Lorraine Rodgers and Aaron Top have laid down a challenge (sort of...). In a recent discussion between some BAS members (Brett T., Lorraine R. and John H.) it was determined that the thinnest new moon sighting (confirmed by image) was over 5 years ago on Feb 3, 2011. That evening, Lorraine and Aaron observed a 21-hour old crescent above the western horizon just east of Sauble Beach (they moved inland to get away from the winds at the shore). The very thin crescent is just visible above the tallest tree branches in Aaron's image below.
Canon 50D with 85 mm f/5.6, 1/15 s, ISO 640 at 6:21 pm Feb 3, 2011
Aaron Top image
So far, this is the thinnest (youngest) crescent moon seen by local amateur astronomers, - an admirable achievement, although it is not a world record. The "official" visual sighting record is held by Steven James O'Meara who spotted a 15 h 32 min moon in May 1990. The youngest moon seen with optical aid is 11 h 40 min by Mohsen G. Mirsaeed of Tehran on Sep 7, 2002. The Sky&Telescope article on thin moons is here: S&T Thin Moons
Note that there is an image taken with the Moon at 0.0 hours age, i.e., at the exact moment of New Moon. Remarkable and true! This was done in daytime by Thierry Legault on July 8, 2013. More information here: Youngest Possible NM As an added comment, if the Moon were a perfect sphere, there will always be a thin crescent of light except at the central moment of a total solar eclipse. The Moon is a real world, of course and has terrain that can reflect light. The S&T article link in the previous paragraph explains this nicely.
Thin Moon Challenge: The info you need
The table below includes both last crescent and new crescent moon viewing opportunities in the next few months. Data is from Starry Night but do the moon age calculation yourself by working from the time of NM to the time of observation. Do the math yourself, do not rely on a program to do it for you, we have found discrepancies of several hours between different astronomy software programs.
Note that not all of those events listed will break the record, but you might want to try for an observation or an image or two with a fatter crescent and earthshine for practice. Note that an observation by a single observer must be confirmed by a second witness to be eligible for the record. Also acceptable is an image of the thin moon in question (with horizon in the view and original camera data intact) and please make sure your camera clock is accurate to the nearest minute or so. Send all reports and/or images to the editor of SGN firstname.lastname@example.org or contact me for more info. Good luck!