When Comparing cameras, you need to look at every aspect of the camera. Size, weight, compatibility, and sensor are some of the things. Even going down to colour can be looked at (Some people like colour-coding their equipment!). But for this comparison, it will solely be down to the sensor, since the camera is the same and it is only a comparison between Monochrome and One Shot Colour, (Mono/MM and OSC/MC) with the advantages and disadvantages of each in the UK. The majority of this can be used worldwide and you can interpret depending on where you are from what is here. I have recently purchased the ZWO ASI 533MM pro camera as an upgrade and I can comfortably do a comparison between these. The 533MC is a more than capable camera but the temptation for a mono camera crept up time and time again until it was too much (and was funding dependant) I’m going to be comparing the following things as it’s the same camera and some parts can be ignored:
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Sensor
The ZWO ASI 533MM/MC cooled and the non-cooled camera uses the Sony back-illuminated IMX533 sensor. This sensor is 11.31x11.31mm with a resolution of 3008x3008 at 9 million pixels at 3.76um pixel size (microns or micrometres).
This sensor is a 1” sensor. The only difference is the Bayer layer on both the mm and mc cameras. Effectively the OSC is the same as the Monochrome camera but with an additional layer that converts the Camera to OSC, generally using an RGGB pattern to mimic the human eye which is most sensitive to the colour green.
The ZWO ASI 533MM/MC cooled and the non-cooled camera uses the Sony back-illuminated IMX533 sensor. This sensor is 11.31x11.31mm with a resolution of 3008x3008 at 9 million pixels at 3.76um pixel size (microns or micrometres).
This sensor is a 1” sensor. The only difference is the Bayer layer on both the mm and mc cameras. Effectively the OSC is the same as the Monochrome camera but with an additional layer that converts the Camera to OSC, generally using an RGGB pattern to mimic the human eye which is most sensitive to the colour green.
In Astrophotography the green tint which OSC have when starting processing is removed since the green can be overpowering in the picture, removing all of the green, or the majority of it in post-processing is always observed. (unless desired in the final image as a personal preference), The colour green is not observed or seen in natural conditions due to the location of the green colour in the wavelength (sandwiched between the blue and yellow. Green stars are nearly impossible due to this and also do not appear in nebula naturally) and as such an OSC will use half the sensor in the green spectrum. In short, you are only effectively using one-half of the colour camera sensor in astrophotography when using narrowband filters.
The Monochrome sensor has no Bayer layer and all images will be greyscale (or black and white). Taking pictures with a mono camera without filters will always give a greyscale picture - making filters essential for mono cameras to be able to achieve a colour picture. Although monochrome cameras lack a Bayer filter, they are far more sensitive and able to collect more data due to using the whole sensor on one colour or wavelength, at the expense of having to use multiple filters (discussed in the next section). You can reduce the green colour used when using mono, especially when taking Broadband targets, like galaxies. While the green will be required to create a full-colour picture while in processing, you can either use less of the green colour or reduce it to your preferences. The green colour will be swapped with a narrowband filter when doing Narrowband targets. This will help you easily create different effects in post-processing (Hubble pallet as an example). |
FILTERS Filters are an important part of Astrophotography and come in varying types:
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As you can see (or read in this case) there are filters for both types of cameras and are generally an essential part of astrophotography, and while this page is for the comparison of monochrome and OSC 533 cameras, the filters are a main part of this and are very much required in the explanation between the two cameras which will give you the information to decide between the both if you are here for that reason. |
Pricing
The price is a key part of the comparison of the two cameras as there is a clear difference between them both. Below shows the difference in prices of the filters and cameras and also shows which are used for which camera.
You can see a clear difference in pricing between both mono and OSC cameras. For starters, the Mono camera is generally more expensive, sometimes by hundreds of pounds. This will sometimes be a deciding factor for some.
You will also notice there is a clear difference in the cost of filters. But not just by which camera you will use but by how tight the band length is on the filters as well as the size of the filters. Single bandpass filters will be generally cheaper than their dual-band and triband filters, but the difference is you need more of them and this is where the price differs - you need more filters with mono cameras. Below you can see which is used for mono cameras. Mono cameras need 7 filters overall (Ha, SII, OIII, and LRGB) to be able to have the versatility to take both broadband and narrowband targets. The key thing to take away with this is the filters will be able to be used on multiple cameras if/when you upgrade.
