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how to focus with a HA filter?
K so I got this HA filter (Lumicon). Bit of a random buy as I have seen this filter used buy many a people on this forum.
However over the year I have not really used it cause I cant focus it. Now recently trying to search this forum ( no luck really) but on google I found this quote :
" For mirror telescopes and apochromatic refractors, a clear filter with the same index of refraction and thickness can be substituted and focus can be accomplished visually. "
Then I also found this bit :
" The Astronomik MC-Clear is a multlayer-coated filter with no special optical effect. It has the same thickness as all other Astronomik-CCD filters and gives you the ability to focus your system with all energy entering your telescope. "
So does that mean that I should use a clear filter to focus, then replace the clear filter with the HA filter and all should be good?
But...
I'm guessing that a filter wheel would be the go as taking the camera out of the focuser, replacing the filter, putting the camera back in would cause the focus to change....
Can anyone confirm or dispel my thoughts please?
Thanks
Bartman
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