Layering LRGB mages & Mono LPS filters.

[Tandum]

Using a One Shot Colour camera to shoot something like M42, you would normally take multiple sets of exposures of varying lengths, process each set individually and then mask them over each other in photoshop so the core isn't burnt out. Do you do the same thing with a mono camera using LRGB or can you just layer multiple Luminence exposures to avoid burn out and then add the colour?

Also, I'm finding this little mono starlight express camera is way more sensitive than any of the OSC cameras I've had. It's even being swamped at times by adjacent street lights and I've not seen that before. I'm thinking a hutech LPS filter might clean this up for me. An LPS filter should do the same for a mono camera as it does for a OSC camera shouldn't it? I guess it will change colour balance but longer exposures is what I'm after.

[AlexN]

with the mono camera I would take individual short frames for each colour and for luminance.. if you only do shorter exposures in the luminance data set, then you will retain the detail in the brighter area, however it will be black and white, as the colour data sets will have a blown out area...

I would use an LPS filter in front of the filter wheel to block out the all the unwanted bandwidths of light before it reaches the sensor regardless of what colour filter you have selected in the filter wheel.. That is, unless, you are using narrowband filters..

An LPS filter will definitely help you out as far as the streetlights are concerned.. but make sure also that no light is actually shining directly into the open aperture of the scope at all... if it is, try to erect some form of light blocking barrier to keep the open end of the scope in shaddow.. as reflections on the objective will have a negative affect also...

[Tandum]

So you think you should create multiple colour images and overlay them like an OSC camera? I thought the Luminance channel was where the detail came from. You can shoot colour binned in low resolution. I thought the luminance channel dictates how bright the colours are. I might have to read up on RGB colour space :(

[troypiggo]

I'm thinking about it like this. Say we use your M42 example. You're shooting the red channel. If you do a long exposure that would blow out the core normally in a OSC, it's still going to blow out the core but it will be pure red (255) instead of pure white (255, 255, 255). Same will happen with green and blue channels.

So if you do different exposures of luminance to end up with luminance that's not blown out, when you apply it to blown out channels of equal 255 value, you'll end up with just grey in the core where the different channels are all the same value.

If you'd done different exposure of each channel so they weren't blown, some channels will be stronger than others and that's how you get colour.

For this reason, if you're doing different exposures in each channel, you'll need to make sure the times match else you'll end up with false colours.

Hope that makes sense. Hard to put in words, but I know what I mean in my head :)