Telescopes

ZWO at the Forefront of Technological Development

ZWO at the Forefront of Technological Development

There have been some recent new additions to the ZWO family of cameras. This highlights ZWO at the forefront of technological development in planetary imaging. Planetary imaging (including the moon and the sun) provides a good introduction to the art of astrophotography. A simple mount and telescope is sufficient. The mount should preferably be GOTO or driven, with a long focal length telescope. Ideally an F-ratio (focal length of telescope divided by its aperture) of approximately 10 – 30 is required for planetary imaging. A higher F-ratio can be achieved by using a Barlow lens, a Televue Powermate or similar.

In order to resolve planetary detail the best option is to take a video of the planet through the telescope. Specific CCD (or CMOS) cameras have been designed with astrophotography in mind. They are inserted into the diagonal of the telescope in the same way as an eyepiece, although a threaded connection is usually also possible.

A USB lead connects the camera to a laptop computer offering specifications required to support the camera. Specifically designed capture software like Sharpcap and Firecapture shows a live view image on the laptop’s screen. These  capture software are supplied with ZWO cameras on a CD or the latest versions can be downloaded for free. Videos can be taken at different frame rates per second using controlled settings available in the capture software and processed using separate stacking software such as AviStack, Registax 6 or Autostakkert 2 (all of these are also free downloads). This software selects the best frames from the video, aligns and then stacks them to produce a final image. This can be processed further with other software, for example Photoshop, Lightroom or GIMP.

A wide range of cameras are available on the market, many of them designed to take a high number of frames per second and have powerful sensors. One family of such cameras is the ZWO ASI cameras that are based on CMOS sensors. ZWO ASI cameras range in price from approximately £100 to £500. CMOS technology has been always cheaper than CCD technology and usually meant some compromise but recently this technology has gone through some incredible developments. Therefore, ZWO cameras now offer even higher value for money and this is especially true for the latest models, the ASI174, ASI178, ASI185, ASI224, and ASI1600, for which cooled and non-cooled versions are available, recently introduced by ZWO.

This article aims to provide some background on earlier ASI camera models and explain the improvements provided by the new, recently introduced cameras. Although Region of Interest (ROI) and binning are featured in all current ZWO cameras, the benefits of these features will be explained here in relation to the latest ZWO camera models.

Earlier ZWO planetary camera models

Mars using an ASI120MM through a celestron EDGE HD8

Mars using an ASI120MM through a Celestron EDGE HD8

The ASI120MC (one shot colour) and MM (monochrome) have been on the market for some time. They offer an excellent value for money, versatile camera for imaging solar system objects. They support a wide range of resolutions enabling them to image the planets, moon and sun (with the correct filters in place for the sun). These cameras connect to a laptop using a USB2 interface. They also have an autoguider port that enables them to be used as autoguiders for long exposure deep sky imaging and a 150 degrees wide-angle lens. These cameras are popular with Worthing Astronomer members for both planetary imaging and autoguiding. A number of images posted on the Worthing Skywatchers facebook page are taken with these cameras.

Jupiter taken with an ASI120MM through a Celestron EDGE HD8.

Jupiter taken with an ASI 120MM through a Celestron EDGE HD8.

The one-shot colour camera can produce colour images without any accessories. However, the monochrome camera requires a filter wheel and a set of LRGB filters to produce colour images at extra cost and requiring a more complex imaging process. The advantage of a monochrome camera is that all the pixels contribute to the image whereas for one-shot colour the pixels are divided into red, blue and green so the sensor is less sensitive. This does affect the final image quality to an extent. It is worth noting that you can also image in monochrome (like a black and white image) and this can produce good contrast and detail on planets, for example the gas bands of Jupiter and the A and B rings of Saturn as well as the moon and sun.

