CCD focusing.

[Ronclarke]

Well set up and aligned OK, pointed towards Capella and using APT's Focus Aid and Batinov Aid I focused spot on using the IR cut filter. When I changed the filter for the AA Tri bander and found it really difficult to focus anywhere near as good as with the IR cut filter! Is this normal with NB type filters?? There was a Full Moon tonight just to help matters!!

 

Ron

[symmetal]

You need a much longer exposure to get a good bahtinov image with narrowband filters, around 10 times that used for wideband.

Also depending on how good your optics are the triband filter will effectively produce a separate bahinov image for each band and the optimum focus setting may not be the same for each band. The wideband image will be an average of the different colour bahtinov images while the tri-band will have 2 or more distinct images superimposed.

Alan