M45 - The Pleiades - LRGB

[PhotoGav]

I have finally started processing various projects gathered at the end of last year. This is the first of them, M45 - The Pleiades, gathered on 23rd and 24th November 2014.

80ED with reducer, QSI 683-WSG and Baader Filters.

RGB = 12 x 300s each

L = 23 x 600s

Total integration time = 7hrs 50 minutes

It should have been 24 L subs to take it to 8hrs, but one sub was wrecked by a bright satellite trail that wouldn't come out in the stacking. I use Nebulosity3 on the Mac and used the Standard Deviation Filter at 1.5, but it was still too evident in the stack. I often see that people can remove sat trails in stacking, but that remains a dark art to me... Any advice greatly received!

I have wondered and looked and pondered whether that brightness towards the bottom of the screen is a gradient or nebulosity. I came to the conclusion that it is nebulosity. What do you think?

Please let me know what you reckon to the image - is the colour any good, have I overshot the mark with the sharpening? I am always keen to get the best out of the hours spent on this hobby, so please don't hold back with the criticism. I have learned most when people question aspects of an image.

I hope you like it though!

[lensman57]

Looks really great , you ought to be pleased.

Are you dithering the subs? If so then with Sigma Clipping it should work. Anyhow don't get hung up on loosing  one sub out of 24, if you only had 8 subs then loosing one is not good but you still have plenty.

A.G

[Rico]

Stunning image. I really like this. How come you have diffraction spikes on some of the stars if you used a refractor?

[PhotoGav]

Thank you lensman & Rico.

You're absolutely right, AG, to only lose one 10 minute sub is not a bad result at all! I'm just curious as to how others manage to clip out such artefacts in stacking.

Good question Rico, I don't really know the answer, but I think it is to do with over exposing the brighter stars and 'light' leaking out of those areas on the chip. Hopefully somebody who actually knows will be able to clarify.

[theo]

That's a nice image Gav. I use Maxim for stacking and find the median combine method normally sorts out the odd trail here and there. Personally I would probably drop the red a tad for the background sky but good work nonetheless.

Pete

[Christopher Davenport]

Nice work GAV, on sigma clipping may be worth sticking it up 3px and do 10 iterations. Although it depends on how large the dithering was if it will work or not. I have started to push up my dither distance.

You have an insane amount of data on a bright object. It has a nice natural feel, but there is a lot more nebulosity in there. (I viewing on my mobile tends to darken things)

[xs2man]

Very nice image.  Looks excellent.

[lensman57]

Thank you lensman & Rico.

You're absolutely right, AG, to only lose one 10 minute sub is not a bad result at all! I'm just curious as to how others manage to clip out such artefacts in stacking.

Good question Rico, I don't really know the answer, but I think it is to do with over exposing the brighter stars and 'light' leaking out of those areas on the chip. Hopefully somebody who actually knows will be able to clarify.

Your diffraction spikes are fine. These are normal for an ED doublet and the more elements there are the more the diffraction spikes due to the many glass to air surfaces. ( wait till you image the flame nebula and the killer star Alnitak ) in fact ED 80 does very well as far as these spikes are concerned.  

You can try and play with the sigma numbers in NEB3 or try DSS to see if it is more successful.

A.G

A.G

[cfpendock]

That's very nice Gav.  Your imaging has certainly become something to aspire to...

Chris

[strutsinaction]

Nice one! Did you bin your RGB or were all subs 1x1?

Regards

John

[PhotoGav]

Thanks all.

Pete - good point about the background colour, I will have a fiddle with that and see if I can improve it a bit.

@Chris Davenport - I'll have a hunt for more nebulosity, though I'm always worried about over cooking these things and ending up just finding noise!

@lensman57 - ah, interesting, so that's where they come from. If the weather ever changes I'm off to the Horsehead, Flame and the lethal Alnitak... Spikes awaiting!

@cfpendock - you are too kind. It is most definitely with thanks to all the great help, advice and feedback from the fine folk here on SGL that I am able to produce anything half decent. It's also got a great deal to do with throwing more money at it and buying the QSI. Astrodons are next on the list... Will the spending ever end?!

John - all subs were 1x1. My next project to process has the RGB data shot at 2x2, so it will be interesting to compare results.

[PatrickGilliland]

Nice image well done - Not sure of Neb 3 settings but I often have trails and I dither at 4 pixels and sigma clip stack (my limited understanding of dithering with sigma clipping says it works buy evaluating the pixel next to it, I have found 4px the most reliable without being too much and is big enough to allow unique pixels on evaluation).  It is very rare I will see a trail even if prominent on a sub. 

As stated above the background could be tweaked it is warm (reddish) and this could be overdoing the gradient you mention, maybe a quick review of the histogram will help - have you tried a gradient removal tool not sure what is in Neb.  PI DBE would tell you if it is there or not....

