Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: Fay on Jul 22, 2010, 18:29:28

Title: M27 in Vulpecula
Post by: Fay on Jul 22, 2010, 18:29:28
20x300 secs, 0.8fr SW120, modified Canon 350D Stacked in DSS.

(http://farm5.static.flickr.com/4080/4818826814_ac0861ba0c_b.jpg)

Title: Re: M27 in Vulpecula
Post by: MarkS on Jul 22, 2010, 19:48:46


Wow! I can see I've got a rival.

That's a great image Fay - good colours, nice round stars, plenty of detail and nicely processed.

A couple of suggestions that might help:
If you make the background less dark you might see some more faint detail. 
Also I would alter the RGB balance to brighten up the blue channel a bit because the modified 350D tends to overemphasize the reds.  I always have to adjust the blue.

Well done.

Mark
Title: Re: M27 in Vulpecula
Post by: The Thing on Jul 22, 2010, 20:11:08
That's really nice Fay. Loads of detail in the nebula.

Referring to Marks comment, just remember that space is not empty, there is stuff in between everything, then it's easier not to hanker after a pitch black background!
Title: Re: M27 in Vulpecula
Post by: Fay on Jul 22, 2010, 22:15:40
Thanks. I have not clipped the black, it was very dark out. I was up until around 1.30. I will have a reprocess & see what happens
Title: Re: M27 in Vulpecula
Post by: Jim on Jul 23, 2010, 08:06:51
That's really lovely Fay, you've set me a challenge now!
Title: Re: M27 in Vulpecula
Post by: Fay on Jul 23, 2010, 08:16:21
Thanks Jim

I have taken the red down a tad

(http://farm5.static.flickr.com/4099/4820597132_d8c5b62868_b.jpg)
Title: Re: M27 in Vulpecula
Post by: RobertM on Jul 23, 2010, 08:42:47
That's lovely Fay, very well processed and a welcome success after the mare you had the night before.  I can't really add that much to that already mentioned but maybe a more general comment that you do tend to process for an inky black and perhaps loose nebulosity because of that.  It is a fine point though as you're obviously getting rather good at processing :)

Robert
Title: Re: M27 in Vulpecula
Post by: Carole on Jul 23, 2010, 08:51:34
Excellent Fay, I am now starting to see the difference of a modded and unmodified DSLR.
One question, what is the reason for the red rings around the stars?

Carole
Title: Re: M27 in Vulpecula
Post by: MarkS on Jul 23, 2010, 09:02:48

Fay,

It looks very similar in style and quality to today's APOD:
http://antwrp.gsfc.nasa.gov/apod/ap100723.html

Mark
Title: Re: M27 in Vulpecula
Post by: Fay on Jul 23, 2010, 09:03:55
Bad processing I should think Carole. I will have another go Robert & bring the background up a bit
Title: Re: M27 in Vulpecula
Post by: Fay on Jul 23, 2010, 09:12:19
I wish, Mark!!
Title: Re: M27 in Vulpecula
Post by: Mac on Jul 23, 2010, 11:40:31
QuoteOne question, what is the reason for the red rings around the stars?

It could also be that the red channel is just out of focus or saturated, being that its a dslr probably not.
I'd agree probably processing.

Nice image.
Cant wait untill i start again.

Mac.
Title: Re: M27 in Vulpecula
Post by: MarkS on Jul 25, 2010, 11:19:01
Quote from: Carole
What is the reason for the red rings around the stars?

I think this is probably chromatic aberration i.e. the fact the different parts of the spectrum will come to focus at different points.  I used to have the same problem when using the Canon on the ED80 with the William Optics focal reducer. I found that the Ha was always more "blurry" than other parts of the visible spectrum and this would lead to "red rings" around stars.  It might be because that particular reducer is not exactly matched to the optics of that particular scope.

Which focal reducer are you using, Fay.  The Skywatcher one ought to give the best results.

In any case, this was one of the issues that led me to buy an astrograph.  I did this before the Skywatcher reducer was launched for the ED80 so I've never tried that one.  But a mirror-based scope will always have less chromatic aberration than a lens-based scope until you start to pay silly money.

If I am right about chromatic aberration then it only affects colour CCDs because when you are doing narrow-band imaging you will always refocus for the wavelength passed by that particular filter.

Mark






Title: Re: M27 in Vulpecula
Post by: Fay on Jul 25, 2010, 12:56:56
Mark, unfortunately I only have the WO flattener, should be for the ZS66. WHen I toj the red saturation down a bit, the rings went. They probably appeared when I did enhance star colour.  I am waiting for an adaptor to be made so i can purchase a SW 120 flattener for the Equinox