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Side by side comparison between 120MM & 120MC cams


budski
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Hi Guys, here is a first rough n ready comparison between the ASI120MC and MM cameras which I picked up last week at AstroFest.

I've yet to learn these cameras operating foibles (of course) but when does anyone read the manual first, eh?

These images were taken within 9 minutes of each other through the same scope (C11) and a TeleVue 2.5x Powermate. Seeing was average to good.

This is my first foray with a OSC camera(all my other stuff is mono) so I've still some work to do in the control and processing departments!

The color cam image is on the left.

post-6215-0-61854200-1361206220_thumb.jp

post-6215-0-06374000-1361206258_thumb.jp

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There's a manual? :)

Well done for doing the comparison though. I definitely prefer the version on the right. To my eye the image on the left looks more noisy and I think there are some ring artefacts at the edge whereas the one on the right looks more "natural" (whatever that means). The left image looks perhaps more blue to me, too, though I think I'd want to check the histograms before claiming that for certain.

James

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Hi James, I agree the OSC image is noisy but that's probably down to me not getting the exposures/set-up right.

It's now a case of going through a steep learning curve which comes with acquiring a new piece of kit but I think the Color cam has great potential. I'll post some more results when the opportunities arise i.e. clear weather!

Bud

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I am finding the learning curve steep with the MC too. I can get results that I would have been happy with say, a year ago. But I don't feel I've really matched what I've been able to do with the SPC900 yet.

James

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Thanks for posting the comparison on these two cameras - still toying with options here so good to see something side by side. The RGB image wins handsdown on this, although as you point out the noise and colour balance will get better with using the OSC. Apart from colour balance and noise though the detail/resolution look almost identical. OSC has to be a big advantage with Jupiter given the high rotation speed, although the mono is 4x more sensitive, you must be able to catch and stack more frames with the colour, than faffing around with the filters - obviously this is where the automatic filter wheel and ascom drivers pay dividends!

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Certainly showing promise Bud.....if i was to suggest anything it would be to dial back the image scale at capture significantly: it might sound a bit unusual but tbh I'm imaging at around f19 with the C14 at around 1.2X/1.25X amplification of native scale (f11 cf. f10 for the C11) and to date (ie, about 4 months) haven't found any seeing which warranted any more than this.....

Not 100% correct because I didn't have the means back whenever to do so (vary, that is) and in recent times clouds have allways been an issue.....but unless I get some really nice seeing I have a feeling that f19 or so is a really "sweet spot" for this camera's pixel-size.

Of course that means you need a bit of improvisation unless you have a Siebert or other 1.2 - 1.25X barlow.....like I did/have with the 2X TeleVue...

One definite fact from my perspective is that with any "reasonable" seeing the scales I mention will allow for very good resampling rates - so the end-images aren't compromised in quality or size! :)

I've just finished trialling the new super high speed drivers from Sam indoors - looking for the opportunity to test them now on Saturn.....hopefully soon. :)

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Certainly showing promise Bud.....if i was to suggest anything it would be to dial back the image scale at capture significantly: it might sound a bit unusual but tbh I'm imaging at around f19 with the C14 at around 1.2X/1.25X amplification of native scale (f11 cf. f10 for the C11) and to date (ie, about 4 months) haven't found any seeing which warranted any more than this.....

I worked out the "optimal theoretic" focal ratio to be around f/25 with this camera which is why I've dropped the extension I use with the SPC900 and now I'm just using the 2.5x barlow with my 127 Mak. If I do any more imaging of Jupiter this apparition I think I might drop back further to just a 2x barlow.

James

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Umm , there's an awful lot of opinions from well respected imagers out in internet land regarding "theoretical" & "practical" optimal focal lengths for pixel sizes, under sampling and then over sampling. Personally, since I'm lucky enough to have a variety of barlow options and I appreciate Darryl's expertise I shall probably stick with F20 rather than scramble to get close to F19 from F15 upwards. This cam does appear to work very well at those focal lengths. It's all a bit academic ATM tho since my C11 is closed up safe in a box !!! :(

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I do prefer the one on the right (RGB), the mono camera does produce better images. To be expected really with using pure grey scale pixels (higher end resolution) rather than a bayer matrix (lots of guessed at pixel values).

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Hi Guys, thank you for all the feedback regarding the ASI cameras- hopefully our gathered experiences will result in a basic operating standard for both the MM and MC units for the types of 'scopes at our disposal. I'm mindful that aperture and seeing will always have a major impact on the final result but 'knowing' the camera will also yield better images.

Darryl, would you mind asking Sam if there's a website we can visit or join a forum similar to Torsten's Firecapture group or Emil's AutoStakkert endeavour to keep up with developments.

In the meanwhile .... "I villl kontinue mit mien experimentz....." as those German rocket scientists used to say in the old films - before blowing themselves up!

Bud

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Umm , there's an awful lot of opinions from well respected imagers out in internet land regarding "theoretical" & "practical" optimal focal lengths for pixel sizes, under sampling and then over sampling. Personally, since I'm lucky enough to have a variety of barlow options and I appreciate Darryl's expertise I shall probably stick with F20 rather than scramble to get close to F19 from F15 upwards.

Absolutely. It's all very well calculating the theoretical values, but I think a good shovel full of pragmatism needs to go into the mix. Especially when you consider that telescope resolution varies with frequency meaning the optimal focal length for the blue end of the spectrum does not have to be the same as the optimal focal length for the red end.

There's a hint of clear sky in the forecast tonight though it looks like fog will put the boot in later, so I might just go out with a fistful of barlows and do some experimentation.

James

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Out of interest I've just done the calculation for "representative" red, green and blue frequencies and come up with the following "theoretically optimal" focal ratios:

blue: f/26

green: f/20

red: f/16

Given the human eye's bias towards red/green I think that ties in pretty well with Darryl's figures. All of a sudden I feel energised to go out and try again with a 2x barlow, and even with the removable lenses on my 2x barlow screwed into the end of the filter on the camera to give a bit less focal length still.

Bah. I want to do some experimentation with full disc Moon imaging, too. Where does the time go?

James

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Darryl, would you mind asking Sam if there's a website we can visit or join a forum similar to Torsten's Firecapture group or Emil's AutoStakkert endeavour to keep up with developments.

This would be great. Yahoo a bit of a dirty word around here, but it's an easy way to set up a discussion group with both web and email access with relatively little pain. In fact there's nothing to stop one of us doing just that, but it might be considerate to mention it to Sam first.

James

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BTW James following on from Darryl's mention of superfast drivers- I have just noticed & d/loaded a new driver from ZWO x.x.x. 1229 . Indoor testing looks pretty good so far. I too may just be tempted tonight- Good luck!

Oooh, I got all excited there for a moment. Then realised I've already got that version installed :)

James

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