TEC-140 Field Flattener


In November 2005 I bought a TEC-140 APO refractor.

Main purpose was to use it during my second stay in Namibia in Mai 2006. To the right you see a test image with the TEC-140 without flattener (Leo 1 dwarf galaxy - full frame luminance).
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Here you see the CCDInspector analysis of the above image.
It indicates a field curvature of 48,6%, the star size drops from 1.7 pixel in the center to 5.2 pixel in the corners.
The little offset could arise from the simple 2" nozzle connection of the STL camera.
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The first dedicated TEC flattener showed some aberration in the outer corners, else was very sharp and well corrected and supplied a very even illuminated field. See a flatfield image and analysis to the right. The little fall-off to the left is caused by the internal 2" filters.
To the right you see an image of the setup. At the camera side of the FF the AP67RT adapter was modified from T2 to the thread of the STL camera providing a distance of 85 mm from the FF flange to the focal plane. clic for full size
The not perfect flattener was replaced by TEC, I received a new flattener personally selected by Yuri. First light was on August 23, a night with steady seeing. To the right you see a CCDInspector analysis (H-alpha) of the first light image:
NGC 6960 (Western Veil).
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The next CCDInspector analysis shows the green channel to the right. clic for full size
The next CCDInspector analysis shows the blue channel to the right.
No refocusing was done when changing the channels.
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I am very satisfied with the performance of the TEC-140 + TEC-flattener. The stars are pinpoint-like out to corners, no significant reflections on brighter stars. Mangification of the image to above 100% size is no problem.
Thanks to TEC for this perfect and powerful imaging instrument.