<s>
A	O
dew	B-Algorithm
shield	I-Algorithm
is	O
a	O
device	O
used	O
to	O
prevent	O
moisture	O
or	O
condensation	O
buildup	O
on	O
the	O
lens	O
of	O
a	O
camera	O
or	O
telescope	O
collector	O
during	O
night	O
observations	O
.	O
</s>
<s>
The	O
dew	B-Algorithm
shield	I-Algorithm
either	O
shades	O
the	O
lens	O
or	O
provides	O
a	O
small	O
amount	O
of	O
warm	O
air	O
directly	O
in	O
front	O
of	O
the	O
lens	O
or	O
collector	O
to	O
prevent	O
dew	O
from	O
collecting	O
on	O
the	O
element	O
.	O
</s>
<s>
Some	O
dew	B-Algorithm
shields	I-Algorithm
work	O
by	O
using	O
a	O
heating	O
element	O
that	O
keeps	O
the	O
objective	O
lens	O
warm	O
enough	O
to	O
keep	O
the	O
dew	O
from	O
collecting	O
.	O
</s>
