Dual-band vs. Mono imaging

I think you’d see the biggest difference in Ha as you’re red-pixel limited on the OSC. While you’re collecting both simultaneously, I suspect you’d want longer integration for faint Ha on the OSC compared to Ha on the mono.

That’s by the numbers, though… if you have limited clear nights from your location, knowing you got both Ha and OIII from the same clear night is beneficial.

@Vroobel images NB simultaneously with mono and OSC cameras and would have some good insight on this question

I image in Bortle 8/9.

Having done both I can say that mono NB imaging is far superior in both signal and resolution (because no strange phenomenon around debayerisation occur, even if drizzle closes the gap a tad, and no cross bleeds between wavelength because of the relative response of the sensor to RGB which is not perfectly separated).

Even gradients are much more easy to correct when capturing data wavelength by wavelength.

The gap is much closer in broadband imaging though.

Astro Hopper · Jun 2, 2026, 11:08 AM

10 h of Ha and 10 h of Oiii taken with mono camera is actually 10 h of each. With OSC 20 hrs of data gives you 5 h of Ha and 5 h of Oiii since only 1/25 of sensor is collecting Red and Blue data and rest is grean. That’s because of Bayer matrix in front of sensor. So all do new OSC sensors are quite good they still are not match for Mono sensors. For Broadband is little different. Broadband is much closer to mono.

Nothing could be more wrong.

In my experience switching from a 294 MC PRO camera with a dual-band filter to a 294 MM PRO camera with narrow-band filters, the images from the monochrome camera were always better, even with shorter full integration times than the color camera. This is especially true for Ha; the color camera only utilizes 1/4 of the pixel because almost the entire signal is captured in the red part, whereas the monochrome camera captures the entire Ha band using the filter. O3 is visible in both B and G-G in color camera.

Vroobel · Jun 2, 2026, 11:23 AM

Who said that Astro Hopper · Jun 2, 2026, 11:08 AM

Alex Nicholas · Jun 1, 2026, 10:55 PM

I think either way will work well.. having done a lot of both though, there is no amount of extra SNR that will match what the mono will give you in resolution… perhaps thats just me, but Id prefer 10h H + 10h O over 20h H/O on an osc camera.

10 h of Ha and 10 h of Oiii taken with mono camera is actually 10 h of each. With OSC 20 hrs of data gives you 5 h of Ha and 5 h of Oiii since only 1/25 of sensor is collecting Red and Blue data and rest is grean. That’s because of Bayer matrix in front of sensor. So all do new OSC sensors are quite good they still are not match for Mono sensors. For Broadband is little different. Broadband is much closer to mono.

Who said that OIII consist of blue only? 🙂

You are right, my mistake about OIII, never the less still norrowband in mono collects at least 25% more Oiii then dual narrowband, and in Ha is much bigger difference. That being said modern OSC cameras are much closer to mono then before but still there is quite big gap between them.

urban.astronomer · Jun 2, 2026, 12:42 PM

As mentioned several times in this thread before:

• The color camera will only collect red light on a quarter of the sensor size due to the Bayer Matrix which is specifically critical for the Ha data.

• For O3, the blue quarter + the two green quarters (thus 75%) of the sensor can be used, so the difference between mono and color camera for O3 is much less compared to Ha.

For IMX571:

Ha/OIII

SII/OIII

The above equations came from an extensive ‘discussion’ with ChatGPT after feeding it with information about the sensor:

I did some experiments with PixelMath, and the results are consistent with PixInsight/DBExtract.

urban.astronomer · Jun 2, 2026, 12:42 PM

To bring some real data on the table: Below, you will find two stacks of Sh2-129 using the same telescope and two different cameras utilizing the mono and color version of the Sony IMX571 sensor. Both stacks are taken from the same Bortle 8 balcony, same time of the year. Dualband from 2022 and mono from 2023.

I don’t doubt that you have a proper intention, but another year, even if it’s exactly the same day in a calendar, doesn’t mean the same condition. This was mentioned in the linked thread or in many similar ones, I don’t remember. That’s why I use exactly the same optics and exactly the same cameras MM and MC (I mean the same manufacturer, not only the same sensor) at the time. Only such a dual-setup is able to provide a reliable dataset. It would be great to have the same-width filters, maybe one day… 😄

urban.astronomer · Jun 2, 2026, 12:42 PM

One should also note that mono sensors often have higher quantum efficiency compared to color sensors. All in all, I would prefer mono if you can.

While I agree that mono is preferable, I do not believe it is accurate to state that mono sensors have higher QE. Base sensors in each case have identical QEs. What’s different is the transmission of the dye based filters used in color cameras in the Bayer matrix versus the interference based filters used in mono imaging. The latter, especially high end ones like Chroma, can have near 100% transmission at the specific emission wavelength being passed through.