Quote:
Originally Posted by LewisM
...all anodising is is cathodically...
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It's the anode, hence the name.
You are correct about using cheap dye. Skywatcher probably figured telescopes are used at night so they didn't need to use a lightfast dye.
Black dyes are the most expensive, the black I use is '
Black BK Excel' from US Specialty which has good lightfastness (8/10 score) at 20um thickness, fine for my needs, but it costs about twice as much as all the other pretty colours.
If I was anodising for daylight use I would use 'Black HBL' (about 4x the price) but it rates 8/10 at 10um and 10/10 at 25um thickness.
There is a very good article about why black is not black here:
http://www.pfonline.com/articles/whe...e-is-not-black