equipment advice

[Salva]

Hi all,

atm I have a Canon Eos 500D with a EF300mm mounted on a Star Adventure Pro.

I'm going to upgrade my equipment and buy:

- William Optics Zenithstar 81 f/6.9 Doublet APO Refractor

- William Optics P-FLAT6AIII Adjustable Field Flattener ... (M48 outside for the T-ring)

- William Optics Copper M48 T Mount

No guiding scope for the moment.

I need a couple of narrow band filters, the flattener mentioned above accept 2" for filter inside. The cost of a narrow band 2" filter is £260 !! ...with this configuration, is it possible to use a 1.25" filter instead of a 2", without losing sharpness etc? How?

Thanks

 

[RT65CB-SWL]

With my SkyWatcher 2"/28mm; (as per my signature); I purchased a 2"-1.25" filter reducer; (link below); from 365astronomy.
https://www.365astronomy.com/365Astronomy-2-to-1.25-Filter-Adapter.html

Visually, I have not seen any vignetting when in use.

[Salva]

Many thanks 

[Salva]

Flattener cost £179 ... is it really necessary? Supposing I have only a 63mm on the lens and 48mm on the T-ring, how am I suppose to insert a 1.25" narrowband filter?

Thanks in advance