Archived posting to the Leica Users Group, 2014/10/10

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Subject: [Leica] Blood Moon Eclipse
From: hlritter at (Howard Ritter)
Date: Fri, 10 Oct 2014 16:10:14 -0400
References: <>

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 

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.


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

In reply to: Message from mark at (Mark Rabiner) ([Leica] Blood Moon Eclipse)