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Hi, people:
Regarding methods, I've never been keen on Pogson's. It puts a limit to accuracy
and relies on rounded off magnitudes. A star of 7.14 will be a 71 star and a
7.15 will become 72, and there is not one full Pogson step between them
(furthermore, there is no difference at all).
I always use two decimal values for the magnitudes and make the rounding offs
after the estimate was made. The delta Scorpii phenomenom was found that way.
And you can see that B.Fraser photometry is almost completely the same as my
visual observations. As John said it's very important which stars you are using
but the method is very important too. There's no point in rounding off
magnitudes, specially of bright stars which are extremely accurate: we're only
making the estimate worse if we round off the values or get stuck to 0.1 mag.
steps.
I've always been checking my own estimates and, with the naked eyes, provided a
good sequence and a not-too red color, the errors are never greater than 0.03
mag.
But in the case of red stars - as all the miras and most of SR's discussed
here-, I think this accuracy is almost impossible to get (- Never said
"impossible".. :-) ) because of less availability of a proper sequence and
because they are not naked eye objects. Even if they were the Purkinje effect
and other color problems get worse the brighter the star: Mira may be bright but
it's always a challenge....
And I agree with Stan in that less people (even one or two), following one star
will be capable maybe to see short amplitude variations. But it's no use to make
this kind of observation when results are going to be mixed with 99 other
people's numbers.
I've just sent a confirmation for two red variables in Centaurus and Carina. If
I only follow my observations I can find periodicities, trends and the like, but
in the case of red stars I know that the mixed result will be dissapointing.
Last months I could see the incredible one full magnitude difference between my
estimates and E.van Ballegoy ones for the interesting changing-period mira R
Cen. My 7.6's were his 8.6's. I thought maybe we have different (very
different...) responses to red, but then I found that sometimes this difference
became almost 0 and that when I watched the star fading he watched it rising and
viceversa. And sometimes he observed T Cen brighter than me, so no correction
for color was possible here.
The point of "self-control" is interesting, because my 7x50's limitting
magnitude here in BA is 8.5, and for red stars, you know it's brighter, maybe
8.2. So it would have been impossible for me to observe very clearly (not a
glimpse but a sharp clear point) R Cen if it was at 8.6....
But it's ok, I think there hasn't got to be "rules" and that people has to do
what they want..., as long as it is useful. So, it's importnat to check out how
you (yourself) are doing with your estimates. People seem to like playing the
"estimating game" and that would be good if the results get lost in their own
folders (or PCs). But if it's not like this, one should be more careful.
> This is an example of a caveat to non-Pogson-type (I don't know the |
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