Raw Frame

The imaged object is the spiral galaxy M51.

Camera is a SC3.3 Toucam Pro. The camera was modified for long time exposure and the original CCD was replaced with a Sony ICX424AL b&w CCD.

This a raw frame  from the M51 AVI file captured with K3 CCD tools.

40 raw frames were captured, exposure time was 30 seconds and camera gain was set at 70%

Dark Frame

Inmedately after the M51 AVI another AVI was captured, this time 10 frames were exposed 30seconds each.

The dark frames avi was averaged in Registax.

The image on the rigth is the resulting dark frame. There is evident glow in the upper left corner due to the CCD amplifier, about 30 hot pixels and some background noise.

28 frames aligned, stacked and dark substracted

Inmedately after the M51 AVI was captured

The best 28 frames from M51 were selected, dark substarcted, aligned and stacked in Registax.

This the Registax output image after stacking.

Levels Adjusted

Histogram adjustement of the grayscale image in Photoshop clearly reveals M51 and companion galaxy.

There is still noise in the image, the hot pixels were removed during the dark frame substraction process in Registax. Due to poor tracking (PE and poor polar alignment) the removed hot pixels (now black pixels) can be clearly seen in a pattern that reveals the tracking deficiencies.

Hot pixels leftovers removed

The clone stamp tool was used to removed the hot pixels pattern.

Denoised Image

The previous image was filtered in NeatImage.

A custom noise pattern filter was created and applied to the image.

Background noise was reduced, there is still some noise in the top in the image due to non overlapping during the stacking process. This is the area of the image we will cropp in the next step.

Cropped Image

The image was again loaded in Photoshop, cropped to removed the portion that did not overlap during the stacking process and some fine adjustment of curves was made to produce the final image.