Comparing star appearance in PC164C and PC164C-EX2 Video Cameras

The PC164C-EX2 is a newer version of the PC164C video camera that claims more lines of resolution and greater sensitivity. The EX2 does appear to show fainter stars than the 164C, but with some compromise in the appearance of the stars. In addition, this change in appearance only happens in conditions of very low light, as can be seen by examining a point source against a background and either darkening the background or stopping down the lens to make the overall scene very dark. The stars take on an odd, diagonally striped and fuzzy appearance that makes it difficult to focus. In contrast, the PC164C stars appear nicely round.

This page shows comparison images of the star cluster M37 when nearly overhead on a clear, winter night. I used a Celestron 11" SCT with focal reducer operating at f/5.7. I fed the video via a dazzle Video2USB converter and captured images of the scene and the star using MetaGuide. There is no indication the Dazzle contributes to the appearance because the effect is the same when viewed directly on a high-def plasma screen direct from video.

Several views are shown: raw views of a single frame for each camera; live, integrated images of 10 frames formed by MetaGuide; a close-up of the star appearance also formed by MetaGuide; and for comparison, a single frame 1 second exposure with a Starlight Xpress h9 monochrome camera.

All views were contrast enhanced to show the greatest range of stars, with a corresponding boost in the noise. This was done aesthetically to show the stars as well as possible for each image.


Wide views of M37 with the EX2 (above) and 164C (below). The left inset shows the star profile and the right is an expanded view of the star. These are direct dumps from MetaGuide. The same bright star is highlighted in each image, and the images are rotated roughly 40 degrees from each other.


Same view as above, but showing a live integrated stack of 10 frames, or about 1/3 second of video. The EX2 shows slightly fainter stars, but they are much broader.


Close ups of stars as shown by MetaGuide. The 164C has nicely round stars, while the EX2 shows the odd, diagonally feathered appearance.


For comparison, a one second exposure with a SXVF-h9 cooled monochrome CCD. The image was captured with binning 2x2 and then resized and rotated to roughly match the above views.


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