Quote:
Originally Posted by codemonkey
I suspect we (or at least I) get better seeing than people assume is typical in Australia. I routinely get 1.8" FWHM L subs with my Esprit 120. Using Ray's handy spreadsheet I can reverse-engineer an approximation of the seeing at my site based off:
0.12m aperture
0.6" RMS guiding
1.8" FWHM stars in the resulting images
= ~ 1.28" seeing
Again using Ray's handy spreadsheet, upping my aperture to 0.2m would reduce the FWHM of stars in the resulting image to approx. 1.63"
I realise these are approximations, but don't know exactly how accurate Ray's formulas are. I do know the aperture of my scope, typical RMS guide errors and resulting star FWHM with confidence though.
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the assumptions make it a bit ropey to backcast like that Lee, particularly in extricating seeing from the effects of guiding RMS. The actual seeing is likely to be in between what the spreadsheet gives with your measured RMS and with zero RMS, but there is no way of being any more precise, so it is what it is and that is still useful information.
you are fortunate to have seeing that good, but it is not unheard of in Australia - just not available in all locations
http://articles.adsabs.harvard.edu//...00101.000.html
pretty good here tonight as well - between gusts it is well under 2 arcsec
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yeah, you need a bigger scope ..... and a bigger mount and .......