The VSS CCD photometry spreadsheet

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Samantha Pierce
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1 The VSS CCD photometry spreadsheet Itroductio This Excel spreadsheet has bee developed ad tested by the BAA VSS for aalysig results files produced by the multi-image CCD photometry procedure i AIP4Wi v2. It uses a esemble magitude calculatio, which meas that multiple compariso stars ca be used to calculate the magitude of the variable star. These istructios relate to versio B2.03 of the spreadsheet although they are expected to be valid for ay versio startig B2. Purpose The purpose of the spreadsheet is threefold. It lets you examie the cotet ad quality of your data quickly ad so helps you to improve your observig techique. It provides a coveiet way of recordig all the relevat iformatio about a observig ru i oe place for future referece, which is importat if the data is to be of scietific use. Ad fially, it makes it very easy to submit your results to the BAA, the AAVSO or aother orgaisatio as part of a observig programme. The spreadsheet is iteded for use with time-series differetial photometry measuremets of a sigle object (plus compariso ad check stars) recorded with either o filter or a sigle photometric filter (eg U, B, V, R or I). Mostly the spreadsheet is self-explaatory if you sped a few miutes lookig through it carefully. I particular, ote the colour-codig of the various cells i the ObsvEqmt ad Results sheets. This tells you which cells you must fill i (red fot) about you ad your equipmet, your observig site, the objects beig observed, ad the observig sessio, which cells are optioal (blue fot) ad which cells the spreadsheet fills i automatically (gree fot). Some of the iformatio, for example about your observig site ad equipmet, will oly eed to be filled i the first time you use the spreadsheet ad ca the be copied for subsequet observig sessios. The iformatio about the objects beig measured will obviously eed to be added each time, or you ca just save several copies of the spreadsheet setup for differet stars. The cells cotaiig calculatios are password protected so you wo t be able to accidetally chage the formulae. Geeral Excel Notes The spreadsheet has bee tested successfully i Excel 2003 to Excel 2010, ad it is expected to work i future versios of Excel as Microsoft usually makes releases backwards compatible. However, it may ot work with Excel cloes like OpeOffice ad Kigsoft. You may eed to alter your Macro security as the spreadsheet buttos use Visual Basic. This may soud a little dautig but this is explaied below. Eablig Macros i Excel 2007 ad Later I Excel brig up the Optios meu. (The locatio of Optios varies i differet versios of Excel but it ca ormally be foud by the left most meu bar for File or the Widows butto.) Next select Trust Ceter (last optio o left had side). Click the Trust Ceter Settigs butto. The select the Macro Settigs. Set Eable all macros ad click OK. Eablig Macros i Excel 2003 I Excel select the Tools meu, the Macros ad fially Security. Set Eable all macros ad click OK.

You should simply click Yes to the message.

2 AIP4Wi Settigs The spreadsheet is desiged to work with the Multi-Image Photometry Tool, foud i the Measure meu of AIP4Wi. Note that you may see the below message whe selectig this Tool. You should simply click Yes to the message. Here is a screeshot of the settigs to select i the Multi Image Photometry Tool to create a output file that is compatible with the VSS CCD photometry spreadsheet.

3 Sheet Explaatios Below are a few words of explaatio about each sheet i the spreadsheet. Buttos sheet This cotais buttos to select iput ad output files, ad to process the data. The butto text is selfexplaatory ad the file ames ad paths ca be maually chaged should you wish to do so, otig that the folder must already exist! There are also some basic istructios at the bottom of the sheet uder the buttos. ObsvEqmt sheet This sheet cotais iformatio about you, your locatio ad your equipmet. The red fot text should be populated as it is used i the output files that go to the BAA VSS ad the AAVSO. Results sheet This is the mai sheet of the spreadsheet ad the oe you are likely to use most. You must eter iformatio i the cells with a red fot about the variable star, the chart, ad the compariso stars. Some iformatio i gree fot comes from the AIP4Wi data file or is calculated. It is worth emphasizig that if the chart/sequece you are usig gives o error values for the compariso stars, the the Referece Error colum should be left blak (colum G i versio B2.03 of the spreadsheet). You should avoid typig zero for the error as this will be treated as though the referece magitude is exact, which it will ever be. Istead type if the quoted error is zero. The Results ad Data Checks colums (colums H to O) are especially useful. They ca tell you whether or ot the compariso star magitude used i the esemble are i lie with the chart/sequece magitude (colum O), as well as the average weight of a compariso star i the esemble (colum K). The really useful part of the whole spreadsheet is you ca select ad deselect compariso stars from the esemble (colum E) to see what effect this has o the calculatio. You may eed to recalculate the spreadsheet after settig a compariso star to Yes or No, ad this ca be doe by pressig F9, but usually calculatio is set to automatic. If you make ay chages the you must press the butto to regeerate the charts, BAAVSS sheet, ad the AAVSO sheet. Calculatio sheet You eed ot cocer yourself with this sheet as it is the esemble magitude calculatio. It is visible if you are iterested i seeig how the calculatio works, but be wared it is ot for the fait hearted! CalcAAVSO sheet Almost idetical to the Calculatio sheet. The oly differece is that if a star is selected as Check i the Results sheet, the it does ot form part of the esemble i the CalcAAVSO sheet, but does form part of the esemble i the Calculatio sheet. Data charts sheet The Data charts sheet is useful for seeig at a glace what your data looks like. There are plots of the measured variable star magitude (mag V ref C), the derived compariso star magitudes, ad the raw istrumetal magitudes. The charts o the left had side do ot iclude error bars to make the poits easier to see, while o the right had side the chars iclude error bars. Just to the right of the charts are some settigs you ca adjust if you wish to bypass the chart automated miimum ad maximum axes values, ad to alter the roudig of the miimum ad maximum axes calculatio.

4 Examples of these plots are show below. BAAVSS sheet This sheet cotais a copy of the data file that is produced for the BAA VSS. AAVSO sheet This sheet cotais a copy of the data files that is produced for the AAVSO. Image sheet The Image sheet is optioal ad provides somewhere for you to store a image of the field with the stars you selected i AIP4WIN. This is very good practice as it provides a uequivocal way of rememberig which stars you actually measured. Data sheet This sheet cotais a copy of the AIP4Wi data file. Versio Log sheet This cotais a list of the differet versios of the CCD spreadsheet, alog with a brief explaatio of the chages.

5 The Esemble Calculatio Below is some optioal readig o the esemble calculatio. Geeral Notes o the Spreadsheet Formulae The formulae i the Results ad Calculatio sheets are completely recreated each time data is imported. De-selectig a star i the Results sheet (settig Iclude i Aalysis to No) chages the results of all the formulae so they o loger iclude this star (o eed to re-import the data). However, it should be oted that to chage which stars are i the graphs, the data must be re-imported with oly the required stars selected. The Esemble Formulae Itermediate Calculatios - Zero Poit Magitudes ad Errors ZPMagitude = Referece Magitude Istrumetal Magitude ZPError Referece Error 2 Istrumetal Error 2 Both of these are multiplied by either 0 or 1 i the spreadsheet formula to exclude or iclude them i the aalysis. Derived Magitude ad Errors Derived Magitude Istrumetal Magitude ZPMagitudes 1 Derived Error 1 ZPError 2 Here is the umber of compariso stars used i the aalysis. So if you have measuremet of 10 comparisos but oly choose to use 5 i the aalysis, the is set to 5 withi the spreadsheet formulae.

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