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I currently have a 40mm Coronado PST. At first I have captured some great images with it. However currently it has major dark patches making it near impossible to actually use at all.

I think this may be due to the focusing component or the etalon being mis-aligned.

In any case I own a small refractor and I a thinking of modifying the PST to use with a refractor.

Any ideas on a good modification tutorial? Is it worth it.

I have actually reviewed a few so far and it all seems a bit straight forward. I understand I would need an energy rejection Filter something like the Baader D-ERF Energy Rejection Filter. To put at the front of the refractor.

However Baader states they will only sell them with the Hydrogen Alpha filters. So anyone know where I can get such a filter by itself? Are their alternatives.