Seeing - How do you determine it?

[BlueAstra]

I often see comments about atmospheric 'seeing'. Values are quoted, e.g. 0.5, 1, 1.5 Arcsec. It's often used as a guide to limiting resolution with a CCD camera, i.e. If System resolution in arcsec/pixel is less than the local seeing, you are maybe not gaining any benefit. My question is, how do you determine seeing at your site?

[xtreemchaos]

I allways go by eye, its a suck it and see thingy, the values in the eg 0.5, and so on really don't mean much unless there got from your location. if it looks good it is good and clarity in your images or eyepiece should be good too.  clear skys , charl.

[ronin]

Wrong topic.

[ollypenrice]

I don't know how to measure it properly* but I go off my FWHM readings for that scope/camera when focusing. I know from experience what the lowest values to date are, so I just base it on that. (In the TEC at 1.8"PP 1.1 is the broadband best while in the Taks at 3.5"PP I can hope for 0.85. If I'm well away from those values I'll shoot colour and set aside the luminance for a more stable night.

However on the ODK14 (0.66"PP) we found FWHM entirely meaningless with values flying all over the place so I can't help regarding your big RC if you have the same issue.

Olly

* Edit: homework: https://www.handprint.com/ASTRO/seeing2.html

To read about how FWHM works you could scroll down the the section dealing just with that. I thought I understood FWHM but there are things here that are new to me. It's a very good article.