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Filters vs color camera

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#1 lexbrook

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Posted 22 August 2019 - 08:36 AM

I'm sure this has been discussed quite a bit but I'm missing something. I'm considering buying an ASI1600 M Pro with EFW vs an ASI071MC Pro. I have a pretty wide field scope and I want to use full field.

 

I can see the desirability of the 1600. You can select the exact correct filter for the imaging task at hand. For most exposures, the EFW glass filters are going to be more transmissive and spectrally pure. That is a real advantage. They still probably attenuate 33% of the light (or more) so exposure times are >3X that of a monochrome camera.

 

So now for the ASI071MC Pro- The filters probably aren't as efficient as the glass EFW filters, AND, the ASI071MC Pro have spectral  'leaks' so the red pixels have significant sensitivity to green light. All things being equal, Except for filter efficiency (unknown) either camera is going to require at least 3X the monochrome equivalent exposure. The ASI071 probably more than the 1600/EFW setup.

 

I would prefer to buy the ASI071 because of the effort fussing with filter wheels, but, if there is a big advantage with the 1600, I don't see it.

 

I'd appreciate any pointers to links or other information.

 

Thanks,


Edited by lexbrook, 22 August 2019 - 08:37 AM.


#2 bobzeq25

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Posted 22 August 2019 - 08:53 AM

I'm sure this has been discussed quite a bit but I'm missing something. I'm considering buying an ASI1600 M Pro with EFW vs an ASI071MC Pro. I have a pretty wide field scope and I want to use full field.

 

I can see the desirability of the 1600. You can select the exact correct filter for the imaging task at hand. For most exposures, the EFW glass filters are going to be more transmissive and spectrally pure. That is a real advantage. They still probably attenuate 33% of the light (or more) so exposure times are >3X that of a monochrome camera.

 

So now for the ASI071MC Pro- The filters probably aren't as efficient as the glass EFW filters, AND, the ASI071MC Pro have spectral  'leaks' so the red pixels have significant sensitivity to green light. All things being equal, Except for filter efficiency (unknown) either camera is going to require at least 3X the monochrome equivalent exposure. The ASI071 probably more than the 1600/EFW setup.

 

I would prefer to buy the ASI071 because of the effort fussing with filter wheels, but, if there is a big advantage with the 1600, I don't see it.

 

I'd appreciate any pointers to links or other information.

 

Thanks,

This, like much of AP, gets complicated.  Really short summary.

 

The Bayer filter is inefficient.  The colors overlap, it's dyed glass which has a lower transmission coefficient than interference filters.  50% of the pixels are green, great for terrestrial, AP, not so much.  <smile>

 

There are resolution concerns (modified by various processing methods), and signal to noise ratio concerns.

 

That said, people make fine images with one shot color cameras.

 

The real issues arise when doing narrow band, and, to a lesser extent, LRGB.  Stacking narrowband filters on top of a Bayer matrix can work (especially for H alpha), but inefficiency increases.  LRGB imaging tricks your eyes, gives fine signal to noise ratio in less time.  You can separate L out in processing from a one shot color camera to get some of the advantages, few do.  The whole idea of OSC is simplicity.

 

Bottom line.  Simply a personal choice.  The greater your light pollution level, and/or the dimmer your targets, the more likely you'll appreciate the advantages of the mono plus filters approach.

 

For many (most?) the big issue is not fiddling with a filter wheel, it's cost.

 

Full disclosure.  I own both.  Even image with the dreaded <grin> DSLR sometimes.

 

This one image used both.

 

http://www.astrobin....4117/G/?nc=user


Edited by bobzeq25, 22 August 2019 - 08:59 AM.

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#3 PirateMike

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Posted 22 August 2019 - 08:59 AM

Narrow band imaging is very much a possibility with the ASI1600MM Pro, not so much with a OSC camera, but NB is more expensive to start.

 

If all you want to do is RGB imaging an OSC camera will be ok, but you'll be missing out on the best part (my opinion) of imaging.

 

 

Miguel   8-)

 

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#4 dhaval

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Posted 22 August 2019 - 09:23 AM

Two things - 

1) I am not sure what the issues you would encounter with using a filter wheel - to be honest, there is no "fussing" with the FW - it is a very simple device that does its work efficiently (within the constraints of its own design and manufacturing of course)

 

2) Most people throw metrics like 3x the time it will require to take a RGB image using a mono camera - not sure where and how those metrics are produced - but it is very likely that they are not accurate. A lot of people fail to consider SNR when producing such metrics. SNR is a great leveler (in more ways than one, if I may add). 

 

There is nothing wrong in using an OSC - a lot of people do that with spectacular results. Same goes for mono cameras - plenty of people produce exceptional images with mono cameras. Mono cameras obviously stand out while doing narrowband primarily because there is no Bayer matrix to contend with and the filters will effectively block out wavelengths of light that are not part of the bandpass increasing the accuracy of the rendered gases both in detail and contrast (I would have said color, but NB images are called false colored images for a reason), but that is not to say that you can't get acceptable NB results with OSC cameras - it takes more time and effort, but you may be able to get those results. Similarly, as has been mentioned many times over, Mono cameras also have the advantage when you are contending with light pollution while imaging. Those filters again are blocking out unwanted light, making it much easier to image with mono cameras. I know that you can put a LP filter on an OSC, but think back to SNR as a driving factor. 

 

CS! 


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#5 Gipht

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Posted 22 August 2019 - 09:40 AM

I have the ASI183MM and the ASI071MC and find myself using both about equally.  The choice of which is usually target specific.  The mono camera offers more flexibility and you can vary exposure times with each NB filter to fit the target and the desired results.

 

The larger sensor size of the ASI071MC is a big plus.  The new dual band up to quad band filters add to the abilities of the color cameras. The processing, and fiddling time are less for the color cameras.  After you have done a Halpha, OIII,  RGB set with a mono camera,  and then you take a picture with the color camera, it does seem a lot easier.

 

Your own personality may factor into the decision.  If you are okay with very good,  then the color camera will likely do.  If you want to be the best, then mono is a better choice.


Edited by Gipht, 22 August 2019 - 01:58 PM.

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#6 Pauls72

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Posted 22 August 2019 - 10:50 AM

 

I can see the desirability of the 1600. You can select the exact correct filter for the imaging task at hand. For most exposures, the EFW glass filters are going to be more transmissive and spectrally pure. That is a real advantage. They still probably attenuate 33% of the light (or more) so exposure times are >3X that of a monochrome camera.

A lot of people with Mono cameras will use a Luminance or Clear filter to shoot the Luminance/Brightness data. Then they use the color filters just for a fraction of the time to get the color data.

I own both Mono and OSC cameras. The exposure time for the OSC are longer, but not 3x as long. Total integration time for a OSC is only like 20-30% longer.

 

This is a long video by Dr. Craig Stark and well  worth the time spent watching. Abouth half way in ex explains some about OSC vs mono with LRGB filters.

https://www.youtube....h?v=IlcaLvKjDd8

 

 

Where a mono camera shines, is using Narrow Band filters. OSC just can't keep up here.


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#7 GiorgioF

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Posted 22 August 2019 - 11:52 AM

My 2cent. I start to make serious AP once I got the monochrome asi1600. Before, a mess.
But I'm under a horrible sky and my only choice is to bit the bullet and a piece at time, buy all the needed filter.
My reflex, modified baader, is only used in clear and dark sky, the few times I can move from home.

#8 TelescopeGreg

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Posted 22 August 2019 - 01:19 PM

OP, I'm facing exactly the same choice.  Currently using an unmodified DSLR.  Liking its large sensor, ease of use; not liking the lack of cooling.

 

The ASI071MC Pro has as large a sensor as my APS-C DSLR, in fact, slightly larger.  Cooled, easy to use.

The ASI1600mm Pro + filters has a somewhat smaller sensor, and the whole filter wheel thing.  Concerned a bit about the combined weight.  The filter wheel is just a matter of a little automation with the at-mount computer.  With good filters (parfocal), should be no big deal.

 

Offsetting the smaller sensor of the 1600 is one point that I haven't seen listed yet...  Most good LRGB filter sets include a notch between the R and G filters for the most common light pollution.  You don't get that with the ASI071.

 

So, larger sensor, ease of use, or smaller sensor, possible microlensing issues, built-in LP notch?  Need to find a coin to toss...




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