[vsnet-chat 7250] [vsnet-obs 53846] Re: data format correction

[Berto Monard]

I am always puzzled why CV is used for unfiltered CCD photometry with the effective wavelength of an unfiltered CCD chip being close to that of the R..Rc band (for non-red sources). 

It's like making R estimates from visual observations, not?


Re: 0003-39  V SCL  2453679.549 CV>16.04 MDJ    V= 10.9 (= about 10.0Rc)
considering the instrumentation that was used, this red star must have made quite a mark on the image for exposures exceeding a couple of seconds... 


BTW I am still utilising UCAC2 for making Rc sequences using the empirical formula
Rc = UCAC - 0.3 (J-K), 
while also
V= UCAC + 0.7 (J-K)     /       assuming J-K = V-R, which holds reasonably (+/- 0.2)

OK, these are not very accurate for magnitudes over 14, but compare them anytime vs calibrated sequences. Derived V mags can also be checked vs ASAS data of constant stars. Such a V sequence interchecked on an image will lead to a set of quite accurate comparison stars for differential photometry.
    
I made 1500+ sequences that way...

Regards,

Berto Monard
Bronberg Observatory / CBA Pretoria


>>> "Sebastian Otero" <varsao at fullzero.com.ar> 09/11/2005 02:17:38 >>>
----- Original Message ----- 
From: "Taichi Kato" <tkato at kusastro.kyoto-u.ac.jp>
To: <vsnet-obs at ooruri.kusastro.kyoto-u.ac.jp>; <vsnet-obs at yahoogroups.com>
Sent: Tuesday, November 08, 2005 9:05 PM
Subject: [vsnet-obs 53844] data format correction


> # CV, CR etc. are for unfiltered CCD photometry

Those observations were actually unfiltered according to the original 
report:

"Mendicini, Daniel José
Santa Fé, Argentina
C 14-F/7  AP - 7 CCD
photometry diferential-unfiltered
Soft IRIS. Catalogo USNO A2.0"

BUT the problem here is that the identifications are wrong for most of the 
stars and the results are not even close to the V mag. from ASAS in any 
case:

Mendicini data ---------------------------------- ASAS-3 V

1744-06 RS OPH  2453679.535 CV 10.17 MDJ  V= 10.7
1744-06 RS OPH  2453679.535 CB 10.92 MDJ
1744-06 RS OPH  2453679.535 CR 10.12 MDJ
1811-46 RS TEL  2453679.519 CV 10.41 MDJ   V= 9.80
1811-46 RS TEL  2453679.519 CR  9.96 MDJ
1811-46 RS TEL  2453679.519 CB 11.16 MDJ
0106-30  U SCL  2453679.561 CV>16.63 MDJ    V= 15.0
0003-39  V SCL  2453679.549 CV>16.04 MDJ    V= 10.9
0044-35  X SCL  2453679.552 CV>15.11 MDJ    V= 11.67
2106-09 VY AQR  2453679.540 CV>15.82 MDJ   V= 13.8

I also wouldn't use USNO as a source of photometric values having PEP, ASAS 
and everything we already know of. Asking for advice or checking what we are 
doing before flooding the databases with wrong data is always recommended...

Cheers,
Sebastian. 




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