While preparing the Venus Transit of 6 June
2012, I've imaged the planet Venus while approaching the Sun. Two
images show the planet at 5°40' (2 June) and 2°17' (4 June) from
the Sun center, and in particular the second one was very difficult to
obtain due to the extreme proximity of the Sun limb. Extreme care was
due to avoid the Sun light entering the telescope.
I've observed from my observatory in the
backyard of my home, in the city center of Tradate (VA), Italy.
Observing conditions were very far from ideal: the seeing was very bad
and transparency even worse due to continuous transiting of clouds, that
on June 2 leaved only a 6 minutes time window.
The cusp extension was remarkable on June
4, while nearly invisible on June 2. Being the elongation of the two
observations nearly one the double of the other, maybe a minimum angle
for the cusp extension observation can be found between 3° and
4°.
Another very interesting observation is the
limb brightening in the Southern hemisphere between 50° to 70°
latitude. For confirmation, I've another image, obtained with a W25
filter (red), that shows the presence of the brightening in the same
way.
Images
Venus
was only 2°17' from the Sun center on June 4, and only 31 hours
from transit entrance. A large cusp extension up to 270° and a
brightening of the Southern hemisphere between 50° and 70°
latitutes are visible.
Venus
on June 2 was more than 5° far from the Sun and nearly no cusp extension was found.
Image
of the setup for imaging Venus very near to the Sun. A Takahashi
TOA-150 apo refractor is piggybacked on the Schmidt in my observatory.
A large diaphragm is sustained by bamboo poles at about 1,2 meters from
the lens. A second diaphragm is present in front of the lens so that no
light from the Sun can enter in the tube. A large cardboard on the
telescope tube shields the other parts from the Sun. A webcam is mounted
at the end of the telescope for imaging.
