Starlight Xpress SXV-M7 User Manual

Handbook for SXV-M7 Issue 1 June 2004

Starlight Xpress Ltd

SXV-M7

CCD camera user manual

Thank you for purchasing a Starlight Xpress CCD camera. We hope that you will be
very satisfied with the results. The SXV-M7 is a high-resolution cooled CCD camera,
especially designed for astronomical imaging. The SXV-M7 uses a Sony EXview
CCD, with 752 x 582 pixels in a 6.5mm x 4.8mm active area. EXview devices have
the greatest quantum efficiency of any interline transfer CCD currently available and
the use of high performance microlenses on the CCD surface gives the greatest
possible throughput of light to the pixels. This camera is a next generation version of
the parallel port driven MX716, but the use of an internal USB2 interface and the
addition of an external guide camera option makes it considerably more effective.

Please note that the SXV-M7 can be operated in several different imaging modes. The
easiest to use is ‘Fast’, which creates an image from a single exposure and so this is
the mode used in the operating instructions below. ‘Fast’ mode does give a slightly
reduced vertical resolution in the output image, but this is barely detectable unless
observing conditions are extremely good. ‘Progressive’ and ‘Interlaced’ modes will
be described later.

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Handbook for SXV-M7 Issue 1 June 2004

Please take a few minutes to study the contents of this manual, which will help you to
get the camera into operation quickly and without problems. I am sure that you want
to see some results as soon as possible, so please move on to the ‘Quick Start’ section,
which follows. A more detailed description of imaging techniques will be found in a
later part of this manual.

‘Quick Starting’ your SXV-M7 system

In the shipping container you will find the following items:

1) The SXV-M7 camera head.

2) A power supply module.

3) A 3 metre USB camera cable.

4) An adaptor for 1.25” drawtubes.

5) A CD with the ‘SXV_M7’ software.

6) This manual.

You will also need a PC computer with Windows 98SE, Windows 2000 or Windows
XP. This machine must have at least one USB port (ideally USB2.0) and at least 64
Megs of memory. If you intend to view the finished images on its screen, then you
will also need a graphics card capable of displaying an image with a minimum of 800
x 600 pixels and 65,000 colours. A medium specification Pentium with between
500MHz and 3GHz processor speed is ideal.

Connecting up:

Plug the 5 pin DIN connector into the socket on the power supply box, and plug the
power supply into the wall socket. The yellow LED on the power supply should light.

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Connect the miniature 4 way power plug to the socket on the rear of the camera and
screw the retaining ring into place. The LED on the rear of the camera will light a dim
yellow. The other connections should not be attached until after the software has been
installed.

Installing the software:

Switch on the computer and allow it to ‘boot up’. Once you have the system ready to
run, insert the program disk into your CD drive and select ‘Setup.exe’ if the disk does
not autostart. The initial installation is to set up the USB drivers required by the SXV
electronics. The files SXVIO.sys and Generic.sys are copied to your
Windows\System32\Drivers folder and SXV_M7.inf is copied to Windows\Inf.
After this, the program ‘SXV_M7.exe’ will be installed into your ‘CCD’ directory
and a new directory called ‘Autosave’ will now exist on the same drive. ‘Autosave’ is
where SXV_M7 will normally store its configuration file, ‘SXVM7.ini’, and any
image files, which are recorded using the ‘Autosave’ mode in SXV_M7 and saved in
FITs format.

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You now need to set up the camera control defaults (shown above), as follows:
Start SXV-M7 by clicking on the icon and select the ‘File’ menu. Now select ‘Set
program defaults’ and a window, which contains the various software settings, will
appear. Suggested starting defaults are as follows:

1) Background Image area Red (or as preferred)

2) Interlaced image smoothing On

3) FITS Unsigned Integer format Off

4) Star mask size (area used for photometry and guiding) 8 pixels

The other default settings are not important for current purposes and may be left as
the software start-up values for now.

Recording your first image:

We now have the camera and computer set up to take pictures, but an optical system
is needed to project an image onto the CCD surface. You could use your telescope,
but this introduces additional complications, which are best avoided at this early
stage. There are two simple options, one of which is available to everyone:

1) Attach a standard ‘M42’ SLR camera lens to the SXV-M7, using a 27mm spacer

to achieve the correct focal distance. M42 thread spacers are available from most
photographic stores, or from Starlight Xpress dealers.

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2) Create a ‘Pin hole’ lens by sticking a sheet of aluminium baking foil over the end

of the 1.25” adaptor and pricking its centre with a small pin.

If you use a normal lens, then stop it down to the smallest aperture number possible
(usually F22) as this will minimise focus problems and keep the light level reasonable
for daytime testing. The pin hole needs no such adjustments and will work
immediately, although somewhat fuzzily.

