How does everyone compare the capabilities of dedicated AP camera's?

[Trippelforge]

I have been shopping around and trying to compare various dedicated camera's. Each one on say ZWOs website lists a bunch of specs along with a page of graphs. When I line them up I get a bit stuck when comparing. I understand that low read noise has a strong correlation with desired dynamic range. And when you line them up you find a sweet spot that falls on the gain scale. But that's where things start to get confusing, such as I am not sure if one location on the gain scale is better than the other. Such as if this (sweet spot) point falls around 180 gain, is it better than if it were 100 gain.

Man that probably sounds confusing... I hope it sort of makes sense. lol

My main curiosity like the title says is how are people comparing the various models? Currently I am trying to find reviews, looking up astrobin examples and scouring forums. But when I have bought anything else (even DSLR) I could just line them up and see pretty easily which was better. Which kind of works for anything you buy in life... however for some reason the CMOS camera's are hard for me to do so. Which is probably due to so many other "specs" listed.

Any advice on how to do this?

 

[Synchronicity]

I've recently bought a ZWO ASI 183MC-PRO and my process was reasonably simple and similar to what you are doing. 

• I searched for that camera and the others I was considering in this forum and read what was said. 
• I searched https://www.astrobin.com for images taken with the camera and my scope - an Esprit 80.
• I entered the scope and camera spec into the Ocular settings in Stellarium and used that to get an idea of the framing and size of various targets I was considering.
• I did the same with the telescope simulator at https://telescopius.com/

For the detailed specification of the cameras I found that price was filtering them down anyway so the list wasn't too big!

HTH

Michael

[Trippelforge]

10 minutes ago, Synchronicity said:

I've recently bought a ZWO ASI 183MC-PRO and my process was reasonably simple and similar to what you are doing. 

• I searched for that camera and the others I was considering in this forum and read what was said. 
• I searched https://www.astrobin.com for images taken with the camera and my scope - an Esprit 80.
• I entered the scope and camera spec into the Ocular settings in Stellarium and used that to get an idea of the framing and size of various targets I was considering.
• I did the same with the telescope simulator at https://telescopius.com/

For the detailed specification of the cameras I found that price was filtering them down anyway so the list wasn't too big!

HTH

Michael

OK so I am doing what people normally do. I think what kind hung me up a bit was when comparing two camera's not far apart and thinking "is it worth it?". And then running through the specs and not seeing much difference. 

 

[vlaiv]

This is really not an easy topic and there is a lot of misinformation and misunderstanding "floating" around.

I'll try to give you sensible answer - or at least partial answer - as it is always better to go into depth on particular parameter to fully understand implications.

There will be a lot of ifs and buts included - such is the nature of the beast.

First of - dynamic range is completely meaningless for astrophotography - I have no idea why so many people get hung up on it. Probably because it is somewhat important metric in daytime photography where some shots need to be taken in shortest time possible.

In AP - we can expose for much longer and we stack many subs. We end up with much much higher "dynamic range" image than single exposure suggests - in fact, we can control what sort of dynamic range we want to end up by selecting number of exposures we want to stack.

Each quadrupling of number of exposures leads to doubling of dynamic range.

 

Ok, back to original question - sensor properties and how do they compare. Well, it depends on use case. I'll list some of them and list what is better depending on circumstances and "impact" - how important that difference is.

Let's start with read noise. Lower is always better

- in modern CMOS sensors if doing RGB / OSC long exposure imaging - impact minimal. With selection of proper exposure length, impact is effectively removed.

- In narrowband imaging - impact raises to medium / high

- In lucky type planetary imaging - impact raises to very high

- If mount performance is questionable and one is doing EEA with short exposures, or lucky type DSO imaging - impact is high

- if one is considering CCD type sensor - impact is high (mostly due to fact that CCD sensors have much larger read noise than CMOS sensors and some of above factors will kick in - like need for half an hour exposures for NB imaging - can mount do that nicely? and so on)

Quantum efficiency - higher is better

- impact is low to medium. No special conditions, higher QE is always better. Only problem can be that there is no single QE number - but rather QE curve, and even if certain camera has higher max / peak QE - other camera can be more suitable due to having higher QE in certain wavelength or range of wavelengths. For example - for IR imaging - QE beyond 700nm is of course more important than peak QE.

(just a note - choice of imaging night or imaging scope can have more impact than difference in QE between two camera models - something that is often overlooked).

Number of bits - inconsequential (again this is mitigated with number of subs stacked / selection of exposure length). Might be important for fringe applications - like single exposure photometry or alike.

