Updated - IC405 Flaming Star Nebula - 26 Nov 2011 02:30 - Rother Valley Campsite

[The Thing]

LX90 8"/Baader Alan Gee II Telecompressor/Canon 350Da/Astro Photo Tool, HEQ5 GEM/EQASCOM/Cartes de Ciel, QHY5/Finderscope/PHD.

12x300s ISO800 processed in Deep Sky Stacker, 10 darks and 7 flats. The darks don't sem to have enabled DSS to remove the amp glow bottom right. Any ideas? Also I've just noticed the satellite trail!

Reprocessed removing sub where guiding had glitched. Set Dark multiplication factor to 3.0 under Settings... and this seems to have cured the amp glow and the flats not being applied ( ?). Also tweaked the stretching and colour balance in DSS.

Full size image here

[Carole]

That's looking good Duncan.  Not tried this one yet, looks like it will need another hour or more.

Glad to see some imaging got done at DSC.

Carole

[mickw]

I don't think it's amp glow.

Nice work, I think the background could do with being a tad darker and you have a black splodge top right

[MarkS]

Looking good Duncan!

The bright patch is definitely 350D amp glow. Are you absolutely sure the darks have been subtracted - it really doesn't look like it to me.

Mark

[julian]

Very good Duncan!
I saw that sub with the satellite trail down load on your laptop.

[Fay]

Really nice Duncan, lik it very much

[JohnP]

That's not at all bad Dunc - Some of the wispy blue/purple stuff in the middle is starting to show through. still looks like you have some minor collimation &/or flattener issues though..

Nice image - John

[The Thing]

Nice work, I think the background could do with being a tad darker and you have a black splodge top right

Ha! Looks like the flats weren't subtracted either. What is DSS doing??? I will have a check of all settings.

[Rocket Pooch]

looks good, that flattener works really well...

[MarkS]

Duncan,

You've removed the link to the original, so it's difficult to see the comparison.  However, there is a dark patch where the usual amp glow bright spot should be.  This might indicate that too much dark has been subtracted (3x too much?).  There is also a strange noise pattern across the whole image which might indicate the same thing.  Or was it on the original as well?

Mark

[mickw]

That's gone weird 

[Carole]

Can't see either image.

Carole

[The Thing]

  :BTW the host server (POWWEB) seems to be having an attack of the porn site search pages and I think this is stopping my images being visible.

[The Thing]

I can see both images now.

[MarkS]

I can see both images now.

Are both images linked to in this thread?

[The Thing]

I can see both images now.

Are both images linked to in this thread?

Yes. The small version is embedded using the IMG tag.

[MarkS]

I meant the 2 different images - the one before and the one after reprocessing.

I wanted to see if the strange noise pattern was also in the image previous to reprocessing.

[RobertM]

Hi Duncan,

That's a very good attempt at a very difficult target even for a cooled mono camera (well I find it so).

Are you going to add more subs at some point ?

Robert

[The Thing]

I have some subs taken in Beckenham before DSC so I may process and add them.

Originals:

Full Size

[Carole]

That re-process looks much better Duncan, where has all the noise gone.

As it was clear last night your thread inspired me to have a go at this subject as well, but mine is MUCH noisier.

Carole

[The Thing]

That re-process looks much better Duncan, where has all the noise gone.

These are the original process where the amp glow wasn't removed by the darks.

[The Thing]

Thanks for all the previous comments. This is reprocessed version with final tweaks to colour, levels, blur/sharpen in PhotoFiltre which seems very happy to process 16bit TIFs unlike GIMP. I have reduced the dark multiplication factor to 2.0000 and used a basic median stack (in DSS).

I think this may be my best image yet.  

Full size

[MarkS]

It's looking much better already - it's a good start to the processing.  