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Point the camera + lens or pinhole towards a well-lit and clearly defined object some
distance away. Now click on the camera icon in the toolbar of the SXV-M7 software
and the camera control panel will appear (see above). Select an exposure time of 0.1
seconds and press ‘Take photo’. After the exposure and download have completed
(between 1 and 3 seconds) an image of some kind will appear on the computer
monitor. It will probably be poorly focused and incorrectly exposed, but any sort of
image is better than none! In the case of the pinhole, all that you can experiment with
is the exposure time, but a camera lens can be adjusted for good focus and so you
might want to try this to judge the image quality that it is possible to achieve.

One potential problem with taking daylight images is the strong infrared response of
the SXV-M7 and this will cause ‘soft focus’ with camera lenses. Soft focus with
camera lenses is much reduced by keeping the aperture setting below F8. IR blocking
filters are available from various suppliers (True Technology, Edmunds etc.) and are
recommended for the best results.

If you cannot record any kind of image, please check the following points:

1) Is the power LED on?

2) Does the software indicate that the camera is successfully connected? An attempt
to take a picture will fail with an error message if the USB is not properly installed. In
this case, try unplugging the USB cable and then reconnecting it after about 5

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seconds. Restart the camera software and see if it can link now. If not, check in
Windows device manager (via ‘System’ in ‘Control Panel’) and see if the BlockIO
device is installed properly.

3) If you cannot find any way of making the camera work, please try using it with
another computer. This will confirm that the camera is OK, or otherwise, and you can
then decide how to proceed. Also check on our web site to see if there are any updates
or information about your camera software that might help. The message board might
prove useful to ask for help with getting your camera operating properly.

Our guarantee ensures that any electrical faults are corrected quickly and at no cost
to the customer.

Enhancing your image:

Your first image may now be reasonably good, but it is unlikely to be as clear and
sharp as it could be. Improved focusing and exposure selection may correct these
shortcomings, and you may like to try them before applying any image enhancement
with the software. However, there will come a point when you say, “That’s the best
that I can get” and you will want to experiment with various filters and contrast
operations. In the case of daylight images, the processing options are many, but there
are few that will improve the picture in a useful way.

The most useful of these are the ‘Normal Contrast Stretch’ and the ‘High Pass Low
Power’ filter. The high pass filter gives a moderate improvement in the image
sharpness, and the effects of image processing. This can be very effective on daylight
images. Too much high pass filtering results in dark borders around well-defined
features and will increase the ‘noise’ in an image to unacceptable levels, but the ‘Low
Power’ filter is close to optimum and gives a nicely sharpened picture, as above.

The ‘Contrast’ routines are used to brighten (or dull) the image highlights and
shadows. A ‘Normal’ stretch is a simple linear operation, where two pointers (the
‘black’ and ‘white’ limits) can be set at either side of the image histogram and used to
define new start and end points. The image data is then mathematically modified so
that any pixels that are to the left of the ‘black’ pointer are set to black and any pixels
to the right of the ‘white’ pointer are set to white. The pixels with values between the
pointers are modified to fit the new brightness distribution. Try experimenting with
the pointer positions until the image has a pleasing brightness and ‘crispness’.

At this point, you will have a working knowledge of how to take and process an SXV­M7 image. It is time to move on to astronomical imaging, which has its own, unique,
set of problems!

*********************************************************************

Astronomical Imaging with the SXV-M7

1) Getting the image onto the CCD:

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It is fairly easy to find the correct focus setting for the camera when using a standard
SLR lens, but quite a different matter when the M7 is attached to a telescope! The
problem is that most telescopes have a large range of focus adjustment and the CCD
needs to be quite close to the correct position before you can discern details well
enough to optimise the focus setting. An additional complication is the need to add
various accessories between the camera and telescope in order that the image scale is
suitable for the subject being imaged and (sometimes) to include a ‘flip mirror’ finder
unit for visual object location.
A simple, but invaluable device, is the ‘par-focal eyepiece’. This is an eyepiece in
which the field stop is located at the same distance from the barrel end, as the CCD is
from the camera barrel end.

When the par-focal eyepiece is fitted into the telescope drawtube, you can adjust the
focus until the view is sharply defined and the object of interest is close to the field
centre. On removing the eyepiece and fitting the CCD camera, the CCD will be very
close to the focal plane of the telescope and should record the stars etc. well enough
for the focus to be trimmed to its optimum setting

Several astronomical stores sell par-focal eyepieces, but you can also make your own
with a minimum of materials and an unwanted Kellner or Plossl ocular.
Just measure a distance of 22mm from the field stop of the eyepiece (equivalent to the
CCD to adaptor flange distance of the camera) and make an extension tube to set the
field stop at this distance from the drawtube end. Cut-down 35mm film cassette
containers are a convenient diameter for making the spacer tube and may be split to
adjust their diameter to fit the drawtube.

