M8 Lagoon Nebula, M20 Helix nebula and NGC6559

[Carole]

My last image from Les Granges

With the huge chip of the Atik 11000 I was able to get 3 objects in one frame.  I've also cropped the individual objects.

Still a lot of learn with processing filter images, but learning all the time.  

Atik 11000, Takahashi FSQ106N and mount Tak EM200 with Baader filters
Lum 7 x 600
Red 6 x 600
Green 8 x 600
Blue 6 x 600
Ha was taken but I left it out as I preferred theLRGB result.

Larger file:

http://cdn.astrobin.com/images/a3cef2c5-2560-420d-971d-d4ccbf5a666e.png

[Carole]

Lagoon on it's own

Larger file:
http://cdn.astrobin.com/images/d859ffef-2a4e-43fd-9991-6ae2593945c5.png


Trifid on it's own (I think the reflection nebula is too purple on reflection - pun - ha!)  I'll re-do it when I get Astroart:

Larger file:
http://cdn.astrobin.com/images/a9fd3d1b-5cc0-419f-8b36-4c60cf98aa45.png

[Carole]

NGC6559 on its own:

Larger file:

http://cdn.astrobin.com/images/684edb73-0eb7-40dd-9e63-fe44bda2d3c5.png

[JohnP]

Looking very nice Carole - a few things going on with the centre of some of the dim stars but loving the widefield.. John

[MarkS]

Carole,

That is a really beautiful widefield.  The colours are great, the star background is excellent with it's dark patches.  Lagoon, Trifid and Cat's Paw are all looking excellent.  I love the blue relection nebulosity of the Trifid.

But, as John says, what is going on with the centres of the mid-brightness stars?  I'm sure this is not an acquisition problem because the dimmer stars look sharp.  Go back to your raw stack and see if you have the problem there and then determine what part of the processing sequence caused it.

You should also have sufficient data to bring out the nebulosity in the Cat's Paw a bit better but the Cat's Paw is a tough one to process.  

If you can fix those stars then this will look great as a poster!  It has huge potential.

By the way, I don't see the same "warm pixel" problem that you had in your Iris Nebula image.  Do you have any idea why?  Did you dither?  Or did the Iris not have sufficent camera cooling maybe?

Mark

[Fay]

Really nice widefield Carole.

Fay

[Carole]

Thanks John, Fay And Mark.

In answer to your comments Mark.  A similar thing happened to the small stars with some stacking when I was doing it at Olly's and he said it was to do with DSS and that it wouldn't happen with Astroart.  I am in the process of getting Astroart, but for some reason the website would not let me pay today and after clicking submit many times and it kept going back to the same page I decided to give up today.  I will give this a re-process as soon as I get AA.  I am slightly suspicious this effect is due to the cosmetic settings in DSS as I have had strange things go on with stars before in DSS when I have set it to reduce hot pixels.  I might give it a try without using this setting which doesn't seem to be working anyway. 

As regards the "warm pixel problem" I think what you are referring to was the load of blue stars I had.  I did actually have them again with this image, goodness knows what it is or what causes it but I seem to have a load more blue stars than any other colour, but I managed to disguise them this time by reducing the saturation in the background. 

I could do with some-one going through the process with me who has a bit of experience.

I didn't realise that NGC6559 was called the cats's paw but it certainly looks like one.

I need to find a way of dithering. 

Coloured filter imaging is a whole new ball game compared to DSLR imaging.

Carole

[MarkS]

Hi Carole,

The black dots in the medium stars are certainly consistent with an over-zealous hot pixel reduction algorithm.

The "warm pixel" problem I am seeing in your images is definitely caused by certain individual pixels on the camera.  Take a very careful look at the dark areas of your Iris image at full size.  You will see very short streaks which have a blue dot at the top right end, a red dot at the bottom left end and with L and B in the middle.  In a few places there are a few streaks running side by side - making it more obvious.  For instance look in the darker area just outside the blue nebulosity of the Iris.  Once you know what you are looking for you will find this consistent pattern over the whole image.  The B dot is more obvious than the L,R and G dots.  This problem could have been fixed with accurate calibration frames (darks and flats) or with dithering.

If you want to use dithering (and I regard dithering as essential)  - the answer is to not use Artemis for acquisition!

In any case, don't panic yet.  I can think of a processing sequence that will identify and "heal" the warm pixels.  But it will have to be done in Pixinsight, IRIS or something equally as flexible.  The idea is to add (without aligning) all the LRGB frames together in one lump and identify the warmer pixels to create a hot pixel map that can then be used to treat each individual sub.   The "identification" step might require a mathematical algorithm - which favours using Pixinsight.

Mark

[Carole]

Yes I see what you mean now about the warm pixels, no I don't seem to have that particular problem with this image.  But I do have lots of extra blue stars for some reason which I have dumbed down. 

As you say I am theorising that

are certainly consistent with an over-zealous hot pixel reduction algorithm.

this is due to the cosmetic settings in DSS which are supposed to get rid of hot pixels, I got holes in stars once with this setting with a DSLR image.  I am going to stack again without using this setting and see what happens.

I will have to look into capture programme for the Atik.  Lots of other people use Atik cameras so there must be a solution, unless they just do mono imaging when the problem would not show up.

The calibration files darks and Bias were ones given to me by Olly.  If they work for him on his set up they should be OK using the same camera surely.

Carole

[MarkS]

But I do have lots of extra blue stars for some reason which I have dumbed down.  

I'm pretty sure it's the same "warm pixel" problem but I'm not sure why it's more obvious in blue.

The calibration files darks and Bias were ones given to me by Olly.  If they work for him on his set up they should be OK using the same camera surely.

They certainly ought to work.  However the evidence here suggests they don't entirely match your light frames for one reason or another.  Maybe DSS didn't apply them properly?

[Carole]

Seems like DSS is not doing the job very well.  I am just having a re-stack without the cosmetic settings and see what happens, just to prove a point if nothing else. 

The extra blue stars look larger than hot pixels to me.  I'll see if I can do a zoomed in crop next time I combine the colours to show you what I mean. 

Can't find dither on Artemis, it does seem to guide but I can't find any settings to do with dithering.  The good news is I have just discovered that APT will connect to the Atik and that does have dithering.  Shame really because I really like Artemis capture.  APT is a bit clumsy handling the CCD temperature. 

Carole

[Carole]

Well the good news is I have done a further stack without using the cosmetic settings and the weird effect to the small stars is no longer present and also I don't seem to have all those extra blue stars either. 

I'll do a reprocess of this as soon as I have some time without that setting.

Carole

[Carole]

OK, I have done another complete stack & process.  I didn't use the cosmetic tab in DSS (which is supposed to get rid of hot pixels) and it now seems to have eradicated the problems I was having before - thank goodness.  

http://www.astrobin.com/uploads/17c6f6f7-c6db-4e92-a9b3-3c6b55c4c4ef.png

[Fay]

That looks good Carole! shame that after a couple of weeks we put them all away and go on to the next one!!!!  not sure if it is good fun or not   

[MarkS]

Excellent re-process. 

It looks fabulous now!