Ar-Glass or IR-Cut Filter - Forums

Topic starter

Nov 19, 2023 · Edited: Nov 19, 2023

Hello fellow Astro-Friends,

do I need an ir-cut filter build into an mono camera used on an refractor as long as I shoot my pictures through rgb/sho filters?

would like to get an imx571 mono but sadly the seller only offers it with an ar-protection glass.

cs and thx
Andi

andrea tasselli

Frequent contributor

Nov 19, 2023

No. Only with luminance and assuming those filters have no IR leak.

Michael Ring

Nov 19, 2023 · Edited: Nov 19, 2023

AR glass is (from my point of view) the better choice because it lets all relevant light in. Yes, you will need an extra UV/IR filter to filter out the unwanted frequencies but for example Antlia recently added an extra IR filter to their R G B L filter set, you would not be able to get meaningful results without AR glass with the new near IR filter.

Also, when you plan to use other filters later you will anyway have to add an extra UV/IR filter with the same thickness as your other filters because the backfocus changes when using filters (0.8mm for filters with 2mm thickness) and only with same backfocus for all filters you will get round stars in the corners for every filter (assuming your filters are parfocal)

Michael

Helpful

Tyrel Smith

Nov 20, 2023

I second what has been said already. Mono cameras don't typically have built-in UV/IR cut filters. It they did it would limit their usefulness to certain demographics that may want to take advantage of their sensitivity in those bands. Instead, a luminance filter is used (typically, but with exceptions) that has the desired UV/IR cut feature. As you hinted, a UV/IR cut filter is not needed in conjunction with RGB or SHO filters, since those filters' bandpass already exclude the UV/IR wavelengths.

A good AR coating on your sensor window (and filters) is valuable to mitigate internal reflection artifacts.

Happy imaging!

Well Written Helpful Insightful

Tareq Abdulla

Nov 20, 2023

AR glass window