Now here are 3 definite steps to improve this further:
1) I think the dark multiplication factor is still too high - leading to a black ring instead of amp glow and some dark streaking.  Try reducing it further to see what happens.
2) The vignetting needs to be corrected - see how it gets darker towards the corners.  If it's too late to shoot some flats then some kind of gradient removal might do the trick.
3) There is too much green in the background and in the Flaming Star.  If that green can be subtracted then the red H-alpha will look much redder and the blue nebulosity will look much bluer.

Hope that helps,

Mark

[Later Edit]
It would give a result something like this:



One final tip:

I sometimes find that the amount of dark subtraction required to minimise the streaking is different to the amount of dark subtraction required to minimise the amp glow.  In such a case, I process twice and judiciously combine the two images to get the best of both.

[The Thing]

Thanks Mark.

Vignetting: I have used flats but DSS doesn't seem to take much account of them. All other images I have processed in DSS have shown the same issue.
Darks: I think I'm flogging a dead horse with DSS, I am going to reprocess in IRIS and see what I get.
Colour: I'm hopeless at gauging colour casts so all comments gratefully received!

[The Thing]

This image has had a few pixels trimmed off the edges.
Everything else is the same. Final tweaking in Photo Filtre. I think IRIS is worth the effort.

Full Size Version.

[MarkS]

So much better Duncan!

It's instantly obvious from the lack of background noise and background streaking that the darks have been subtracted properly now.  It makes so much difference.

I agree, IRIS is definitely worth the effort.

Well done.

Mark

[The Thing]

Thanks Mark.

[Fay]

Marks comments are always so helpful, he is honest & constructive, & everyone turns out to be a happier bunny than when they started     

[RobertM]

That's quite a massive difference from the first version.  You've done a very good job on processing and teasing out more of that elusive Ha but I think it would show even better if the black level was moved up a bit to give more contrast.  The background looks quite noise free now and I think the image could take it.  

Fay, I think we all try to be like that in our own way !

Robert

[Fay]

everyone certainly does Robert, & it is so helpful

[The Thing]

I have had another go at this. Same framing courtesy of APT. 20x300s from the backgarden in Beckenham last Sunday night (it was so clear and dark). Processed in Iris and Photo Filtre. Binned x2 in IRIS. I hope my processing is getting better. One change, an extra 2mm in the spacing of the FR from the CCD. Unfortunately it doesn't seem to have improved the star shapes in the corners.

Full size here

[MarkS]

Sunday night was certainly one of those very rare nights!

Your latest version is easily as good as the Rother Valley version and you've done a good job of processing it.  It's an excellent result from Beckenham. 

As for star shapes, you are seeing the typical SCT distortions - I don't think changing the corrector spacing will much much difference.  I myself did many experiments with the Alan Gee and got results very similar to yours.

Nice one.

Mark

[mickw]

I think I prefer this version to the Rother Valley one.
There's a lot more contrast in the detail

[RobertM]

I agree with Mick, there's a lot more nebulosity and detail showing plus you've lost the river effect of the first.  Could be the bad stars in the top left are a result of collimation - was it spot on ?  Collimation will be even more critical with these reducers because of the spacing requirements and the large chip you're using.

Robert

[Fay]

you did well there Duncan. especially being local, probably because of that rare night

[The Thing]

Thanks everyone. Next time I do this object I will rotate the camera to get more of the pretty bits in! The asinh colour stretch in Iris is great and Photo Filtre has a 'Revive Colours' function that did just that!

Q. I have 12 more subs taken after a meridian flip - is the best way to combine then to process them separately and add the final image to the first?

Could be the bad stars in the top left are a result of collimation - was it spot on ? 

The scope was freshly collimated. I am tempted to disassemble the secondary holder as this scope is terrible at holding collimation, one screw particularly seems to always require a lot of adjustment. I have a sneaky feeling that the scope looses collimation during an imaging run as the first subs look better in this respect than the last.

[MarkS]

Q. I have 12 more subs taken after a meridian flip - is the best way to combine then to process them separately and add the final image to the first?

I would do the calibration (pre-processing) on them then rotate them before using them as part of a single stack with the others.

Mark