Nonetheless great image - hope you take as advice only I am certainly no expert

Paddy

[PhotoGav]

Thanks Paddy, advice is what I'm looking for, so thank you for your input. I do dither my subs, I think the setting is 'high' in APT. It certainly works well. In conjunction with the St dev filter, I can normally deal with sat trails. The trail in question is very bright, I think it might even be the ISS, will have to check. I will have a fiddle with settings in Neb3 and see if it helps.

I haven't dared go near PI yet... I did try GradientXTerminator, but it was no use and caused more damage to the image than good. I will have a look at the background levels and see if that can be improved.

[jeremile]

Hi,

This is a great image with beautiful colors.

I love that!

Jérémy

[PatrickGilliland]

Thanks Paddy, advice is what I'm looking for, so thank you for your input. I do dither my subs, I think the setting is 'high' in APT. It certainly works well. In conjunction with the St dev filter, I can normally deal with sat trails. The trail in question is very bright, I think it might even be the ISS, will have to check. I will have a fiddle with settings in Neb3 and see if it helps.

I haven't dared go near PI yet... I did try GradientXTerminator, but it was no use and caused more damage to the image than good. I will have a look at the background levels and see if that can be improved.

DBE is way forward quite easy to use and plenty of videos on it.

Introduce features in PI one at a time but DBE is probably one you should learn up front as it will sort out any issues of flattening.

Its a great image though cant detract from that!!

Paddy

[lensman57]

Thanks all.

Pete - good point about the background colour, I will have a fiddle with that and see if I can improve it a bit.

@Chris Davenport - I'll have a hunt for more nebulosity, though I'm always worried about over cooking these things and ending up just finding noise!

@lensman57 - ah, interesting, so that's where they come from. If the weather ever changes I'm off to the Horsehead, Flame and the lethal Alnitak... Spikes awaiting!

@cfpendock - you are too kind. It is most definitely with thanks to all the great help, advice and feedback from the fine folk here on SGL that I am able to produce anything half decent. It's also got a great deal to do with throwing more money at it and buying the QSI. Astrodons are next on the list... Will the spending ever end?!

John - all subs were 1x1. My next project to process has the RGB data shot at 2x2, so it will be interesting to compare results.

Here was my last year attempt when the weather let me image, get ready for it.

A.G

[Martin-Devon]

That's a nice M45 Gav, and be careful not to be too taken in by the possible gradient - there is a natural red-ish nebulosity area that come's through on one side of M45, you'll see it in some of the wider LRGB images so don't take that out. Personally I think LRGB is harder than narrowband, and coupled with the huge stars in M45 it's a really tough target, so you've done a good job with this one.

Martin

[lensman57]

That's a nice M45 Gav, and be careful not to be too taken in by the possible gradient - there is a natural red-ish nebulosity area that come's through on one side of M45, you'll see it in some of the wider LRGB images so don't take that out. Personally I think LRGB is harder than narrowband, and coupled with the huge stars in M45 it's a really tough target, so you've done a good job with this one.

Martin

Very good advice Martin, the dust around the wider area of M45 is decidedly orange-brown.

A.G

[PhotoGav]

Thank you Martin. Indeed, my research of other deeper M45 images did show a large amount of dust all over the place, hence I left the lighter patches alone, deciding that they were real and not artefacts. As for colour, interesting that there is so much orangey-brown in a subject that is normally associated with blue. I'm going to check those histograms when I get back on the Mac and see what the numbers reveal.

As for going deeper in this target - what is required; more stretching of this data, further longer subs, more subs of same length (and should they be L or RGB or all four), a darker site (I feel that I was approaching my sky's limit with 600s L subs) or, probably, all of the above?! Also, would 600s RGB subs, rather than the 300s that I chose, have been deeper or would the stars have started to be over exposed? My setup is running at f6.7. Hah, there's another way to deeper data - a faster scope... That Tak winks at me from the pages of IKI yet again!

[Twisted Lip]

Top notch as ever Gav!

Will

[ollypenrice]

It's certainly nebulosity. You can see it in wider field images on the net. This is a great image of a tricky target.

Olly

[PhotoGav]

Thank you Will & Olly.

[steppenwolf]

How come you have diffraction spikes on some of the stars if you used a refractor?

I suspect that the four diffraction spikes that I am seeing on the brighter stars are a result of the sensor in use - the KAF 8300 micro-lenses are known to produce this artefact.

[ciels noirs]

Great shot Gav, love the nebulosity. 

Martin

[lensman57]

I have really enjoyed looking at this image and keep coming back to it. It is nice and subtle. Last week one evening while the moon was high up and next to M45,  I tried to image it using a modded canon 1100d. The result was horrible, noisy and with the main stars all saturated even with a clip filter and only 360s exposure.

A.G