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ASI120MM-S first impressions


JamesF

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in case you'd missed the news, the ASI120MM-S (and ASI120MC-S) are new versions of the ASI120MM (and ASI120MC) cameras with a new USB3 interface rather than the USB2 interface in the original models.  Mine arrived a few weeks ago though I've had no chance to actually try it out for real imaging yet, so these are my initial observations based on testing on my desk.

The camera arrives with pretty much the same kit that the USB2 model had:

asi120mm-s-1.jpg

As well as the camera body itself there's a CCTV lens and cap (in the photo above the lens is already inserted into an adapter to fit the M42 thread on the front of the camera; the lens has a standard C/CS size thread), a 1.25" adaptor and cap, a USB3 lead and an ST cable.

The photo also shows that compared with some of the earlier USB2 camera models the sensor window has been considerably reduced in size.  My early 120MM has a threaded opening large enough to accept a 1.25" filter (into which I have fitted a clear optical flat to try to keep the sensor clean).  I believe as a result of numerous people raising the issue of keeping the sensor clean on the older models this new one has a clear window permanently fitted (I believe the MC model uses an IR-cut window but I'm not certain).

The USB socket on the camera is the new USB3 standard B socket.  I assume that the extra depth required to mount this on the PCB is also the reason for the camera body being a couple of millimetres deeper than the original model:

asi120mm-s-2.jpg

(The older model is on the right with the lens cap still on.)

In terms of software support, the new camera works quite happily with Fire Capture, SharpCap, oacapture etc. though a new version of the drivers is required.  It's also desirable to update the capture software as there is a new "overclock" setting that doesn't exist on the older cameras.  The USB3 interface also appears to work nicely on Apple hardware whereas the older camera needed different firmware which resulted in reduced performance.

And what about performance?  I struggle not to get broken frames on my original ASI120MM with a USB Traffic setting higher than 40, so I ran some benchmarks (this is just transfer rates, not saving frames to disk) with the USB Traffic setting at 40 in 8-bit mode and an exposure time of 3ms.  The frame rates achieved were as follows:

1280x960  13fps

800x800    26fps

800x640    33fps

640x480    55fps

320x240   240fps

With the new camera I can adjust the USB Traffic setting through the full range from 40 to 100 and the overclock setting from 0 to 30 without broken frames.  Varying those two settings but leaving the exposure time at 3ms the new camera gave me the following results.  The frame rate columns are Overclock = 0, USB Traffic = 40; Overclock = 30, USB Traffic = 40; Overclock = 0, USB Traffic = 100 and finally Overclock = 30, USB Traffic = 100.

1280x960   24fps    31fps  55fps   71fps

800x800     55fps    71fps  72fps   87fps

800x640     80fps  103fps  84fps  116fps

640x480   110fps  142fps 110fps  142fps

320x240   224fps  290fps 224fps  290fps

(These are all measured with oacapture, but I understand other people are getting pretty similar figures from FireCapture and SharpCap, and I found pretty much the same results on my Linux desktop and my MacBook Pro.)

Depending on the settings it appears that the new camera can handle from approximately double to around triple the frame rates of the older model at anything but the smallest frame sizes.  These figures are a little below what's advertised on the ZWO website, but a) that's marketing for you, and B) I've made no attempt to optimise the performance of the test machine for capture in any way at all.  I'm sure I could push those rates up a little if I were desperate to do so.

The real question I guess is how useful this increase in frame rates is.  For solar and lunar imaging I think it could be a real benefit being able to sustain high frame rates at full resolution.  For planetary imaging I'm really not sure at the moment.  On the one hand it's all very well being able to do 100fps, but if you have to reduce the exposure time and wind up the gain to be able to actually produce frames at 100fps perhaps it isn't such a great idea.  Pure throughput may not be the only reason for considering these cameras however.  The new USB3 model seems very stable where the USB2 version could be a bit less reiiable and sometimes produced broken frames when approaching the limits of its performance or occasionally just wouldn't work with some USB chipsets.  And if you want to use Apple hardware the new camera is definitely an improvement.

There's also the issue of hard disk speed to consider.  70fps at full frame resolution is going to produce a huge amount of data -- about 1GB every twelve seconds or so I reckon.  I shouldn't be surprised to find that the IO subsystem on many peoples' imaging machines becomes the bottleneck at that point.

Fortunately I discovered yesterday that 1TB SATA III SSDs are now available :D

James

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Fortunately I discovered yesterday that 1TB SATA III SSDs are now available :D

Considering that SSDs have lowered in price very quickly, and that Intel announced a 2TB SSD a few months ago.  :shocked:  SSDs are presenting good value nowadays.

Good luck with the new ZWO, the updated interface does look promising!

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Thank you.  As soon as I have some time I shall try doing some solar imaging with it.  Planetary is going to have to wait until Jupiter returns to the night sky later this year I think.

James

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  • 2 months later...

I'm glad I found this thread, thanks for the write up James, I've been thinking about replacing my synguider with the asi120mm and using it for guiding and a better route to get some decent moon shots.

I notice you mention using a MacBook pro, which is where I'd like to ask a question...

With the obvious issues using usb hubs with these cameras that is advertised and came to light very recently in another thread, and a few Mac limitations, I wondered how you get on with it and usb3.

