Beginning monochrome imaging - Forums

Topic starter

Jun 15, 2023

Hey

I am moving to monochrome imaging and am a bit in doubt about whether I need a light pollution filter with my new ASI2600MM.

When shooting narrowband - I believe that I would NOT need one.
Shooting in the LRGB channels - does it make sense to use one in those channels?

If so - which is recommended?

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Christian Koll

Jun 15, 2023 · Edited: Jun 15, 2023

Christian,

with monochrome imaging and RGB-filters you'll only get the specific part of the spectrum that is passed by that filter.
Some RGB filter sets intentionally have a gap between the green and red part of the spectrum in order to leave the yellow parts out - that's where most of the light pollution is - the Antlia V Pro filters, for example.

If you'll need a light pollution filter instead of the L filter depends on your local sky conditions.
But note that it is "instead" and not "additional to"!
You're not supposed to add a second filter on top of a basic filter.

What Bortle sky or location are you imaging from?
What telescope, camera and filters are you planning to use?

CS
Chris

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Christian Bennich

Topic starter

Jun 15, 2023 · Edited: Jun 15, 2023

I will be imaging with the ASI 2600MM Pro under a Bortle 5 sky with the Skywatcher 200 PDS and an EQ6-R Pro mount.
My current filters are the ZWO Narrowband filters and their LRGB ditto.

I know those filters are somewhat entry level

TakFan

Jun 15, 2023

Dear Christian,

I am under Bortle 7 skies with an 2600MM Pro and see no need for a light pollution filter.

CS
Dirk

Marcelof

Jun 15, 2023

Bortle 5 is not so much light pollution. In any case the trick to image in LRGB in this case is to take a lot of very low exposure frames and not use any other type of filter. And by a lot I mean a lot, under Bortle 8 I'm taking exposures of 15s, about 800 frames per channel and that's about the minimum to get moderately good results.

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Sean van Drogen

Jun 15, 2023

I shoot from Bortle 9 and use a slightly tighter Lum filter but most pollution is taken care of in processing.

Joe Linington

Jun 15, 2023

I am shooting under bortle 5/6 with the same filters but slower scopes and 294m camera. I am able to take LRGB subs limited by blowing out the stars but my camera has a puny well depth. I have taken up to 3 minute lum to try and catch dust (stars all blown out) and it was fine as far as light pollution goes, nothing that DBE or GraXpert couldn’t handle. Try a run close to blowing the stars out (a few hundred maxed pixels in Nina) and see how bad the gradients are. It might surprise you.

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Brian Puhl

IOTD Staff

Jun 15, 2023 · Edited: Jun 15, 2023

Bortle 5 is not so much light pollution. In any case the trick to image in LRGB in this case is to take a lot of very low exposure frames and not use any other type of filter. And by a lot I mean a lot, under Bortle 8 I'm taking exposures of 15s, about 800 frames per channel and that's about the minimum to get moderately good results.

Wait... What? 15 seconds?

Op, you don't want to stack filters, if that's what you were thinking. Your LRGB set will be fine. Luminance is really just a fancy UV/IR filter. Either way each filter is only letting a specific wavelength through, and it will be much more efficient than your color camera that you're used to. Bortle 5 isn't all that bad, you'll just want to get good with background extraction.

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Nick Grundy

Jun 15, 2023

I'm in similar sky (bortle 6) and unless you have some really specific nearby light source ruining things, you should be fine with just the SHOLRGB filter set. The moon will be the biggest issue you want to plan around. Stick to HA/S2 around the full moon time. Shoot broadband RGB targets around new moon.

switching to mono was probably one of the best changes I made last year. You won't regret it

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