[vsnet-chat 5953] CCD-V Vs visual observations = U ORIONIS

["Sebastian Otero" <varsao@fullzero.com.ar>]

Some days ago through the AAVSO discussion list, a couple of observers asked
worried about the ultimate fate of visual observations in the middle of the
CCD age.
The answer was that both visual and CCD observations complement each other
and are not comparable.
I agree with that.
Visual work will never stop existing, there are simply too many stars up
there ;-))

This time I want to call the attention to one very well-known star: U
Orionis, a bright mira.
This star is in the CCD program of the AAVSO and is "over-observed" visually
by its members and all observers in the world.
I took a look at the quick look data for this star and I was surprised -in a
bad way-...
I found a lot of incoherent CCD data full of mistakes mixed with coherent
visual observations.
It is difficult to tell if these are mistakes arisen from typos, wrong
reductions, wrong observations, worng identifications.....
At JD 2452638.7993 there are two sets of observations with the same date and
different magnitudes(V= 7.31 and 7.26)! (PDO)
Nine days later, the star was measured by other observer (WGR) at 6.97 with
a B-V of 3.69 !!!!!!
BUT a day after that, MTK recorded it a t 7.38 with a B-V of 1.79......
Another three days and WGR found it bluer again at 1.53 with a V mag of
7.13.
BUT only a day was necessary to the star to fade to 8.01 and to gain a bluer
color of 1.07 !!
Two days after that, the color was typical of a cepheid: 0.91 (V= 8.11)
And the following day the star turned into an O3 star..... V= 8.17,
B-V= -0.26.......
By JD 2452661.5404 the color was back to normal (1.72) at V= 7.26
BUT the same day, MTK measured a V mag of 7.65 (B-V= 1.76)
By JD 2452665.5004, WGR came back and measured 7.47 (1.74), so the color
remained constant.
But two days after that, it turned to a cepheid again with V= 7.97, B-V=
0.93
The latest observation is from MTK at 8.15 at JD 2452675.487, and the
following day, "NADAV" (is this an actual observer's code??) reported 10.4:
visually...... I see the point in the colon.......;-((

So visual observers shouldn't worry too much.....
The only useful data on U Orionis is that reported for most of them.
U Ori varied only between 7.2 and 7.6 in this period....
CCD Observations can be very useful..... (potentiallly)
Visual observations too.
Both need to be done accurately. Both need to be revised before pushing the
SEND botton.
I am not a CCD observer but it makes no sense to report these results.....
When someone has the oportunity to do it better than visuallty, this
oportunity must be taken.
I assume photometry is a difficult thing to do but if the results are like
these ones (and I am realizing that finding someone who actually makes it
better than the visual observers is a very rare thing...) no efforts should
be wasted...
I think that observers should have the advice of the experienced to get good
results before reporting observations.
If not well-managed, the art of photometry can be worse than the worst
visual observations. Looking at the star, you can see that something is not
happening. When you're only looking at numbers gotten from a camera, you
might not become aware of the actual behaviour of the star if your results
are not related to reality.....
And that is happening too much too often  for my like......

Yes, these data is unvalidated... but...how can you validate this?
Observers need to be more careful in reporting data that is evidently in
error.
The quick look pages are full of typos, wrong magnitudes (e.g. "0"),
misidintifications..
Another example:

1207-43  MU CEN     JAN 31.5030  2452671.003   <13.8   SRX
1207-43  MU CEN     FEB 01.4940  2452671.994   <13.6   SRX
1343-41  MU CEN     FEB 04.4861  2452674.9861    3.6   WJD
1343-41  MU CEN     FEB 07.4688  2452677.9688    3.5   WJD

MU Centauri and mu Centauri can't be confused as the same star !!
They even have different designations, so why this mistake takes place?
Someone has to make at least a rough control on the data included in the
listings.
Software on variable stars needs to be case sensitive. I never understood
why AAVSO insists in calling l Carinae "L CARINAE". This is not the same
star. Upper case and lower case are assigned to different stars in the
Southern hemisphere.
From the MU Cen and mu Cen confussion, it looks like the same star has
undergone a 11 mag. outburst!!!!
"Nova West 2003" ! ;-))

There are lots of lightcurves out of scale just because someone input a
wrong magnitude that left the star (with a true amplitude between 9.1 and
9.9) with a scale from 0 to 10 mag.........

I don't want to have a panick attack every time I take a look at the quick
look files.....
Observers should be more responsible for their work and there needs to be
some control that prevents these useless observations to see the light.

Best wishes,
Sebastian.


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