The offers the same technology as the ASI120 (with the exception of the all sky lens that would need separate purchase) but is only available as a monochrome camera. It has an older but larger sensor and therefore a wider field of view (FOV) in most telescopes. This makes it suitable for the moon and the sun but not so much for planets. It is the equivalent of a 9mm plossl eyepiece whereas the ASI 120 is equivalent to a 6mm plossl eyepiece. This is an excellent low budget alternative for beginners who want to do solar and lunar imaging.

The ASI130M (now discontinued so only available second hand) offers the same technology as the ASI120 (with the exception of the all sky lens that would need separate purchase) but is only available as a monochrome camera. It has an older but larger sensor and therefore a wider field of view (FOV) in most telescopes. This makes it suitable for the moon and the sun but not so much for planets. It is the equivalent of a 9mm plossl eyepiece whereas the ASI 120 is equivalent to a 6mm plossl eyepiece. This is an excellent low budget alternative for beginners who want to do solar and lunar imaging.

The moon taken with a ASI130 through a Celestron EDHEHD8

The moon taken with an ASI 130 through a Celestron EDGE HD8.

 

Also worth a mention is the ASI034. This is the most affordable planetary camera and is ideal for a beginner with a lower budget. It does not have the resolution capacity of the ASI120 and ASI130 and is only available as a one-shot colour version. The original version did not have an autoguider port, however ZWO introduced a new version recently that includes a standard ST4 guide port (and they also changed the colour to the more usual for ZWO red).

Jupiter taken with an ASI034 through a Skywatcher Virtuoso.

Jupiter taken with an ASI034 through a Skywatcher Virtuoso.

 

The new ZWO family members

ZWO have shown their capability of keeping pace or even being in the forefront with technological development in CMOS cameras. The following cameras have only recently come on the market and offer the potential of significant improvements in performance relative to older ZWO cameras.

 

ASI 120MC-S and ASI120MM-S

These recently introduced cameras offer the same technology as the earlier ASI120 and have been upgraded from USB2 to USB3 technology. This allows the camera to capture at higher frame rates per second. This means that for a given length of video Registax or autostakkert has more frames to choose from, increasing the number of “good quality frames” for stacking and improving overall image quality. In this country poor sky conditions often mean that higher frame rates do not result in better image quality. However, it is good to have the potential when the opportunity arises. These cameras are back compatible to USB2 but you lose the advantage of higher frame rates.

 

ASI 224MC and ASI 185MC

These new and latest cameras are USB3 compatible, have an autoguider port and come with an all sky lens. The IMX 224 sensor offers Sony Exmoor and NIR technology. Exmoor technology improves picture quality under low illumination by incorporating wavelengths from the near infrared (NIR) part of the electromagnetic spectrum. Sony has also taken advantage of new technology to reduce the amount of noise typically inherent in CMOS sensors resulting in a very low readout noise and high Quantum Efficiency (QE). These two technological developments offer an increased quality of planetary image compared to older ASI cameras.

The ASI185 is practically the big brother of the ASI224.The difference is that the ASI 185 has a larger sensor. It also has a slightly higher readout noise (although still extremely low) and the same pixel size. The ASI224 is therefore better for planetary imaging whereas the ASI185 is better for the moon and sun. The ASI185 would still be suitable for planetary imaging with larger telescopes with a long focal length or by using a good quality Barlow lens or Televue Powermate. An alternative is to take advantage of the ROI (Region of Interest) feature that uses only part of the sensor of the ASI185 to capture only the image of the planet. (All ZWO ASI cameras support ROI so it can also be used for the ASI130 for planetary imaging.)

The ASI178 is in a separate category with very large 6.4MPixel resolution and 14bit ADC. Although it has a small pixel size that might suggest that this camera is not as suitable for astronomy, a mode called “binning” can be used to combine pixels to achieve bigger pixel size although this does reduce resolution. As with the ASI185, ROI (Region Of Interest) can also be useful when imaging with this camera. Otherwise this camera is also well suitable for microscopes.

