CCD vs CMOS optimised filters

[GalaticBoba]

Hi all, quick question, I'm just looking into filters and wondering if there really is a difference between these types? Or is it just a marketing thing?

Like these examples? 

https://www.firstlightoptics.com/baader-filters/baader-narrowband-ccd-emission-line-h-alpha-filters-2.html

https://www.firstlightoptics.com/baader-filters/baader-high-speed-65nm-narrow-band-filter-cmos-optimised.html

 

Also on the subject of filters, some are optimised for fast or slow scopes. I have medium to slow scopes right now (f4.4 to f10). But will definitely be buying faster ones down the line. So should I get the faster filters now or get cheaper ones and later get expensive more optimised filters, once I've figured out my exact setup?

[vlaiv]

Not sure what "optimized" stands for - is it CMOS optimized or F/2 optimized.

In any case - either can be true and not a marketing trick.

Interference are essentially reflection filters - meaning they reflect light that is not within designated pass band.

With fast optics - such as F/2-F/3 - there is significant change of the wavelength as filter sees it (not actual wavelength) - because part of beam hits filter at an angle and relationship of thickness of reflective coatings to wavelength changes - easiest way to cross the road is straight ahead and if you cross it at an angle - it takes longer.

Therefore - you can optimize filter for fast optics.

On the other hand, CMOS technology differs from CCD in pixel shapes / micro lens and sensor cover window. Often interference filters create reflection halos with CMOS sensors, so it is again possible that there are optimized coatings that take this into account and reduce reflections created by filters.

For actual filters you linked - well, have no idea. I do know that Baader had to deal with reflections in several of their filters and maybe they perfected technology and these are really optimized for CMOS.

[GTom]

Same question here for Baader's LRGB-set: older stock says CCD optimized, no haze, no reflections etc, new stock is "cmos optimized". Any practical difference between the two?

[Adam J]

1 hour ago, GTom said:

Same question here for Baader's LRGB-set: older stock says CCD optimized, no haze, no reflections etc, new stock is "cmos optimized". Any practical difference between the two?

Not sure but what I can tell you is that my CCD optimised set work just fine with my CMOS camera.....so not much space for improvement. 

Although if the chart is anything to go by the newer set is cutting at 400nm instead of 380nm on the blue filter.....would have thought that would be more dependent on the correction of your camera but it might indicate higher blue / violet sensitivity in CMOS in comparison to CCD....though i am not sure that is true. 

My experience though is that is you are poorly corrected in Blue 400nm wont cut it you need to be at more like 420nm to see a significant improvement. 

Adam

Edited July 11, 2023 by Adam J

[GTom]

Indeed, cutting at ~450 would bring visible advantage if you have lenses in the imaging train. I'll have a 3x Barlow (svbony sv213), will check how much purple fringing does it add to the picture. It is claimed to be an APO Barlow, still, APO's have trouble with deep blue too (the Scope is an sct, shouldnt be an issue):

Edited July 11, 2023 by GTom