The MacBook only has 2 usb3 sockets, so if you have this as a guide cam, an imaging cam and a mount connected, not to mention the possiblities of a usb focuser and filter wheel, does this new version work ok with a usb hub now?

Or is it better trying to use a thunderbolt port for the other bits?

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I'm glad I found this thread, thanks for the write up James, I've been thinking about replacing my synguider with the asi120mm and using it for guiding and a better route to get some decent moon shots.

I notice you mention using a MacBook pro, which is where I'd like to ask a question...

With the obvious issues using usb hubs with these cameras that is advertised and came to light very recently in another thread, and a few Mac limitations, I wondered how you get on with it and usb3.

The MacBook only has 2 usb3 sockets, so if you have this as a guide cam, an imaging cam and a mount connected, not to mention the possiblities of a usb focuser and filter wheel, does this new version work ok with a usb hub now?

Or is it better trying to use a thunderbolt port for the other bits?

I've not seen any problems using these cameras with a USB3 hub to be honest.  My main development environment for oaCapture is a Linux PC with two USB3 ports.  One of those I bring out to an Orico 8-port USB3 externally-powered hub and I've not seen problems when using the camera connected to that.

Off the top of my head I can't recall if I've ever tried anything similar with the MacBook Pro I'm afraid.  Regardless, the USB3 version of the camera does seem to be far more reliable when used with Apple hardware than the USB2 version.

I can't say how well it will work when combined with other peripherals as well.  My next release of oaCapture will include limited filter wheel support and there's more hardware support to come so I guess that will make itself obvious in the fullness of time.

I've only tried Thunderbolt for connecting FireWire cameras.  In general I've not managed to get those to work yet because the OS is doing something I don't yet understand.

I'm sorry I can't really be of more help :(

James

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James, 

Thanks for the write up. Been using my 120MM-S for a second time for Lunar and the results were pretty good (IMO). I do use OA capture though ;-) and yes I did fill up over 20GB of my start disk to the point the mac air started to whine about it 8-). had to offload the captures onto a separate disk then start again. Thinking of using a separate 2TB USB3 disk...seen one for about £80.

You mention the sensor is covered by a lens (not the all sky one). I am pretty sure my camera has obtained a dust mote on the sensor already (and its been treated with kid gloves). assume some wonder fluid, and the relevant lint free cloth would be ok to clean it with. decided to seal it off with an IR pass filter (the Baader one). 

Regards

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Hi James (and others). My ASI120MM-S didn't come with the CCTV lens. Could you please help me to find a suitable combination of a lens + adapter which will fit?

For example, would a combination such as this one work?

- lens - Megapixel Fisheye Lens 1/3" 1.25mm CS Mount Fish Eye Lens

- adapter - M42 To CS adapter

Thank you

I believe those should work.  The camera is definitely intended to take a CS-mount lens, though a C-mount lens would work with a suitable spacer, too.  The adapter looks right as well.  In fact it looks exactly like the ones I have.

James

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James, 

Thanks for the write up. Been using my 120MM-S for a second time for Lunar and the results were pretty good (IMO). I do use OA capture though ;-) and yes I did fill up over 20GB of my start disk to the point the mac air started to whine about it 8-). had to offload the captures onto a separate disk then start again. Thinking of using a separate 2TB USB3 disk...seen one for about £80.

You mention the sensor is covered by a lens (not the all sky one). I am pretty sure my camera has obtained a dust mote on the sensor already (and its been treated with kid gloves). assume some wonder fluid, and the relevant lint free cloth would be ok to clean it with. decided to seal it off with an IR pass filter (the Baader one). 

Regards

Pleased to hear it's working well :)  I know there are 1TB SSDs now.  I'm just waiting for them to get a bit cheaper :D

I have a fairly early 120MM that has no protection for the sensor and it used to get noticeably dusty.  Fortunately the opening was the right size (and threaded) to take a 1.25" filter, so that resolved the problem.  The later models appear to have a smaller opening in the case, and the most recent MM/MC models (and all the USB3 ones as far as I'm aware) have a clear (for the MM) or IR-cut (for the MC, I think) window covering the sensor as well.  These should be optically flat.

The window should help to keep the sensor clean, but if you still have dust on it you can unscrew the front half of the case to get at the sensor and clean it (I use Baader Optical Wonder fluid and a microfibre cloth over the end of a cotton bud).  It sounds alarming, but opening the case up is the way that ZWO recommend the sensor be cleaned if/when it is required.

I've found a good way to check for dust on the sensor is to plug the camera in with a clear plastic end cap in place over the nosepiece, in a reasonably well lit but not excessively bright room.  By adjusting the exposure and (mostly) the gain, it's often possible to pick out dust spots that would be hard to find otherwise.

James

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For example, would a combination such as this one work?

 

- lens - Megapixel Fisheye Lens 1/3" 1.25mm CS Mount Fish Eye Lens

- adapter - M42 To CS adapter

You can also pick M42 lens from ebay which have bit longer focal lengths (from 35 up to ~200 mm). That could be even used for some widefield imaging at bigger resolutions than 2mm of focal length would provide :D

And SSD isn't that much needed. 7200 RPM good HDD can handle it. I have been using a HDD with CMV4000 giving 90 FPS of 2048x2048 frame.

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  • 5 months later...

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