[Leica] Blood Moon Eclipse

[Howard Ritter]

The Earth rotates at the rate of 360 degrees/24hrs, or 15 deg/h. This is also 15 minutes of arc per minute and 15 seconds of arc per second. For an object near the celestial equator, this same relationship holds. A movement of 7-8 seconds of arc in a half-second exposure is less than one-half of one percent of the Moon’s diameter of about 1800 arc sec. At a FL of 400 mm, this would smear the Moon’s image by a negligible amount. The motion of the Moon in its orbit is in the opposite direction, tending to reduce the effect, but is too slow to make any visible difference anyway.

If Adams made his landscape photos that included the Moon with slow emulsions, very small f-stops, and a long exposure, he’d have run into this problem.

When I take astrophotos of the Moon through my 1100mm FL telescope, however, the Moon’s image takes up nearly the height of the frame, or much more under higher magnification, and an electrically driven telescope mount is essential to avoid exactly what you’re referring to.

—howard


On Oct 10, 2014, at 12:20 AM, Mark Rabiner <mark at rabinergroup.com> wrote:

> The moon itself moves to fast for a half second. Its in the Ansel Adams
> Photo Series books. But the moon is typically over exposed. And was nice you
> didn't do that.
> 
> 
> On 10/9/14 9:31 PM, "Howard Ritter" <hlritter at bex.net> wrote: