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05-17-2022, 05:46 PM   #1
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Calculating back focus for Astrophotography

Hi There - I was wondering if anyone knows the distance from the sensor to the edge of the lens opening for the K-70 camera. I'm trying to get an idea of this distance which will help me when I'm setting up my image train for Astrophotography.

Thanks

John

05-17-2022, 09:19 PM   #2
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On the top of the camera there is a symbol which looks like a circle with a line running through it. This marks the position of the sensor.
05-17-2022, 11:33 PM - 1 Like   #3
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For K-mount cameras including the K-70, the "flange focal distance" (distance from the medium - sensor or film - to the lens mount) is 45.46mm
05-18-2022, 03:35 AM - 1 Like   #4
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QuoteOriginally posted by BigMackCam Quote
For K-mount cameras including the K-70, the "flange focal distance" (distance from the medium - sensor or film - to the lens mount) is 45.46mm
Excellent...thanks for the quick reply. Exactly what I was looking for

05-18-2022, 07:57 AM - 1 Like   #5
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If you happen to use any other camera, Wikopedia has a good list of backfocus values (flange focal distances) for various cases. Handy to have.

https://en.wikipedia.org/wiki/Flange_focal_distance
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