Narrowband with OSC?

[BlueAstra]

Is it necessarily true that you can't do narrowband images with the OSC camera + narrowband filters? I have a mono camera and shoot NB SHO @ 1x1 and colour @ L(1x1)+RGB(2x2). I understand the colour camera has a filter matrix above the CCD chip. Does this prevent good NB images in a similar way a conventional SLR IR filter attenuates the red end (hence the usual IR conversion mods)? Or is the lower sampling resolution a problem? I've read you need a similar time on target with NB or OSC to get similar quality images for RGB images. OSC may be a better solution for me in a heavy LP area, but I still want to do NB. Any views?

[Tim]

You CAN do NB images with it, but for the most part it is a frustrating option.

As only 1 section of the matrix allows red light through, Ha and S2 signal is affected and takes correspondingly longer to capture as in effect only a quarter of the array is gathering light.

SteveL used the method extensively, and experimented with various methods.

I also live in very heavy LP, and have a OSC for grab and go and star parties, and a mono camera for home imaging, mainly in narrowband due to LP.

You could try splitting up the channels from an exposure on your DSLR to get an idea of the differences in capturing various colours. The Blue and Green channels gather Oiii, Green the most with half the array to work with, and a little on the red side gathers Oiii too. I have somewhere the results of an experiment I conducted into this very thing actually, but heaven knows where I have saved them. The result was that I stuck with the mono camera.

Hope that helps

Tim

[Gina]

I use DSLRs with NB filters. You lose resolution by 4x and sensitivity by 4x as well so you need a lot longer exposures and a lot more of them to get a result. Exactly the same applies to an OSC astro CCD or CMOS cameras. Though astro cameras are usually cooled which helps with the noise (a noise reduction can be also achieved with DSLRs by cooling).