Schurs Astrophotography

Ultra Thin Moon at noontime
Just over a day from New Moon
with the
Orion 10" f/3.9 Newtonian Astrograph
July 2, 2016
Uploaded 7/3/16

Left: daytime moon very close to the Sun. Right: Telescope setup required to image this encounter.

This was
certainly one of the most difficult lunar imaging sessions I
have ever done! With the thin crescent moon only 24 hours from
new, the only time I could actually image the crescent was at
noon at the zenith. Even if I had a perfect eastern horizon,
the seeing down that low would have been excruciating. Fortunately
the seeing I had at the zenith permitted some details to be resolved,
and the transparency was good for a typical monsoon high humidity
afternoon. To be able to image with the high sun blasting my
black telescope tube, I wrapped the scope with a huge silver
mylar space blanket. Next I had to add a big black internally
carpeted baffle on the front of the tube so that the direct sunlight
would not enter the focuser from the side. By removing only the
two inch dust cap on the front scope cover, I could then safely
point the scope at the sun and center it by its projected beam
on a white paper. An interesting trick when you do this, is to
project the sun about four feet away onto a white card. Then
the beam is nearly parallel coming out of the eyepiece. When
you point away from the sun in a featureless blue sky, the view
is in infinity focus. The setting circles (manual mind you) were
dialed in to the RA of the Suns current position. (DEC is always
right on a permanently mounted base) Next the moons current
position was dialed up using a planetarium program Stellarium
to get the current lunar coordinates.

When a wide field
ocular was inserted, the moon was just barely visible in very
brilliant light blue sky! Fortunately, the camera is much better
at seeing low contrast objects like this, and using the IR filter
to cut through the bad daytime seeing made it easy to see the
moon and some surprising features! The whole idea here was to
see if there was a contrast boost using the IR filter vs just
visible light. The result of THAT experiment will surprise you...

Note: Conventional usage of South is up in all images, more info below.
(So Rik, stand on your head please.)

Here you can see the difference between a normally exposed
image on the left with no filters, and the image on the right
with an IR pass filter. While the signal to noise is the same,
the sharpness in IR is 2 - 3x better! To compare the S/N,
the brightness of the same bright patch on the moon was measured. Then
the background sky in each image. The Delta B indicates the contrast.
It was the same - 21 ADU. So next to the Sun, where the sky is
really more white than blue, and with tons of dust and vapor back scatter,
there is no contrast boost.