I live in a bortle 6 zone and my neighbors have lots of light in their backyards which turns my bortle 6 into a 7 easily. I only have view on HII regions this time of year and I shoot with a miniCAM8M. The L filter that comes with it is just Luminance + UV/IR Cut, no light pollution filtering. AI tells me to do Ha for the luminance with long exposures and short RGB exposures for the stars.
I don’t believe AI is ready to be trusted 100% so I ask here. Is it possible for me to shoot HII regions ?
How to shoot HII Region in mono in light polluted zone
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Yes and AI was partly right. I’m in B8 and here’s what I do. For narrowband I’ll often use the Ha frame or a combination of all the narrowband frames (superlum) to serve as the L frame. For broadband objects I’ve found it to be extremely effective to use a IR pass filter to create the L frame. I still have to struggle with RGB but without the near IR filter, these objects would be almost imposable to image from my location.
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To my humble opinion, the use of a NB Halpha filter is mandatory. L filter by itself, whatever exposure time, cannot separate Halpha signal from the continuum due to pollution.
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Or, shoot short (30 second) exposure’s for the stars and capture Ha and OIII for an HOO image. Also, you could add S if you desire SHO.
I live in B7 and have had good success with both using a Minicam8M.
I realise that I have read the initial post too quickly , since the minicam does include NB filters.
The problem in heavy polluted skies is to achieve a good balance between stars (including colour calibration) and nebulae.
A good hint would be to “scout” forehand the intended area with e.g. Stellarium with the narrow band northern sky survey , in H, O and S band : signal density, for instance in S, will provide indications to adjust exposure time or even the opportunity to acquire images in an area where spectral response is too low to be worth the time spent.
It will maybe be necessary to use several sessions, depending of unobstructed field of view on ground :
one session with LRGB to get a good star coverage, and colorimetric calibration, with short exposures
one session with NB sequences , band selection according to the target area, with longer exposures compatible with sky background signal. More efficient if you have the 3nm filter version
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