I nominated this photograph due to its great historical relevance. This picture was taken in the observatory that Percival Lowell established in Flagstaff, Arizona. In addition, there is proper copyright information.
The original image came from the Lowell Observatory. I would suggest contacting them (or the Friends of Lowell, since they provided an email address) and explain that you are requesting a large version of the image for encyclopedic use. It looks like they have a lot of archives on the man, so they doubtless have a photo to scan. For an image this famous, though, they probably have a good online version for people who ask. — 0918BRIAN • 2006-03-19 07:47
FYI, this picture is on a "History of America" trading card (Card # 57-06, offered by subscription only In 1979-1981) with the following caption:
"Lowell The Gifted Author & Astronomer Observing The Planet Venus During The Daytime."
Great Story Of Him On The Back Of The Card.