This ASI178 offers the same technology as the ASI224 and 185 but takes it even further. It has a very high resolution capacity and the Sony Starvis and Exmoor R technology that offers significant low light sensitivity by incorporating a back illuminated sensor and very low noise. Therefore, it seems that this is a very versatile camera with potential in various fields of application, including various types of astronomical imaging.

ASI174 MC and MM

This camera is currently the top of the range of ZWO cameras. It comes in monochrome or colour, is USB3 compatible and has an autoguider port. The highly advanced IMX174 sensor has Global Shutter technology as opposed to Rolling Shutter technology. This concerns how the sensor reads the signal produced by each pixel and turns it into an image. In rolling shutter technology information from rows of pixels is gathered together and used to produce the image. Using information from rows of pixels can produce a back-log in information transfer and slow down the process. However, in Global shutter technology each pixel is read simultaneously. This minimises the potential for image distortion through motion blur during video capture that can compromise the final image. The IMX174 also maintains a very high frame rate, the highest of all the ASI cameras. Additionally, it has high sensitivity in low illumination, low noise and high contrast between light and dark areas (high dynamic range). Its large sensor makes it suitable for the moon and the sun rather than planets. Similar to the ASI178 and ASI185 the use of ROI can also yield good results for planetary imaging – especially when a high focal ratio is achieved with larger telescopes.

 

Deep sky imaging with the latest Cooled ZWO cameras

Very recently ZWO introduced a range of cooled ASI cameras for the 224, 185, 178 and 174 models. These cameras offer the same technological advances of the non-cooled versions described above and can be used for planetary, lunar and solar astrophotography. However, they also contain regulated 2 stage TEC cooling device that allows temperatures of 35-40°C. This allows these cameras to also be used for imaging of deep sky objects (DSOs).

The most recent cooled editions to the ZWO family are the ASI1600 and the ASI290 (The costs represent an introductory offer until 31 May 2016). Cooled and non-cooled version are available, monochrome and in colour. The ASI1600 has the largest sensor for deep sky objects and possible length of exposure. The ASI290 is a planetary camera and has a slightly smaller sensor that the ASI224 and smaller pixels leading to a higher resolution. It also has a higher fps compared to the ASI224. The cooled cameras do not have a wide-angle lens.

The cooled temperature reduces the background noise produced by DSLR cameras during the required long exposure astrophotogaphy of deep sky images. There is an added practical consideration in that the cooler needs a 12V power supply either through the same or a different power supply used for the telescope mount.

The range of sensor sizes from the smallest ASI290 to the mighty ASI1600 allows choice over what size of DSO you wish to image. The ASI 224 and 290 are suitable for DSOs such as planetary nebula whereas the ASI1600 can be used for larger DSOs such as the Andromeda galaxy and the Orion Nebula.

The equipment required for deep sky imaging is different to planetary imaging. A GOTO equatorial mount is reguired that can be accurately balanced and polar aligned. In addition to the ZWO cooled camera (imaging camera) an autoguiding camera is required that locks onto a guide star and feeds information back to the equatorial mount to allow accurate tracking over a long period of time. This allows the camera to take series of long exposure images.

Registax and Autostakkert are not normally used for processing deep sky images. Each exposure is typically stacked in software called deep sky stacker (free software). This helps to further reduce background and improve detail. The stacked image can be further processed is software such as GIMP or photoshop to produce a final image.

Conclusion

The ZWO family of planetary imagers offers a wide range of different cameras to meet the different interests and budgets of club members. The relatively low budget ASI0134 still offers the potential of good images showing significant detail on solar system objects. The new ASI224 offers a higher budget versatile and powerful planetary imager that we believe is set to become a best seller in its price range. Finally, the outstanding ASI174 offers the potential for stunning images of the moon and sun but at an increased cost. None of these new developments should take anything away from the original ASI120 offering an excellent value planetary imager with an autoguider port and an all sky lens. For those members with a higher budget and interest in deep sky imaging, the latest release by ZWO of Cooled ASI cameras offers the potential for outstanding deep sky images as long as the right equipment is used. The sky is literally the limit!

