[Aavso-photometry] Adequate FOV size?

[Keith Graham]

> Necessary field size is largely dependent on the brightness of the
> target object and the distance from the galactic plane.  I rarely
> if ever have trouble at 11.5x11.5arcmin with the 1.0m telescope
> for the "sweet-spot" objects around 14th magnitude, but quite
> often have trouble getting good comp stars when trying to observe
> some 9th magnitude object.

Agreed. I was thinking of only the fainter objects. If there are no brighter
comps nearby when the star goes into outburst, this could be a problem. But
even so, I find most of the charts I use have comps nearby that will cover
the outburst mags.

Keith









>    Larger fields often have other problems, such as vignetting,
> poor flatfielding, curved focal plane (so not all objects are
> in focus), and optical distortions.  Probably 20x20 is a convenient
> compromise.
> Arne
>
> Keith Graham wrote:
> > I see that a large FOV (30'x30') appears to be favored by some. I must
say that I have a 11.5'x11.5' fov with my ST9e and LX200 12". It is a very
rare occasion when I cannot get the variable and 3 comps from an e chart
within my fov. For photometry, I will use only f charts when available, and
these are well within my 11.5' x 11/5' fov. I will resort to the e charts
when no f chart is available, but even then there are plenty of comps from
which to choose that lie in my fov.
> >
> > Cheers,
> >
> > Keith Graham
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