I am putting a 120ST with 2" diagonal and manual mount on my Christmas wish list. This will be for 3 Degree+ wide field viewing/skywalking of big nebula, M31, the Milky Way. I currently do this in my ED80/SSIV and I use an Amici prism diagonal, which is great because it helps when seeing big star fields and big objects for it to align with my RACI finder and star charts.
With the 120ST, I want to go to 2", but still get those big correct image fields with an Amici. This narrows me to Baader choices: one with a 38mm clear aperture ($300) and the other with a 44mm clear aperture with BBHS coating on the reflective edge for $720 (!). The $720 astro grade one, though, would then let me use pretty much all 2" EPs, even TV 55mm (yes may get some very slight vignetting with 46 mm field stop EPs.
My question is: my plan is eventually to use NV with my 120ST (especially for when I can't get to a dark sky spot). Before I drop $720 on an Amici prism diagonal, I want to know if Amici prism diagonals can be used for NV. Namely, does the Amici prism absorb the deeper IR part of the spectrum (like dielectric coated diagonals don't reflect the deep IR)? Would the BBHS coated one be truly better at this (like the BBHS coated mirror diagonals do very well for NV), or would a non-BBHS amici work just fine for NV?
I welcome input from anyone using any Amici with NV, because that would answer the core question on the interaction of the prism and >700nm wavelength light.
(And related to all this, feel free to comment, since the TV PVS-14 NV system is limited to 40 degrees FOV, does it really make sense to use 2" with NV, or should I just scan around the Veil, NA/Pelican, etc. with 1.25" EPs and NV (still with amici is the plan, so need to know the answer to the main question). I do this now with my ED80 and 1.25" 40mmx43 deg Plossl and /24x68 deg ES Eps, and it is fun (ie not horrbile). I just see one side of the Veil or other, or see the Pelican or NA, just not both their entireties at once....and that just forgoes all this expense for 2" EPs, 2" filters, etc. and would gets me $$s for an NV set-up that much sooner).
Thank you and CS!
Edited by ABQJeff, 18 October 2020 - 04:19 PM.