Another popular solution to the ‘find and focus’ problem is the ‘flip mirror’ unit.
These operate on a similar principle to the single lens reflex camera, where a hinged
mirror can drop into the light path and reflect the image through 90 degrees into a
viewing eyepiece.

In this case, the camera and eyepiece are made par-focal with each other by locking
up the mirror, focusing the camera on an easy object, such as a moderately bright star

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and then flipping the mirror down to view the same star with the eyepiece. Once the
eyepiece has been locked into the correct position, you can use it to focus on the
image by lowering the flip mirror and operating the telescope focus wheel until the
image is sharp. When the mirror is raised, the image will fall onto the CCD surface
and should be accurately in focus. Most flip mirror units allow several adjustments to
be made, so that the image can be centred properly in the eyepiece and CCD fields,
which are not necessarily coincident when you first buy your unit!

Opinions vary as to the utility of flip mirrors. They are a convenient way to find and
focus, but they add quite a bit of extra length between the camera and telescope. This
can be very inconvenient with Newtonians, and not a lot better with SCTs, especially
if the assembly is somewhat flexible. They also make it difficult to use a focal reducer
with your camera, as the rapidly converging light cone from a reducer cannot reach all
the way through the flip mirror unit to the CCD surface. If you are using one of the
popular F3.3 compressors for deep sky imaging, you will NOT be able to include a
flip mirror unit in front of your camera and a par-focal eyepiece is your best option.

Whichever device you use, it is necessary to set up a good optical match between your
MX7 and the telescope. Most SCTs have a focal ratio of around F10, which is too
high for most deep sky objects and too low for the planets! This problem is quite easy
to overcome, if you have access to a telecompressor (for deep sky) and a Barlow lens
for planetary work. The new Meade F3.3 compressor is very useful for CCD imaging
and I can recommend it from personal experience. It does not require a yellow filter
for aberration correction, unlike some other designs, so it can be used for colour
imaging. Barlow lenses are less critical and most types can be used with good results.
However, if you are buying one for CCD imaging, I recommend a 3x or 5x amplifier,
or the planets will still be rather small in your images. As a guide, most CCD
astronomers try to maintain an image scale of about 2 arc seconds per pixel for deep
sky images. This matches the telescope resolution to the CCD resolution and avoids
‘undersampling’ the image, which can result in square stars and other unwanted

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effects. To calculate the focal length required for this condition to exist, you can use
the following simple equation:

F = Pixel size * 205920 / Resolution (in arc seconds)

In the case of the SXV-M7 and a 2 arc seconds per pixel resolution, we get

F = 0.0082 * 205920 / 2 = 844mm

For a 200mm SCT, this is an F ratio of 844 / 200 = F4.22, which is easily achieved
with the Meade converter and appropriate extension tube (as supplied with the
converter). Moderate deviations from this focal length will not have a drastic effect
and so any F ratio from about F3.3 to F6 will give good results.

The same equation can be used to calculate the amplification required for good
planetary images. However, in this case, the shorter exposures allow us to assume a
much better telescope resolution and 0.25 arc seconds per pixel is a good value to use.
The calculation now gives the following result:

F = 0.0082 * 205920 / 0.25 = 6754mm

This is approximately F34 when used with a 200mm SCT and so we will need a 3.4 x
Barlow lens. Such lenses are not available, but the common 3x version will be good
enough for all practical purposes.
An accessory that you will find valuable is the ‘M42 to T’ adaptor. These are short
tubes that carry an external M42 thread at one end and an internal ‘T’ thread at the
other end, and are available from most photographic supply shops. The T thread is the
same diameter as the M42 (42mm x 1mm) thread but has a pitch of 0.75mm and is
used for many astronomical accessories, such as telecompressors. An M42 to T
adaptor will allow you to easily interface with virtually any device in the astronomical
catalogue.

Achieving a good focus:

Your starting point will depend on the focus aids, if any, which you are using. With
the par-focal eyepiece, you should slip the eyepiece into the drawtube and focus
visually on a moderately bright star (about 3rd magnitude). Now withdraw the
eyepiece and carefully insert the camera nosepiece until it is bottomed against the
drawtube end and lock it in place. With the flip mirror unit, all that is needed is to
swing the mirror down and adjust the focus until the star is sharply defined and
centred in the viewing eyepiece. Now lift the mirror and you are ready to start
imaging.

SXV_M7 has a focus routine that will repeatedly download and display a 100 x 100
pixel segment of the image at relatively high speed. This focus window may be
positioned anywhere in the camera field and can be displayed with an adjustable
degree of automatic contrast stretching (for focusing on faint stars). To use this mode,
start up the software and select the MX camera interface (File menu). Set the camera
mode to ‘Fast’ and select an exposure time of 1 second. Press ‘Take Picture’ and wait
for the image to download. There is a good chance that your selected star will appear

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