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Old 28-04-2015, 03:26 AM
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skysurfer
Dark sky rules !

skysurfer is offline
 
Join Date: Dec 2011
Location: 52N 6E (EU)
Posts: 1,056
Which large Halpha filter ?

I have a Baader 7nm wide 48mm diameter Halpha filter which works excellent on the T-ring adapter on my telescope and with a step down adapter on the Canon 85mm f/1.8.

But for a Canon 70-300L (aperture 55mm) and the Canon 200mm f/2.8L (aperture 70mm) this filter is too small.

The Astronomik fullframe clip in filters ($429 for 6nm wide FF clipin filter) are too tedious to (un)install in the camera in the dark.

Two alternatives: a 72mm screw-on filter which is however not real narrowband as it allows everything above 640nm. But that is compensated by the fact that the longer (redder) wavelength is more anttenuated by unmodded EOS (656nm: 25%). But with $118 it is rather affordable and easy to install. But will this not lower contrast considerably ?
http://www.robtics.nl/product_info.p...oducts_id=5011


The alternative is a 65x65mm square filter sheet from Baader, also 7nm wide. Installation can be done by putting within on a 80mm PVC plumbing pipe cap with a 65mm hole in it and putting that over the front of the lens.

http://www.teleskop-express.de/shop/...ungefasst.html

Does somebody have experience with that Lumicon (fake ?) Halpha filter ?
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