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Handbook for the SXVR-M25C

Issue 1 June 2009

16

Relatively little nebulosity is visible at this time, but it will be revealed later. If you
zoom in on the raw image, you will see that it has the regular grid of brighter and
darker pixels, caused by the Bayer matrix filter grid on the CCD.

Now apply the colour synthesis routine, using the same offsets that gave good results
with the daylight image tests.

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Summary of Contents for SXVR-M25C

Page 1: ...r astronomical imaging It is a third generation version of the very popular SXV M25C and incorporates many substantial improvements and extra features These include a built in fully programmable USB 2 super fast computer interface an autoguider control port and output and optional integrated dual serial ports for filter wheel and telescope control It also includes a CCD temperature monitoring circ...

Page 2: ...t section which follows A more detailed description of imaging techniques will be found in a later part of this manual Quick Starting your SXVR M25C system In the shipping container you will find the following items 1 The SXVR M25C camera head 2 A universal AC power supply module 3 A USB camera cable 4 An adaptor for 2 drawtubes and M42 Pentax thread lenses 5 A guider output to guider port lead 6 ...

Page 3: ...it for Windows Explorer to open with the list of folders on the ROM Now find the SXVR M25C folder and run the SETUP EXE file that it contains this will initiate the self install software which will guide you through the process of installing the SX camera software SXV_M25C_usb exe onto your computer Now connect the USB cable to the socket on the camera rear panel Windows will report Found new hard...

Page 4: ...e shows as faulty try clicking on it and selecting properties and then update driver Following the on screen instructions will allow you to re select the correct inf file SXVIO_M25C_325 inf and driver files SXVIO sys and generic sys which should fix the problem Now connect up the power supply and switch it on The supply is a very efficient switch mode unit which can operate from either 110v or 220...

Page 5: ...onths Under indoor conditions the low airflow will limit the cooling capability and you should use a set point of no lower than 5C for stable cooling You can determine the optimum settings for your camera and ambient conditions when you have some experience of using the system but do not try to operate at extreme cooling when the air temperature is high Recording your first image We now have the c...

Page 6: ...of the 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 ...

Page 7: ...re that the power indicator lamp is on and that the cables are properly home in their sockets 2 If the screen is completely white the camera may be greatly overexposed Try a shorter exposure time or stop down your lens See if covering the lens causes the image to darken 3 If the USB did not initialise properly the camera start up screen will tell you that the connection is defective Try switching ...

Page 8: ...is control panel contains several options for correcting colour bias and noise 1 Daylight Image If an unfiltered lens is used the infra red content of the light will tend to produce a Green Blue shift in the balance A partial correction of this bias is provided by selecting this option but the best option is to use an infra red blocking filter when taking daylight shots see 5 below 2 Light Polluti...

Page 9: ...sise fine details Most useful for sharpening planetary images but will also increase the noise content I suggest that you switch on the Colour smoothing filter and the Anti alias filter you can experiment with the other options as you gain more experience Now click on Create image and you should see that the grid pattern disappears and is replaced by colour image data If the colour is roughly corr...

Page 10: ...nd the start of the main burst of histogram data or you will introduce colour errors into low saturation parts of the image Just move the sliders by small amounts in the clear area below the main peak until the background is nicely balanced In some cases the histograms may all start a long way above zero usually in astro images with a lot of light pollution In this case slide the start point setti...

Page 11: ...tart 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 cr...

Page 12: ... and too low for the planets This problem is quite easy to overcome for small CCDs if you have access to a focal reducer for deep sky and a Barlow lens for planetary work However the CCD in the M25C is too large to be fully illuminated by most standard SCT scopes and you may not be able to take satisfactory images with such an instrument One very successful option that may be open to you is to fit...

Page 13: ...lly 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 then lock it in place SXV_M25C_usb exe has a focus routine that will repeatedly download and display a 128 x 128 pixel segment of the image at relatively high speed This focus window may be positioned anywhere in the camera field ...

Page 14: ...ope with an operating sidereal drive If so you are now in a position to take a moderately long exposure of some interesting deep sky astronomical object I will deal with planets later As most drives are not very accurate beyond a minute or two of exposure time I suggest that you find a fairly bright object to image such as M42 M13 M27 or M57 There are many others to choose from but these are good ...

Page 15: ...f capturing your images For the same reason it is not wise to use old dark frames if you want the best possible results however some software allows you to scale library dark frames to match the image e g AstroArt and this can be useful as a time saver Bias frames are somewhat more useful than dark frames when using the SXVR M25C A bias frame is essentially a zero exposure dark frame and records a...