Sensor size - major impact (depending on application)

For planetary - it is minimal impact and small sensors are often preferred. For lunar / solar it has medium to high impact - if one wants to do full disk captures or minimize number of panels when doing mosaics - but there is caveat.

Scope needs to support the sensor size - it needs to be corrected over whole sensor for sensor size to be useful. For planetary scope needs to be diffraction limited or better over sensor size and for DSO - stars should be nice round and tight over sensor.

For DSO it has major impact as dictates speed of capture when paired with appropriate optics. Larger sensor size allows one to capture same FOV with larger aperture scope - which turns into speed when working at set resolution (larger aperture captures more light).

I can't really overstate how important this can be. Imagine pairing 10mm diagonal sensor with 4" scope and pairing 20mm diagonal sensor with 8" scope. Both scopes are same design, F/ratio and are supported by the mount for simplicity sake (of course - all of these factors need to be taken into account). They will cover the same FOV and with choice of binning will operate on same resolution / sampling rate (arc seconds per pixel).

8" scope will be x4 faster - or it will produce the same image in 1/4 of the time.

Just to compare that with QE - say we have state of the art sensor with QE of 90% versus very basic sensor with QE of 50% - that is only 80% improvement. Above is 300% improvement in speed.

To reiterate - sensor size - major impact if : scope can provide corrected field over whole sensor, sensor can be paired with appropriate optics and of course that size is utilized (not so in planetary) - then it will provide massive speed boost

Pixel size - low to medium impact

As long as one knows how to bin data if needed and selects sensible working resolution - pixel size is not very important.

Dark current / how low can cooling system go ....

If there is set point temperature control - impact minimal, otherwise - depends on how well dark current is behaving. Amp glow is major issue for non cooled cameras / camera that don't have set point cooling (like passively / air cooled).

Next are things that don't really show in stats:

- ability to calibrate sensor properly - high impact (thermal stability, linearity, issues with amp glow and so on)

- microlens effects or other artifacts - medium / high impact (but personal preference and depends on use case)

- any quirks that sensor might have - again depends on use case and if that will pose an issue.

[happy-kat]

Maybe compare different astro cameras with your existing 500d. If your main interest is DSO what are you finding is limiting your astro images with your 500d? Are you currently also guiding your setup? 

[Adam J]

On 10/11/2022 at 19:41, Trippelforge said:

I have been shopping around and trying to compare various dedicated camera's. Each one on say ZWOs website lists a bunch of specs along with a page of graphs. When I line them up I get a bit stuck when comparing. I understand that low read noise has a strong correlation with desired dynamic range. And when you line them up you find a sweet spot that falls on the gain scale. But that's where things start to get confusing, such as I am not sure if one location on the gain scale is better than the other. Such as if this (sweet spot) point falls around 180 gain, is it better than if it were 100 gain.

Man that probably sounds confusing... I hope it sort of makes sense. lol

My main curiosity like the title says is how are people comparing the various models? Currently I am trying to find reviews, looking up astrobin examples and scouring forums. But when I have bought anything else (even DSLR) I could just line them up and see pretty easily which was better. Which kind of works for anything you buy in life... however for some reason the CMOS camera's are hard for me to do so. Which is probably due to so many other "specs" listed.

Any advice on how to do this?

 

If you want to avoid all the issues with technical specifications and just keep it simple, then look at Astrobin as you have been doing and combinations of different cameras with your desired imaging scope. Look at the FOV of the targets that have been imaged, look at the integration times. Then make a choice. 

The reality is that while some people (myself included) can get really hung up on camera choice, every single cooled dedicated astronomy camera currently available new on the market is going to vastly outperform your current DLSR. 

So if the technical approach to camera selection is not for you then just look at astrobin and dont worry about QE, noise and even pixel size too much, you can always bin anyway. 

If you are interested in the technical choice then read vlaivs reply above. 

Also dont just look at ZWO other companies make equally good cameras in my opinion and you could save some cash. 

I will say don't get anything based on the IMX294 or IMX492 sensors as those things are a pain in the bottom to calibrate - but will still give better results than the DSLR. 
 

Adam

 

Edited November 17, 2022 by Adam J

[Trippelforge]

1 hour ago, Adam J said:

If you want to avoid all the issues with technical specifications and just keep it simple, then look at Astrobin as you have been doing and combinations of different cameras with your desired imaging scope. Look at the FOV of the targets that have been imaged, look at the integration times. Then make a choice. 

