Secondary Mirror question

[Astroscot2]

Hello all.

Im looking at building a small astrograph, 6" F4 ,  my aim is to buy the component parts rather than make them myself,  regarding the optics does anyone know of a method or program that can calculate the secondary mirror size requirement to fully illuminate an APS-C size sensor?

 

thanks

[almcl]

Think there are several, but does this one help?  You need to translate the 100% illuminated circle figure (on the specs tab) to whichever APS-C sized sensor dimensions  you're using, but otherwise it seems to work

https://stellafane.org/tm/newt-web/newt-web.html

 

[Astroscot2]

30 minutes ago, almcl said:

Think there are several, but does this one help?  You need to translate the 100% illuminated circle figure (on the specs tab) to whichever APS-C sized sensor dimensions  you're using, but otherwise it seems to work

https://stellafane.org/tm/newt-web/newt-web.html

 

Thank you