NIRISS is an instrument on the James Webb Space Telescope. It has a "non-redundant aperture mask" which obviously covers most of the area of the sensor. It seems to be advantageous for high contrast ...
I am not sure whether this question might be better suited for crossvalidated or stackoverflow, but I will give it a try here: I have a map of the full sky in in the healpix format, units are $\rm ...
Currently 22-23mag could be the limit to make a spectrum for ground based 10m class telescopes, 21-22may may be easy for them. 4m class telescopes could handle 20mag? I am not sure. 2m could be ...