LRGB and Light Pollution

[russellhq]

Being new to mono CCD imaging, I'm trying to get my head around using LPS filters with the LRGB set-up.

I've read that some use the LPS filter in place of the L filter, but I wonder if there's mileage in using the LPS filter in front of the filter wheel (on the nose pipe), so all filters get the LPS treatment, much the same way as a OSC would get filtered?

[Uplooker]

Good question, I am intereste in the replies.

Ian

[libraryman]

I'm in the same position, having read most of the info available, I have just received my Ida's p2 from first light optics.it has been fitted into the nose piece of my qsi 583, I'm assuming that it will live there and cover lrgb...I have on order a narrowband filter, the p2 will cover that as well but given the bandpass of the nb filter, I doubt it will impact it at all.

At least that's what I've garnered from reading the info on line.

Ray

[markarian]

This question is current for me too.

Just got a 460EX mono and I've been trying it using an old Lumicon Deep Sky filter in front of all filters.

However, my images after combining LRGB are showing lots of overly red stars. Could this be caused by the filter?

Cheers

Mark

[RikM]

I use LRGB and NB filters and have a LPR filter mounted in front of the whole lot. I made a few test images with / without the filter and for my local situation, with my set-up, it was better with the LPR filter in front of all filters rather than just using a LPR for luminance. Other people with different LP sources / skyglow etc. and different camera / optics will find differences when they test it! There doesn't seem to be a 'one size fits all' answer to this. 

[russellhq]

Rik, did you find it changed your colour balance and did you change the weightings of the filters to compensate? Or did you just stick with 1:1:1 for RGB? Sorry, I'm new to the LRGB technique and still have a lot of questions

[RikM]

I shot 1:1:1 for the tests and don't take much notice of the colour balance to be honest. I set a target black point in PS and just click the button and it is more or less balanced. What I looked for was contrast and structure in the colours. Without the filter, I found the colours were lower contrast and somehow muddy looking. With the filter, it was cleaner and easier to process. I shot colour weighting a only with the filter in place and it does seem to blue sensitive. I use something like 1.3:1.4.1.0 for RGB as a starting point. I do find I can get tighter focus in blue and green than in red, so I do often get red halos to real with. I think that is more to do with dust/light pollution than the light pollution filter though.

[libraryman]

It does seem to be case of your local situation...I was led to believe that the Astronomik CLS filter is better suited to severe pollution and the idas filter suited to mild / moderate pollution, the Astronomik being more aggressive!

The Astronomik is suspected to give more colour cast!

Ray

[markarian]

I have the Astronomik CLS for my modded DSLR and it definitely did add quite a signifiant colour cast to the image.