Greg's M42 (with step by step process guide)

[Tim]

Original thread here > http://stargazerslounge.com/index.php/topic,38633.0.html

Greg was kind enough to send me the tiff file of his image above.

There are many and varied approaches to processing the pictures, here's my take on Gregs pic, with stages listed.

1) Crop image to remove large area of amp glow. (Solution to this problem is shorter subs and a batch of dark files.)

2) Star trails. The image was taken unguided, which really demonstrates how well Gregs mount is set up, as the star trails were minimal for a 3 min exposure at this FOV. To counter them, a very crude but effective method can be employed. Simply create a duplicate layer in PS, and set the blending method to "Darken". Zoom in on a central bright star, and then nudge the layer around with the arrow keys until the stars get as close to round as possible. On Gregs image, I just did this with one extra layer, but with badly stretched stars, you can do it from two or three sides.

3) Background. To get a more even background, I used Pixinsight LE (free) to do a dynamic background extraction. This simple tool takes an average of the pixel values all over the original, then subtracts these from the image. The new tool in the paid version of Pixinsight is even more impressive, but this one is pretty amazing too.

4) Noise. For a very rough first noise removal, I created a seperate duplicate layer, did a harsh dust and scratches filter in PS, then applied it over the top as a "soft light layer" at 50% opacity. This saves the stretching being done on so much noise. (Solution to the noise is more subs, and shorter exposure times. It was hard to tell from the tiff how much noise was from the camera, but dark frames should help as well. Noise reduction was inevitable for this single image, but it is far better not to have to use this if possible, as it nearly always gets rid of the fainter details.)

5) Stretching and layering. To try and bring out a bit more nebulosity but not highlight the noise, layers were used bit by bit. This bit is easier to demonstrate than explain....... Also, I use the Local Contrast Enhance tool in Noels actions to, erm, increase the local contrast. Then blending just the lighter and darker colours produced in turn helps to bring out a bit of detail. Bit tricky on just a single image really, stretching works best on data heavy stacks of many images. Also, as the colour was a little too blue and magenta as it comes off the camera, I selected those colours and altered them a little to bring them more into line with what a OSC CCD will produce.

6) Final noise reduction. I used GreyCstoration this time, which works like the noise reducers you pay for, but is free.

The image is 180 secs at iso200. That big fast OTA (F4) has really pulled in the light. However, some of the detail that could have been recorded has been overexposed, even at iso 200. If the single 180 sec image had been 6 x 30 secs images at iso800, most of the problems could have been avoided, and so processing becomes ever so much easier, bringing out the details is a hell of a lot easier than fixing whats wrong!

Even so, I am shocked at how much light has been captured at iso200 in just 3 mins. I know that if I did that with my kit at home, i'd just have an orange smudge as a picture.

Thanks for letting me play Greg, here's how the pic came out after my attempts.

(click to enlarge)

[James]

Wow. Nothing more needs to be said!

James

[Ant]

Very nice indeed for a single sub :shock:

My location sounds like yours Tim, in three minutes I'd hve very little!

Ant

[FLO]

Excellent idea Tim

... I am shocked at how much light has been captured at iso200 in just 3 mins. I know that if I did that with my kit at home, i'd just have an orange smudge as a picture.

He does have a very nice sky!

Here is the view from only a stones throw away:

[Tim]

drool!

[Greg]

Holy S..... :shock: :shock: :shock: :shock: :shock:

Thanks for letting me play Greg

It's me that should be thanking you...I'm honoured THANKYOU....

Earlier in the month I took some darks and about 20x30 sec sub's..I'll send em over if you want, Tim...

I'm stunned....Thankyou very much...

[barkis]

Great job TJ. You've got right into the processing side, and maybe your step by step guide could be placed in the primers as a reference, unless there is already one there.

Ron.

[Tim]

It would only really apply to this image Ron.

Martins primer is the keystone for all images really, and is pretty much the basis of these steps.

[Tim]

Holy S..... :shock: :shock: :shock: :shock: :shock:

Thanks for letting me play Greg

It's me that should be thanking you...I'm honoured THANKYOU....

Earlier in the month I took some darks and about 20x30 sec sub's..I'll send em over if you want, Tim...

I'm stunned....Thankyou very much...

Yeh, definetly Greg