Page 16: ...e but it will be revealed later If you zoom in on the raw image you will see that it has the regular grid of brighter and darker pixels caused by the Bayer matrix filter grid on the CCD Now apply the colour synthesis routine using the same offsets that gave good results with the daylight image tests ...

Page 17: ...these as your experience increases As a rough guide the Filters menu can be used to sharpen soften or noise reduce the image Strong High Pass filters are usually not a good idea with deep sky images as the noise will be strongly increased and dark rings will appear around the stars but a Median filter can remove odd speckles and a mild Unsharp Mask Radius 3 Power 1 will sharpen without too much in...

Page 18: ...y shown how a suitable focal length can be calculated and produced using a Barlow lens Many camera users comment on the difficulty of finding the correct focus when taking pictures of Jupiter etc This is usually due to poor seeing conditions which are only too common but may also be due in part to poor collimation of your telescope Please ensure that the optics are properly aligned as shown by sta...

Page 19: ...es when you come to process them they are MUCH brighter with a correspondingly better signal to noise ratio This means that aggressive sharpening filters may be used without making the result look very noisy and so some of the effects of poor seeing can be neutralised A raw image Try applying an Unsharp Mask filter with a radius of 5 and a power of 5 This will greatly increase the visibility of an...

Page 20: ...th a separate guide telescope rigidly mounted alongside your imaging telescope I personally use it with a 70mm aperture F10 inexpensive refractor as a guide scope but a shorter focal length lens will make more guide stars available in any given region of sky See the picture below To use the autoguider first orient it so that the connector plug is roughly parallel to the declination axis of your mo...

Page 21: ...refractor guide scope in the author s garden the camera shown is the older SXVF version but the connections are the same To use the autoguider please proceed as follows 1 Having started the SXVR M25C software open the autoguider control panel by clicking on the autoguider menu button ...

Page 22: ...ct for imaging is properly framed in the main CCD image leave the guider menu and use the main camera control panel as necessary 6 Re open the guider control panel start imaging and try to locate a clearly visible guide star If necessary make adjustments to the guide telescope or off axis guider until one is found 7 Press Stop and then press Select Guide Star Use the mouse to left click on the sel...

Page 23: ...ular you may need to alter the guiding parameters or investigate the rigidity and drive performance of your mount A lot of information can be deduced by watching the behaviour of the guide star in the guider frame If it is continually moving between two locations either side of the green cross then the RA or Dec pixels per second value is set too low The higher these values are set the gentler the...

Page 24: ...he optical system of the telescope Dust motes act as inverse pinholes and cast out of focus images of the telescope aperture onto the CCD chip where they appear as shadow do nuts Most optical systems show some vignetting at the edges of the field especially when focal reducers are used This causes a brighter centre to show in images especially when there is a lot of sky light to illuminate the fie...

Page 25: ... horizon Now take several images with exposure times adjusted to give a bright but not overloaded picture A histogram peaking at around 128 is ideal Averaging flat fields together is a good way to reduce their noise contribution and so recording 4 or more images is a good idea To use your flat fields they must first have a dark frame subtracted Although this may appear to be unimportant with such ...

Page 26: ...lem to cure or on the CCD faceplate very difficult to eliminate entirely When small particles collect on the window they may not be noticed at all on deep sky small F ratio images as they will be very much out of focus However if a powerful contrast boost of the image is carried out they may well begin to show as the shadow Do nuts mentioned earlier Images taken with a large F ratio optical system...

Page 27: ... One gentle wipe from one end to the other with no return stroke will be found to be the most effective action DO NOT rub vigorously and be very careful to avoid scratching the window 6 Before re assembly make certain that the inside surface of the front window is also clean and then carefully replace the camera front barrel and screw it into place If the heat sink seal is disturbed renew it with ...

Page 28: ...sb astroart com Maxim DL is another popular choice and you can find out more by visiting http www cyanogen com Some details of the camera and CCD characteristics CCD type Sony ICX453AK Exview interline Bayer matrix imager CCD size Active area 23 4mm x 14 9mm CCD pixels 3032 x 2016 pixel array Each pixel is 7 4 x 7 4uM Well depth Full res mode 30 000e Binned 2x2 mode approx 40 000e Mean visual QE 6...

Page 29: ...l only be used for normal purposes described in the standard operating instructions and within the relevant safety standards of the country where the equipment is used 2 Repairs under guarantee will be free of charge providing proof of purchase is produced and that the equipment is returned to the Service Agent at the Purchaser s expense and risk and that the equipment proves to be defective 3 The...

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