colour ccd camera

[rwc23q]

I'm hopefully about to embark on DS imaging soon and was wondering, can you use a colour ccd camera to take images  and then use narrow band Ha filter, stacking all the images?

Forgive the question, but trying understand it all before I get cracking.

Thank you.

Rob

[david_taurus83]

You can but its not as effective as a mono camera for narrowband. What camera do you have in mind?

[jimjam11]

2 hours ago, david_taurus83 said:

You can but its not as effective as a mono camera for narrowband. What camera do you have in mind?

Agree. Unless you cannot afford a mono setup skip osc and maximise your imaging efficiency. 

[rwc23q]

3 hours ago, david_taurus83 said:

You can but its not as effective as a mono camera for narrowband. What camera do you have in mind?

I have an ZWO ASI 224mc with ir/uv cut filter and a neximage 5 (just for planetary work).

Currently have slt mount, but have an eq5 pro on order. 

Was just curious as to whether I could use an Ha filter as well to add definition to deep sky objects.

[jambouk]

Without the IR-cut filter the red pixels will be sensitive to Ha; but you need to see where the IR-cut filter kicks in. You’ll only be using 25% of pixels with an Ha filter on though because of the Bayer matrix. The 224 is a CMOS rather than a CCD but potentially splitting hairs. You’ll have to have very long exposures with the Ha filter on compared to the images in full OSC mode. 

[symmetal]

Here's the colour response of the 224MC. The Ha filter will pass a narrow wavelength band centred around 656nm so as mentioned above the red pixels will give a reasonable output but the the green and blue pixels will give much less. Putting an IR/UV cut filter in front isn't necessary, as the Ha filter has a much narrower width pass band so will cut IR and UV anyway, as well as the blue and green wavelengths. IR/UV cut filters normally pass wavelengths between 400 and 700nm.

Alan

Edited August 28, 2020 by symmetal

[rwc23q]

50 minutes ago, jambouk said:

Without the IR-cut filter the red pixels will be sensitive to Ha; but you need to see where the IR-cut filter kicks in. You’ll only be using 25% of pixels with an Ha filter on though because of the Bayer matrix. The 224 is a CMOS rather than a CCD but potentially splitting hairs. You’ll have to have very long exposures with the Ha filter on compared to the images in full OSC mode. 

That is a fair point about the bayer matrix. I didnt consider that. Would it still be the same using a y800 codec (as believe that 'turns off' the bayer filter but could very well be wrong).

[DaveS]

No, the Bayer filter is a physical layer of RGB filters over the photosites.

[rwc23q]

50 minutes ago, symmetal said:

Here's the colour response of the 224MC. The Ha filter will pass a narrow wavelength band centred around 656nm so as mentioned above the red pixels will give a reasonable output but the the green and blue pixels will give much less. Putting an IR/UV cut filter in front isn't necessary, as the Ha filter has a much narrower width pass band so will cut IR and UV anyway, as well as the blue and green wavelengths. IR/UV cut filters normally pass wavelengths between 400 and 700nm.

Alan

thanks for this, makes sense now. I think I'm trying to sprint before I have even started to crawl, but cannot stop myself thinking ahead.

I will have to see how I get on with the  scope/ mount and camera first then think about a non colour camera. 

I would really like there to be no cloud on my rest days, just not when I'm working! Not been able to get out for about 4 weeks now due to shifts and weather!

 

[jambouk]

The Bayer Matrix is a physical thing; the green and blue pixels won’t significantly register photons of wavelength 656nm. This plot shows that:

From: https://astronomy-imaging-camera.com/product/asi224mc

[rwc23q]

2 minutes ago, DaveS said:

No, the Bayer filter is a physical layer of RGB filters over the photosites.

Thanks for clearing that up for me. Thought it was worth an ask. Will have to get a mono set up in the future, but babybsteps for now.

[jambouk]

We are not saying you can’t use an Ha filter with a OSC camera, just making you aware of some of the limitations. Very few things are black and white in astronomy.