The reality is that while some people (myself included) can get really hung up on camera choice, every single cooled dedicated astronomy camera currently available new on the market is going to vastly outperform your current DLSR. 

So if the technical approach to camera selection is not for you then just look at astrobin and dont worry about QE, noise and even pixel size too much, you can always bin anyway. 

If you are interested in the technical choice then read vlaivs reply above. 

Also dont just look at ZWO other companies make equally good cameras in my opinion and you could save some cash. 

I will say don't get anything based on the IMX294 or IMX492 sensors as those things are a pain in the bottom to calibrate - but will still give better results than the DSLR. 
 

Adam

 

 

I kind of flipped through some stuff on AB and noticed that the more affordable options were pretty capable. The only companies I really had checked out were ZWO and Player One. You mentioned saving some cash? What other companies are worth checking out?

[Adam J]

6 hours ago, Trippelforge said:

 

I kind of flipped through some stuff on AB and noticed that the more affordable options were pretty capable. The only companies I really had checked out were ZWO and Player One. You mentioned saving some cash? What other companies are worth checking out?

I would need to know more about what you are trying to image and with what scope if I am to make a suggestion. 

[drjolo]

23 hours ago, Trippelforge said:

I kind of flipped through some stuff on AB and noticed that the more affordable options were pretty capable. The only companies I really had checked out were ZWO and Player One. You mentioned saving some cash? What other companies are worth checking out?

I would be very conservative on comparing the camera capabilities on fully processed AB images - you can easily find images made with old CCD sensors looking better than images made with 80% QE new CMOS sensors. Image processing skills play a big role.

What vlaiv wrote is the best approach to conclude such big topic in such a short post. Selection the camera requires some context - at least available optics, sky quality and preferred targets should be also considered. 

Edited November 18, 2022 by drjolo

[Trippelforge]

16 hours ago, Adam J said:

I would need to know more about what you are trying to image and with what scope if I am to make a suggestion. 

My son and I are purely targeting DSO images, pretty much any objects that are reachable for us. So far we have gotten typical things like Andromeda, dumbbell, whirlpool and a few open clusters. So pretty much anything bright enough that we can capture. 

I am using a 80mm ED Triplet (f/7), on a motorized CG-4 with a Canon 500D (w/NINA).  

Originally I was looking at the "planetary" Uranus-C and it's ZWO equivalent (non-cooled). My budget got bumped up a bit due to XMAS, but still is only around 800. So I am not sure if anything is even reachable yet for us.

I have looked through ZWO, Player-one and SVBONY.  Although it seems like SVBONY isn't as highly regarded as ZWO.

The one thing though that I have been told is to simply skip out on a dedicated and go with a newer DSLR (modded). I really didn't want to do that but it kind of seems at this point that I may not have much choice if I want to upgrade my camera. 

 

Edited November 18, 2022 by Trippelforge

[drjolo]

Modded modern DSLRs are quite capable cameras. There are some useful filters available (light pollution, narrow dual band), the field of view is reasonable, easy to use without computer (just programmable remote shutter release cable). Focusing with live view and digital magnification is easy. Also QE is not bad when compared to dedicated OSC cameras. 

[Trippelforge]

39 minutes ago, drjolo said:

Modded modern DSLRs are quite capable cameras. There are some useful filters available (light pollution, narrow dual band), the field of view is reasonable, easy to use without computer (just programmable remote shutter release cable). Focusing with live view and digital magnification is easy. Also QE is not bad when compared to dedicated OSC cameras. 

I did take a look at this site and these models: https://www.astrogear.net/collections/astro-dslr-cameras

But I had a hard time figuring out which one would be the best price vs performance. 

 

[drjolo]

It depends if you maybe already have any Nikon or Canon lenses - then you may fit the camera to your equipment. 

Canon 6D and Nikon D600 are proven performers, but they are full frame cameras and your triplet will require some decent flattener to cover that area.

Nikon D5300 and D5500 are also quite well, they have the same sensor as QHY247C camera which I owned for some time and was very happy about it. 

Friend of mine recently purchased modded Rebel T7 (2000D) and I am really surprised with low noise and quite good sensitivity. 

T4i (650D) is also good performer in astrophoto, however it is a bit older model.

It looks they have a selection of the cameras, that are quite good for astrophoto, and the price is more less proportional to the outcome you may expect. There is also a reasonable entry at their page https://www.astrogear.net/blogs/guides/mirrorless-vs-dslr-vs-cooled-cameras , but I have no experience with mirrorless cameras for astroimaging, so cannot comment on that 

Edited November 18, 2022 by drjolo