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Rosette Nebula

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發表於 2008-1-1 12:06:20 | 顯示全部樓層 |閱讀模式
Inspired by Andy's great attempts, I have given it a go at this object over the past two nights while weather permits. Below are two images in a more traditional palette. Not sure if I've over-processed the images. Comments are most welcome. I have much to learn...

Here are some technical details.
Image #1: EF300/2.8, Ha=12x600s, O3=6x600s, S2=6x600s
Image #2: EF600/4, Ha=13x600s, O3=3x600s, S2=3x600s
Both: EM-200, ST-2000XM self-guided, Astrodon filters
Rosette HOS 20071230_1p5.jpg
Rosette HOS 20071231_1p3.jpg
發表於 2008-1-1 12:56:44 | 顯示全部樓層
Hi Angus,

Nice to see your great work! Both yours and Aandy's are just simply splendid and stunning. I would prefer sharpen a bit more for your version but this just the personal preference.

Cheers,

Eric
發表於 2008-1-1 13:20:46 | 顯示全部樓層
Great shot! Would be interested to see your Ha images.
 樓主| 發表於 2008-1-3 10:01:46 | 顯示全部樓層
Thanks for the comments.

Andy, this is already narrowband with all 3 channels. I just used Ha for red, so it appears very different from your version.
發表於 2008-1-3 12:02:33 | 顯示全部樓層
原帖由 anguslau 於 2008-1-3 10:01 發表
Thanks for the comments.

Andy, this is already narrowband with all 3 channels. I just used Ha for red, so it appears very different from your version.


I meant to show only the Ha.
 樓主| 發表於 2008-1-3 23:54:59 | 顯示全部樓層
Andy, as per your request, below are the Ha images. I have shown the original data with less processing and lower contrast. There are still quite a lot of "black holes" if you look closely.
Rosette Ha 600s 20070330 p1.jpg
Rosette Ha 600s 20070331 p1.jpg
發表於 2008-1-4 04:29:12 | 顯示全部樓層

回復 6# 的帖子

I used EM200 and SXV-M25C One-Shot Camera to take this 720s image with Bin 2x2 with dark and flat subtracted.  Only one 720s image  was used, no stacked.

How can I get rid of the vignetting on the right?
The gradient on the left is from the dark frame.  How can I get rid of it?

On the brighter star, there seems to be some blooming and a glow around it.  How can I get rid of them?  Or it is a lens alignment problem with my scope and camera?

When I open the FITS file in Photoshop with the FITS Plug-in, I want to save it as JPEG for posting here.  It was not an available file format to be saved.  What can I do?  I can only save it in GIF file from Photoshop CS2 "File-Save for Web".

[ 本帖最後由 ultraman 於 2008-1-4 10:08 編輯 ]
Rosette_Nebual_Ha_Sky90_Red.gif
發表於 2008-1-4 09:36:34 | 顯示全部樓層
Angus, thanks for the information. Now I know how much data can be acquired in a F2.8 system and a little longer exposures.

Tommy, why don't you open another post and start from there?
 樓主| 發表於 2008-1-4 12:10:31 | 顯示全部樓層
原帖由 ultraman 於 2008-1-4 04:29 發表
I used EM200 and SXV-M25C One-Shot Camera to take this 720s image with Bin 2x2 with dark and flat subtracted.  Only one 720s image  was used, no stacked.

How can I get rid of the vignetting on the r ...

Ultraman, let me try to comment on your several queries:

1) flat-fielding should get rid of vignetting if done properly. How did you do it? You mentioned you subtract the flat? If you really mean that, its not right since flat should be divided. There are no easy ways to do flat-fielding in Photoshop. Did you use other software? I use ImagePlus. Many others use MaxIm DL or others.

2) If you get a "gradient" from your dark. You should also get it on your light frame. After you subtract the dark, your light frame should look fine. If the "gradient" only appears on your dark frame, may be there is something wrong. You should check your procedure. On the othe hand, its  a good idea to take multiple dark frames and than average or median combine them to form a master dark before use. Similarly for flats.

3) Glow around bright star is kind of normal. You can reduce the "glow" by various methods. I found the easiest to use photoshop actions by Noel Carboni (http://actions.home.att.net/Astronomy_Tools.html). I highly recommend his tool set, very useful. I can't see any obvious blooming on your image. If there are, you can remove it manually or use some tools to assist.

4) I usually just use Save As in photoshop to save my files. Note that you need to set the mode to RGB and 8-bit before you can save as jpeg in earlier versions of photoshop.

On the other hand, I also found Russell Croman's GradientXTerminator (http://www.rc-astro.com/resources/GradientXTerminator/index.html) an indispensible tool to remove gradient - which is very serious at my site. Without proper dark, flat and gradient removal, you cannot bring out all the details in your image.

Hope this helps.

[ 本帖最後由 anguslau 於 2008-1-4 12:14 編輯 ]
發表於 2008-1-4 13:07:19 | 顯示全部樓層
Tommy,

1, How did u take your flats? Can you show us the image?
2, How did u take your darks? Can you show us the image?
3, M25C should be ABG therefore you will not get any blooming.
4, Using the PS Tools is straight forward but somehow uncontrolable therefore I found only some of the items are usable.
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