Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: Whitters on Apr 25, 2011, 13:28:36

Title: Whales and Hocky Sticks
Post by: Whitters on Apr 25, 2011, 13:28:36
NGC4656 and NGC4631 otherwise known as the Hocky Stick and The Whale.
Scope William Optics 110mm f6.5
Camera Starlight Xpress MX916
Filter Astronomics IRBlock
Date 24-04-2011 23:04 GMT
Subs 600 seconds
Total integration 25*600 - 4Hours 10minutes
Processing  Sigma stack, DDP, and curves and Levels

Dissapointed as the focus was rather soft

(http://www.astrocats.co.uk/Astronomy/Images/MX916/2011_04_24/NGC4565_NGC4631.jpg)
Title: Re: Whales and Hocky Sticks
Post by: doug on Apr 26, 2011, 08:56:36
Wow, Paul!  That looks like well deep sky stuff.  Whereabouts are they in our polluted skies?   

Doug.
Title: Re: Whales and Hocky Sticks
Post by: MarkS on Apr 26, 2011, 09:08:46
Paul,

That's a great capture. 

I don't think the processing does it justice, though.  I can't put my finger on the exact cause but the background looks too black and the transition zone from the "whale" and "hockey stick" to the black background looks very pixellated/posterised.

Mark
Title: Re: Whales and Hocky Sticks
Post by: Mike on Apr 26, 2011, 10:02:57
Yeah somethings not right. Its very noisy for that amount of subs and the stars are rugby ball shaped. Also, as Mark said, it has a pixelated look to it, especially around the edges of the galaxies.
Title: Re: Whales and Hocky Sticks
Post by: JohnP on Apr 26, 2011, 11:33:56
Paul - that's a potentially very good image although looks like something definitely not right with your processing. I ditto what Mark has said - for that length of exposure & from your dark location I would expect a beautifully smooth, noise free image - looks like something weird has happened with processing.

John
Title: Re: Whales and Hocky Sticks
Post by: Whitters on Apr 29, 2011, 22:59:15
I will have another go at the processing this time not using the DDP but the focus was very soft, the FWHM was very high on the raw images, much higher than in my previous images with the same setup. I think some of it was my mistake but the seeing was very wobbly that night. This was the main reason for not taking too much time on the processing, but I will have another go.

Doug to answer your question they are in Canes Venatici and they are really quite bright around mag 10.5 with a surface brightness around 14. The only tricky bit was finding a guide star that was bright enough.