Using a telephoto lens with a 2 inch Optolong L-enhance filter

[M3 16]

Hello, I want to use a 2 inch Optolong L-eNhance filter with a 70-200mm f2.8 lens. Since I will use an astronomy camera in the future, I do not want to buy a clip filter. But there's one thing I'm worried about: How much vignetting will a 2-inch filter create with a lens with a filter diameter of 77 mm? Does changing aperture or focal length reduce vignetting?

Edited 12 hours ago by Cornelius Varley
formatting corrected

[Elp]

2 hours ago, M3 16 said:

lens

Is it a Canon lens? (Or dslr lens, not mirrorless).

[M3 16]

2 hours ago, Elp said:

Canon lens mi? (Ya da dslr lens, aynasız değil).

I am using nikon d5300

[Ratlet]

Are you planning on putting the filter on the front of the lens?  You won't get vignetting but you will increase the f ratio.  You'll end up about f4.6 

[M3 16]

2 hours ago, Ratlet said:

Filtreyi lensin önüne koymayı mı düşünüyorsunuz? Gölgelenme olmayacak ancak f oranını artıracaksınız. Yaklaşık f4.6'ya ulaşacaksınız. 

Yes, I'm thinking of using the filter by putting it in front of the lens because I don't seem to have any other option.

[Vroobel]

You didn't answet this question:

 

8 hours ago, Elp said:

Is it a Canon lens? (Or dslr lens, not mirrorless).

 

A possibility of placing 2" or 1.25" filters between the camera and the lens depends on a construction of the lens.

 

[Elp]

Nikon D5300? So a typical dslr lens and Nikon F mount.

You can adapt Nikon F to Canon EF, then use a ZWO eos to m42 adaptor (there are two types) to connect an astro camera. The eos adaptor comes in a filter drawer type taking up to 2 inch filters or a standard type which you can screw up to 2 inch filters into.

I'm not overly family with Nikon but my last lens needed an aperture control adaptor in order to change the aperture manually (or I could have step down ringed the front of the lens), I don't have a Nikon body to do the switching. The other issue would be filtering the lens if using your Nikon. You can put the filter out front but you'll be stopping the aperture down which can be counterproductive on larger glass.