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michaelmorris

CLS filter for luminance data with CCD?

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michaelmorris    1,594

I'm just starting down the rocky road of mono CCD imaging from my light polluted back garden. I'm planning to do both RGB and narrowband imaging.

For the RGB imaging It is common to combine this with luminance data collected through an IR cut filter. Given my levels of light pollution, would I be better off shooting luminance subs through something like a CLS CCD filter?

Thanks

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red dwalf    336

you could use the cls filter, the annoying thing about them is they are ok for LRGB but not really needed for narrowband plus i used to get a bit of reflection with my pollution filter, you could also use the HA filter for luminance if the target is rich in HA.

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michaelmorris    1,594
13 minutes ago, red dwalf said:

i used to get a bit of reflection with my pollution filter.

Is this a common problem with CLS-CCD filters?

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ollypenrice    17,351
42 minutes ago, red dwalf said:

you could use the cls filter, the annoying thing about them is they are ok for LRGB but not really needed for narrowband plus i used to get a bit of reflection with my pollution filter, you could also use the HA filter for luminance if the target is rich in HA.

Nooooo!!!!!  :icon_mrgreen:  The effect is horrible. It turns everything pink and creates blue star halo effects. You can certainly get away with a little Ha in luminance but I don't exceed 15% myself. 

I don't have an LP filter so I can't help on how it works as an L filter.

Olly

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CLS like filters are incredibly effective at suppressing the effect of the orange light from low pressure sodium street lamps. Should still be some help with high pressure sodium (yellowish white) lamps. Against white CFL/LED type light pollution they are pretty much useless. Narrowband filters help greatly with white light pollution on suitable targets. Taking mono Ha pictures  of emission nebulas is the least hassle from my light polluted garden (white CFL lamps).

 

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red dwalf    336

if you have very light polluted skies like me then another thing you could do is take shorter subs with LRGB but loads more of them as this tends to help with horriable gradients you get.

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michaelmorris    1,594

I'm aware of the use of Ha to enhance the red channel a bit.

My interest is in techniques to get better luminance data for combination with RGB data on non-Ha  rich targets such as open clusters, galaxies and comets when shooting in light polluted skies.

Edited by michaelmorris

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ollypenrice    17,351

A very large amount of your work to beat LP will be in post processing. It is remarkable how a good use of DBE in Pixinsight or GradX in Ps wil l rescue the seemingly un-rescuable.

Olly

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michaelmorris    1,594
8 hours ago, ollypenrice said:

A very large amount of your work to beat LP will be in post processing. It is remarkable how a good use of DBE in Pixinsight or GradX in Ps wil l rescue the seemingly un-rescuable.

Olly

I agree that GradientXterminator is a brilliant piece of software.  However, I would still like to work with the best data I can.

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swag72    5,381

I use a Hutec IDAS LP filter as my luminance filter.....its in my wheel in the filter slot, so I don't use it for RGB or NB.

My sky conditions aren't great, but I think it helps. It means that my filters are not psrfocal, no where near it with the Hutec and Baaders,  but I auto focus, so its no problem.

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michaelmorris    1,594

Thanks for the advise folks. I've just managed to pick up a CLS-CCD filter secondhand on ukastrobuyandsell. I'll see how I get on with that.

Cheers.

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michaelmorris    1,594

CLS-CCD filter arrived today.  What's more it's been a (relatively) clear night, so I got to test it too. :icon_biggrin:

I'm pleased with the result.  Here is the result of of 3 x 10 min subs of M101.  This test has also given me the opportunity to test out APT's 'CCD Flat Aid' tool.  It seems to have worked well.

m101_600sec_cls_withflats.thumb.jpg.5d9b302d8132257b15a7ea3204bcd599.jpg

Obviously this is only a test and in the real world I would probably be looking at around 20 x 10 min subs?

I would also like to test this on a relatively dim reflection nebula to see if the CLS-CCD filter still performs acceptably on a more challenging target.

Edited by michaelmorris

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