Date: 2021 April 19 UTC
LBTO Observer: Olga Kuhn
Lead Partner Observer: Charlotte Wood (ND)
Other Partner Observers: Peter Garnavich (ND), Rick Pogge (OSU, at start)
Telescope Operator: Steve Allanson

Moon phase: 1d before First Quarter

Summary:

No observing due to bad weather.  Humidity reached 100% just after sunset and
stayed high most of the night.  Frost and light rime ice accumulated on the
enclosure.  While the humidity dropped later, it was not enough to allow the
ice to sublime and blowing ice particles were visible in flashlight beams.
The night was called at 10:15UT


Calibrations: 

Repeated LUCI long-slit spectral calibrations (flat fields and
comparison lamps) from the previous night because these were impacted
on the LUCI2 side by the DX beam splitter not being parked after
daytime work, and the beamsplitter shadows the bottom part of the
slit.

Because of a grating tilt fault, only use LUCI1 files luci1.20210419.0021 and up,
and LUCI2 files luci2.20210419.0037 and up.


Completed Programs: 

none


Details (All times UT):
----------------------------------

01:40 - LUCI long-slit calibrations
        G200 zJ 1-arcsec slit flats and arcs, this time with the DX beam splitter
	out of the way.

02:17 - closed due to threatening clouds

02:54 - Humidity is ~100% and the summit is enshrouded in fog

...

09:30 - Humidity down to 80%, but there is frost and light rim accumulation
        on the building plus blowing ice visible in a flashlight beam.

10:13 - Humidity back up to 85%, not going down enough to sublimate the light
        ice accumulation on the building.

10:30 - calling the night over