Image Processing

The images astrophotographers record on their cameras are usually a long way short

of the glowing deep space Nebulae, or dramatic spirals arms of a distant galaxy you see

on web-sites or in magazines. Image processing can improve the image more dramatically

than any investment in bigger/better hardware. With that in mind, I thought I would outline

the processing steps that take the raw images to their final gleaming appearance.

Everyone has their own techniques and tricks of the trade, and I'm quite happy to share mine.

This series of images of M42 - The Orion Nebula -

were taken using a 30 second exposure with the Canon 300D

on The Orion 100mm Refractor - FL = 600mm

Stage 1

M42 - Unprocessed

This is a 30 sec exposure - ISO 1600

at prime focus on the Orion 100mm F/6 Achromat

Stage 2

M42 - Dark Frame Subtracted -

Unsharp Masked and balanced for brightness/contrast/colour levels

Stage 3

M42 - Passed through 'Neat Image' to

smooth noise. This image looks as detailed

as the 3 minute image from the Meade 127mm

Refractor on the Home page.

That's because the Meade is F/9.7 and

The Orion is F/6. The trade-off is image size and signal to noise.

2011 Update

The Orion Nebula

using an F/4 Newtonian

and Nikon D5000 DSLR

2011 Update

The Orion Nebula

processed to show a

little more in the core

These images of M51-The Whirlpool Galaxy

were taken from the backyard with varied exposures

from 30 seconds to 2 minutes. I had six frames with trailing

on four of them, so used the best two frames to stack

Stage 1

M51 - The Whirlpool Galaxy

Barely seeable on the unprocessed image.

89 sec at ISO 1600 at prime focus

Stage 2

M51 - Dark Frame Subtracted -

Unsharp Masked and balanced

Stage 3

M51 - Noise Smoothed using Neat Image

2010 Update

Wow have things changed!

This is the improvement from using way more

images in the stack and from using a 1250mm focal length SCT compared to a 600mm FL refractor for the previous M51 images.

This is an even greater stack of 21 images

now using a Nikon D5000 which has 12.2 Megapixel sensor and improved noise reduction Although I took dark frames, I didn't use them in the stack.

M51 with an 8" SCT and focal reducer at F/6.3

this is a stack of 21 images. The more images you have to stack, the smoother and less

noisy the images becomes.