(all prices are of 2023 and from a single source - Rother Valley optics)
Pricing
The price is a key part of the comparison of the two cameras as there is a clear difference between them both. Below shows the difference in prices of the filters and cameras and also shows which are used for which camera.
You can see a clear difference in pricing between both mono and OSC cameras. For starters, the Mono camera is generally more expensive, sometimes by hundreds of pounds. This will sometimes be a deciding factor for some.
You will also notice there is a clear difference in the cost of filters. But not just by which camera you will use but by how tight the band length is on the filters as well as the size of the filters. Single bandpass filters will be generally cheaper than their dual-band and triband filters, but the difference is you need more of them and this is where the price differs - you need more filters with mono cameras. Below you can see which is used for mono cameras. Mono cameras need 7 filters overall (Ha, SII, OIII, and LRGB) to be able to have the versatility to take both broadband and narrowband targets. The key thing to take away with this is the filters will be able to be used on multiple cameras if/when you upgrade.
(all prices are of 2023 and from a single source - Rother Valley optics)
Narrowband and Broadband targets
The two types of targets which people take will be dependent on the individual's perspective and what they enjoy taking the most. Some people prefer galaxies, others prefer nebulae and some like both with no wavering advantage between them. Whatever your favourite is taking these pictures will generally bring joy. In some cases, mono cameras will have distinct advantages over OSC cameras. One can use the whole sensor for the same wavelength/ colour. Taking far more data per shot over the OSC camera at the expense of having to change filters per wavelength/ colour. Granted you can buy a filter wheel which avoids this, a simple turn of the wheel, a refocus, and you are on your way again. But with an OSC camera and a dual-band filter/ UV IR filter, you can set up and forget about it all night (or for however long you are out) without the need or worry of having to change the filter. Even post-processing is far simpler - stacking the images of the night and you instantly have a colour picture and all that is left is refining that picture. Processing pictures with Mono cameras is far more complex (well not so much complex but in-depth). You will have to stack each filter and process these individually and then stack them before you even get a colour picture, and let's not forget the new learning curve you have to take. The process is far more in-depth and takes longer, but generally, the picture is far more detailed in less time over the OSC, but at the expense of more cost, more time swapping filters out and processing the pictures. Taking Broadband targets with Mono cameras will utilise 4 filters. LRGB, The main filter through this for detail is the Luminance filter, or the UV/IR filter. You will be stacking more of this over the RGB colours. The RGB filters are there to give colour to the detail and a ratio of 1:1 L to RGB. This means for every hour of Luminance you have one hour of RGB (20 minutes of each). If the target has a narrowband in there also, you can add Ha to the mix at a time frame of 3:1 Luminance to Ha. |
The main thing to take away here is the ratio needs to be the same on the RGB, you can alter how much RGB you use, but the same time per filter is needed to have a balanced colour picture at the end.
To do this in OSC, as mentioned, you just use the UV/IR filter and walk away. If you want additional Ha to the picture, use a dual-band filter for about 25% of the total time, extract the red from the final image of this and add it to the UV/IR to add additional Ha.
Narrowband targets with Mono cameras will be target-specific. Some Targets will only have Ha or have a combination of Ha and OIII. Some will have Ha, OIII, and SII and how much you use per filter is dependent on the target and can vary. But for Ha-only targets, I will generally use either Ha and OIII or HaRGB style pictures. The disadvantage with monochrome is you can’t use one filter and get a colour picture. Using two types of Narrowband filters you will be able to play about with the pallet colours to get different colours.
To do this in OSC, as mentioned, you just use the UV/IR filter and walk away. If you want additional Ha to the picture, use a dual-band filter for about 25% of the total time, extract the red from the final image of this and add it to the UV/IR to add additional Ha.
Narrowband targets with Mono cameras will be target-specific. Some Targets will only have Ha or have a combination of Ha and OIII. Some will have Ha, OIII, and SII and how much you use per filter is dependent on the target and can vary. But for Ha-only targets, I will generally use either Ha and OIII or HaRGB style pictures. The disadvantage with monochrome is you can’t use one filter and get a colour picture. Using two types of Narrowband filters you will be able to play about with the pallet colours to get different colours.
Pros and cons
We have discussed both cameras, with luck fairly. And to recap here is a breakdown:
There is a lot to take in when considering Monochrome and OSC cameras. There are pros and cons between them both. As mentioned, with OSC cameras you just put the desired filter and walk away, with mono cameras, you have to think about multiple filters. Then there is the point of the weather! Here in the UK, the weather changes like no tomorrow! We could have clear skies all night by the weather apps we follow, and yet a cloud can come in and ruin that all in a short time frame.
When taking pictures this will have to be a deciding factor also. If your night is cut short, with OSC you will be able to see results instantly, but with monochrome, if your night is cut short and you are missing data from other filters, you will have to wait until you can finish them off before seeing a colour picture.
British weather isn’t known for its constant clear skies! At best, we see a couple of clear nights per month, unless we are lucky and it unexpectedly clears up and if you are like me and have to travel out for Astrophotography, the nights are even less.
The cost of the equipment will also be a deciding factor. Mono cameras and filters will set you back a small chunk of money. Add to this the higher-end filters, and if needed filters for faster optics (which hasn’t been included in this as it is out of scope) which raises the cost more.
As an example high-end filters which are used for faster optics will start to set you back £500-600 per filter. These are filters which have a 3mn bandpass designed for fast optics - this is an extreme example and you can get Ha, SII, and OIII filters for less than that but the point is the cost for the cost of one filter will be the cost of a dual-band or even a tri-band filter and you will need 3 narrowband filters (not to mention the LRGB filters), with OSC you will need two filters UV/IR and a dual-band filter.
We have discussed both cameras, with luck fairly. And to recap here is a breakdown:
- Mono you will use the whole sensor for one filter but only about 50% with an OSC and a dual-band filter. (little more on broadband targets)
- OSC you can set up and go with one filter all night.
- Mono you will need multiple filters per target
- Filter and camera pricing will be a driving factor - mono is more expensive, and with high-end filters, even more so.
- More variety with the mono camera and the end result. While it is possible with OSC, it is not nearly as effective as mono cameras.
- Mono will require more filters and will require a filter wheel (not necessary in all cases, if you are happy to swap out filters manually, then a filter drawer will work also)
- New learning curve for mono processing
- OSC you will get a colour picture per sub-exposure and once stacked. With a mono camera, you will have to process individual filters and then stack them for a colour picture.
There is a lot to take in when considering Monochrome and OSC cameras. There are pros and cons between them both. As mentioned, with OSC cameras you just put the desired filter and walk away, with mono cameras, you have to think about multiple filters. Then there is the point of the weather! Here in the UK, the weather changes like no tomorrow! We could have clear skies all night by the weather apps we follow, and yet a cloud can come in and ruin that all in a short time frame.
When taking pictures this will have to be a deciding factor also. If your night is cut short, with OSC you will be able to see results instantly, but with monochrome, if your night is cut short and you are missing data from other filters, you will have to wait until you can finish them off before seeing a colour picture.
British weather isn’t known for its constant clear skies! At best, we see a couple of clear nights per month, unless we are lucky and it unexpectedly clears up and if you are like me and have to travel out for Astrophotography, the nights are even less.
The cost of the equipment will also be a deciding factor. Mono cameras and filters will set you back a small chunk of money. Add to this the higher-end filters, and if needed filters for faster optics (which hasn’t been included in this as it is out of scope) which raises the cost more.
As an example high-end filters which are used for faster optics will start to set you back £500-600 per filter. These are filters which have a 3mn bandpass designed for fast optics - this is an extreme example and you can get Ha, SII, and OIII filters for less than that but the point is the cost for the cost of one filter will be the cost of a dual-band or even a tri-band filter and you will need 3 narrowband filters (not to mention the LRGB filters), with OSC you will need two filters UV/IR and a dual-band filter.
