Thanks, Paul. I don't mean to be argumentative either. I think what we are (both) talking about is a critical field of view, at the pixel level. I found this interesting quote:
<start quote> Image Scale in Pixels Unlike astronomical CCD camera users, DSLR astrophotographers do not often deal with single pixels because there are too many of them. Even a pinpoint star image usually occupies six or eight pixels on the sensor. This is a good thing because it means that star images are much larger than hot pixels. Still, it can be useful to know the image scale in pixels. To find it, first determine the size of each pixel in millimeters. For instance, the Canon XTi (400D) sensor measures 14.8 x 22.2 mm, according to Canon's specifications and has 2592 x 3888 pixels. That means the pixel size is 14.8 divide by 2592 or 0.00571 mm vertically and also 22.2 divided by 3888 or 0.00571 mm horizontally. Now find the field of view of a single pixel; that is, pretend your sensor is 0.00571 mm square. Suppose the telescope is a common 20-cm (8") f/10 Schmidt-Cassegrain with a focal length of 2000mm. Then: Field of one pixel = 57.3 degrees times (0.00571 mm divided by 2000mm) = .000016359 degrees or .59 arc seconds. As with astronomical CCD cameras, the pixel field of view works out to be close to the resolution limit of the telescope. <end of quote> When you are talking about an object that is only 47 arc seconds wide (at it's closest directly overhead) we would appear to be talking about an 8 pixel wide image. I need to learn more about how SR works to determine whether it would help or hinder with such a target. (or I could just try the next time with it OFF and compare). :) -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