ZWO ASI technical details

ZWO ASI NON-COOLED CAMERAS

ZWO ASI034 ASI130 ASI120 ASI120-S ASI224 ASI185 ASI178 ASI174
Target Planets

(Moon)

(Sun)

Moon

Sun

Planets

(Moon)

(Sun)

Planets

(Moon)

(Sun)

Planets

(Moon)

(Sun)

Planets

Moon,Sun

DSO

Moon

Sun

DSO

MOON

SUN

DSO

Colour / Mono Colour Mono C or M C or M Colour Colour Colour C or M
Max Res 728×512 1280×1024 1280×960 1280×960 1304×976 1944×1224 3096×2080 1936×1216
Frame Rate 95 30 30 60 150 108 60 164
USB 2.0 2.0 2.0 3.0 3.0 3.0 3.0 3.0
Sensor Size (diag) ¼”

(4mm)

½”

(8mm)

1/3”

(6.09mm)

1/3”

(6.09mm)

1/3” (6.09mm) 1/1.9”

(8.58mm)

1/1.8”

(8.92mm)

1/1.2”

(13.33mm)

Pixel Size 5.6µm 5.2µm 3.75µm 3.75µm 3.75µm 3.75µm 2.4µm 5.86µm
Sensor ASX340CS MT9M001 AR0130CS(C), MT9M034(M) AR0130CS (C), MT9M034 (M) IMX224 IMX185 IMX178 IMX174LQJ (C) IMX174LLJ (M)
Exposure 64µs – 60s 64µs-1000s 64µs-1000s 64µs-1000s 32µs-1000s 32µs-1000s 32µs-1000s 32µs-1000s
Guide Port No Yes Yes Yes Yes Yes Yes Yes
QE (%) 55 75 75 75-80 ~80-85 78
Read Noise 1.5e 3.3e 2.2e
Output 8 bit 12 bit 12 bit 12 bit 12 bit 14 bit 12 bit
Wide angle lens Optional Optional Yes Yes Yes Yes Yes No
Cost [2]

(inc VAT)

£108.40 £170.10 £145.20 (C), £159.80 (M) £223.80 (C),

£244.80 (M)

£299.80 £349.80 £349.80 £549

ZWO ASI COOLED CAMERAS

ASI (Cooled) 224 185 178 174 290[3] 1600[3]
Target[1] P, M, S, DS P, M, S, DS M, S, DS P, M S, DS P, DS P, M, S, DS
Colour/monochrome C C C or M C or M C or M C or M
Max resolution 1304×976 1944×1224 3096x

2080

1936x

1216

1936×1096 4656x

3520

Max frame rate 150 (10 bit ADC) 108 (10 bit ADC) 60 164 170 23
USB 3 3 3 3 3 3
Sensor size 1.3” 1/1.9” 1/1.8” 1/1.2” 1 /2.8 4/3”
Pixel size 3.75u 2.3u 2.4u 5.86u 2.9u 3.8u
Sensor IMX224 IMX185 IMX178 IMX174 IMX290/291
Max exposure 1000s 1000s 1000s 1000s 2000 2000s
Autoguider port Y Y Y Y Y Y
QE (%) TBD TBD TBD 78% TBD TBD
Cost[2] £632 £638 £668 £809 (C),

£849 (M)

£584 (C),

£623 (M)

£970 (C), £1140 (M)

[1] P – Planets, M – Moon, S – Sun, DS – Deep Sky

[2] Price at 365 astronomy who are the UK distributor of ZWO products:

http://www.365astronomy.com/search.php?mode=search&page=1

[3]   Please note that the ASI290 and ASI1600 are also available as non cooled version in colour and monochrome.

http://www.365astronomy.com/search.php?mode=search&page=1

Article by Andrew Spencer and Zoltan Trenovszki

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Posted on September 23rd, 2015.