Aperture size for Solar Filter

[Putaendo Patrick]

I am planning to buy a sheet of mylar solar filter and make my own filter for a 120mm refractor. The lens cap however has a secondary opening approx. 60mm in diameter.

My question is whether I gain any significant benefit from a 120mm aperture filter, or whether I will get more or less the same results from the smaller aperture. Thanks everyone.

[Drop Of Sun]

I'd go for full aperture. You'll be able to get in much closer and see finer detail if you go full aperture. There is quite a big difference in detail between 60mm and 120mm!

It's a little bit like viewing the moon with a 60mm refractor versus 120mm, much finer detail to see in the 120mm as you go higher up in power.

I still use a 60mm scope sometimes (solar and lunar) for portability, but if you have the 120mm out anyway, I'd go large!

[Stu]

Agreed, the added resolution of 120mm is well worth having

[Moonshane]

+1

[Gazabone]

+2

[Steve Ward]

A4 is 210mm x 297mm , I'd make the holder to fit your dewshield OS diameter (which will be quite a bit bigger than 120mm) and the opening size to suit half the sheet , this will give you two filters from one sheet ... and a corner offcut will be big enough to make a small filter to fit your finderscope to save faffing about with extra "solarfinders" ... 

[Putaendo Patrick]

Thanks everyone! It seems there is no debate on this: 120mm (in a larger holder as Steve mentions) it will be.