Temperature comparison and image quality

Effect of temperatures on image quality

To show the dramatic effects of imaging under poor thermal conditions I have made three videos for you to consider. They show how much of an effect is caused by having your mirror out of thermal equilibrium.

NOTE: These videos use the DivX codec. If you can't get them to play then go to The DivX Site and download the free DivX player bundle that will include the codec and plugins for your operating system.

Firstly here is the temperature chart for that night, with my comments added in white. The associated video file is shown in red.
Click on this image for the larger version with text you can read :-)

Here are the three videos that correspond to the graph:

20051031-233805.avi (3Mb)
Temperatures dropping rapidly, conditions poor for imaging.
Note: Requires the DivX Player
20051101-005311.avi (2.8Mb)
Mirror 1 degree C warmer than ambient, boundary layer present.
Conditions poor for imaging.
Note: Requires the DivX Player
20051101-030059.avi (3.1Mb)
Mirror within 0.25 degrees C of ambient.
No boundary layer or tube currents, conditions good for imaging.
Note: Requires the DivX Player

As you can see there is a dramatic difference in image quality between these videos! They were all taken with exactly the same equipment and camera settings, the only difference between them is the thermal conditions.

Anthony Wesley
9th Novemner 2005