[AZ-Observing] Re: Pickering Scale/Equal Magnitude Doubles

Hi Andrew,

No, I do not try to compensate the Pickering scale scope-to-scope and agree
with you completely that the effective seeing for the instrument you are
using is what counts and what should be recorded.

After I get my technique perfected on the Pickering scale, as best I can
anyway :o),   I will try to equate those scores with Brian Skiff's equal
magnitude doubles method.  In other words is 2" seeing equivalent to
Pickering 5 or 6 or 7??

As to Brian's method does anyone know what magnification should be used to
test seeing? Brian's list of equal magnitude doubles contains mostly
magnitude 6-7 pairs at various fairly tight separations.  Since some folks
can split doubles at much lower magnification than others, do we need a
standard magnification (ie. 50x/inch of aperture) to make results
consistent?

Another question is whether it is appropriate to use brighter stars when
testing seeing with smaller scopes.  Lastly, in using Brian's method, if I
can easily split a 2.5" pair must I then try a 2" pair and so on down the
list until I find the separation that I cannot split?

Regards,

Bill Wood
Fountain Hills, AZ



> -----Original Message-----
> From: az-observing-bounce@xxxxxxxxxxxxx
> [mailto:az-observing-bounce@xxxxxxxxxxxxx]On Behalf Of Andrew Cooper
> Sent: Thursday, July 17, 2003 9:30 AM
> To: az-observing@xxxxxxxxxxxxx
> Subject: [AZ-Observing] Re: Pickering Scale
>
>
>
>
> There are many reasons why different instruments would be affected by
> seeing to different degrees, from the way seeing interacts with
> smaller/larger apertures, seeing issues in the instrument itself, and
> observer quality and bias (how good are your eyes?).
>
> So do you try to compensate the scale for the instrument you are using?
> Or, as I often do, just call it as you see it, the effective seeing for
> the instrument you are using. I believe this is appropriate because it
> records the quality of the observations, and is not meant to be a record
> of what any other instrument would see that same night and location.  I
> want to know why I did or did not see a particular dim central star or
> wisp of detail.  Pickering or other observer (non instrument) methods
> are just a way to standardize the scale.  Not perfect, but better
> than nothing.
>
> If you are doing an observatory site evaluation or making observations
> with an instrument this might be different, you would need a more
> rigorous and quantitative method.  But for us visual observers I would
> not worry about calibrating instrument differences.  I'll use the same
> methods on the 90mm APO or the 18" dob and let the notes stand on
> their own.
>
> Andrew

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