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Need help understanding dedicated Astro Cams

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#1 Young Padawan

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Posted 02 October 2022 - 07:05 PM

Greetings,

 

As a relative newbie to Astrophotography I'm currently working with a DSLR (the Canon EOS 5D MKIV). I'm looking to get into a full frame One Shot Color (OSC) astro cam. Specifically, I'm looking at the ZWO ASI2400MC Pro (I know it's pricey, but it'll be a retirement gift that I have plenty of time to grow into).

 

My questions are:

 

1. Is post processing more complex / difficult with these kinds of cameras? The reason I ask, is because the definition I found for a OSC camera says it's "a color camera in which three color-separation negatives are made with a single exposure by using semitransparent reflectors to divide the beam that has passed through the lens so as to form three geometrically identical images on three plates or films through three different color filters". This sounds very daunting to an amateur like me. 

2. Will I still need to capture, Dark, Bias, and Flat frames?

3. What are the pros and cons (other than price) of a OSC camera?   

4. Will I be able to get longer exposure times with a dedicated Astro Cam? (my current setup is the Sky-Watcher EQ6-RI, with a Red Cat 71, QHY PoleMaster Polar Scope, ZWO Electronic Auto-Focuser, and a ZWO ASI290MINI guider arriving this week)   

 

Thanks for your help.

 

Clear Skies!


Edited by Young Padawan, 02 October 2022 - 07:07 PM.


#2 idclimber

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Posted 02 October 2022 - 07:10 PM

What scope? Very few will do full frame well other than very expensive ones. IMHO with the gear you have listed I would instead look at the 2600mc. 


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#3 idclimber

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Posted 02 October 2022 - 07:13 PM

Greetings,

 

As a relative newbie to Astrophotography I'm currently working with a DSLR (the Canon EOS 5D MKIV). I'm looking to get into a full frame One Shot Color (OSC) astro cam. Specifically, I'm looking at the ZWO ASI2400MC Pro (I know it's pricey, but it'll be a retirement gift that I have plenty of time to grow into).

 

My questions are:

 

1. Is post processing more complex / difficult with these kinds of cameras? The reason I ask, is because the definition I found for a OSC camera says it's "a color camera in which three color-separation negatives are made with a single exposure by using semitransparent reflectors to divide the beam that has passed through the lens so as to form three geometrically identical images on three plates or films through three different color filters". This sounds very daunting to an amateur like me. 

2. Will I still need to capture, Dark, Bias, and Flat frames?

3. What are the pros and cons (other than price) of a OSC camera?   

4. Will I be able to get longer exposure times with a dedicated Astro Cam? (my current setup is the Sky-Watcher EQ6-RI, with a Red Cat 71, QHY PoleMaster Polar Scope, ZWO Electronic Auto-Focuser, and a ZWO ASI290MINI guider arriving this week)   

 

Thanks for your help.

 

Clear Skies!

 

1 processing is the same as it is for your DSLR. 

2 Doing a library of bias and darks at one gain and temperature will be a lot simpler. You will still need flats every night. 

3 the main advantage is lower noise with a cooled camera that you can set to a single temperature. 

4 exposures should be similar. 


Edited by idclimber, 02 October 2022 - 07:13 PM.

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#4 danb35

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Posted 02 October 2022 - 07:15 PM

> Is post processing more complex / difficult with these kinds of cameras?

 

No, it's identical to a color DSLR.

 

> Will I still need to capture, Dark, Bias, and Flat frames?

 

Yes--or perhaps dark flat instead of bias.  There will still be thermal noise, electrical bias, and optical aberrations, which are corrected for by these calibration frames.  However, a cooled camera can be kept at a set temperature, so you can build a library of dark frames at that temp rather than needing to re-take them every session.

 

> What are the pros and cons (other than price) of a OSC camera?

 

Compared to what?  Compared to a DSLR, probably the biggest "pro" is the cooler, which both reduces thermal noise and maintains a constant sensor temp, the latter of which is helpful for the reason noted above.  The other pro is Ha sensitivity.  Other than cost, the biggest "con" is that it isn't useful for much else; you can't just take it off the scope and use it for vacation pictures.

 

Compared to a monochrome astro cam, it will cost less, but you won't be able to use narrowband filters as effectively.


