[Aavso-photometry] V0567 Oph

[Shawn Dvorak]

Arne has already answered your questions but I'll throw in my 0.02 on a 
couple of points.

Stan Walker wrote:
> 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.
>
I, too, thought about this when pulling the Mira and ZAnd star data.  
However, I confined myself to the Miras on the NMO ("needs more 
observations") list which by definition were not getting enough 
estimates, visual or otherwise.  The ZAnds are, as a class, 
under-observed by AAVSO observers, and their ranges are fairly small 
which makes them more challenging for visual observers.  I do agree, 
somewhat, that the wholesale importation of the ASAS data is not 
desirable - there's already a perfectly good web interface for 
collecting this data.  As Arne mentioned, a VO-type link would be the 
better way to go to provide seamless access to ASAS (and other 
databases) within the familiar ID interface.

> 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!
>
Visual observers seem to be continuing without much impact, as far as I 
can tell.  Data from the ASAS, NSVS, SDSS, TASS, and other surveys have 
been available online for some time (though not within the ID). The 
existence of ongoing large-scale surveys will naturally mean that visual 
*and* CCD observers will have to change their observing programs to fill 
other niches.  Once the ASAS data started pouring in I began giving 
preference to targets north of that survey's coverage zone, as well as 
targeting fainter objects and those with smaller ranges - areas where 
ASAS falters.  I've also been doing more time-series on transient events 
like CVs since nightly surveys like ASAS don't provide enough time 
resolution.

> 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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>
>
>