FWHM do you trust these numbers when judging seeing?

[stargazer]

...I do not.........not entirely.


I am not sure if I missed a previous discussion on this subject:
is there a consensus on judging seeing with this FWHM methode...?
any standard???
I am talking about the life-view-window when focusing on a star...

which stars are allowed to be used, to have this FWHM as a standard-
instrument...?
- hight above horizon?
- stellar magnitude?
- spectral class of star?
- luminance filter or none?
- type of CCD?
- software used for evaluating seeing via FWHM (life-view)?
- etc...?

it is my humble but e x p l i c i t experience over the years that:

- there is a huge difference in those values if you use an OSC or mono
CCD (I am talking about the focus window - so life-view)
- if you take another star you will get different FWHM values
- if you take another software it will also differ significantly - it
should not, but it does, that is a fact!
- pickering suggests something else than FWHM tells you about seeing.
- people use this values as a 'pseudo-standard' obviously, not
realizing that different software was used, and therefor they compare
incompareable things...(?)

there seems to be no standard on this subject,...?
so, I do not trust these numbers.

I rather got with pickering's scale, even if this is very much
dependant on personal experience and of course this scale was made
with a scope, only a couple of HR deep sky imagers use: a refractor...
(-:
{[(which quite frankly in my eyes is the very best dedicated telescope
for any kind of high resolved photography... *GGG* - don't take that
too seriously, I am only joking)]}

honestly: any thought on this?
I'd really appreciate clarification - if there is such - cos I am
afraid by posting these numbers we are comparing apples and pares, as
we say here in austria...

if there is no standard, we could think of one, shouldn't we ?

best regards,
Dietmar
PS:
BTW: FYI I have added a crop on one of the luminance layers of the M57
image I recently posted, that is supposed to illustrate what was in
the data I acquired. DDP+ sharpen, pos constr. deco in CCD stack,
wavelets in registax and smart sharp as well HP filter was globally
applied to that crop)
http://www.stargazer-observatory.com/m57.html

[JMS]

Hi Dietmar, I agree with you. FWHM is dependent on a number of factors and each star is different. I don't concern myself with how ideal the night sky is, I am just happy when its clear and I can image. My problem, which is a growing one, is light pollution. Right now my skies are mag 5, which means I can see all stars in the little dipper. Soon, I am afraid, that number will decrease. I am detemined to fight light pollution any way I can (legally) which includes opening my big mouth, writing articles, notifying politicians, and educating the youth.
I don't really know a perfect way of determining the quality of seeing, wish I could come up with one. I can guarentee yours is better than mine.


Joe