The TEC Field Flattener (FF) has been designed for correcting field curvature and off-axis astigmatism of the APO140. The FF has a wide-spaced two-lens design that corrects abberations most efficiently.
The combination of the APO140 with the FF gives a highly corrected field. Distortion on the edge of the field is less than 0.5%.
|
Distance from the center
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0°
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1.4°
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2.0°
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Spot size dia. w/o FF (mk)
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9
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145
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320
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Spot size dia. with FF (mk)
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9
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15
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14
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Back focus distance: 85mm / from flange to the focal plane
Max diameter: 112 mm
Length: 104 mm
Weight: 1.2 lb
Lens coatings: Broad band anti-reflection coating (BBAR)
Includes : FF assembly with two covers.
3 major components:1. Threaded adapter with mating thread to the thread of Starlight focuser draw tube end2. Lens assembly permanently installed in to the threaded adapter3. Pentax outer bayonet ring
The camera end of TEC FF has the same dimensions and design as Astro-Physics’s Field flatteners - this lets you use a wide variety of AP photographic assessories.
The distance from FF’s base plane to the focal plane is 85mm, holding this distance is morecritical for Pentax 6x7 and 35 mm cameras and less critical for CCD cameras with small chipsize.