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Hi Ray,
Most of my images are with 4x worth of teleconverters (which I assume is equivalent to a 4x Powermate). The 12" Sky-Watcher Dobsonian is 1500mm f/5, so I assume my effective focal length is 6000mm at f/20.
Using a 2.5x and a 5x Powermate, Evan's setup is 22500mm at f/75.
Nearly all of my planet images use the central 640x480 pixels, whereas Evan has used the entire 5184x3456 sensor reduced by 4.8x to 1280x720 in camera.
As a result: 15/4.8=3.125x in 720p vs 4x in 640x480 crop mode, which seems to match the images sizes we both have.
Using the full HD 1080p mode with the 5x and 2.5x Powermate will give a 1.5x greater image size compared with using 720p, but also drop the fps to 30fps.
Using the 640x480 crop mode with the 5x and 2.5x Powermate will almost fill the 640x480 frame with Saturn's disc!
Cheers,
Tom
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