This was taken as part of the calibration procedure. I shot this picture of the Space Needle from Kerry Park. That ought to tell you how much magnification 1300mm really is. From the Kerry Park vantage point, the Space Needle is 1kM (0.61Mi) away.
At 1300mm focal length on a cropped body camera, the lens has a Field Of View (FOV) of 1 deg x, 0.7 deg y, 1.2 deg diagonal. Framing a subject is therefore like picking a needle in a haystack – for a comparison, a stock Russian AK47 assault rifle can expect to shoot about 5 minute-of-angle accuracy, an American M16 about 3MOA. The fact that what this camera sees is only about 30x wider than what an infantry rifle shoots ought to tell you how hard it is to aim.
To facilitate aiming … I gimped onto the camera mount a cheap Chinese copy of a Bushnel HoloSight. It works by projecting the illusion of a floating cross hair and aiming reticle about 5 ft in front of the shooter. The rail was … hastily attached to the original tripod mount ring (which is too weak to hold the weight of the telescope and DSLR) and taped in place with clear packing tape (hey, it’s a quick prototype). Then, with the sights set on the Space Needle, I locked the camera tripod head and bought the aiming crosshairs on the space needle to correspond to what the camera sees, using the bullet drop and windage adjustment knobs on the sight.
Total setup was about .00 for the sight and rail, and about 1 hr of design time and some 3D Printing magic. Version 2 of the mount will incorporate a less ghetto sight rail, as well as a front bi-pod and rifle stock and pistol grip attachment to allow shooting without a heavy tripod.
And I wasn’t kidding about being able to read the Exit sign over the emergency exit…
By: ttstam