Coronado PST 1st light

[Peter Drew]

I think the sweet spot size is somewhat a function of the aperture of the etalon. That of the PST is only 20mm whereas the Lunt60 is 35mm. It's worth repeating that increasing the blocking filter size increases the field of view and not the sweet spot size so you end up with a larger expanse of field that is not "on band". 

[andre2]

Update. Try to adjust the tuning wheel slightly to the left or right, while you put the scope in the right position and at the right momend and a bit pations.( maby the position of the sun, seeing eye get used to the wavelenght play also a role but dont know for sure) Good luck to recieve full disk!  André from holland.