M81 Bode's Galaxy

[johnrt]

Here's the results of my first attempts at autoguiding. This was shot using my unmodded 1000d, 90mins exposure in 5 minute subs stacked in DSS with darks, flats & bias and then processed in pixinsight.

Nowhere near as good as the other M81 posted this week, but I'm really happy with the results. The ability to get 5 minute subs has really advanced my imaging.

[Space Bat]

Hi John,

Nice image

Have you tried using PI from start to finish and then - last touch ups with photoshop?

PI stacks the images better and have found it much eaiser to adjust gradients - background noise, and other issues much easier to eliminate from a PI stacked source rather than stacking in DSS and then fixing in PI.

I must admit that I went the DSS route and then PI. But now a bit more familiar with PI have found that DSS is now redundant.

Chris

[johnrt]

I managed to get a better stacking result just using pi, but I think I lost a lot of detail because I couldn't apply any darks/flats etc in pi, as far as I can see it doesn't support them yet, and then removing the red wash over the stacked image.

I have my camera booked in with astronimiser for a mod so I hope it's not the camera that is producing the red wash over everything.

[johnrt]

Here is an unedited sub from the above image. 5 min exposure, iso 800 auto white balance.

As you can see a lovely pink/red wash. When I stack the subs this gets amplified. Will more darks combat this? Would a light pollution filter help?

[Space Bat]

Hi John,

Ok try doing the screen transfer autostretch - this will likely turn your image bright red... but if a different colour or mixed, carry on as the same.

Now scan your picture with the curser around the image and look at the bottom bar there should be readings for Red Blue and Green (R, G and with a reading which is changing as you move over the image....look at an area which is continously poor (large reading of one colour say R: 0.2140

Now - press/hold ALT and then N this will bring up the preview tool.

Select an area away from the object galaxy/nebula...etc in the areas which described as above, this should then show as preview 1, you can either leave it as just 1 preview, however if you feel not enough area covered with the preview window - presss Alt N and bring up the tool again and select other areas.

If you have multiple previews you need to add them together which is done by selecting Script (at the top tabs) and go down and select preview aggregator in utilities I think (sorry at work so from memory) This will bring up a window with all your previews in.

Now: bring up background neutralisation tool..in the reference box you need to select your preview or aggregated preview.

Leave the minumum and other settings alone at this stage (but can be played with for better results when familiar) adjust the maximum threshold (second scroll bar down) to just over the figure seen when measuring with the pointer on the previews..and type in or adjust bar to just above the 0.2140 as seen earlier say 0.2150.

Apply or drag instance to your main image or if unsure to your previews...

usually on mine it will go from a very red image to a white opaque(ish) image - you will see with the pointers that the colours are more balanced and no real large variances.

From here I will use the screen transfer to autostretch and the image will have ditched the large amounts of Red as seen before main image of DSO is brighter and is ready for Cropping and DBE or vice versa...

After DBE I may colour balance - but then its remove screen transfer - disable icon and start the histogram tool and do some stretching....

Most of this is in Harry's webguides, so can't take the credit

Chris

[harry page]

Hi

Chris you are at it again , we will have to upgrade your standing

John

What chris say is correct , and is easy to correct the red , also how it written appears harder than it is , if you look on my website you will a couple of quick demo's with your problem

Harry

[Space Bat]

A quick stab its not great, but jpeg didn't offer much to play with

[johnrt]

Chris, brilliant advice. Thanks very much.

Harry your website is a godsend. Thanks.

[harry page]

Hi John

We aim to please

Harry

[johnrt]

This is the results, stacked and processed in pi, using the guides from above. M82 has kept it's detail much better using pi, I think the background is still a little noisy?

updated with noise reduction

[harry page]

Hi

Good progress

Have you got to the noise reduction bit ACNR

Harry

[Space Bat]

You can play with the histogram, by individual colours to remove unwanted washes of colour - this can be done by in the real time preview window, on the left you will see your colour tabs R,G and B select the colours individually and clip or adjust untill the image gets darker and removes background colour, then press the combined RGB directly below. This should remove most of the unwanted noise colours for background.

You can then do more by selecting the ACDNR filter as harry mentioned, this is quite tricky to explain you need to view the tutorial.

Another thing to try is the SCNR tool which can remove individual colours that may be noise, I use a few clones to practice how much I need to remove, where I drop the slider to 0.10 and try a few higher values up to 1 to see how much coloured noise in the image to remove. I tend to leave the protection method as average neutral.

Chris

[johnrt]

I've one back and worked through all the tutorials one by one, as I was jumping about and doing things in the wrong order, and included the colour calibration tool.

[Space Bat]

Much improved

PI is mind boggling - but the more you progress the more you start to see how to get the best out of it.

There is so much trial and error tweaks to get your head around when fiddling with the values in the tools....good job we are blessed with enough down time to practice

Chris

[harry page]

Hi John

Now that's a lot better , a huge difference in only a day or two

Now if you have listened to me groaning on for hours I bet you need a rest

Look forward to seeing some more of your images

Harry