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Elephants Trunk Nebula in Ha

Paxo

By Paxo
in Imaging - Deep Sky

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Paxo

Paxo

Posted
Posted

Finally a reasonably clear, but damp, evening. Having seen the magnificent efforts of others on this forum of this subject, I thought I would give it a go in widefield. Managed 45 minutes worth of data before clouds were spontaneously appearing, finally one overhead where I was imaging 9 minutes into a 10 minute sub. Details:

Scope : WO Megrez 72 with Meade 0.63 Focal reducer

Camera : Atik 314L

Filter : Astronomic Ha 13nm

Software : Artemis Capture

Sub length : 600 seconds (x4)

300 seconds (x1)

Guidescope : WO FLT110

Guidecamera : Meade DSI II Pro

Software : Phd

Sub Processing : DSS and PS

8148_normal.jpeg

(click to enlarge)

Pleased with how this turned out (apart from a minir issue with filtr CCD spacing causing rings round the bright stars) as it was an imaging experiment using a focal reducer with what is usually my guidescope. All I need is another clear night to have another go in colour at a little higher magnification.

Steve..

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RobH

RobH

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Nice widefield Steve :clouds2:

I'm sure we can all relate to losing exposures at the last minute due to that pesky cloud !

The rings are common when using NB filters. I get the same.

Apparently the Astrodon filters have anti-reflective coatings which minimise this, but Astronomik don't.

You can reduce the size of the ring by moving the filter closer to the chip in theory, but in practice this isn't always possible.

The big one on your image has been made worse I suspect when you've stretched the image. This has also stretched the ring.

Try stretching the image by very little, then select the ring only, and reverse the curve you used to stretch the image. Do several iterations of this and you'll minimise the effect of the ring....you'll need to experimant as each image will obviously need a different approach.

To make it easier, and make sure that you don't leave an obvious line, feather the selection by a couple of pixels (CTRL/ALT/D)

You can hide the 'marching ants' selection line by using CTRL/H.

Cheers

Rob

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Paxo

Paxo

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Thank's for the tip Rob, greatly appreciated. With my set up it is impossible to get closer to the ccd so it looks like the processing option (as I've just checked down the back of the sofa and didn't find £800 for a full set of Astrodon filters :mrgreen: , but I did find a fiver I thought I'd lost/spent). I actually did very little post processing on this one, got some work to get out of the way this morning :clouds2: , might get a chance this evening (as it doesn't look like I will be imaging at any rate) to hone it a bit better.

Steve..

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RobH

RobH

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£800 for a set of Astrodons....ouch :)

Weather here is lousy too.

The rings are pretty easy to lose if they're not sitting in nebulousity, as you just pull them back with curves, and can then get rid of them completely by carefully using the clone tool.

If they do sit in nebulousity though, it's a bit more tricky.

I took some close up shots of the bubble on Saturday and had my first look at them last night. I have one of those rings right in the bubble itself so I'll be experimanting for a while trying to get rid of it I expect....it's how you learn though :clouds2:

Cheers

Rob

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Paxo

Paxo

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Thanks for the comments.

Had a couple of hours between jobs so managed to sit and get some processing done. Managed to increase the contrast and eliminate out the halo's. Definately an improvement :clouds2:

8150_normal.jpeg

(click to enlarge)

Steve..

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Whippy

Whippy

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That's quality Steve, like it lots :clouds2:.

I read somewhere that the 13nm does (or can) leak IR which causes the Halos and that it can be cured by adding an IR block filter with the Ha. If this is true or not, I'm not sure but I'll give it a go next I'm out as I got halos doing the Pacman neb with my ZS66.

Tony..

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Paxo

Paxo

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That's the one Steve...loads of detail there :clouds2:

Tony, I didn't realise that about Ha filters....interesting, I'll stack an IR blocker and have a play too.

Cheers

Rob

Thanks from me too Tony, plausible I suppose with near infrared (IR-A) @ 700 nm–1400 nm . All we need is for the cloud gods to ply ball to try it Rob.

Steve..

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Whippy

Whippy

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Indeed Steve, it's plausable although I haven't noticed any halos when doing HA with my ZS110. Perhaps it's maybe a focal length/ratio issue in that a faster or shorter scope may cause it? I have not got a clue, but next time it's clear we shall see...

Tony..

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