[Aavso-photometry] V0567 Oph

[Stan Walker]

Hi Shawn,

I read your post with interest. Two questions/thoughts.

Firstly, is ASAS3 calibrated? Arne has stated, I think, that it's just V 
filter photometry but uncalibrated and untransformed. So if this is the case 
it may well contain errors amounting to the slope of the response plue the 
colour difference. Could this issue be clarified and referred to in all 
future posts?

Secondly, and this is more in Arne's territory, what is the point in 
including ASAS3 data in the International Database? The implications are 
that this is a repository for amateur measures. ASAS data is available on 
line from their website in a rather more detailed manner than it can be 
published in the ID. It has limitations which are detailed in their database 
but it's impossible to carry the nature of these across to the AAVSO area.

As a user of both I am a little frustrated that I have to remove the ASAS 
data - and throw it away - from measures I download from the IB. The IB 
contains some good transformed BVRI measures which tend to be submerged in 
the mass of slightly lower quality ASAS V measures.

Still on this topic, will not the inclusion of ASAS data tend to discourage 
visual observers?  Being supplanted by a large scale mechanical operation it 
is not a positive way of encouraging visual measures. And the V of the 
Johnson UBV system is not equivalent to classical visual measures which 
define the behaviour of variable stars over the past century or two. I think 
both you and Arne need to think much more seriously before these measures 
are added to the database!

I'm not decrying ASAS's role but I think that it would be much more useful 
in searching for new variables - do we need any more? - and working on the 
low amplitude objects such as SRs with half magnitude ranges. For the larger 
amplitude objects visual observing is adequate and fits the historical 
methods much better. Why mess about with something which isn't broken? Maybe 
you should get out behind a telescope more?

Regards,
Stan


----- Original Message ----- 
From: "Shawn Dvorak" <sdvorak at rollinghillsobs.org>
To: "Aavso-Photometry" <aavso-photometry at mira.aavso.org>
Sent: Wednesday, July 01, 2009 12:26 PM
Subject: Re: [Aavso-photometry] V0567 Oph


> Arne mentioned the script I wrote to pull ASAS data and submit it to the 
> AAVSO.  It's a fairly simple Perl script that parses through an input list 
> of stars and pulls off the ASAS data for each target star as well as 
> suitable nearby comp and chk stars.  The comp and chk stars aren't 
> necessary for using ASAS data since it's already reported in calibrated V 
> mags, but the AAVSO input format requires it.  Using them was also a good 
> check on the data.
>
> I used the script to import the ASAS data for all of the Mira and Z And 
> stars in the AAVSO programs and they worked pretty well for that.  The 
> biggest problems I ran into were: poor fields that had few/no good comp 
> and chk choices; and problems with mis-ids when stars were faint.  These 
> cases required some manual interventions but most stars were processed 
> without any manipulation.
>
> Shawn
>
>
> arne wrote:
>> James Roe wrote:
>>> Last night I was supporting a student project looking at V0567 Oph.  We 
>>> got
>>> some good data and I submitted it to the data base (it was in VSX but 
>>> not in
>>> the validation file, but it is now I guess).  I looked the star up in 
>>> the
>>> ASAS3 database and found a ton of measurements which I used to specify a 
>>> C
>>> star in V (but no data in B nor Ic).  We took data in B and Ic but I'm 
>>> not
>>> sure how to prepare the data without C stars in these bands?  Advice 
>>> please?
>>>
>>> Also, is there a way I can help get the ASAS data into the AAVSO data 
>>> base
>>> for this star?  Is this what data mining is all about?
>>>
>> We're working on an automated way to get ASAS data into the International
>> Database.  Until then, contact Shawn Dvorak, who has scripts to
>> pull off ASAS data on specific stars.
>>
>> V567 Oph looks like a field that I have not yet calibrated at NOFS
>> nor SRO.  Therefore, you have to look for other calibration photometry.
>> There is always Tycho2 to give you basic B and V photometry of
>> nearby comparison stars. The TASS Mark IV patches photometric
>> catalog will give you rough Ic magnitudes for your comparison stars.
>> You can also use CMC14 or DENIS magnitudes and transform to obtain Ic.
>> You can determine BVIc yourself via all-sky methods.  Finally, you
>> can submit the raw differential data using the AAVSO extended format,
>> identifying the comparison star that you used, and let a future
>> researcher calculate its true magnitudes once the comparison
>> star is properly calibrated.
>>
>> In a few months, you should be able to use APASS calibrations to
>> take care of the entire problem.
>> Arne
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