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Advice needed


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I am just starting out with astrophotography. I have tried imaging M81 and M82 but the images look very over exposed and after putting them through DSS the TIF file is almost completely white. I realise that I need to edit it in photoshop but as a complete beginner I am not completely sure what way to go or if it is (as I suspect) so over exposed that it is a lost project. If I adjust the levels the image becomes pink.

Any help or advice would be greatly appreciated.

 

Screen Shot 2017-05-07 at 14.11.53.png

Screen Shot 2017-05-07 at 14.10.45.png

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Are you imaging from a light polluted location?

If so this would explain how you have ended up with such a bright background.

The data doesn't appear to be clipped though so you should be able to get something respectable by adjusting the channels individually to bring the red into line with the blue and green and setting the black point.

Use both levels and curves to improve the faint bits without making the background too bright.

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15 minutes ago, D4N said:

Are you imaging from a light polluted location?

If so this would explain how you have ended up with such a bright background.

The data doesn't appear to be clipped though so you should be able to get something respectable by adjusting the channels individually to bring the red into line with the blue and green and setting the black point.

Use both levels and curves to improve the faint bits without making the background too bright.

The light pollution isn't too bad. The moon was bright though so maybe that has contributed. I didn't align the channels so will try that. I took 5 minute exposures so might try 3 minute next time to see if that makes a difference.

14 minutes ago, newbie alert said:

Did you align the peaks in dss

 

No. I am re-stacking now so will try that. Thanks.

 

9 minutes ago, newbie alert said:

Or could be light pollution from street lights or the moon...on a thin high cloud..is your camera modded?

Camera is not modded. I wanted to experiment a little before taking the plunge.

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It's quite normal with DSS to get a very pale image afterwards. So don't be alarmed by that.  

What length subs did you do?  I suppose it could be possible you have washed them out.  It is easier to advise if you post up what equipment you are using and what length subs, and if a DSLR what ISO etc you are using.

Carole 

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1 hour ago, newbie alert said:

No. I am re-stacking now so will try that. Thanks.

you don't need to restack,just find the auto save file..

There is no need to restack,  just open the autosaved file with dss.  On the processing part choose open picture file then  press the reset buttom and adjust the rgb sliders as mentioned above. 

Edit: quoted the wrong post,  but newbie alert has mentioned it already :)

Edited by Atreta
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17 hours ago, carastro said:

It's quite normal with DSS to get a very pale image afterwards. So don't be alarmed by that.  

What length subs did you do?  I suppose it could be possible you have washed them out.  It is easier to advise if you post up what equipment you are using and what length subs, and if a DSLR what ISO etc you are using.

Carole 

The equipment was SW 80ed (St80 guide scope), Cannon 450D unmodded. 5 minute exposures with ISO 800.

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I live in the suburbs of London, and am very light polluted and 5 minute exposures with a DSLR 800 ISO is standard and should be just fine, so I doubt the subs are washed out unless you have some local bright lights.  

Carole 

 

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3 hours ago, happy-kat said:

On the camera where was the histogram peak on one of your subs?

Very nice first image :-)

I didn't check on the camera. Here is one frame in photoshop. What should I be looking for? 

Screen Shot 2017-05-09 at 14.55.47.png

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That's is over exposed. You want the peak pretty much the mirror opposite of what you have I think, looking for a clear edge from the left. 800 iso would be worth trying next time.  There are some histogram examples by waxtuser.

Edited by happy-kat
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Well done. Once you've aligned your colour channels (which you can do in DSS though I'd use Photoshop) the principles are these:

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Firstly move the black point slider to the right to meet, at least, point 1 which is the start of the data line. (In fact I'd move it to about point 2 in this case because that long flat line on the left is your over-bright background. However, be very careful not to get it too close to the left hand side of the peak because, if you do, you will 'black clip' precious faint data.

Secondly, move the white point slider (the one on the right) to point 3, again so that it reaches the start of the data line. These are your stellar cores, usually.

Setting the black and white points to the start of your data lines on the histogram means that you will be able to exploit the full range of brightnesses available on your screen.

Thirdly you can begin to 'stretch' the image. The easiest way is to move the mid or grey point slider to the left (4). After each stretch go back to Levels to check the black and white points and the data line. As you become more ambitious you can stretch in Curves rather than  Levels and create custom stretch curves of your own.

You made a great start.

Olly

 

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