The North American and Pelican Nebulas in Color

In the last week I've had two wonderful clear dark skies to get out and photograph this gem that crosses the zenith around 10:00pm this time of year (August).  As previously photographed, these aer the pelican and north american nebulas shot through my Takahashi E-160 telescope and my modified canon 350d.  The first shot is a hydrogen alpha only photograph:

Click on this thumbnail to see the full resolution photograph.  The deep thick knots of nebulosity here show up as almost white.  Using a deep red hydrogen alpha filter I am able to reject all sources of light pollution and isolate just the nebula itself, this results in a very very rich nebula field in a fairly short exposure.  This is a grand total of 15 minutes exposure time.  Both of these nebulas are visible to the naked eye in VERY dark skies just to the southeast of the bright summer star Deneb. 

Next up is the same photograph only shot in color.  Whenever I post a color photo like this the immediate response is "cool!  will I see that in my telescope?", the answer sadly is no way in hades!  Reason is is that this is a very dim nebula with all of its surface brightness spread out over a very large area.  Because of this, your eye will tend to see grey, this is the natural tendency of our eyes when faced with discerning the shape or color of a very dim object.  However, long exposure photography solves this dilemna for us as the camera serves to collect light over a long period of time giving us all the glorious detail seen in this photos.  This is a 42 minute total exposure time.  Six individual 7 minute photos were combined in photoshop to generate this image.  I've been asked before how come I don't just take a 42 minute exposure and why go through the process of compositing so many sub exposures?  Answer is simple, these images all build up noise on the sensor (all electronic light sensors build up noise, unwanted grain shows up on the image), by layering them you increase the signal to noise ratio, in other words, the more photos, the more nebula, and the noise is random, so it ends up cancelling out all the noise of the other images, so you end up with a nice smooth background.  There are some wonderful tutorials on this on the web.  Next up is the trifid and lagoon nebulas, a colorful section of the sky with both red hydrogen alpha emission and blue reflection nebulas intersected with dark dust lanes.

Comments

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There are some wonderful tutorials on this on the web. Next up is the trifid and lagoon nebulas, a colorful section of the sky with both red hydrogen alpha emission and blue reflection nebulas intersected with dark dust lanes.

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It is beautiful!!!