Fog on the Camera Window?

Sh2-155 - Cave Nebula
Home Monroe, CT
Date: 7-12-20
Camera: ZWO ASI1600MM-Pro
Telescope: Astro-Tech AT115EDT 115mm Refractor Telescope
Barlow: None
Focal Length: 805
f/7
Focal Reducer: AstroTech Field Flatterner/Focal Reducer
Mount: Orion Atlas Pro
Filter Wheel: ZWO EFW 8 x 1.25"
Filter: ZWO Ha
Focuser: ZWO EAF
Autoguiding: ASI120 Mini attached to an Agena 50mm Guide Scope/ZWO 60mm Guidescope
Exposure: Ha 1 x 240s
Gain: 139
Offset 21
Sensor Temp: -10 C

Outside Temp: 20 C

Processing: None

Other:

It was very humid and poor transparency.  Hazy clouds moved in as well.  Autoguiding was poor, the guidestar was lost several times.