A question about filtering light polution

[NickK]

Is it possible to remove a portion of light pollution (ie street lights which work on a specific wavelength) by taking an image with a filter than only allows the street light frequency through?

Then you could subtract this frame from the subsequent imaging frames to reduce the stray light and improve contrast.

[dlp]

Clever idea, but you just need a light pollution filter - it cuts out the street light and similar frequencies. Skywatcher, Baader, and Astronomik are some of the popular ones. I think I'm right in saying that the Astronomik is the only one to make a clip filter that goes inside the camera, so you can use it on a Canon DSLR. The others are for scope eyepiece use.

David

[dph1nm]

Then you could subtract this frame from the subsequent imaging frames to reduce the stray light and improve contrast.

This might improve the colours, but it would do nothing for the extra noise added by light pollution, which is the real problem.

NigelM

[BlueAstra]

Clever idea, but you just need a light pollution filter - it cuts out the street light and similar frequencies. Skywatcher, Baader, and Astronomik are some of the popular ones. I think I'm right in saying that the Astronomik is the only one to make a clip filter that goes inside the camera, so you can use it on a Canon DSLR. The others are for scope eyepiece use.

David

Note the clip filter stops you using the IS lenses.

[RikM]

Can you get an adaptor for a 2" Eyepiece LPR filter so that you can screw it onto the objective end of a 300mm DSLR lens?

Rik

[Glider]

I do that for wide field with my Canon 18-55mm lens. It needs a 58mm to 48mm step down ring. Then it accepts 2" astro filters.

[RikM]

Perfect, that's exactly what I'm after.

Rik

[Glider]

Check your 300mm lens takes 58mm filters, otherwise I got my step down ring from Rother Valley Optics who had a fair range of other sizes.

[RikM]

Thanks, I will check it, but I have the 18-55mm lens as well.

Rik

[BlueAstra]

Here is another source of camera step up/down rings:

Stepping-Rings

[ollypenrice]

Great thread a few years too late for me! I could NOT find step down rings for love nor money whan I wanted them. Oh well.

Olly

[RikM]

Just checked my 300mm lens and it is a 62mm. (good shout Glider, thanks) Will I have big problems with the images if I do 62-58 --> 58-48 --> 2" LPR?

Sorry for hijacking your thread NickK.

Rik

[Psychobilly]

It will probably Vignette but flats should help...

Billy...