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Old 16-05-2019, 12:20 AM
RyanJones
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Camera combination image

Hi all?

I have a question ? I have both a modified and unmodified Canon 350d. I love my modified one for deep space imaging because of its ha sensitivity but the trade off is the lack of color in everything else. My unmodded camera doesnít capture anywhere near the same levels of Ha but does bring out beautiful Oiii blues and yellows etc.

My question is, would there be any benifit to combining subs from both cameras to give my images a better colour range while still capturing the Ha . Effectively like you go about NB combinations. And if so, what would be the best way to combine them ? Will putting into DSS sort it out or will that just average everything out and give me neither ?

And I guess while Iím here Iíll ask ? Is the lack of blues etc simply because the Ha overwhelms the rest ? So theoretically if I took more subs then the blues etc. would start to come through to balance out ?

Thank you for your responses in advance
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Old 16-05-2019, 10:28 AM
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Hmm. I wonder, I'm no expert but your modded camera will still be getting the same B/G as the unmodded. Is it just a matter of processing to pull those colors out?
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Old 16-05-2019, 11:03 AM
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Quote:
Originally Posted by ChrisV View Post
Hmm. I wonder, I'm no expert but your modded camera will still be getting the same B/G as the unmodded. Is it just a matter of processing to pull those colors out?

Not really.. The absence of IR cut filter not only allows more IR to Red channel.. As G and B filters are not perfect, they will pass excess if IR as well, so the whole colour balance will be affected.
If you want to use modified camera for terestrial photography, you must use external IR cut filter.
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Old 16-05-2019, 11:11 AM
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Well this is what I thought Chris but it seems like the Ha is so much greater that it tints my blues and yellows into browns and magentaís. I was just thinking if I could overlay the low Ha data that I could create a better colour range. I do notice that when people are imaging NB, their exposure times are different between the different filters. I assume ( but certainly donít KNOW ) that they do this because the O3 and S2 are more feint than the Ha ? Happy to be told Iím wrong and why though.
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Old 16-05-2019, 11:30 AM
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Ryan did you do a custom white balance after your camera mod?
I did it using a 13% grey card under the sun and am also using a LP filter when I used my modified DSLR and it works great, no problem showing the blue in M20.
I have the cards, message me if you want to borrow them.
cheers
Bo

Last edited by traveller; 16-05-2019 at 11:44 AM.
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Old 16-05-2019, 11:57 AM
RyanJones
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Hi Bo,

Thank you for that great suggestion. I did try doing a custom white balance just with a white piece of paper in daylight but at the time I was using a non CCD filter ( armature mistake ) so it didnít have the I/R cut that Bojan alluded to. Do at that time I was swapping filters in and out and havenít returned back to it.
Iím happy to buy the grey card if you can give me the details of what Iíd need to buy ? Is it just a ď standard ď 13% grey card ? Do you take the shot through the scope with all filters in place ?

It would be great if this works out to be the fix to my excess red issues. Thank you
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Old 16-05-2019, 12:24 PM
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Sent you a message Ryan.
I am happy to lend you my cards. Don't buy more plastic
Bo
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Old 16-05-2019, 12:25 PM
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Thank you so much Bo. I really appreciate it
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Old 17-05-2019, 11:50 AM
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I don't use 1 shot colour cameras, but maybe the answer is to use the non-Ha sensitive camera to give your basic colour and then create a synthetic luminance from the colour to which you add a SMALL amount of the Ha data (which will primarily be only in the R channel of the Ha sensitive camera). You also want to add a SMALL amount of Ha to the other red channel and then regenerate the RGB. There are tutorials all over the place describing this type of processing. My favorite way of doing this is described by Adam Block using Photoshop. For sure, too much Ha will overwhelm all the other data as you have already observed. In my opinion, Ha data is data that gives very interesting detail...but too much and the reds will blow out everything. Really, I think you just want the detail.


Peter


EDIT: " Modified cameras with enhanced hydrogen alpha sensitivity result in hydrogen alpha dominating the images of nebulae, hiding the multiple colors and processes present. An unmodified camera shows these colors and their varying intensities better so you can discern chemical and physical processes and composition."


Interesting read: http://www.clarkvision.com/articles/...rstellar.dust/

Last edited by PRejto; 17-05-2019 at 05:34 PM.
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Old 19-05-2019, 12:29 AM
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Thank you Peter,

Thatís exactly what I was hoping to do and youíve described it perfectly. Added bonus is that I use Photoshop already for processing so Adam Blocks techniques should make sense to me. Thank you for your help. Itís really appreciated.
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Old 20-05-2019, 02:23 PM
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Very interesting discussion, it explains a lot.

I had a DSI III Colour camera and its output were LRGB files. In ImagesPlus the best results came from tweaking the L file before using Combine LRGB. Maybe you could try the modded camera output as Luminance and tweak it fully before combining with the stock camera RGB files.

GlennB
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Old 20-05-2019, 03:45 PM
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Hi Ryan,


This technique is described very well in Adam's tutorial on processing M1. It's worth every dollar in my view!


Peter
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Old 20-05-2019, 09:24 PM
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Definitely an interesting question.

As long as you're not clipping digital signal at any point in the spectrum I'd argue that you should only use the modded-camera. It will contain the spectrum you'd obtain from the stock camera plus great red/Ha.

Almost any astrophotography needs colour balancing these days and you can control colour balance as you wish within software (as long as no data was clipped during collection phase).

You won't/shouldn't increase your signal to noise in any way combining stock and modded (over just using the modded for the longer total period) and certainly won't gain in resolution.
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Old 20-05-2019, 09:50 PM
RyanJones
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I seem to have opened an interesting topic ? And thank you all for your input .

I’d imagine there wouldn’t be a huge amount of people with 2 identical cameras, one modded and one not that would have bothered doing what I’m suggesting.

I agree with the theory that whatever photons hit the sensor, they will be the same in either camera in the shorter wavelengths and only greater in the shorter and so good processing should be able to extract the colours. I guess it’s how unevenly balanced the levels of the photons are that I’m struggling with. On that note, can I ask, why when I see NB images are the intergration times different for each filter ? And does this extrapolate back to what I’m suggesting where the unmodded camera is effectively my O3 filter and the modded is my Ha ? ( I understand that’s not correct in the literal sense )

Thoughts ?
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