[Aavso-photometry] CCD 'fainter-than' question

[Wolfgang Renz]

>> If its a less than a 3 sigma detection, it should be probably reported
>> as a 'fainter than' with the value of the background + 3 sigma as mag
>> But this mag value is unfortunatly nothing that is available with usual
>> photometry software. So maybe someone of the experts can recom-
>> mend how it can be fast and easily determined.
> 
> I am not sure what you mean.
> Can;t you get that number out of _any_ software that does photometry?

Not necessarily, some simple ones hide everything except the mag or
delta mag values.

But I meant the mag value to use for the 'fainter as' to be reported

I've just made a Mira photometry with some measurements below SNR
3 down to SNR 0.2 (which is of course just noise):
#,Image,Obj,Magn,Std?,Error,Error(T),X,Y,Col,Row,Bagkgr,S/N,Resid.,Net Count,Filter,Date,Time,JD - 2453000,Airmass,Exp Time,Weight,Object,Object
1,HV_Vir.fts,1,14.1000,*,0.0133,0.0134,609.615,654.057,609.615,654.057,108,81.1,0.0000,15067.4,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
2,HV_Vir.fts,22,18.3602, ,0.5877,0.5944,732.713,723.969,732.713,723.969,107,1.8,0,297.827,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
3,HV_Vir.fts,23,20.8089, ,5.6841,5.6727,964.941,433.693,964.941,433.693,108,0.2,0,31.2236,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
4,HV_Vir.fts,24,19.0179, ,1.1263,1.0913,858.000,128.000,858.000,128.000,108,1.0,0,162.512,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
5,HV_Vir.fts,26,18.2622, ,0.6146,0.5450,992.553,141.438,992.553,141.438,108,2.0,0,325.948,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
6,HV_Vir.fts,27,18.1889, ,0.5030,0.5079,546.208,821.348,546.208,821.348,107,2.1,0,348.735,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
7,HV_Vir.fts,33,18.8217, ,0.9170,0.9112,324.052,752.881,324.052,752.881,108,1.2,0,194.689,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
8,HV_Vir.fts,35,19.4107, ,1.5484,1.5663,301.009,425.941,301.009,425.941,108,0.7,0,113.175,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
9,HV_Vir.fts,39,18.4497, ,0.6835,0.6474,448.693,62.319,448.693,62.319,108,1.7,0,274.263,V,2008-05-24,04:21:01,1610.681262,1.1673,90.000,1.000,HV Vir,HV Vir
Aperture Photometry Calibration Results
Zero Point Calculation for 'HV_Vir.fts'
Calibration Summary:
Zero point: 20.356
Rms Error : 0.000 mag
Standards : 1
Aperture Summary:
R1=10.00, R2=20.00, R3=30.00, E=0.000, Theta=313.00

How would you report them as < x mag ?
How would you determine x ?

Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO



----- Original Message ----- 
From: "Michael Newberry" <mnewberry at mirametrics.com>
To: "Wolfgang Renz" <w_renz at onlinehome.de>; "Bob Crumrine" <rcrumrin at rochester.rr.com>
Cc: "AAVSO-PHOTOMETRY" <aavso-photometry at mira.aavso.org>
Sent: Wednesday, May 28, 2008 5:37 PM
Subject: Re: [Aavso-photometry] CCD 'fainter-than' question


> [...]
> 
>> I think that its generally accepted that a 3 sigma detection above the
>> noise is sufficient certain to report such a measurment with its high
>> error.
> 
>    yes.
> 
>>
> 
> Michael
> 
> [...] 
> 
> 
>