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M101 (the twelfth night)


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Greetings fellow space travelers,

Last night was my twelfth night under the stars imaging. The less said about the eleventh night the better, but it was largely a catalogue of failure. And the last few beautiful clear nights I've missed with a chest infection :)

Therefore nothing was going to stop me going out last night to try to make up for lost ground. I started on the Makarian chain but realised but was getting such strong gradients from the moon (the street light bathing the inside of my OTA with orange light wasn't helping either) made me give up on that target, and I moved to something more suitable near Zenith - M101.

Ambient temperature was 12 degrees C, and my entire dark library was taken in the fridge. I had planned to take darks during the setup time but I forgot, largely because I was talking with my wife. Reading my son a story also meant I lost the twilight for my flats. I managed to collect 14 x 5 minute lights before conditions detoriated (moist air reflecting light pollution).

I then collected darks while packing up and while looking for my tracing paper for flats (I couldn't find any) I had a brain wave. By placing my iPad over the front of the scope and navigating to a blank web page, I was able to use my iPad as a makeshift EL panel. It works great for my 6" Newtonian and gave me the best flats I've ever used.

I took 7 darks and 16 flats.

I am happy with the collected data for an integration time of 1hr, 10 minutes under below-average seeing, heavy light pollution and a half moon. However the background noise is quite severe and using the "Space Noise Reduction" feature in Noel's actions was the most effective method for removing the noise (I tried various Photoshop filters and PixInsight tools). Unfortunately, the galaxy was also affected by the noise reduction. Pulling the galaxy out into a second layer gives me a sharper galaxy but a jarring cut line between the untouched galaxy layer and the noise-reduced background. So I just applied the noise reduction across the board.

Before noise reduction:


After noise reduction:


Equipment used:

Skywatcher 150P Newtonian

HEQ5 PRO mount, EQMOD, CdC

ST80 & PHD guiding

1000D (modified), MPCC, CLS-CCD and APT software

If anybody feels like they are able to make a better job of processing than I, or just wants to have a play with the data - here's a download link: http://dl.dropbox.com/u/3717210/M101_Stacked.tif

Clear skies to everyone,


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Thanks chaps :)

I was absolutely thrilled to get this image and the data is relatively clean (it did have to be heavily processed to get to this level - I presume that's where all the noise/over processed look comes from).

The key thing I learned was how unbelievably temperamental dark frames are and how they need to be taken "just so" at the same temperature as the lights to get the best out of the image.



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