Welcome on board!
The size of the blocking filter (BF) is determined by the focal length of the scope being used. The minimum size would be 1/100 the focal length ie 10mm for 1000mm
Larger filters just give a wider field of view.
The blocking filter is just one element in a Ha solar telescope.
You need an effective energy reducetion filter (ERF) then an etalon type filter which produces a series of narrow bandwidth "spikes" one of which is centered on the Ha, then finally a BF. The blocking filter and works closely with the etalon and "blocks" all the other spikes other than the one at Ha.
Unfortunately the coatings of the internal ERF on some scopes deteriorates (looks like "rust") and fails. This is NOT unsafe, but it does significantly effect contrast and resolution.
Some ERF filters last many years, others may fail in a couple of years...don't know why...
The external Baader D-ERF seems to be less prone to deterioration.
Coronado Blocking Filters
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Re: Coronado Blocking Filters
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer