ZWO ASI 183mm Pro Review
A monochromatic camera (mono) is often referred to as a gold standard camera for astrophotography. I had the urge to use one again, so I got my hands on a ZWO ASI 183mm Pro for review. This camera was sent to me from First Light Optics for review.
I’ve had the ZWO ASI 183mm Pro for some time now in order to get a good handle on the camera and its qualities. In this article I’ll be sharing my feelings about the ASI 183mm pro.
The sensor used within the ZWO ASI 183mm pro is a Sony IMX183 sensor. The main difference between the ASI 183mm pro and the ASI 183mc pro is of course one’s mono, the other is colour. The monochrome camera hasn’t got what’s known as a bayer matrix – or ‘Colour Filter Array’.
Without this CFA, the 183mm pro can’t detect individual colours. It will just collect the entire visible spectrum at once without assigning them their own colour pattern. Therefore all 4 pixels of a certain block of photosites will collect photons. When we add our own filters to the mix, then all 4 pixels of that block will collect the same colour. This increases the signal to noise ratio of any given image, and is the primary reason why mono cameras like the ZWO ASI 183mm pro are praised as being more sensitive.
The ASI 183mm Pro uses a 12-bit ADC sensor. ADC means analogue-to-digital-charge. Wavelengths of light come in as a sine wave – up and down like sound. This is an analogue signal. So the ADC charge is how the camera converts an analogue signal to a digital signal that makes sense to a processor.
12-bit ADC means that the image you take can have up to 4096 shades of grey. This helps smooth an image out. As you could appreciate, having many more smaller steps between two colours will make the transition smoother. This means the resulting pictures are quite smooth as well. However 12-bit is the lowest ADC you’ll probably see these days on cameras. Others can have 14 and even 16-bit ADC sensors.
That, however, doesn’t mean this isn’t a capable camera.
Read Noise: 3e – 1.6e (available at the highest gain)
|Dynamic Range||12.5 – 8 stops|
The ZWO ASI 183mm Pro has a rather small 13.2mm x 8.8mm mono Sony IMX183 sensor, with pixels that are a tiny 2.4um big. This makes the camera well suited for shorter focal length telescopes. However due to the smaller sensor size, you’ll have a much narrower field of view.
This caught me out in the past with using a 183 on my Sky-Watcher Evostar 80ED. A point I’ll get into a bit later – I’ve used 183 sensors before. But due to the field of view afforded by the 15.9mm diagonal sensor I found myself wanting a wider telescope.
The combination of sensor size and tiny pixels however affords the camera a rather substantial 20.18megapixels of resolution. Some might argue this is excessive for astrophotography however due to the atmosphere. In reality this gives you images that are 5496 x 3672 pixels in size. This is a nice amount of pixels for printing your photos out.
Each photo records a decent amount of data however, and individual file sizes are 39.4mb big. These are the largest individual file sizes I’ve dealt with over all the cameras I’ve used for astrophotography so far.
Full well is a measure of how many electrons an individual pixel can absorb before it becomes pure white. So by definition this can also dictate exposure times for given targets. But that’s some deep maths that I haven’t found the answer to yet.
The full well of this camera is 15000 electrons. To put that into English, this is one of the smaller values I’ve come across in my astrophotography journey so far. it is also decided by the 12-bit sensor depth as mentioned earlier. Bigger here is usually better.
However when you turn this camera to 120 gain -unity gain setting – which is where I imagine 90% of users will be, your full wells become about 4000. That’s a loss of 73%.
This begins to turn this camera from a long exposure camera to more a rapid fire camera. Shorter exposures, say 2 minutes. Again, it’s not like you can’t use longer exposures. But you have to be mindful that you’ll white out your pixels a lot sooner.
The specs boast an extremely low read noise of 1.6e. What isn’t advertised as readily is the fact this read noise is only accessed at the very highest gain setting. Where you have the smallest wells and lowest dynamic range. So in practice this should only be used for lucky imaging.
The quantum efficiency – a fancy way of saying how well this camera uses the light it catches, is about 84%, it drops off towards Hydrogen-Alpha but it’s still over 60%. Some ranges are even almost 100% judging by the chart presented by ZWO. So it’s a very sensitive sensor and can use the light quite effectively, giving you a nicer image with less exposure times theoretically.
This sensor suffers from amplifier glow. That’s the electro-luminescent glow found as a starburst on the side of the frame. Look at this dark frame and this light frame. You see that big glow? That’s the amp glow.
This can be a menace. I had trouble calibrating this out nicely in the past but the ZWO calibrates nicely with dark frames. It’s alarming to see at first, but it isn’t irreparable. You just need to take your time calibrating your images with it. It gets worse with the longer exposures.
Use and suitability
In practice I would use this camera for about 2-3 minute long sub exposures depending on the target. In narrowband I stuck to about 5 minutes. I have used the 183 sensor to do 10-15 minute long exposures with narrowband and the images are just generally tinted with a glow that made it seem overexposed and difficult to calibrate.
For narrowband targets on modestly dim objects like the Elephant’s Trunk Nebula I found 5 minutes to be okay with a small refracting telescope – the SharpStar 61EDPH2.
When I shot the Perseus double cluster I was sure to just keep the exposures shorter. I used 30 second images and I think it came out quite nicely. True a star cluster doesn’t usually have many faint details you’re trying to capture however, and shorter is generally better – especially with the shallow wells with the camera.
Otherwise though I found nothing to really complain about with the exposures. They seemed nice, the dynamic range was decent, and there was a fine amount of room during editing.
In terms of suitability, this camera as mentioned is great for shorter focal length instruments. Under regular seeing conditions the camera is best on telescopes between 248mm and 742mm. Let’s look at some of those examples – remember the smaller sensor gives a tighter FoV.
300mm: M16 Eagle Nebula
400mm: M78 Casper The Friendly Ghost Nebula
600mm: M101 The Pinwheel Galaxy
The effect of this sensor size can be clearly demonstrated by pitting it against a ZWO ASI 071mc Pro which has a 1.5x APS-C sensor. So again, if you’re looking at buying this camera. Just be sure to research the FoV you’ll get.
Being a Pro camera, it has two stage peltier cooling, which can get the sensor 40-45 degrees below ambient. That doesn’t always mean you need to crank the cooling to the maximum however. Though looking at the given chart from ZWO, -15’c seems to be a great place to cool down to. Although I have a video from Dr Glover of SharpCap who sheds more light on camera cooling.
To use the cooling, you do require a standard power cable. Sold separately of course. You can get the ZWO one for £30, but what I personally use is the Lynx Astro versions. I’ve also previously written a blog post about how I power my equipment as well. The ASI 183mm Pro can also be cooled by the ZWO AsiAir Pro & plus which is the setup I used it with.
I have seen some people comment before, and I experienced this with a 183 from a different manufacturer, where the sensor window can condense up due to the cooling vs ambient temperature. To combat that, ZWO do sell a heater ring that can be retrofitted, and that’s what this model I have from FLO has on it.
The sensor cooling ring can be seen above – the yellow part.
The camera can be used for planetary work. The smaller sensor does lend itself for that, and when put onto a longer focal length telescope you would over sample, but that can be beneficial for sharp high resolution planetary, solar or lunar photographs.
I haven’t used the video mode myself personally. I’m mainly a deep sky astrophotographer until the planets reappear now. But the frame rates look mighty respectable at high resolutions, and very fast and lower resolutions.
If you’re after a fast small sensor camera that boasts a lot of resolution for making large images of the planets or the Moon – like I would enjoy – then this could certainly be a contender.
At the time of this review the ZWO ASI 183mm Pro Camera clocks in at £947 for the cooled version or £669 for the ZWO ASI 183mm uncooled mono versions. For that you get the nice effective sensor as well as some extras.
But that is a big price tag for a lot of people to pay, so hopefully this review helps your decision making.
The camera has its nice red anodised appearance. Simiar to the entire ZWO range. So good luck picking it out of a police lineup.
It also only weighs 410grams (14.4oz) so it’s very light and doesn’t add much to the imaging setup. On its own, that is. Don’t forget its a mono camera so you will need a filter wheel and filters. I used Optolong LRGB Filters, Optolong SHO Filters and a ZWO Filter Wheel.
And as all other pro series cameras from the ZWO range. It comes with a USB3-B type connector for the actual camera control, and 2 USB2 ports as a built in hub for controlling almost anything. Usually you’d use it for the auto-focuser and the filter wheel. I’ve had my mount and my guidance plugged into the USB hub before too and it works fine.
Whilst the 183mm might be getting on a bit in its life. It isn’t by any stretch out of date or obsolete. The sensor is very small but packs a punch even at 12-bit depth. With a wide enough setup it can be a very effective and sensitive deepsky imaging camera, a lucky imaging camera, EEA camera and also a high resolution solar system camera.
Best suited for more shorter exposures than very long heavy exposures, but with large file sizes. It will give you a nice end result, but you’ll need more memory on your computer if you plan to use this camera for a long time.
I found it responds nicely to using darks, flats and dark flat frames for calibration especially darks, definitely they’re needed to calibrate out the significant amplifier glow on the right hand side.
The small sensor also has an advantage of using what is in theory the best part of your optics. The centre of them. Especially with lens optics like refracting telescopes. The size though does mean your widefield telescope suddenly is a lot tighter of a field of view than you might be hoping for.
If you’ve done your homework and know the FoV works well with your instruments or what you want to buy, then I think the 183 could be a very nice mono camera for your collection. It’s extreme sensitivity allows you to collect light effectively and with shorter exposures. The shallow wells might limit very very long exposures though. But that doesn’t mean this camera is not incredibly capable.
Take your time familiarising yourself with the camera and the calibration required and you’ll end up with high resolution high quality images – teamed with nice optics of course – that are a great size for 4k desktop wallpapers or printing.
I hope this review has been useful for you. Thanks for reading.
I wish you clear skies, keep looking up and keep them cameras clicking.