Overall thoughts
We have gone through a lot of the major points in both Monochrome and OSC cameras. And as always, I’m not here to tell you what to go for, I’m just here to tell you the pros and cons between them and hope it helps you understand them both and make an informal decision on which to go for.
If you are new to Astrophotography, I would say go with OSC cameras, they are far easier to use and to process pictures. The aim is to get more people into the hobby, not scare them out of it! Whether you stay in OSC or move to monochrome is the main point of this post.
I swapped from an OSC to a mono recently staying with the 533 version camera from ZWO and also buying both LRGB and SHO filters designed for fast optics. It has set me back some change, but for me, I love the challenge of the new process. (I don’t love changing the filters throughout the night mind… Filter wheel will be on the cards soon…) but this is just me and not everyone will feel the same, but the biggest challenge is the weather. I do all mine in a Bortle 4 location in the middle of nowhere and I can see the cloud move in, giving me an advantage and I can change my timings on overall exposures to try and get all the data I need. Not necessarily the total exposure I want, but at least I have some in each filter type. This would be more difficult in a back garden where it may be harder to see this (the other end of this is you may have more nights for AP).
Below are some examples of both MC and MM versions but on different scopes.
below left
Veil Nebula 533mm 5 and 45 mins hours of overall data at F/2.8 (equal parts Ha and OIII)
Below Right
same target 533mc 2 hours overall data at F/2
The focal ratio is important here as at f2.8 I am collecting half as much data. for every min at F/2.8 it is just under 2mins at F/2 of equivariant data
We have gone through a lot of the major points in both Monochrome and OSC cameras. And as always, I’m not here to tell you what to go for, I’m just here to tell you the pros and cons between them and hope it helps you understand them both and make an informal decision on which to go for.
If you are new to Astrophotography, I would say go with OSC cameras, they are far easier to use and to process pictures. The aim is to get more people into the hobby, not scare them out of it! Whether you stay in OSC or move to monochrome is the main point of this post.
- Is monochrome photography for you?
- Do you have enough time and patience to take multiple exposures on multiple filters, individually process them and then stack them?
- Can you cope with losing a night's data from changing weather and not having enough of each filter to process the data to make a colour picture?
- Do you want instant gratitude for a night's work and getting results regardless of how much exposure you have?
- Have you taken into account the cost of mono compared to OSC? Have you considered it relative to your current setup (fast optics F2/F3) which will raise the cost of the filters
I swapped from an OSC to a mono recently staying with the 533 version camera from ZWO and also buying both LRGB and SHO filters designed for fast optics. It has set me back some change, but for me, I love the challenge of the new process. (I don’t love changing the filters throughout the night mind… Filter wheel will be on the cards soon…) but this is just me and not everyone will feel the same, but the biggest challenge is the weather. I do all mine in a Bortle 4 location in the middle of nowhere and I can see the cloud move in, giving me an advantage and I can change my timings on overall exposures to try and get all the data I need. Not necessarily the total exposure I want, but at least I have some in each filter type. This would be more difficult in a back garden where it may be harder to see this (the other end of this is you may have more nights for AP).
Below are some examples of both MC and MM versions but on different scopes.
below left
Veil Nebula 533mm 5 and 45 mins hours of overall data at F/2.8 (equal parts Ha and OIII)
Below Right
same target 533mc 2 hours overall data at F/2
The focal ratio is important here as at f2.8 I am collecting half as much data. for every min at F/2.8 it is just under 2mins at F/2 of equivariant data
Below are first attempts at NGC1499 for processing. This is from the same data and processed slightly differently. Overall exposure time 2 hours with Ha and OIII. (HOO, HOO and HOH - the two HOO was processed slightly differently, removing some of the saturation of the nebula out of the picture which created the first picture)
This is a good example of "I should have used HaRGB" as this Nebula is near enough pure Hydrogen. (Ha and Hb)
This is a good example of "I should have used HaRGB" as this Nebula is near enough pure Hydrogen. (Ha and Hb)
Below is the first picture with monochrome camera - NGC 6992 - The Bat Nebula. The Ha was slightly out of focus and the clouds came in far faster than expected, resulting in me only getting 40 mins per channel (Ha and OIII). I also never calibrated the scope before use which has not helped the picture.