just discovered something cool

Richard Crisp

I just discovered something cool

I am using the baader narrowband set on the ap180edt f/9 right now. first time to use them on anything but the pentax 6x7 lenses (150, 200, 300mm so far)

anyway on the big apo i found that they are parfocal!

so on a well color corrected scope, the filters are parfocal at 673, 656, and 500nm wavelengths

that's a nice and unexpected benefit!

it sure takes time to test gear though: you get all set up to use one configuration and then hate to switch to something else: halfway through a multi-night image etc: once I get on a roll shooting images with one system configuration I tend to stick with it for a while. Anyway it is nice to get to use the filters on the big apo. Hopefully I will have some results to show pretty soon.


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