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I would like to observe the Sun through my 7″ f/9 refractor.
Advice is to use a 2″ Herschel wedge, as the 1.25″ makes to small an image, but is my telescope to big for this kind of observation?
2″ wedges are made by Baader, Lunt and Lacerta (maybe others too) Lunt says: “The 2″ model performs best on refractors with apertures of 6” or less”,
Is there a limit? Will the heat be too much for larger telescopes?
Perhaps the advice indicates that the brightness of the image may still be too bright. If that is the case, a ND filter should complete the task, especially as (7/6)^2 is only 1.4 and the increased IR load will be quite small.
Maybe consider a full-aperture filter over the objective? I have used aluminized mylar film with great success, admittedly with smaller apertures.
The telescope aperture could also be stopped down i.e. 4″ with all the other safety measures suggested above.
Eric
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