Capability of SBIG st-i Guider Kit

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Capability of SBIG st-i Guider Kit

Postby ngc7000 » Fri Jul 12, 2013 1:09 am

Has anyone used the SBIG st-i Guider Kit with the STi camera/guider and small 100 mm f/2.8 guide scope? If so what is the maximum focal length it can be used with a refractor for successful long exposure guiding? Is it adequate to guide a 6-inch F/7 Astro-Physics refractor of focal length 1100 mm?

Mike
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Re: Capability of SBIG st-i Guider Kit

Postby ngc7000 » Mon Jul 15, 2013 4:58 pm

Here is the answer to my question on the capability of the SBIG ST-i guider kit according to SBIG Support:
The ST-I at 100mm FL is capable of guiding to about 1 arcsecond. This is true no matter what the FL of the main scope. The questions are (a) whether the main scope and mount are capable of tracking to an arcsecond and (b) whether one arcsecond accuracy is enough for your intended application. If you are using a DSLR with say 5.5 micron pixels and your focal length is 6x7= 42 inches, then each pixel is resoving about 1 arcsecond. So the ST-I at 100mm is tracking to the pixel resolution of your system. If you want to track to one-half pixel resolution or one-quarter, then you should double or quadruple the focal length of the guiding lens.
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Re: Capability of SBIG st-i Guider Kit

Postby cybermystic » Mon Jul 15, 2013 6:00 pm

Possibly no answers as this question would have been better placed in the cameras or general technical section rather than in images??
Greg
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http://www.newforestobservatory.com/
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Re: Capability of SBIG st-i Guider Kit

Postby Dennis » Mon Jul 15, 2013 6:23 pm

One answer you may like to consider is the capability of current guiding s/w. It first of all has to find a centroid (of the guide star) and most modern s/w can do this to 0.01 pixel. That allows you a 10:1 difference in your scope/guide scope given the same pixel size and you still get a 0.1 resolution of the guide star centroid.

Dennis
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