I bought one of these cheap USB temp monitors from fleabay a month ago.
One of these
http://www.ebay.com.au/itm/PC-USB-Po...item2a166c534a
Just posting a quick report to say this thing is awesome. I have it connected to my Mount Hub Pro which sits on top of my scope and provides a USB hub as well as dew heater , power controler and robofocuser.
This allows me to monitor the temp of the air right next to my scope.
It has a very nice little interface that shows a graph of ambient temp and trend line as allows emails to be sent or alerts when temp drops below certain value.
You can set the frequency that it monitors the temerature. I sample every 1 minute.
attached is a screen shot of the interface from 5 minutes ago while I am imaging.
I use this to determine if I need to refocus the scope. more than 3 - 4 degree drop and its time for a refocus.
Hard to beat for the grand price of $10. Took about 2 weeks to arrive by snail mail from Hong Kong.