4hrs of M101

[Sam]

Ok, so it's not up to the standard of the awesome images posted lately but I think this is my best galaxy so far. It's 62 X 4mins subs autoguided at ISO 1600 with a canon 1000D through an 8" reflector on an EQ6. I got the data over two nights, last night and the night before. I had a real problem with guiding the first night and only managed 1hr 20 of data, but last night was much better. the moon made it challenging but luckily there was plenty of sky between the moon and M101. M101 was the first image I took last year that actually resembled a galaxy so that is posted as well to compare how much 1 year has improved things (I hope you can tell which one!).

Sam

[Roy Batty]

The improvement is clear to see, nice capture Sam. Just one comment though, have you thought about darkening the background a bit more? If so I'm sure it would be more dramatic and contrasty.

cheers

Keith

[Sam]

Thanks Keith, I shall give it a go now.

[steppenwolf]

Great improvement over time and a good image in its own right

[Sam]

Here's one with background darkened a bit more:

[Aza]

Good job on that one Sam

May I ask why you have chosen ISO 1600? I keep thinking of changing up to ISO 1600 for the galaxies, but I am worried about losing the colour from ISO 800.

Whats your opinion on this?

[Imahumanbeing]

They are fantastic pictures sam, loads of detail and great colours!

[Sam]

Arran,

I picked ISO1600 after reading the posts this week regarding DSLR capabilities and from the quite large discussion across a number of threads I thought the best option for my camera would be ISO1600 for about 4 minutes - or however long to get the histogram above half way (which with the moon out ended up being about 4 mins). I am reluctant to push the subs beyond 5mins due the risk of loosing subs to Gatwick Airport traffic. If ISO800 preserves the colour a bit better I might have to give that a go.

Sam

[Aza]

Yeah I am in the same boat

Trying to figure out the optimum settings to use...blooming nightmare though trying to get it right! Just wish there was hard and fast rules!

[Tim]

Great pic Sam, really nicely done. I prefer the first image at the top of the post, it has traces of the very very faint bits on the outer edges, and is very natural looking.

Getting the background 'right' for these galaxies is a tough job.

[Psychobilly]

Very nice indeed Sam

Peter

[Starjumper]

Great capture Sam.

John

[RobH]

Corker of an image Sam, great capture, your focus and guiding are perfect.

I prefer your first image. after you changed the black point, you lost a lot of faint detail.

I've had a play as I couldn't resist messing with such good data

I reset the background levels to 15/15/15 for R.G.B, then used curves to get rid of the magenta tinge.

The way I did this was to choose the green channel only, set my point by holding down CTRL, and left clicking on a mid tone area in the galaxy, then setting several anchor points either side of this, then carefully boosting the green, green being the opposite, colour wise, of red.

This negates the magenta hue while leaving the background alone. Experiment with it a bit, it's a very powerful colour balancing tool.

I then sharpened a little, and then faded the sharpening effect to LIGHTEN (EDIT-FADE-FADE UNSHARP MASK- FADE TO LIGHTEN)

This leaves the sharpening but gets rid of any star halos.

After that, a play with curves overall.

Cheers

Rob

[MartinB]

Excellent Sam, you've pulled loads out here. Rob's colour retouch and processing advice is spot on. I've always created a star layer when sharpening but that "fade to lighten" sounds a real timesaver.

[Sam]

I've had a go at reprocessing to try and preserve the faint stuff and the detail but get rid of the bright background. It's sort of worked, though it's been a very useful exercise so a big thanks to Rob for the advice:):

Sam

[RobH]

Almost there Sam....great reprocess.

The background is still a little on the red side though.

If you did any curves adjustments after levels, try resetting the levels to 15/15/15 again for the blackpoint.

Cheers

Rob

[Sam]

Thanks Rob,

What's the 15/15/15 mean. I don't have photoshop but I followed what you meant with the curves function to find the right bit to change. I just don't know what the numbers are.

Sam

[RobH]

Hello Sam.

The 15's are seen in the levels dialogue box in photoshop.

Absolute black is 0/0/0, meaning a level of zero for RG&B

I always set my 'blackpoint' higher than this, at 15 each. That way, you don't lose any faint detail while processing. You can always make the background darker when you're finished, but in general keeping it up a bit from absolute black is a good idea.

If all of the numbers are equal, your background colour will be evenly balanced.

In photoshop, you can preset these levels, then just click on a background area of your image, and the colour balance will be set evenly.

Cheers

Rob

[Sam]

Thanks Rob, I try and find how do the same thing in Pixinsight.

Sam

[Sam]

I think this is about the best I can get out of this image. This time I think I've got the black points sorted. I've just got to practice the same techniques slightly more subtly. Thanks to Rob for highlighting what can be done with the curves and aligning the different channel black points.

Sam

[ollypenrice]

Great stuff and a fascinating thread! One of my spiral galaxy dodges (and I know a lot less about processing than others on the forum) is to alter the blue and red curves thus; I boost the dim blues slightly and dim the bright ones. And I do the opposite for the reds, boosting the bright ones slightly and further dimming the dim. I stress slightly. This helps differentiate between the evolved population 2 stars of the halo and the hotter, bluer, population 1 stars of the spiral arms.

Please feel free to deplore this method!

Olly.

[Beyond_Vision]

Thats coming along nicely Sam and some great tips Rob

Regards

Kevin

[RobH]

Neat idea Olly

[Sam]

Ok, I promise this is the final iteration and I think this might be best one I've managed so far. I just went through the PixInsight tutorial on bring out large and small scale structure details:):

Sam

[Aza]

I definitely think thats your best one Sam!

Good job