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Lp filters and the use of


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I live in a class 5 bortle area and was thinking of putting a lp filter on to help out with the light pollution.

But after reading a post on here im not sure it would help much as one if the posts said they only help with the cast from the sodium lamps which are no longer used around me .

The lights near me are the led type .

My question is is this correct so the lp filter would make little difference to my images .

Regards Baz

Edited by barrie greenwood
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22 minutes ago, Sp@ce_d said:

That's interesting.

I didn't think anything could deal with LEDs, as they emit light across the spectrum. I thought that any filter which cut out LED light would also cut out starlight.

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+1 for the D2. We have both types of streetlights nearby, so it seemed ideal. 

I'm Bortle 5 and it definitely improved contrast for me, although I did find it a little harder to recover a reasonable color balance when using this filter.

 

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According to the light pollution map I'm in a Bortle 5/6 area but the local town (south) and an equally close very large industrial estate (south east) means that anything below the celestial equator between SE and S are heavily light polluted. All street lighting in this part of the county is now LED and I suspect the industrial estate lighting is either still HP sodium or has been changed to LED.

Early last year I imaged Orion with a 50mm lens on my unmodified APS-C camera and having to deal with removing severe LP gradients during processing, I decided to purchase an IDAS D2 clip-in filter and tried again.  Although the light pollution background was slightly less (but certainly not significantly less), the bright star abberations introduced into the image together with a reduced colour spectrum meant that the original image was infact far better.  The abberations were probably due to the low focal ratio I was imaging at (f2.8) so at normal telescope focal ratios it may not be such a problem, but as the filter removes mainly the 550nm to 650nm region of the spectrum (yellow to orange) I could not fully replicate the colour range of the unfiltered image.

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