Working with DSLR photometry for several months, I found that existing Data Reduction Spreadsheet is not completely fits my needs, especially when I tried to capture time series for HADS variables.
So I've created my own spreadsheet for time-series treatment. Currently it supports V and B magnitudes only (R-channel is ignored) and it uses "narrow field approach", when we can neglect differential extinction (I'm using Canon EOS 600D in conjunction with SkyWatcher 150/750, so my field of view is rather narrow).
The spreadsheet can also calculate average \ stdev for several measures related to one observation, like existing Data Reduction Spreadsheet does.
The spreadsheet (along with a short description) can be downloaded from my Google Drive https://drive.google.com/open?id=1waZvRStTXmKOp32iabfXEvOOOQzXXhy6
[note on 16 Apr 2018: Due to false virus alert while uploading EXE-installer of one of my other tools to my site, the download from it was disabled (I'm vaiting for a reaction to my appeal from Google), so I changed a link to Google Drive]
Transformation procedure follows “AAVSO DSLR Observing Manual V 1.4”, section 6.5, however it slightly differs from one used in existing Data Reduction Spreadsheet.
First, it, by default, does not use "known" B-V of the target. Instead, target's B-V (for each measure) is derived from instrumental (b-v) using B-V transformation coefficients (see description for details). However, if you know resonable B-V value of target, you can use it instead of calculated one.
Second, one can use previously measured transformation coefficients (Tbv, Zbv, Tb_bv, Tv_bv), obtained from "standard field". There is also a possibility to use transformation coefficients, derived from the current set of compstars.
The spreadsheet contains an example of AE UMa time series (I've recently uploaded these data to AAVSO)
If you find the spreadsheet useful, I'll be glad to get any comments/criticism about it.
Sincerely yours,
Maksym (PMAK)
Hi Maksym,
thanks for making your spreadsheet available to other DSLR photometrists. I've downloaded the ZIP file and will take a close look over the coming days.
I also do a lot of time series DSLR photometry and use a modified version of the Data Reduction Spreadsheet to analyse them.
I'm collecting a time series of the EB/KE eclipsing binary TU Mus right now so tomorrow I'll process and measure the images. It will be interesting to see how results from our two spreadsheets compare. Cheers,
Mark
Hi Mark,
It would be very interesting to compare two approaches (and also make an independent check of the spreadsheet :) ). "Data Reduction Spreadsheet" (R-I_V2.6.xslx) approach is based on current ensemble of compstars and, if I understood correctly, current instrumental magnitudes are required to calculate transformation correction [because we need zero point ZPv: (V-v) = -Tv_bv *(B-V) + ZPv ]
When we rely on transformation coefficients determined from standard fields we should rely on Delta(B-V), in this case (again, if I understood the things correctly) we only need Tx, so there is no problem with zero point.
Best regards,
Max
Hi Maksym,
Thanks very much for sharing your spreadsheet! I have in the past used the Data Reduction Spreadsheet after participating in the DSLR photometry Choice course run by Mark. I have run a few measures through both spreadsheets and found there to be good agreement using the two approaches. The unmodified standarrd spreadsheet, as you say, is not very suitable for time series observations. Perhaps Mark could share his modified spreadsheet with us!?
Have you considered including an airmass calculation in your spreadsheet?
Thanks agian for sharing and I have found this very informative.
Regards,
Dave(BLD)
Hi Dave,
Thank you very much for your interest!
Actually, I've already implemented air mass calculation in the spreadsheet (using Excel macro which works as a spreadsheet function based on an algorithm from original "Data Reduction Spreadsheet"). Now I'm checking if all works correctly and probably will share the new version soon.
One remark about calculations based on catalog values of B-V for compstars and calculated B-V from observed b-v for target: it works only if calibration process (namely, flat field division) does not alter color balance of an original image. Only in this case we can use a formula B-V = Tbv*(b-v)+Zp for estimation of a "real" B-V (which I use in my spreadsheet) where Tbv and Zp were obtained from the standard field (and where Zp is a characteristic of your sensor, not an arbitrary constant).
I currently use IRIS and can say that IRIS does not disturb color balance because it uses neutralized flat field ("grayed", if you use "DSLR workflow"). So you should check if your software works the similar way.
Max(PMAK)