, but this will be covered later and is less effective than the direct
hardware connection.

The guiding mode is fixed at 1x1 binned, as Cmos imagers cannot operate in a true 2x2, or higher,
binned mode.