Andy wrote:
In US night, as defined for pilot certification, flying currency, and
flight logging, does not start at sunset. It starts one hour after
sunset. Flying a day VFR certificated glider 10 seconds after sunset
is not night flying and requires no special pilot qualification. It
does however require the glider to have approved night lighting. I
assume then that a day vfr certificated glider with approved lighting
may legally fly 59 minutes after sunset.

According to FARs, a pilot with a normal pilot certificate (it's
possible to get a "no night flying" restriction) has no further
requirements for flying at night while SOLO. There is a currency
requirement for carrying passengers:

61.57.b) Night takeoff and landing experience. (1) Except as provided
in paragraph (e) of this section, no person may act as pilot in command
of an aircraft carrying passengers during the period beginning 1 hour
after sunset and ending 1 hour before sunrise, unless within the
preceding 90 days that person has made at least three takeoffs and
three landings to a full stop during the period beginning 1 hour after
sunset and ending 1 hour before sunrise, and-
(i) That person acted as sole manipulator of the flight controls;

The odd thing is that 1.1 defines night:
Night means the time between the end of evening civil twilight and the
beginning of morning civil twilight, as published in the American Air
Almanac, converted to local time.

So I guess they want the experience to be in "total darkness"...

And finally, the FAI Sporting Code:
4.5.4 Night flight
A flight that continues beyond the hours of legal daylight in the
country concerned shall not be validated, except where the glider and
pilot comply with the laws of that country for night flight.

So in the USA, this would seem to be Sunset, unless the glider has
legal position lights.

Do any US registered motor gliders have approved lighting? Have their
owners operated between sunset and night?

Stemme and Katana immediately come to mind.

-Tom