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M98


x6gas

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Hi all,

Had to work very hard to get anything vaguely decent from this data as I only had 9 usable 180s subs in the blue channel so lots of noise... I also had some nasty dust bunnies in the green channel and no flats:BangHead:.  Data captured on one night in March (in fact the morning of the 28th)...  I'd held off processing it as I intended to collect more data as this was really me just shaking a new scope down and getting SGPro auto-focus etc sorted but the then bad weather meant that months later when we finally got some clear skies I quite forgot it as I grabbed data for the Whale and M94.  It's a bit low in the sky now for me so won't get a chance to add any more data until next year.  As a result I've processed two versions... the first with a more gentle stretch to the background so that the noise isn't too noticeable.   I guess I could have gone more aggressive with the noise reduction in PixInsight but I dislike the vaseline look when over applied so was maybe a bit cautious.

M98 doesn't seem to be imaged all that often for some reason but I hope one day to capture all of the Messier objects so this was another one to tick off.  It's classed as an intermediate spiral and lies around 44 million light-years from Earth.  It can be found in the constellation Coma Berenices and is part of the Virgo Cluster.

Taken with this summer's galaxy hunting kit: CEM60EC; SW Esprit 150; Atik EFW2 with Astrodon filters; Atik OAG, QHY5L II with PHD2; Atik 460ex.

R: 18 x 180s, G 16 x 180s, B 9 x 180s for a total integration time of just 2.15 hours.  Captured with SGPro and processed in PI and PS.

1838418844_M98RGBv1.thumb.png.04f9c12b777fce37276f2d1332de4984.png

422581992_M98RGBv2.thumb.png.e4a20d31290963e1f447d20b2db29196.png

Won't win any awards but I'm pleased to get anything out of such a skinny data set.

Thanks for looking.

Cheers, Ian

 

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In case it's of interest I had a go at processing this with a false luminance made up of a stack of all of the RGB subs.  It's allowed me to stretch the data and sharpen it a bit more...

766781771_M98LRGB.thumb.png.db51ab0456fb157dcd9a75c1daf312a7.png

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Very nice result. I took 6 hrs of data on this with an Esprit 150/ASI 178 and found the colour to be unusually strong during the processing, was that your experience?

There are LOTS of distant galaxies in the background.

 

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17 hours ago, tomato said:

Very nice result. I took 6 hrs of data on this with an Esprit 150/ASI 178 and found the colour to be unusually strong during the processing, was that your experience?

There are LOTS of distant galaxies in the background.

 

Many thanks for the comment Tomato.

I must I didn't find the colours particularly strong, but then I don't have much data, obviously.  I've rediscovered the LAB colour boost process that boosts saturation without introducing too much chromatic noise and applied that, but not at full strength.  I also ran a couple of different processes, one gave the galaxy a very yellow colour, and the second much bluer.  The final images above are all composites of the two with the yellower version used just for the core of the galaxy.  I actually did the same thing with a recent image of M94 too as I quite like the result...

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Very many thanks Robin.

I would usually use 300s subs for a target like this, and collect a lot more data.  I'm honestly not sure why I chose to take 180s subs - think I was just trying to see how it would come out...  BTW, I went through a phase of capturing different length subs for each of the RGB channels but don't bother now; the Astrodon filters mean that you're not suppose to need to do that but even when I was using Baader filters then it didn't seem to make much difference to the end result.

Only having 27 minutes worth of data in the blue channel was a real challenge, I have to say, and there is no doubt that the image has suffered as a result.  Having processed the data a couple of times it's my view that an hour per channel of decent subs would really be the minimum for 180s sub-exposures and it really should be at least 2 hours per channel.  Obviously the more data the better, weather permitting,  and I ideally I personally aim for around 4 hours per channel in 300s subs (as I did for recent images of M94 and C32 - the latter needs a full reprocess as the data is better than my processing skills would suggest) as I don't see much of an improvement with more data than that on galaxies.

Clear skies, Ian

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Interesting information Ian, thanks.  Until recently I'd been using 600s for everything but have just changed to 300s for RGB , 600s for L and 1200s for NB. I have tended to take an additional 3/4 frames of blue using the Baader filters.

I'm renting APP at the moment as well as having a subscription for PS and LR.  PI sounds quite complicated.  Do you think the 45 day trial period is long enought to get to grips with it? 

Like you I need to understand why to use certain commands and processes rather than just follow someone elses recipe.  I gave up on StarTools (because of the lack of documentation) in favour of PS which along with LR I use for wildlife photography.

I run data capture (SGP and PHD2) on a laptop and then move to a MAC for all processing.  Hoping I'm not stretching this thread too far in a wrong direction.

