Absolute quantification of viral DNA

[Buni]

I would like to use qPCR for absolute quantification of viral DNA in unknown samples. So far I have used a standard curve generated by a 10 fold dilution series of a known quantity of genomic viral DNA (this was calculated using a nanodrop) and from here I have been able to work out the amount of ng of viral DNA in each sample. Does anybody have any ideas/comments on whether this is the best way to quantify the amount of viral DNA in each sample.
Is it possible to work out the copy number of my initial starting template of genomic DNA (ie first dilution of standard curve) and then from here quantify each sample based on copy number? If so any tips on how I can do this calculation!

Thanks.