NGC7023 Iris Nebula in polarized light

NGC7023 Iris Nebula Simple Polarigram
3/4th Aug 2007
Object name: NGC7023 Iris Nebula
Magnitude: 7.1
Size: 10 8
Classification: EN+OCL
Apparent RA: 21 01 35.5 Apparent Dec: +68 10 10
Constellation: Cepheus

Following the lead given by Richard Crisp on Color Astronomical Imaging using Polarizing Filters, here us my first attempt using a polarizing filter to produce a coloured image. A suitable polarising filter can be purchased fairly inexpensively.

4 sets of approx 6x180s exposures were taken with the polarizing filter at 000, 135, 045 and 090 degrees.

The upper image on the right shows the 000 data as red, 045 = green and 090 = blue.
This image shows some colour variations, although I think the green streak from 8 oclock to 2 oclock and the fainter red streak from 10 oclock to 4 oclock are down to diffration from something in the optical train. Probably the focuser protruding into the lightpath, or something.

My LRGB image of NGC 7023 is here

The lower image shows the following: Red = 135-045, green = 000-090, blue = 000-045.

Both images have been layered with a luminosity layer to provide better detail.
NGC7023 Iris Nebula Stokes plus lum
NGC7023 Iris Nebula Stokes plus lum REPROCESS

Results can vary quite a bit with processing. I've just tried to do the Stokes Polarigram and got a different result (See right), but ultimately indicates the same polarized regions of the Iris Nebula. For some reason I ended up 45 degrees out with respect to the first image!

Captured in ArtemisCapture, calibrated in ImagetoolsCa, DDP in maxim, thuggery in photoshop.

This image was autoguided using my 400mm focal length refractor and my black and white SC1 webcam.

Current Imaging equipment configuration

Exposure Details :

Polarizing 30x180s on 200mm @ F5 (1000mm focal length) with ART285 (Sony ICX285)

Curdridge Observatory, Southampton,UK