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Testing 150mm F8 Skywatcher ED - Open Cluster NGC 3532

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About this observation
Observer
Peter Anderson
Time of observation
16/04/2020 - 01:30
Object
Open Cluster NGC 3532
Observing location
Brisbane, Australia
Equipment
150 mm F8 Skywatcher ED
Exposure
30 secs X2, 2000 ISO
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The purpose of the exercise was to test the performance of the Skywatcher ED using a full 35mm frame  camera. The Camera used was a Canon 5D Mark II. This is a heavy unit and there was some 'sag' in the focusser. It was not helped by the fact that for the objects imaged, the long axis of the sensor was near vertical. (The focusser need to be more securely clamped in future - probably simply by tightening the focus lock.) This 'sag' resulted in the image losing its fine focus particularly on the extreme right of the frame.

The camera adaptor supplied with the instrument attaches securely and was most satisfactory - even allowing for rotation of the camera.

An examination of the images reveals that there is no appreciably vignetting, even in the corners.  The image remains in focus across the image except for the extreme long axis sides, and of course the corners. This is a very fine measurement and the image above reveals only a hint of this loss of sharpness. (If any reader is interested I can supply further images.)

My usual camera is a Canon 70D - much easier to operate in these circumstances with an articulated touch screen, and the smaller ASP-C sensor. There is absolutely no discernable drop off in fine focus using a sensor of that size.

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