The following image was annotated using information from USNO B1.0
B, R and I magnitudes were taken from the dataset of:
Vizer using USNO B1.0
Enter NGC4676 then "Submit Query"
Select the first list element that display
Select "Aladin Image"
This will display the DSS POSS-II overlayed with the dataset from USNO B1.0
Clicking on a star will display the information from the dataset in the text box at the bottom.
Now taking the magnitudes shown I then fed them to the spreadsheet program to
calculate the Vmag from the given B/R/I based upon Jansky flux constants, see:
Vmag calculator for USNO B1.0 dataset
