[Aavso-photometry] Need High-dec (B-V)~0 stars & Secondary Extinction Pairs (3 new additions for your lists);

[Daniel Majaess]

Hi Richard, sorry for the tardy reply and thank you for your previous 
list of extinction pairs that you allowed us to have. Interestingly 
enough, I was actually using an RA/DEC globe at school and going through 
the list I tabulated from Vizier, although your star selector option 
sounds pretty neat aswell =)   I would love to get a hold of your 
spreadsheet and perhaps I could supplement it further aswell with the 
stars I have found.

Daniel.

RICHARD MILES wrote:
> Daniel Majaess wrote:
>   
>> So I am now thinking of shifting gears and adopting the
>> protocol outlined in Henden's book whereby a bunch of different stars
>> (at varying airmass) with (B-V)~0 are imaged.  I was wondering if anyone
>> had a list of high-dec, bright (7.5-9.5 mag) stars with a color (B-V)~0,
>> and also they need to have well-defined visual and blue magnitudes so
>> Hipparcos data will not cut it.   Any suggestions would be lovely =)
>>     
>
> Dear Daniel,
>
> I have developed some spreadsheets specifically for conveniently measuring 
> extinction in V and I bands but have not advertised these as yet.  I can 
> send you one or other of them off-line.
>
> For instance for measuring atmospheric extinction coefficients, kv, and 
> exo-atmosphere zeropoint Zv, I have two spreadsheets; one using stars where 
> (B-V)~0 and a second where (B-V)~0.8.  (The difference between the two is a 
> measure of second-order effects/transformation coefficients - especially useful when working unfiltered.)  Here's an extract from the former 
> spreadsheet:
>
> LIST OF 568 NON-VARIABLE, 'MONOCHROME' 'BLUE' EXTINCTION STARS TAKEN FROM 
> HIPPARCOS DATABASE
> meeting the following criteria:
>
> 6.00 < V < 9.00
> 0.0004 < delta HpMag < 0.0024 mag
> 0.010 < (B-V) < 0.040
> 0.01 < (V-I) < 0.07
> No other field star having delta V < 6.0 mag within 60 arcsec
> No other bright field star nearby which might confuse identification
> All variable stars excluded
>
> The spreadsheet is Excel-based and contains four sheets:
> 1.  Source data from Hipparcos used as a look-up table by the other sheets
> 2.  Star selector sheet - you put your latitude, longitude and date/time in. 
> You then can specify the airmass range you wish to work at and it highlights 
> those Hipparcos stars available together with their azimuth and altitude. 
> It even tells you what the approximate exposure time is for each star so 
> that the image is say no more than half-saturated.
> 3.  Data reduction sheet - here you cut and paste from AIP4WIN format and it 
> calculates the slope and intercept plus some error calculations.
> 4.  Plotting sheet - here you have two plots - one is all the points from 
> the reduction of individual images, the second is block-averaged points for 
> each star.  I should add that I generally take a series of images for each 
> star such that the average value is a more accurate figure than that from 
> any single image.  The image series can be anywhere from 7 to 21 images 
> (always an odd number though).
>
> Hope this gives you a feel for how this works.
> Cheers,
> Richard Miles
> Dorset, UK
>
>
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