ZWO ASI120MM S USB3.0 CMOS Astronomy Camera

Well I just got my ASI120MM S USB3.0 camera through via DHL. Ordered it direct from ZWO Optical on AliExpress and paid £250, then had to pay an extra £19 on import duty etc. But still a bit cheaper than buying from 365Astronomy – they were also out of stock at time of ordering.

The video shows below me unboxing it, and what it looks like.

This is a still image of my desk at 1280×960 on the ASI120MM S with the CCTV lens attached.

I used the default capture software AMCap to get this still. Remember to install the correct drivers from the CD or from the ZWO website before you plug the camera into the PC.

The CD is quite good it comes with ASCOM, PC drivers and ST4 software, as well as all the different ZWO camera driver versions. There is also some PC and Mac software on the disc. PHD2 and oaCapture for the Apple Mac and FireCapture and SharpCap as well as PHD2 for the PC.

I have now installed the camera on my observatory PC. The install was easy. I also installed the ASCOM drivers as well FireCapture and SharpCap 2.

I began with SharpCap 2, but found the best fps I could get was around 70fps at 640×480 (it was 30fps at 1280×960). Other people had reported around 100fps. So I loaded FireCapture – which I must say seems to have a lot more functionality than SharpCap.

I tried my tests again in FireCapture and at 640×480 I was now getting 106fps-116fps. So it seems which software you use makes a difference, unless some other settings were different.

It appears that the ASI120MM S is a very sharp camera and so far I am very impressed with it.

QHY5 vs DMK21 for Guiding

I have always used my QHY5 for guiding, most of the time attached to a Skywatcher 9×50 finderscope and it has worked quite well.

But while at Kelling Heath this year I purchased an Altair Astro 80mm guidescope. Did I need to? I don’t know, may be a 60mm would have been a good upgrade as opposed to going for the larger 80mm. But anyway, I have now started to realise that the original QHY5 does suffer from some image degradation in the form of banding. (I do already use simple dark frames with the QHY5 camera).

Now instead of purchasing a QHY5 II Mono, I have been thinking about using my DMK21 AU618 camera instead.

I know the DMK21 sensor is half the size of the QHY5, so finding a guide star may be harder – but I bet the quality of the image will be a lot better. Plus it would mean I would not need to purchase a new camera but use the DMK21 that I already own.

So on the next clear night I shall try out the DMK21 for autoguiding and see what happens and report back.

UPDATE: 11th November 2014

Well last night I went out and tried the DMK21 for guiding. It worked OK, in Maxim DL the guiding calibrated OK. But the actual guiding itself was not that smooth, certainly not as smooth as when I use the QHY5.

I don’t think the small sensor and field of view is a major problem, as I found lots of stars in the field of view. But it could be because the DMK21 is only 640×480 – the sensor is so small you can’t bin the camera, so it lacks the sensitivity that you can get with the QHY5 camera when you bin the images as it’s 1280×1024 pixels.