ASI120MC-S or 120MM Mini?

[RussellH]

Looking for a guide camera, the ASI120MM-S and the MM mini are currently the same price.

I’m wanting to use them with the ZWO Off-axis Guider, so neither will be getting much image anyway, but given the colour camera is future-proofed with USB3, would there be any reason to choose the MM instead?

Thanks. Russell.

[Imme]

The mono will provide much more sensitivity. If you’re using an OAG then I’d suggest the only option you have is the mono.

I have both....here’s a sensitivity test i did a while back.

http://www.iceinspace.com.au/forum/showthread.php?t=169472

[RussellH]

Well, that seems rather definitive. Thanks for the response, and thanks for doing the original test!

[ChrisV]

Have you thought about the 290mm mini, or is it out of budget. I haven't used oag much but the 290 has a slightly larger sensor which might make it easier to pick up guide stars.

Some also use the 174 (or is it the 178) although it's sensor is slightly larger than the prism in the zwo oag - so that might be a bit of a water?

[RussellH]

Yeah the 290 is out of my price range for now. Just since I am getting a new scope and am interested in oag, I didn’t want to buy a separate guide scope now only to abandon it soon after to go oag.

[kosborn]

I'm using the ASI120MM-S as the guide camera on a 10" Newtonian with the ZWO OAG. I've never had problems finding a guide star. My imaging camera is the ASI1600MM. With that sized sensor there has been no problems with the OAG prism getting in the way of the image circle.


Kevin

[RussellH]

Thanks Kevin. I wasn’t too worried about the prism intrusion on the image, it’s just something extra to adjust for when setting up. Good to hear you have no trouble finding a guide star. Seems there’s a wide variety of opinions on that issue. Not sure if it comes down to camera quality or just user experience in knowing how to drive the oag.

[RussellH]

So I've been researching cameras all morning and have come across a generic versions of the 120MM, the T7M (and the T7C for the colour version). Several brand names exist - Lovosky, SvBony, or unbranded, but they all seem to have pretty much the same specs as the ASI120 USB2 range, at least from the sensor side. They got for about $200 on eBay, so $50 less than the ZWO versions. The colour is more prolific and is only around $150.

I'm thinking I'm likely to upgrade down the track if all goes well, even if I get the ZWO 120 camera, so maybe I should save the $50 and get the mono one for now. It shows as having a much large dynamic range than the colour one (115dB vs 82dB for the 120MM sensor), although from reading the spec sheet on the sensor, that's only if HDR mode is enabled, which I don't know if that's configurable in standard camera control software, or has to be done low level by the developers.

I also came across a couple other cameras, the SV105 and the SV205. Their specs as presented look attractive at first, for their very cheap prices (about $70 and $140), especially with the SV205 being 8MP and USB3. Looking in detail at their sensor specs though, they only have 10-bit A/D converters, which I imagine will show a significant quality loss compared to the ASI line, which are all 12/14/16 bit devices. Still, I'd be interested in seeing some images from the SV205 for planetary imaging.

[Imme]

ASCOM compliant???

[RussellH]

Apparently, yes.

There may be some caveats. I did see an old thread elsewhere of someone having issues using the ST4 connection, with swapped pin-outs, but I'll be doing all USB control anyway, so not really an issue for me, if it is an issue. Others have reported working fine. $50 cheaper and I'd have bought one already, as there is some risk with these clone devices. Sometimes it's the luck of the draw on quality control. I'm still researching before committing.

[RussellH]

So I haven’t been able to find many comments on the T7M. One said it works great as a drop in replacement for the 120, and another couple having driver issues. I think at this stage it’s worth the extra $50 for me to have something that works out of the box, so I’m going back to the 120 at this stage.

[dikman]

I know nothing about these cameras but I'm a bit perplexed by the reference to dB as dB is a sound measurement?

[RussellH]

No, when talking about sensors, dB is all about the response range of signals. In this case I was referring to the dynamic range, as in how wide the individual light levels that the sensor can detect.

[dikman]

We live and learn. It originated as a measurement in telephony systems (which is where I've always used it) and it naturally followed that it is used in the audio field. I had no idea it had been hi-jacked and morphed into more general usage.

[RussellH]

Yes sound levels is what I think of usually. I’m no expert, just going by the manufacturer specs. the also use it for signal to noise ration, just noise is bad pixels in this case, not sound.

[Camelopardalis]

If you can spring for the extra $100, the ASI224MC is well worth it...much more sensitive than (practically) anything else on the market right now, I’ve used one as a guide came for several years and would save you the grief of a colour filter wheel if you used it for planetary.

[RussellH]

Already ordered the 120 unfortunately. Looks $150 more currently, so not something I would have considered at this stage anyway. I’ll keep it in mind for upgrades though down the track. Once I have everything running I’ll be able to identify any shortfalls properly. Good thing with astro gear is that it can usually either be sold, or re-purposed.

[Tarn_M]

How was the 120? Looking for a guide camera myself.