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Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: Carole on May 22, 2011, 15:03:47

Title: M27 Dumbbell Nebula
Post by: Carole on May 22, 2011, 15:03:47
I had intended to do 5min subs but I had to reduce the length to 3 1/2 mins in order to image between the gaps in the clouds, so I was suprised to get this from only 3 subs last night (several had to be discarded due to clouds).

3 x 210 secs + darks flats and Bias  800 ISO
ED120 and Modified Canon 450D + CLS Filter
Guided on NEQ6

Planning to add to this as and when:

(http://gallery.orpington-astronomy.org.uk/albums/userpics/10047/normal_M27_21-5-11_3_x_3mins_31_secs.jpg)
Title: Re: M27 Dumbbell Nebula
Post by: MarkS on May 22, 2011, 15:24:39

Very nice Carole.  I can't believe it is only 3 subs!

With a CLS filter, M27 is a very worthwhile target - even from a light-polluted location.

You have lovely round stars and quite a lot of nebulosity.  However, I think you overcompressed the jpg.

Mark
Title: Re: M27 Dumbbell Nebula
Post by: The Thing on May 22, 2011, 16:04:34
That's super Carole, like I said on the other thread, it was worth it last night.
Title: Re: M27 Dumbbell Nebula
Post by: Carole on May 22, 2011, 16:12:54
QuoteHowever, I think you overcompressed the jpg.
I'm not quite sure how you can overcompress a Jpg, but I did use a couple of Noel's actions on it and I think that automatically compresses to 8bit (which I did not realise).  

I did wonder whether I might have slightly overprocessed it and was waiting to see what you guys said.  

I am hoping to add more to it, so will not worry too much about trying to improve this image as I'll have to start stacking and processing again anyway.

Thanks Duncan and Mark.

Carole
Title: Re: M27 Dumbbell Nebula
Post by: MarkS on May 22, 2011, 16:30:28
Quote from: Carole
I'm not quite sure how you can overcompress a Jpg

Generally speaking, when you create a jpg there is a dialog box available somewhere that lets you control the quality i.e. the compression.
Title: Re: M27 Dumbbell Nebula
Post by: Fay on May 22, 2011, 16:35:59
That has come up well Carole
Title: Re: M27 Dumbbell Nebula
Post by: Carole on May 22, 2011, 16:42:05
Thanks Fay,

QuoteGenerally speaking, when you create a jpg there is a dialog box available somewhere that lets you control the quality i.e. the compression.
Ah yes, well generally I don't tend to alter that unless I need to create a small file for some reason (and definitely not images, I just let it go on autopilot).  Maybe I should lift the level for images.

Carole
Title: Re: M27 Dumbbell Nebula
Post by: RobertM on May 22, 2011, 19:17:02
That's lovely Carole, you must have been up quite late for that one...
Title: Re: M27 Dumbbell Nebula
Post by: Carole on May 22, 2011, 19:30:50
Quoteyou must have been up quite late for that one...
Yes I was Robert, I started off doing M57 (but I need to get a lot more data). 

Can't remember now why I changed to M27, I think it was due to cloud positions.  Went to bed at 2.30am.

Carole
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