Hi Pat,
I used a grey card (11-13% from memory) under sunny day to do my custom white balance. I cannot comment on the 60Da but know that it is sensitive to the Ha (656nm) but the in camera processing makes the images taken in daylight look "natural".
You will see on the spectral data that LP filters filter out the unwanted street lights in the sodium and mercury vapour type (yellow and light green) and is therefor only useful in light polluted site. For country dark sites, a LP is not needed for reflectors and an IR.UV filter is needed for refractors.
Raymo, I respectively disagree with your assessment that one needs both modded and unmodded DSLR as a modded DSLR simply opens up the spectral response range. The only difference is when a LP filter is used.
As for my M20, I acknowledge that it does not show up the blue reflection nebula as some others. But bear in mind it was taken with a LP filter on, which does limit the darker blue/violet colours. This is explained in this discussion here
https://www.cloudynights.com/topic/5...-modification/
Summing up, a full spectrum mod is very useful to capture the full spectral response of a CMOS sensor, but adding a LP filter limits its response range. A modded DSLR will perform best when used under dark skies without a LP filter.
Cheers
Bo