Sunday, January 30, 2011

Go Long! (in focal length)

Been a bit since I've posted - not for lack of trying.  I've been pounding sand trying to get my head around image processing ultrawide field images.  That would be an essay for another day ... suffice it to say that it has been, ah, challenging.

By ultrawide field I am talking about 24mm or less (lens f.l.).  Unless you are in the Atacama desert there are challenging light pollution gradients to deal with.  That and a whole host of other processing details I've been largely unsuccessful at dealing with - largely related to DSLR imaging.

So I decided to take a break and go "long".  For me that is all the way back to 100mm f.l.  Taking in mere degrees of sky feels like drinking from a teacup.  But oh how much easier it is to process the images!  I imaged Orion's belt and sword for much of the outing and then took just 30min of the M46, M47 region to finish off the night. 

M46 and M47 and a host of Open Clusters.  Click for ginormous* or here for flickr.
* ginormous - a favorite word of mine.  I come to find out that it is now (as of 2007) officially recognized by Merriam Webster dictionary.  For international visitors, it is a neologism - a word made from a combination of two words.  In this case "gigantic" and "enormous".  I will now feel free to use it frequently and without shame.

One of my observing pals, Dan, had M46 centered up in his 10" Meade outfitted with a binoviewer.  A visual treat with the little planetary nebula floating inside the spray of open cluster stars.   Been a while since I've actually done any visual observing and I'm glad I have friends to keep me honest.

So naturally, after he left, my dark imaging nature took over and I decided to try and take a picture of it.  I figured there was little chance of capturing the planetary at the image scale I was working at but if you drill down, sure enough, there it is.

Click image and look for the tiny green-blue dot in the upper cluster (M46).  That's the planetary nebula.  Cool.
This whole area is littered with open clusters.  Other than some admittedly spectacular exceptions I was never fond of looking at open clusters visually.  Taking pictures of them are somewhat more fun - at least they seem easier to pick out from the background stars.  Below is an annotated version.

click for full size or here for flickr
I may have to re-think my strategy for shooting ultra-wide.  I thought I would save time and effort by shooting single frames with a wide angle lens but I think I am now going to pursue doing mosaics.  That will bring it's own set of, ah, challenges, but I don't call this place Cilice for nothing.

Taken at Montebello Open Space Preserve, CA  January 27, 2011
Canon T2i (stock), Canon 100mm f/2.8L Macro IS USM @ f/4
Astrotrac Travel System Mount
15 120sec exposures @ ISO800
32 darks
no flatfielding, vignetting and gradients removed in PixInsight
128 bias frames
calibration, registration and post-processed in PixInsight

Monday, January 3, 2011

Cassiopeia to Taurus

Here is another widefield taken back in October at the Calstar event.  One great thing about astrophotography is that you can take data quicker than you I can process it.  This provides endless hours of "fun" back home when the rain clouds come or the moon visits.

Of course this can be mitigated with a proper understanding of the underlying principles of detector physics and processing methodology.  Combine this understanding with a smooth efficient workflow and now you can drastically shorten the time from camera to presentable image.  I'm not anywhere near that point yet so, well, there you go.

The more I learn the more how much I realize I dont' know.  Being curious by nature (and not a little bit obsessive) this drive me nuts.  So many variables and branch points along the way.  So many ways to attack the problem and so much equipment and software tools to throw at it.  Science, hardware, software, art, wonder, ... what's not to like!

This was taken with the 10-22mm EF-S lens at 14mm and stopped down to f5 to mitigate the worst of the vignetting and corner aberrations.  My camera isn't modified to have the IR cut filter removed so the hydrogen alpha regions are muted but even so there is a hint of what lies in those star clouds.  Also evident is intersteller de-blueing (or intersteller reddening if you like) which results in stars located in the dense Milky Way arm appearing redder than they actually are .  Open clusters galore and a couple of our closest galactic neighbors.

There is even a very special guest appearance by Comet Hartley-2 which was visited by the re-missioned Deep Impact (EPOXI) probe not long ago.  Here is a extra credit question for the nerds out there.  Can you guess the date the image was taken by the location of the comet?  Answer below in the image info.  We'll see Hartley-2 again in 2017 as he continues his rounds of the solar system.

Cassiopeia to Taurus.  Click image to see at full res.  Click here for flickr.
If you want to see a version without yellow text all over the place click here.

I have a couple more widefields yet to process along with a couple hours of M33 data sitting in a unopened folder.  Moon?  Rainclouds?  I can get my astronomy fix with or without you!

Taken at Lake San Antonio, CA  October 9, 2010
Canon T2i (stock), Canon EF-S 10-22mm @ 14mm  f5
Astrotrac Travel System Mount
33 120sec exposures @ ISO1600
128 dark frames from my library
no flatfielding, vignetting and gradients removed in PixInsight
128 bias frames
calibration, registration and post-processed in PixInsight