Cocoon Nebula. Some questions

[MattJenko]

Hi,

I managed a run on the Cocoon nebula last night, but in my haste didn't plan on needing to do a flip after about an hour... This post therefore contains multiple questions:

- How do you manage flips - do you rotate the camera after the flip and try and get it as close as possible during the run? Do you simply carry on with no interference and then flip all the images after the fact? How do you manage to ensure the framing remains at least vaguely consistent, as I like the framing in the pre-flip, but after, most of the dust lanes were out

My answer at the moment is that I am going to simply avoid flips in future!

Here is my pre-flip image: 10 x 300s with a previously shot library bias and dark. No flats, had too many issues with them in the past, I just manually processed the gradient out using a dupe image subtraction. ED80, HEQ5, modded Canon 450D - guided.

My question on the image is that I would like some feedback, as I still think I have overdone this and its all too sharpened, too processed, but I would like some honest feedback.

Thanks for looking.

[RobertI]

Hi Matt, I can't answer any of your questions but that looks like a superb image to me! 

[johnrt]

This might not help but my capture software Artemis lets you drop markers to highlight bright stars and then when you flip just rotate the image on the screen 180 degrees and line up with the markers and off you go again. Learning a routine that works for you when flipping is pretty important as if you want to spend some serious imaging time of a target flipping is pretty much unavoidable I'm afraid.

[MattJenko]

Cheers Rob. I am certainly pleased with it and the flipped version, although the one after the flip is not framed as well : http://www.astrobin.com/full/130076/0/

The second image was with a lower ISO - I forgot to turn the iso down for the first image

John - I had a sinking feeling that dealing with flips is something to get used to. I am using EOS utility on my Mac as my Canon capture software, so nothing fancy like Artemis. I also don't want to spend $150 on Registar right now either. My imaging runs to date have been no more than an hour or so really, I haven't had the ability or the weather to do long ones yet, although last night was to be my first multi hour session, but the clouds rolled in at 1am ending that hope. This means flips have never been an issue to date. I will be trying again on Tuesday and assume that for me, for now, flip-avoidance is the way forward. Thanks.

[libraryman]

I'm sure the term "(Flipping Eck)" was coined by an astro-imager...it's a nuisance to be sure, i don't touch the camera, my view is that flats would suffer..rather i rotate them in processing.

I believe that one way to delay the flip would be by going weights up before it crosses the Meridian, something that i am just trying to get my head around..i have tried it but my guiding suffered somewhat.

Nice image, my preference would be for a little star reduction but i am far from the best person to post an opinion on image quality.

Ray

[lensman57]

Hi,

I managed a run on the Cocoon nebula last night, but in my haste didn't plan on needing to do a flip after about an hour... This post therefore contains multiple questions:

- How do you manage flips - do you rotate the camera after the flip and try and get it as close as possible during the run? Do you simply carry on with no interference and then flip all the images after the fact? How do you manage to ensure the framing remains at least vaguely consistent, as I like the framing in the pre-flip, but after, most of the dust lanes were out

My answer at the moment is that I am going to simply avoid flips in future!

Here is my pre-flip image: 10 x 300s with a previously shot library bias and dark. No flats, had too many issues with them in the past, I just manually processed the gradient out using a dupe image subtraction. ED80, HEQ5, modded Canon 450D - guided.

My question on the image is that I would like some feedback, as I still think I have overdone this and its all too sharpened, too processed, but I would like some honest feedback.

Thanks for looking.

That is a great image, well done. The only software that I know that is capable of stacking with a flip is Nebulasity, there is a setting like rotation and something that does the trick. I too am very reluctant to spend  the money on Registarthough it does the job very well all accounts.

A.G

[andrewluck]

You don't say if your mount is computer controlled using EQMOD (this is the HEQ5 you're talking about?). If not, then this is the way to go as it makes this sort of problem go away. A plate solving program such as Pinpoint or Astrotortilla used with EQMOD enables you to:

1. Find your target easily with a slew, plate solve, sync re-slew process
2. Re-centre to the same point as a previous image. Plate solve the previous image, slew, plate solve, sync and re-slew

Some people use rotators to re-locate the guide star post flip. As previously pointed out though, this does cause problems with the flats. Otherwise, pretty much any stacking software will be able to cope with flipped images. An Avalon M-Uno could relieve you of the requirement for flips but the outlay is considerable.

As for the processing, my preference would be for less sharpening in the stars as they look rather harsh and a little more smoothing in the dark nebula. However, these are minor points.

Andrew

[MattJenko]

Thanks Andrew, I use a Mac, so use EQMac and PHD, so no plate solving software that I am aware of. I take your point about the sharpening, think this is too bright and in your face a bit. Will have another go and try keep it smoother and see how it looks.

[MattJenko]

Here is a less aggressively sharpened image, which I have to say, I prefer. How would I go about experimenting with smoothing the dark nebula areas?

[ollypenrice]

I can't be bothered with trying to get plate solving to work so I do flips by eye. I take the pre-flip image and rotate it 180 in a software that shows it stretched and clearly visible. I then align the post-flipped image to that by eye. I don't want to get confused wth my darks and flats being at 180 so I don't do any screen rotations. Software fans will do things otherwise. If one day they tell me how they do it then I might try it!!

lly

Edit, Ooops, should have said, you have a nice Cocoon there. Do forgive me. I'd drop the saturation a bit on the main nebula and the background sky, but not the stars. You have all those field stars nice and tight and, yikes, they are a problem on this target because they can really dominate. But your good craftsmanship has kept them under control.

[andrewluck]

Much better star colours in the new version and they're a lot less obtrusive.

For the dark nebula there are a couple of things that can help. There's not much signal in there so you want to avoid boosting the colour saturation in these areas as you'll just be emphasising chromatic noise. A layer mask will help here. If you're using Photoshop then duplicate the layer and then copy it into a layer mask on the new layer. Adjust the levels on the mask if required then apply a gaussian blur to the mask. After that, apply your colour saturation/vibrance adjustment. The black areas in the mask will be affected less.

If required you can invert the layer mask and apply a slight gaussian blur to the image, this will smooth the darker areas of the image and help reduce noise.

Avoid sharpening the darker areas of the image. I also prefer to avoid sharpening the stars at all. This image would suit the application of a high pass filtered 'overlay mode' layer on top which you can paint into the image over the nebula, again using a layer mask.

Olly, Is there a tutorial for these techniques here already?

Andrew

[MattJenko]

Thanks for the advice and positive feedback. I have tried out a couple of the suggestions and left the saturation much lower. This version is more muted, but nice in its own right. No one right way to do this is there!

[andrewluck]

Gets my vote.