Using extreme back-focus on Venus to 'gauge' seeing

[jabeoo1]

Title kind of explains it to be honest but I just did the following with a newtonian reflector:

1) Target Venus in the eyepiece (Jupiter did not work any where near as well)

2) Back focus until its big, blurred, and the spider & secondary mirror is visible clearly as part of the bloated & out of focussed disk.

3) Take note of the atmospheric turbulence.

4) Hold you hands in front of the light path and view the heat from your hands to illustrate the sensitivity to the views. 

Does this really give a useful visual representation of the thermal events effecting seeing conditions or am I pointlessly messing around with my telescope with no scientific value at all ?

[Peter Drew]

I find it's a very good representation of what the ambient seeing conditions are like. Be aware though, that these disturbances can also be caused by tube currents so allow sufficient cool down time before further assessment. 

[mikeDnight]

Not sure its scientific but at least you seemed to enjoy yourself doing it.

Venus is a notoriously difficult subject to study partly because of its brilliance and partly because its usually low in the sky.

With regard to estimating seeing, that is usually done by looking at stars close to the zenith, not low down. Estimating seeing conditions by examining an out of focus image of Venus would not give an accurate estimate of general seeing conditions. It could however give you an idea of the turbulence affecting the observation of Venus itself. For example, if Jupiter is refusing to reveal much detail, by racking the image out of focus, you can tell if the atmosphere is turbulent. Sometimes by doing this you can see rapidly moving currents of air, almost like looking through a fast moving river. When this happens it tells us a weather front is coming in.

I think its best to leave hands well out of the way while observing. If you can detect heat from your hands affecting the image it could only ever be detrimental to the overall view.

Mike :-)