Narrowband imaging of M82

Blog the previous nights viewing. Link to images on the gallery or simply describe what you observed the night before. Leave the technical and howto in another forum.
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rwilkinson
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Narrowband imaging of M82

#1 Post by rwilkinson » Sat Mar 08, 2014 10:03 am

Last night I had an opportunity to continue my experiments with narrowband imaging using a monochrome LX-webcam and filter-wheel. Although there was some hazy cloud around, the moonlight wasn't too bright, and M82 was high enough in the sky to work with.
I was using the camera on my StarWave 80ED, operating at f/4.6 (using my Celestron focal reducer), and the filter-wheel was loaded with Hydrogen-alpha, Oxygen-III and a blue "nebula" filter. These are the results with each filter:
m82h.jpg
30x 1-min with H-alpha filter
m82h.jpg (32.29 KiB) Viewed 3154 times
m82o.jpg
30x 1-min with O-III filter (the hazy cloud got a bit thicker during these exposures)
m82o.jpg (32.32 KiB) Viewed 3154 times
m82n.jpg
30x 1-min with blue "nebula" filter
m82n.jpg (29.98 KiB) Viewed 3154 times
This morning I processed and stacked them, using the H-alpha image for the Luminosity & Red channels, O-III for Green and "nebula" for Blue:
m82_7mar.png
LRGB stack from 3x 30-min filtered exposures
m82_7mar.png (38.61 KiB) Viewed 3154 times
I noted that the supernova (2014J) seemed to have faded noticeably since last month.
And I also remembered that I'd done some similar tests with M82 back in October, using a Celestron 80mm f/5 achromat, so I've managed to align these two images for comparison:
m82_sn.gif
M82 in October 2013 and March 2014
m82_sn.gif (15.14 KiB) Viewed 3154 times
As well as the apperance of the supernova, this clearly shows the difference in optical quality between the simple achromat and ED 'scopes!
But it was a clearer night back in October, so I caught a little more of the fainter parts of the galaxy then.

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More experiments with imaging of M82

#2 Post by rwilkinson » Mon Mar 24, 2014 9:55 am

For a comparison with my recent narrowband experiment, last night I fitted my original Philips SPC880 camera: this has the original tri-colour (RGB) CCD and firmware (i.e. not the RAW bayer-mode output). This was certainly a lot less hassle than using the monochrome camera and filter-wheel: just a single framing and focusing operation, rather than having to re-focus for each of the colour filters. And then the post-processing was a bit more straightforward too.

I'd not done such a good job with my polar-alignment this time - the image drifted about a third of the way across the field over the hour, and most of the individual frames showed slight trailing. So after calibrating with Offsets and Darks, Registering and stacking (using Sigma-clipping), I applied some Richardson-Lucy deconvolution, after which the stars looked much less elongated.

Finally I used the Colour Stretch and even tried some Wavelet filtering too:
m82_23mar.png
M82 on 23-Mar. 38x 90-sec with Philips LX webcam through StarWave 80ED at f/4.6
m82_23mar.png (86.99 KiB) Viewed 3086 times
The supernova is fainter now, but still quite distinct.

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