Okay, there seems to be a lot of talk about image quality on CN and vendors sure like to use terms like "pin-point stars" or "fully illuminated and corrected" fields but how often do you find REAL WORLD results presented at full image scale and/or with minimal processing? Similarly, how often do you see FWHM and eccentricity measurements presented in a plot covering a full APS-C field? Not very often I think.
In any case, I would like to start a thread/topic that allows users to show how their systems are performing using actual images at a full 1:1 pixel scale and hopefully with plots showing the full-field performance in FWHM (star size, expressed in arc seconds) and eccentricity (star roundness).
First some caveats, YMMV, not all tools report the same results, not all cameras will give the same results (pixel size, Bayer patterns, mono versus one-shot-color, filtered or not), and individual results may vary by both user, event or session, technique, and sample of equipment (who, when, how, what).
In any case, here is my first contribution with results from an approximately two-year-old Tele Vue NP127is at prime focus (660mm with no correctors or reducers) on an unmodified Sony NEX-5R camera (APS-C format). The image scale at capture was 1.5 arc seconds per pixel and the image matrix showing the system's performance is shown at that same reproduction (1:1, or 1.5 arc seconds per pixel). This image is based upon a stack of 16 subs, each exposed for 30 seconds under red-zone light pollution with NO filters, with all processing done in PixInsight version 1.8 (core Core 01.08.03.1123). The image had a very slight crop (approx. 100 pixels) from each edge to remove processing artifacts from the registration and stacking. The cropped image is 4704 x 3116 pixels in size and each sample in the corner-to-corner and edge-to-edge matrix is 396 pixels square (the matrix image is 1196 x 1196 pixels so that it just fits within the posting guidelines on CN).
First the actual image matrix (processing included dynamic background extraction, color calibration, and a simple histogram stretch). This is an RGB image that was processed as a 32-bit FITS file and then saved as a JPEG (after conversion to an 8-bit image in PixInsight). The target field was centered on the globular cluster M5 and the field angular size is approximately 118 arc minutes by 78 arc minutes in size (2.0 x 1.3 degrees).
Edited by james7ca, 11 June 2015 - 03:16 PM.