[AZ-Observing] Re: Eridanus Goodies
- From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 29 Jan 2004 00:14:53 -0700 (MST)
Along with Andrew and Matt's comments, I have two others:
1) When I was doing a lot of survey-type visual observing---always
with the same telescope and same magnifications as per Steve, I found
that after going after all too many objects that were really too faint
for convenient viewing, I would finally come across an "ordinary"
galaxy bright enough to be in the Shapley-Ames catalogue, and would
describe it as "large", even though it was only 2' across. It was simply
that it was so much larger than the 20"-30" stinkers I'd been looking
at previously. Fortunately I have always tried to give size estimates
in angular units, tied to nearby field stars if possible, so that the
subjective side could be controlled with real numbers.
2) I think if you go through the original GC (not the NGC) and
make a list of a representative sample of object size-categories
assigned by Herschel, then match those with reliable angular diameters
(say using galaxies or globulars, where consistent sizes are well
in hand), I think you'll find that "large" ranges over a factor of
at least five if not ten in angular size. I recall there being an
S&T article (maybe Scotty Houston column?) showing exactly this.
Thus I think the argument that "I use roughly the same magnification as
Herschel" produces consistent results is probably spurious. The test,
naturally, would be to take Steve's observations and apply the same
method (what range of actual sizes does "large" apply to?) to look
for the consistency.
\Brian
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