Thanks

Edited by rubecula
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3 hours ago, rubecula said:

 I gave up on StarTools (because of the lack of documentation) in favour of PS which along with LR I use for wildlife photography.

I’m not sure when you last looked at StarTools but v 1.6 has lots more Interactive help.
When you press the ? query on most topics it takes you to web based help giving you an in depth discussion on the processing tool, a big improvement on the earlier versions IMO.

If you want to find your own workflow then PixInsight is set up to do that, but I found 45 days too short to really get to grips with it, especially if you intend to do all of your calibration and stacking in there. Having said that, I was sufficiently impressed to purchase a license.

Apologies to @x6gas for hijacking your thread.

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3 hours ago, rubecula said:

Do you think the 45 day trial period is long enought to get to grips with it?

In honesty Robin, unless you can spend a couple of hours on it every day, I don't think so!  I've gone down the route of doing pre-processing manually rather than using the script and I barely got through that in the trial period!  Of course if you just follow a tutorial then you can at least get through a whole process.

The software is really, really capable and there is lots about it I like but the documentation is, frankly, awful if you want to properly understand what you are doing.  Some of it is so technical it's ridiculous and other processes are not really documented at all (even some pretty basic ones).  Warren Keller's book is useful but far from comprehensive (that would be virtually impossible in fairness).  From what I can work some of the online tutorials are plain wrong too, but there are lots of tutorials and the PI forum is helpful too with the developers often answering questions which is incredibly helpful.  The user interface also takes some getting used to and feels like something written with little regard to usability (see for example icon naming conventions).  Now all that said, when I got used to the basics and its idiosyncrasies I quite enjoyed learning it - still am learning it, of course, but still exporting to a layers-based photo editor for final processing...

As it happens I couldn't get on with StarTools at all but I am pleased I purchased PI - my advice would be get the trial, follow some tutorials (starting with this one) and try to work out whether you like the interface and if you do, go ahead and buy it.  As I say, it is very powerful and allows you to do a lot with the linear image...

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10 minutes ago, ollypenrice said:

Very attractive and super processing.

Olly

Very many thanks for taking the trouble to comment Olly - I've always really appreciated the encouragement you give to SGL members and your images remain an inspiration.   :icon_salut:

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14 hours ago, x6gas said:

 - my advice would be get the trial, follow some tutorials (starting with this one) and try to work out whether you like the interface and if you do, go ahead and buy it.  As I say, it is very powerful and allows you to do a lot with the linear image...

Thanks Ian,  I'll give it a try on my most recent images and see how they turn out.

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You've done a great job with the processing.  The galaxy looks nice and smooth without being plasticy.  I do think the synthetic luminence has worked very nicely. 

I see that you haven't captured a plain luminence.  Have you found this works better than L and binned RGB?   

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21 hours ago, Tom OD said:

That came out well. The background is nice and smooth.

Tom

Many thanks Tom - as I've said, the lack of data meant that I had to do more noise reduction than I would normally...  and all things considered it hasn't come out too bad.

15 hours ago, MartinB said:

You've done a great job with the processing.  The galaxy looks nice and smooth without being plasticy.  I do think the synthetic luminence has worked very nicely. 

I see that you haven't captured a plain luminence.  Have you found this works better than L and binned RGB?   

Ah thanks Martin!

The synthetic luminance did help on this one due to the lack of data.  The stacking algorithm took care of the dust buddies on the green filter in the luminance stack and it gave me something with enough signal to sharpen.  I've just done the same with some data of M101 that I captured earlier in the year and that I'll post shortly, but it's had much less of an impact on that which has a couple of hours data per channel.

So I have to be honest that the main reason why I didn't shoot luminance in this image is because I knew I had dust bunnies on my L filter and didn't have time to take everything apart and clean it properly.  I haven't used flats on this image at all, but when I do use flats I tend to use them to correct vignetting only and keep my imaging train as spotless as possible to avoid dust bunnies.  My images are better with flats but I don't want to capture a set of flats for every filter and every image so that's the compromise I'd usually take.

Now all that said, I was keen to see how things work just capturing RGB with no luminance so have given it a go with a number of spring galaxy targets.  The results are OK but of my own galaxy images (e.g. M51, M81) I prefer the ones where I have captured luminance and binned the colour - I recall that they were easier to process too...

Cheers, Ian

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2 hours ago, x6gas said:

The results are OK but of my own galaxy images (e.g. M51, M81) I prefer the ones where I have captured luminance and binned the colour - I recall that they were easier to process too...

Cheers, Ian

Yes, this is what I have found with my MN190.  You get so much more signal for a given time without any apparent star bloating (with my sampling rate anyway).  

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