Mono CCD + filters - Can you do this with a DSLR?

[swag72]

This is probably a really silly question, but I've been thinking about it and so thought I'd ask anyway!!

If you use a mono CCD and filters, then you can pull each colour out of the respective image then combine them for a colour image - Right?

Can you do the same with a DSLR set to mono setting and with the same filters?

Does this show that I am thinking about this hobby?!!!

[Hawklord]

Not really. You'd gain nothing by doing this. There is a colour (Bayer) matrix in front of the dslr sensor so in effect you'd lose 2/3 of your data with each filtered sub. Tricolour imaging with a mono gives you a greater sensitivity if it's cooled and better resolution since it will use all the pixels for each colour. You can though use an light pollution filter in front of the dslr which most of us have to do. This keeps the native tricolour image of the dslr but gets rid of a lot of the orange skyglow!

[ollypenrice]

In fact the Bayer Matrix is one red, two greens and a blue but the main point made above is quite right. (R and B would lose 3/4 and green 2/4.) The loss of resolution is not quite as bad as it might at first seem because the software interpolates a continous synthetic luminance layer based on what it 'sees' in the matrix image. In other words, if you have an 'edge' running across the matrix and this is, say, an Ha feature visible only to red pixels, the software will fill in that edge on the other pixels blind to Ha. Or so is my understanding. Some one shot colour camera users do use an Ha filter to apply, once debayered, to the red channel of their image. Of course, shooting with one pixel in four is slow going.

I did a test for Astronomy Now comparing otherwise identical one shot colour and mono CCD cameras and found that there was, from a dark site, not a great deal of difference between them in terms of end result. I think the mono does bring a tiny gain in resolution and is quicker for a given standard of final image. It seems to vary from object to object though. I would use the mono for galaxies and the OSC for nebulae, based on a year or so of using both. However, I often cheat and use the mono to shoot an Ha layer to add to the OSC image.

Interesting issue since OSC is often regarded as second best. I have mixed feelings myself.

Olly

[shaunster]

Using the mono setting on a dslr doesnt make it shoot in mono, it still shoots in colour and post processes the image into mono

I cant see any gain of using rgb filter with a slr, but maybe a Ha filter on moon nights will mean you can still shoot reasonable results, provided the camera is modded

[swag72]

Using the mono setting on a dslr doesnt make it shoot in mono, it still shoots in colour and post processes the image into mono

That's the crux of it then I guess. In my new to the journey mind, I thought that by taking the pic in mono setting , using RGB filters, you'd be able to blend the colours back in afterwards. At least I know why it won't work.

Thank folks.

[dmahon]

I did a test for Astronomy Now comparing otherwise identical one shot colour and mono CCD cameras and found that there was, from a dark site, not a great deal of difference between them in terms of end result. I think the mono does bring a tiny gain in resolution and is quicker for a given standard of final image. It seems to vary from object to object though. I would use the mono for galaxies and the OSC for nebulae, based on a year or so of using both. However, I often cheat and use the mono to shoot an Ha layer to add to the OSC image.

Interesting issue since OSC is often regarded as second best. I have mixed feelings myself.

Olly

And some would say that comparing the same camera in OSC and mono is not a fair comparison - the mono version, after adding filters and wheel, will be far more expensive. In many cases, the cost of the filters and wheel will be such that one could have bought a OSC camera one or two steps higher up the manufacturers range.

[ollypenrice]

And some would say that comparing the same camera in OSC and mono is not a fair comparison - the mono version, after adding filters and wheel, will be far more expensive. In many cases, the cost of the filters and wheel will be such that one could have bought a OSC camera one or two steps higher up the manufacturers range.

Quite right. I did make this point in my article. In the case of the Atik 11000 that I covet the difference is huge since you need magabuck 2 inch filters.

Shooting Ha is not about avoiding the moon, only. There are structural details in nebulae which sing out loud in Ha but not in normal broadband red. Eg the 'curtains' behind the horse or incredibly tenuous emission nebulae like Barnard's Loop, Simeis 147 etc. Here in an RGB image in either camera you get almost nothing.

Olly

[Demonperformer]

I tried taking some shots with my canon 1000d set to mono mode and found that they were considerably more 'blocky' than the same shot taken with it set to standard mode. I would think this reduction in resolution would override any benefits.

[Coco]

good question Sara..

[Coco]

Found on Google search

DSLR Narrowband filter space images | Flickr - Photo Sharing!