12 replies to this topic

[Lgood]

I'm still learning the technical terms for astronomy cameras, but I was gifted a ZWO ASI 071MC Pro about 2 years ago. I don't have a guiding system, but I do have a tracking mount. I'm thinking about ordering the new ZWO ASI 585MC Air that has the guiding camera and WiFi system built-in to compensate. I'm worried that because the 585MC Air isn't "fully focused" on the camera and instead has the other features, that the images won't look quite as nice as the 071MC Pro. Is this an unreasonable concern?

[afd33]

The main sensor in the 585MC Air is the same as the sensor in the 585MC Pro, the one without the guide camera and asiair built in. The quality of the photos isn't affected at all by having the extra stuff built in. I'll add that if anything, the 585MC Air will probably have slightly better picture quality because the sensor technology is slightly newer.

Edited by afd33, 21 June 2025 - 07:12 PM.

[DeepSky Di]

I still use my 071MC. It is easy to use and calibrate, although it does have some amp glow. The 585 has a much smaller sensor than the 071 so it will be like cropping the 071 image for the same target. It may be better (and cost less) to get a guide camera, guide scope and ASIAIR.

 

Regarding the Air cameras - there are benefits for simplicity, cabling and travel. There are downsides for flexibility and reconfiguration. For example, aseparate guide system and ASIAIR can be used with other cameras.

 

What OTA are you using with the camera?

[DeepSky Di]

Here's the Heart and Soul Nebulae with a RedCat 51, an 071MC and a 585MC modeled by Stellarium. Stellarium is free for computers so you can try this for yourself on other targets.

 

Both Heart and Soul fit into the 071. Only a bit of the Heart fits into the 585. The red outline shows what the camera would see.

 

071 has 4944 x 3284 pixels and 23.6mm x 15.6mm sensor

585 has 3840 x 2160 pixels and 11.2 x 6.3mm sensor

 

The 585 sensor is newer, and more sensitive, both of which are benefits. But being smaller it's going to be hard to fit larger targets into it without mosaicing. 

 

 

 

Attached Thumbnails

• 
• 

[Sacred Heart]

Lgood,

 

This is just me, I would keep the ASIair separate from the cameras.  Okay there are benefits to having the ASIair built into the camera, but if you swap cameras out you will need all your cameras with ASIair.  ASIair as a separate component, I see it as more flexible.  Yes more cabling / routing, but once that is figured out you are off and running.

 

Just me,  Joe

[Riaandw]

I still use my 071MC. It is easy to use and calibrate, although it does have some amp glow. The 585 has a much smaller sensor than the 071 so it will be like cropping the 071 image for the same target. It may be better (and cost less) to get a guide camera, guide scope and ASIAIR.

 

Regarding the Air cameras - there are benefits for simplicity, cabling and travel. There are downsides for flexibility and reconfiguration. For example, aseparate guide system and ASIAIR can be used with other cameras.

 

What OTA are you using with the camera?

Been daydreaming about the integated guide chip. This is a really good consideration though. No quickly throwing a DSLR on this one or any other camera. Much less versatile. 

[Zambiadarkskies]

I'm still learning the technical terms for astronomy cameras, but I was gifted a ZWO ASI 071MC Pro about 2 years ago. I don't have a guiding system, but I do have a tracking mount. I'm thinking about ordering the new ZWO ASI 585MC Air that has the guiding camera and WiFi system built-in to compensate. I'm worried that because the 585MC Air isn't "fully focused" on the camera and instead has the other features, that the images won't look quite as nice as the 071MC Pro. Is this an unreasonable concern?

A lot depends on your OTA of course, but If I was gifted an APS-C sized 071 I can promise you I would be happy to use it compared to buying the tiny 585 and the air device built in.  Just get a cheap 120mm guide cam and a 30mm scope and some free software and away you go.....  Of if the air control option appeals then just buy an AIR mini.  

 

But to really answer your question the OTA and tracking mount details would be helpful. 

Edited by Zambiadarkskies, 22 June 2025 - 03:02 AM.

[Marcin_78]

The camera you own (ZWO ASI 071MC Pro) has a sensor pixel size of 4.78µm, which is great for imaging faint DSOs.

 

The other camera (ZWO ASI 585MC Air) has a sensor pixel size of 2.9µm, which is much worse for imaging faint DSOs – you will need almost 3x longer imaging time for a single sensor pixel to gather the same amount of photons:
(4.78/2.9)^2 = 2.72

 

The smaller sensor pixel will show you more details of bright objects, but for faint DSOs all that matters is to gather as much signal as possible. It's up to you what is more important to you – details of bright objects or visibility of very faint objects.

 

EDIT:

 

Let's make some calculation for SNR. Let's assume that a single sensor pixel 4.78µm with a particular shutter speed (single integration time) gathers ON AVERAGE 8 photons from a very faint object. Let's assume also that we take and stack 100 images.

Single image: SNR for that object = square root of 8 = 2.83
Stack of 100 images: SNR for that object = 2.83 * square root of 100 = 28.3

 

A single sensor pixel 2.9µm is smaller, so it would gather with the same shutter speed ON AVERAGE only 3 photons from the same very faint object:
8 photons * (2.9µm/4.78µm)^2 = 2.94 photons rounded to integer number of 3 photons

 

Single image: SNR for that object = square root of 3 = 1.73
Stack of 100 images: SNR for that object = 1.73 * square root of 100 = 17.3

 

So, with the same shutter speed the SNR for the same very faint object is clearly worse when sensor pixel size is smaller.

