Off-axis Solar Filter

[matelot]

Hi, all,

I've some Baader solar film left over from my 400mm telephoto and DSLR, so figured cutting out a disc in the new SL 8" Dob firm-fitting plastic dust cover rather than faff with cardboard/glue/duct tape etc. Seems eminently suitable for the purpose.

And then I found divers threads (all over t'internet) on off-axis solar filters - but next-to-no solid explanations and only supported by deleted photos... I gather that off-axis simply relates to a non-centred aperture, designed to avoid the secondary shadow and vanes. Being non-centred means a naturally smaller aperture and resultant stopping down. Is that correct?

Given the Sun, how does an off-centre aperture compare to a rather larger centred aperture in respect of resolution? I could accept what I've found to date and make a decision (go small then open up if necessary), but respondents' opinions change over time.

Cheers, all. 🍺🍺🍺

[newbie alert]

Yes you're quite correct on the off axis , and the stopping down way of thinking..  you don't need it full aperture to gather light as the sun's bright enough as it is. .. not sure on the diffraction from the spider vane , but solar using baader film white light is fun...

As a suggestion join the Solar chat forum for clarification... Safety of your eyes is a premium 

Enjoy 

[Gabby76]

Placing the opening between the spider vanes will get rid of the diffraction spikes and stopping it down to 100mm or so will provide a more than bright enough image. 

Remember to either make a filter for your finder scope or remove it entirely so you do not accidentally use it.