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#5 17.5Dob

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Posted 02 October 2022 - 07:38 PM

There is no difference between a modded dSLR and an astrocam besides the cooling....The processing is exactly the same, but will be slightly easier with the astrocam and the addition of building a "dark  library" . though you can do the same thing with a dSLR but it will be more time consuming. Cooling will help reduce thermal noise, but depending on your particular shooting conditions, the difference might only be a few percentile points. Many people assume the difference will "night and day" greater, when in most cases it is only incrementally better. It is a case of spending $4,000+ in the case of a FF astrocam, to eak out that last few % of performance.

Something else to consider is that very few scopes are able to fully illuminate a FF sensor. Many scopes struggle to illuminate an APS-c sensor once reducers are added to the image chain. Beyond the cost of a FF astrocam ($4,000+), the cost of a compatible scope can become considerable as well. If you are not already using computer control at your scope, an astrocam has to have additional computer control and an additional 12v power source.. A dSLR can always be used as stand alone unit.


Edited by 17.5Dob, 02 October 2022 - 07:38 PM.

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#6 mayhem13

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Posted 02 October 2022 - 09:18 PM

As mentioned prior, dedicated Astrocams have a distinct advantage in their ability to keep the sensor cool and at a desired consistent temp……many here use this to their advantage to create what are known as dark frame libraries where noise is consistent to the set temp given a range of gains used. Other than that, as a class of color cameras all using CMOS tech, there’s no difference.

 

BUT……sensor format/size?…….that’s an IMPORTANT consideration on a few fronts. Asi2400 Pixel size and sampling rates don’t align with your focal length but the asi6200 gets you closer.

 

Only the best optics and precise integration of both produce flat fields across a full frame sensor without artifact. Even with 2” filters, you’ll likely be dealing with vignette in post processing. It’s important to ask yourself if the added cost of a ff sensor over an APS C are justified if in the end, your cropping your frames to the same end result?

 

Given your scope, I personally would choose the 2600 smaller sensor and pixels for a manageable frame and better sampling rate match…..not to mention the savings


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#7 unimatrix0

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Posted 02 October 2022 - 09:32 PM

Well, processing isn't exactly same with like a DSLR. 

 

You have to get in peace with using .fits files.

 

There are a couple fits viewer available free, my favorite is asifitview from ZWO.  Once associated with .fits, it will auto-stretch the files to optimum brightness, so you don't have to mess around with sliders and curves to see what your picture will look like once it is stretched.   

 

Advantages are greater than DSLR raw files, such as embedded in the header is the location/coordinates/camera temp and other camera settings and focal length and so on.   

So many people are not taking advantage of this feature, while stacking programs read this information for photometric color calibration and you can also use the info in there to re-slew to the same exact position and rotation fast, if loaded into the framing function of any of the imager software. Temperature is also there, so figuring out what temperature the camera was while taking lights is easy. 


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#8 Alex McConahay

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Posted 02 October 2022 - 10:03 PM

>>>>>1. Is post processing more complex / difficult with these kinds of cameras? The reason I ask, is because the definition I found for a OSC camera says it's "a color camera in which three color-separation negatives are made with a single exposure by using semitransparent reflectors to divide the beam that has passed through the lens so as to form three geometrically identical images on three plates or films through three different color filters". This sounds very daunting to an amateur like me.

 

I don't know where you got that definition, and once upon a time it may have been accurate. But modern OSC (One Shot Color) cameras work by having the light pass through an array of colored filters. THen software automatically figures out which colors the individual pixels should be. (And no, it is not much more complicated than that.)

 

 

>>>>>>>2. Will I still need to capture, Dark, Bias, and Flat frames?

 

Yes, because these frames correct for problems that are inherent in all astroimaging, regardless of the type of camera. 

 

3. What are the pros and cons (other than price) of a OSC camera?  

 

Your Canon 5 costs more than the typical entry level astro camera. It is an OSC camera. I think you meant to ask what is the difference between the Canon and the dedicated astro camera. And that has been answered by others (namely the cooler). But there are also form factors (weight and size) and connectivity. In both these concerns an astro camera is better for a telescope. 

 

4. Will I be able to get longer exposure times with a dedicated Astro Cam? 

 

Yes, generally, because the cooling in the astro camera allows greater signal to noise. 

 

 

On further notes. The astro camera will probably be less noisy (because of the cooling) and therefore easier to process. The Canon and dedicated use different file formats to save data (inconsequential since the Canon RAW file is easily converted to the FITS of the dedicated camera).  Otherwise, the processing is pretty much identical.

 

Alex




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