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Rosette - With all the wrong gear (unguided)


Bizibilder
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Attached is last night's attempt at the Rosette - all the wrong gear as it was with an unmodded DSLR, unguided, low down and heading towards the murk above the neighbours houses! Anyway, I had a go and got this image - Quite surprised that I actually managed anything at all!

58mins in 2min subs at ISO800 Canon 1000D, 24 flats and 20 darks, SW ED80PRO on HEQ5 unguided.

It needs a lot more in its favour - maybe next season!!

post-17157-133877559144_thumb.jpg

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Hi.

Thats a lovely image of an object that is dissappearing fast in the west.

To say you were using the wrong equipment, i tend to dissagree there.

I dont have any experience using DSLR,S,but if your camera was modded,i,m sure the colours would have been much stronger.

Take heart,and well done.

Mick.

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Good try and you've got more than you think.. carry on processing.

I just pulled the Red channel curve, if you split the image into HSI rather than RGB and play with the H&S, with full 16bit data you'll get much more than this

Go on.. play!

Derek

post-21647-13387755917_thumb.jpg

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Great result, particularly given that the Rosette is fast disappearing into the West! I had a go at the Rosette myself with my unmodded Canon, and I was very pleased with the result, although it did need at least 3 hours-worth of 5 min subs.

Get that guiding sorted!

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Thanks Derek - but can you explain your terms please? I am a relative newbie to PS and keep falling off the learning curve!!

Luke - I've seen your image of the rosette - very nice! BTW first guided image just taken tonight!!!

Edited by Bizibilder
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The first thing I thought when I saw your image was, "There's a lot hiding in here!" and Derek's processed version confirms it. A beautiful Rosette - well done, I bet you're really chuffed with that, especially for 2 minute subs.

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Thanks Derek - but can you explain your terms please? I am a relative newbie to PS and keep falling off the learning curve!!

Luke - I've seen your image of the rosette - very nice! BTW first guided image just taken tonight!!!

Ok firstly, I used a program called IRIS, it is free but not so widely used.. I'm still getting to grips with new functions despite starting with it over 10 years ago.. new bits keep turning up :-).. There are several other packages, some free, some not. You'll have to choose but it looks like you're ready to benefit from post processing.

RGB/HSI

I'll assume you know RGB, if you plot for a single pixel it's RGB values on a 3D plot you'll get x=R,y=G and z=B, then you can change you're axis so instead of xyz cartesian coordinates you use polar coordiantes.. length,angle1,angle2, or just rotate your cartesian coordinate system through some angle. Once you've done this then you can change the image appearance like you do with the TV, 'colour', 'contrast', 'brightness'.

HSI. Hue, Saturation and Intensity. Intensity is just brightness, Saturation is like the 'colour' button on the TV, zero the saturation and you have a B&W image. Hue is what 'colour' the actual pixel is, be it green, blue purple pink whatever... not how colourful/B&W the pixel is or how bright it is.

Once you have that then you can push the saturation so you reveal what colour you actually have.

Ha Performance

You should also take a glance at EOS40D / EOS50D comparison

This shows the performance of some of the Canon cameras, other makes/models will be similar. Note the performance at 650nm (Ha) with and without the IR block filter.

With a IR block it's QE at 650nm is very low compared to the rest of the red channel, and almost zero compared to the green. Thus it is important to be able to strengthen the nebula colour in the red channel without disturbing the rest of the image.

Curves..

a curve means the intensity of all the pixels are changed such that some non-linear realationship is applied. i.e.

new_pixel_value = log(old_pixel_value)

or

new_pixel_value = old_pixel_value * M + sqrt(old_pixel_value) * N

etc.

Here you could 'play' with the constants M & N... usually in software these values would be on sliders to make it more intuitive.

By applying a 'curve' to the red channel what I did was to enhance the mid level Red leaving the bright and dark reds where they were. Thus this is a crude fix for the poor Ha problem. A much better fix would be to make a star layer, remove that from the image leaving the nebula, then boost and colour correct the nebula, then add the stars back in... There are some excellent walkthroughs in the imaging techniques section of this forum, please take the time to read through them, they will help with star layers.

I hope I haven't lost you.

Derek

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No, you havn't lost me - thanks for the descriptions. I will add them to my ever increasing pile of notes and tutorials to be read through and followed!!

I do have IRIS installed but for some reason I can't get the command line box to open - I think it may be time for a delete and reload!

Thanks.

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No, you havn't lost me - thanks for the descriptions. I will add them to my ever increasing pile of notes and tutorials to be read through and followed!!

I do have IRIS installed but for some reason I can't get the command line box to open - I think it may be time for a delete and reload!

Thanks.

Ah! yup I've had that problem

Command line button looks like:

==>

==>

right next to the button that looks like a camera.

If you've opened it once on a dual screen setup and placed it on the other screen, then you standby and restart (not turn off) but with the other screen missing, the box stays on the other screen even though it isn't there, so you can't see it.

Solution:

plug in the other screen.. and just to add insult to injury, if the box is on the left screen, and your new screen pops up on the right, (as per M$ default) then you have to shift the new screen across to the left, then you see the box and can move it onto the centre screen.

I've spat blood over that bug.

Derek

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I just went back to the IRIS webpage looking for something else.

Just below the download bit is

"If after a new installation of IRIS some dialog box disappear, do not panic: (1) exit IRIS, (2) delete the IRIS.INI file in the WINDOWS directory, (3) re-run IRIS. "

Hope this helps

Derek

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