Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: Daniel on Oct 11, 2008, 20:37:05

Title: M45 14x300s ISO 800
Post by: Daniel on Oct 11, 2008, 20:37:05
Hi all, here's another from last night, Believe it or not, I've always failed at getting a decent image of this one, so finally, I've got a decent amount of nebulosity coming through.

Anyway, setup was same as with rosette nebula except with only 14 subs this time (had 2 hours on it, but came out to find it had been in meridian flip for an hour!)

Daniel
:O)

(http://farm4.static.flickr.com/3196/2932484568_e93db9e070_o.jpg)
Title: Re: M45 14x300s ISO 800
Post by: RobertM on Oct 11, 2008, 21:27:25
That looks excellent, might try that myself when it gets a bit higher in the sky.  What are the black blotches on the left had side ?
Title: Re: M45 14x300s ISO 800
Post by: Daniel on Oct 11, 2008, 21:57:54
Hmm, i noticed those too, not sure, actually I had a few anomalies with this image which i got rid of, some strange green blob things, no idea what they were either. also I might post a sub I took attempting to image the witches head last night, 3 bright objects in close proximity to eachother passed through my sub, normally, i'd think this was just an aircraft,(wing, tail lights) but they were still travelling through shot about 3 minutes later. anyway, I'll post it later to see what you all think.
Title: Re: M45 14x300s ISO 800
Post by: Fay on Oct 12, 2008, 09:51:02
You certainly try hard Daniel. Very nice, I wonder what the little black blts are as well. Bits & pieces that appear on images are a right pain! You rarely get off scott free!

I don't know how you & Robert, Mark etc get up for work in the morning
Title: Re: M45 14x300s ISO 800
Post by: JohnP on Oct 12, 2008, 13:49:24
Fay - colour balance looks OK on this... The black dots are very weird though & there are lots of them.. Are they on the individual subs? John
Title: Re: M45 14x300s ISO 800
Post by: Fay on Oct 12, 2008, 14:31:49
John,

I am thinking you think that M45 is mine, as I replied before you. It is Daniel's M45
Title: Re: M45 14x300s ISO 800
Post by: Rocket Pooch on Oct 12, 2008, 14:47:44
John they are because the software have taken dark from the subs and now there is - or 0 values, Fay use clone stamp in photoshop you can get rid of these easily.

chris
Title: Re: M45 14x300s ISO 800
Post by: Fay on Oct 12, 2008, 15:47:15
Chris. it is Daniels image
Title: Re: M45 14x300s ISO 800
Post by: JohnP on Oct 12, 2008, 16:09:19
OK - It's Daniels's... Sorry... John
Title: Re: M45 14x300s ISO 800
Post by: MarkS on Oct 12, 2008, 16:53:12

Daniel,

That's a great image.   The nebulosity looks good.  Did you use any filter?

As Chris says, it is caused by the dark subtraction.  Best way to get rid of those black spots is to use sigma stacking.  A cut-off of 2.5 or, failing that 2.0 should getr rid of those specks.

Mark
Title: Re: M45 14x300s ISO 800
Post by: Daniel on Oct 12, 2008, 17:04:31
Thanks guy's, i'll have to try re-stacking then. I used a CLS on this, but friday night was quite special, I can rarely see all stars in cassiopeia, but that night they were all quite visible.

Daniel
:O)
Title: Re: M45 14x300s ISO 800
Post by: RobertM on Oct 13, 2008, 17:09:14
I think this helps explain why the dark specs appear on the dark subtracted image.  They could be due to lighter specks on the darks see the following page for a possible explanation http://www.narrowbandimaging.com/dark_spikes_page.htm (http://www.narrowbandimaging.com/dark_spikes_page.htm)