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SXVF-H16
User Manual
27 pgs2.86 Mb0

Starlight Xpress SXVF-H16 User Manual

Handbook for the SXVF-H16 Issue 1 August 2006
Starlight Xpress Ltd
SXVF-H16
CCD camera user manual
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Handbook for the SXVF-H16 Issue 1 August 2006
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 SXVF-H16 system
In the shipping container you will find the following items:
1) The SXVF-H16 camera head.
2) A power supply module and cable.
3) A 3 metre USB2 camera cable.
4) An adaptor for 1.25” drawtubes.
5) An adaptor for 2” drawtubes and ‘Pentax’ thread lenses.
6) A guider cable for ‘ST4’ style mount guiding inputs.
7) A CD with the ‘SXVF_H16’ software.
8) This manual.
You will also need a PC computer with Windows 98SE, Windows 2000 or Windows XP. This machine must have at least one USB2.0 port and at least 256 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 in a minimum of 1024 x 768 pixels and 24 bit colour. A medium specification Pentium with between 1GHz and 3GHz processor speed is ideal. Please note that the SXVF-H16 is not designed for USB1.1 operation and will give inferior results if used on USB1.1.
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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Handbook for the SXVF-H16 Issue 1 August 2006
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 SXVIO_H16.inf is copied to Windows\Inf. After this, the program ‘SXV_H16_usb.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_H16 will normally store its configuration file, ‘SXVH16.ini’, and any image files, which are recorded using the ‘Autosave’ mode in SXV_H16 and saved in FITs format.
Please note that the version of SXVIO.sys supplied with the H16, is an improved issue that should replace any copy that is already resident on your machine. Failure to update will result in a tendency for white spots and streaks to appear in your images.
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Handbook for the SXVF-H16 Issue 1 August 2006
You now need to set up the camera control defaults (shown above), as follows: Start SXV-H16 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) FITS Unsigned Integer format Off
3) Star mask size (area used for photometry and guiding) 8 pixels
4) Telescope guiding to autoguider socket
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 SXVF-H16, using the 27mm
spacer to achieve the correct focal distance.
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Handbook for the SXVF-H16 Issue 1 August 2006
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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Handbook for the SXVF-H16 Issue 1 August 2006
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-H16 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 SXVF-H16 as this will cause ‘soft focus’ with camera lenses. Soft focus is much reduced by keeping the aperture setting below F8. Also, IR blocking filters are available from various suppliers (True Technology, Edmunds etc.) and are recommended for the best results when using a lens.
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 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 BlockIOClass device is installed properly. If all looks OK, try checking the ‘Disable VID/PID detection’ in the ‘Set program defaults’ menu and try again.
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Handbook for the SXVF-H16 Issue 1 August 2006
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 SXVF-H16 image. It is time to move on to astronomical imaging, which has its own, unique, set of problems!
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Astronomical Imaging with the SXVF-H16
1) Getting the image onto the CCD:
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 H16 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
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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 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
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Handbook for the SXVF-H16 Issue 1 August 2006
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 H16 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 Meade F6.3 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 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)
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