 

Now let's see what happens when we use 2.72x longer imaging time for the smaller sensor pixels size, so the stack will be 272 images instead of 100 images:

 

Single image: SNR for that object = square root of 3 = 1.73
Stack of 272 images: SNR for that object = 1.73 * square root of 272 = 28.53

 

So, with smaller sensor pixel (2.9µm) we need 2.72x longer imaging time to get the same SNR (for that object) as with the sensor pixel size 4.78µm.

 

Clear skies!

Edited by Marcin_78, 22 June 2025 - 06:49 AM.

[Lgood]

Thank you for the responses. I use a ZenithStar 81 scope for imaging and my mount is a Sky Watcher HEQ5 Pro. Part of the appeal of the all-in-one design is the ease of use since I'll be going to grad school in a few months. I'll look at how expensive getting the separate guide scope setup would be.

[Sacred Heart]

Lgood,

 

Your image scale is 1.76 with the 071 camera, and 1.39 with a 533 or 2600 camera, 1.07 with the 585 camera.  Your guiding and seeing conditions have the final say on how much detail you can actually get / see in a picture.  Seeing conditions have to be average to good and you must guide / track at or under your image scale.

 

That said, the 585 may work, the 071 is a safe bet, and so is the 533 & 2600 cameras, my opinion.  Also my opinion, having a dual sensor camera is okay until you put a light blocking filter on.  Usually the guide camera does not see through a light blocking filter   Usually there is an OAG or a separate guide scope,  but now people are doing it.  The guiding exposure may be lengthened or the gain is raised on the guide camera, I'm not sure.

 

Anyway, back to the 585 camera, the FOV is much smaller in the 585 vs the 071. so for smaller targets maybe the 585 or for planets and the Moon the 585,  that's up to you.

 

If it were me I would want to keep things simple and keep cost down.  For me, I'd get a separate guide scope / OAG and camera, the 220, and an ASIair or use my laptop / Tablet or something.  Yeah, all that would put you close to that 585 in price, but I already have the 071 camera and if I want another camera I don't need another camera with ASIair built in.

 

Amp glow has been around for a long time and can be dealt with.  People take excellent pictures with CCD, DSLR cameras, so that 071 is not so much old school as you think.  Take a look in Astrobin for DSLR cameras, older SBIG and QSI cameras, you will see some nice shots.

 

Just me,   Joe 

[DeepSky Di]

The camera you own (ZWO ASI 071MC Pro) has a sensor pixel size of 4.78µm, which is great for imaging faint DSOs.

 

The other camera (ZWO ASI 585MC Air) has a sensor pixel size of 2.9µm, which is much worse for imaging faint DSOs – you will need almost 3x longer imaging time for a single sensor pixel to gather the same amount of photons:
(4.78/2.9)^2 = 2.72

 

The smaller sensor pixel will show you more details of bright objects, but for faint DSOs all that matters is to gather as much signal as possible. It's up to you what is more important to you – details of bright objects or visibility of very faint objects.

 

EDIT:

 

Let's make some calculation for SNR. Let's assume that a single sensor pixel 4.78µm with a particular shutter speed (single integration time) gathers ON AVERAGE 8 photons from a very faint object. Let's assume also that we take and stack 100 images.

Single image: SNR for that object = square root of 8 = 2.83
Stack of 100 images: SNR for that object = 2.83 * square root of 100 = 28.3

 

A single sensor pixel 2.9µm is smaller, so it would gather with the same shutter speed ON AVERAGE only 3 photons from the same very faint object:
8 photons * (2.9µm/4.78µm)^2 = 2.94 photons rounded to integer number of 3 photons

 

Single image: SNR for that object = square root of 3 = 1.73
Stack of 100 images: SNR for that object = 1.73 * square root of 100 = 17.3

 

So, with the same shutter speed the SNR for the same very faint object is clearly worse when sensor pixel size is smaller.

 

Now let's see what happens when we use 2.72x longer imaging time for the smaller sensor pixels size, so the stack will be 272 images instead of 100 images:

 

Single image: SNR for that object = square root of 3 = 1.73
Stack of 272 images: SNR for that object = 1.73 * square root of 272 = 28.53

 

So, with smaller sensor pixel (2.9µm) we need 2.72x longer imaging time to get the same SNR (for that object) as with the sensor pixel size 4.78µm.

 

Clear skies!

Good thought, and this would be the whole story if the two sensors were equally sensitive. They are not.

 

Other relevant sensor specs:

 

ADC bit depth - how many shades of gray the sensor can see. 071, 2600 and 533 - 14 bits; 585 - 12 bits.

Full well depth - how much light a pixel can capture before overflowing to adjacent pixels

Quantum efficiency - how much of the light shining on the pixel is actually captured -  071 about 50%, modern sensors up to 91%

Aspect ratio: APS-C sensors 3:2; 533 1:1 (square) and 585 16:9.

Read noise

 

So the 585 has small pixels and should capture less light but is more sensitive - enough to make up for the smaller pixels?

We may be used to the 3:2 aspect ratio and some dislike square aspect ratio; arguably 16:9 is rather elongated and will require more attention to framing.

 

In the end judging a sensor by its specs can only go so far. Trying it out in Stellarium and searching Astrobin make up for the fact that we don't get to test sensors before purchase.

[t-ara-fan]

The 071 has 5x the chip area of the 585.  What were they thinking with that tiny little thing? 

[Helyis]

You already have a very nice aps-c camera. I really don't see why you are even considering a small sensor camera like the 585. For nebulae imaging, that's a dowgrade in many aspects.

Using the asiair is already very convenient, you just have a few cable to plug, that's sincerely nothing.

I, once again, agree with ZambiaDarkSky