ASI-678MC vs ASI-585MC

[Pixies]

OK. I can read the specs and understand what they mean. But I have no experience when it comes to making real-world interpretation. So, when they say:

ASI-678MC

• sensor size: 7.7 x 4.3mm
• Resolution: 3840 x 2160 
• Pixel size: 2μm
• ADC: 12bit
• Peak QE: ~83%
• Read Noise: 0.6e
• Full Well: 11270e

ASI-585MC

• sensor size: 11.2 x 6.3mm
• Resolution: 3840 x 2160 
• Pixel size: 2.9μm
• ADC: 12bit
• Peak QE: 91%
• Read Noise: 0.8e
• Full Well: 47000e

So the 678 has higher resolution, better read noise (at  whatever gain), is slightly more efficient; but 585 has bigger pixels and 'fuller' wells (no idea how best to put that). But what does this mean when it comes to the real-world use of them.

I've been following @Chris's topic with interest, and @PeterC65's posts regarding getting started with the IMX585 for EEVA. But here's the question....

When it comes to using these cameras with a small (400mm fl) scope for EEVA-type imaging. Which is the most suitable? I get the feeling that the 585 might lend itself better to long-exposure imaging and the 678 to planetary?

 

Cheers

 

 

[ONIKKINEN]

If the goal was to do a bit of both, the 585 would probably be the better choice based on the specs (bigger sensor too, for DSO stuff seems like it would be the deal maker and breaker here). The 2 micron pixels in the 678MC are really not ideal for DSO stuff, although its not a disaster as you could just bin on camera when doing EEVA for DSOs.

For planetary either camera will do the trick if they are matched with the right scope/barlow combination.

If we use the critical sampling formula for lucky imaging: f_ratio=2/wavelength x pixel size (both in microns where 0.5 microns for green light can be used to approximate an RGB capture) comes out to f_ratio=4x pixel size. so an f/8 scope will be natively "ideal" with the 678. f/10 scopes are pretty close too, but might be oversampling a little bit. The 585 needs f/11.6 to be ideal, which is also easy to reach with many scopes using a 2x barlow with a short nosepiece to control the barlow strength.

So i think either will do the trick given the right kit, but the 585 is more versatile for sure. Just for planetary/lunar, the 678 is very convenient for natively f/8-f/10 scopes or the typical f/4-f/5 newtonian with a barlow. Choices choices!

[vlaiv]

ASI-585MC

[Chris]

Hey Pixies, if you're doing any kind of DSO work I can recommend opting for the 585 for it's larger sensor, better for framing a variety of targets.

The pixel size between the two cameras isn't vastly different in the scheme of things, however the extra well depth of the ASI 585 is handy when taking longer exposures to help avoid each photosite becoming saturated and electrons bleeding into neighbouring photosites - stars should be tighter and more colour accurate with a deeper well depth sensor the way I understand things. 

I agree with the above replies  

 

 

 

 

[Elp]

I've always looked at the 585 out of the new cameras, but saved a lot of money by getting the 485 used which is nearly the very same camera and the amp glow calibrates out with the 485. Full Well Depth is also a very good selling point but if you look at the graphs zwo provide, that FWD max number drops off extremely quickly when the gain goes up from zero.

[PeterC65]

I'm using cameras for EEVA only and not AP, and I already have an Altair GPCAM2 327C (Sensor size: 5.6 x 3.1mm, Resolution: 1920 x 1080, Pixel size: 2.9μm, ADC: 12bit, Peak QE: ?, Read Noise: 0.8e, Full Well: 11844e).

I've gone for the 585, actually the Player One Uranus-C, because it has a physically bigger sensor and therefore captures a wider field of view for given optics. The 327C just feels like I'm looking through a keyhole, and even with a reducer there are some targets (M45, M31) that don't fit into the field of view. I've become a fan of plate solving and that needs a good amount of sky to see enough stars to work properly. EEVA needs short exposure times and therefore high gain, which usually means amp glow, and both the 585 and 678 are supposed to be devoid of amp glow.

So far, I've been using my 72mm F6 APO with the camera and that combination has worked fine. The 2.9μm pixel size of the 327C and Uranus-C is ideal with this scope (see Astronomy Tools), covering the central region of appropriate pixel size with my x2.25 Barlow at one end an x0.5 reducer at the other.

Just for information, I tried the 327C camera with my Skymax 127 last night and found it disappointing compared with the 72mm APO. I think the issues are:

• less light because of the higher F ratio, requiring longer exposures,
• more difficult to focus because the MAK uses a mirror control knob and because less light makes it hard to see the Bahtinov mask diffraction pattern,
• there was more wobble as the scope is bigger (and my mount is not ideal).

Bear in mind that the Uranus-C hasn't arrived yet!

 

[Pixies]

Thanks everyone. The 585 it is, then.

 

Mother! Time to sell more children!