Tuesday, August 31, 2010

Pale Blue Dot

I processed another image last night.  This morning I showed it to my 6 year old daughter and asked her what she thought of it.  After some thoughtful consideration she said, "it's the Earth".   Kids always see the the obvious.

"Earth"  aka M27, the Dumbell Nebula
When she said that I was reminded of the "Pale Blue Dot" image.  In case you don't remember refresh your memory. Pale Blue Dot.

But of course it isn't the Earth - it is a very wide field image containing the planetary nebula,  M27 "the Dumbell Nebula".   In a planetary nebula, atoms of the expanding gas shell are excited to emit light by a super hot central star.  I explained this to my daughter and she wanted to know how much bigger it is than the Earth.

hmmmm.  Wikipedia to the rescue.  About 1.4 light years radius in the long direction.  Wow.  Bigger than I thought.  Unsure how to explain a light year to a 6 year old ...
{I mean really, I know what a light year is.  I'm just not convinced we humans can meaningfully connect with distances much beyond our direct experience.  I can imagine it.  Just can't feel it. }
    ...  I just settled for "much much bigger than our whole solar system".  You know ... we all know how big that is right?

Unfazed she replied, "so, bigger than a million billion Earths".  She likes that number - million billion.  If she can hold that in her head then maybe I should ask her about the whole light year thing.  Anyway, I quickly answered in the affirmative and scooted us down for breakfast before she prodded longer at the edges of my knowledge.

This isn't a very common image scale to show off M27.  I just wanted to shoot something with my new 100mm EF-L lens and it was cloud free in Velpecula at the time.  In truth I thought it would be larger.  But I kind of like the perspective - especially since I now know it is 2.8 light years across.  Also in the image is a bunch of open clusters and a globular cluster.  Can you find it?

Here is an extreme crop of the frame.  Pretty cool what 100mm focal length projected on a 18M pixel sensor can do.

It didn't occur to me until I was writing this that early observers of these objects coined the term planetary nebula because of their similarity to the planets.  Exactly what my daughter thought.  She would be in good company with Messrs. Messier and Herschel.

Image details:
Taken at Ghost Ranch near Abiquiu, New Mexico August 3rd, 2010
Canon T2i (stock), 100mm EF-L @ f3.2
Astrotrac Travel System mount
Imaging temperature range: 60-62F
19 60sec exposures @ ISO3200
50 darks, 30 flats (1/5" ISO 100) 28 flatdarks
pre-processed and stacked in Nebulosity
post-processed in PS4

Saturday, August 28, 2010

Flickr goodness and more

OK, so say you have some hard won images that you want to share.  Now what?   You could:
  •  Print them and hang it on a wall (let's hold off until we get something worth printing first).
  • Save them on your laptop and show the occasional passerby. Interactive but rather limited in audience.
  • Email them to people.  Easier but kinda pushy.
  • Start a blog.  This works better - you can let people know it exists and then they can visit or not.  You have the option to share more widely.  Somewhat interactive if you enable comments.  You can advertise as widely as your ego desires.  Good if you feel like writing in addition to displaying the images.
  • Post to relevant forums.  Option to direct people to blog or other distribution point. Highly interactive. Invites co-dependent commenting with such heartfelt and detailed sentiments such as: "Wow!" or "Nice pic!"
  • Use one of the bazillion photo sharing sites.  But which one?
  • Some combination of the last three.
I'd like to use this blog as a central hub.  But might be nice to have the linked images on a photo sharing site.   They all have advantages and disadvantages.  Zenfolio, pbase, Picasa web albums, Flickr and so forth.  I already have Flickr and Picasa web album accounts but discovered something really cool about Flickr last night.  If you share one of your images with the astrometry group and they will plate solve your image, post some nifty info in the comment field, and highlight interesting features ... like this:

When you mouse over one of the boxes there is a little pop up that identifies the object, star or whatever.  Very cool.

If you want to try it just go here:

Try it!

Just mouse over the image.  Below is some other info like the pixel scale and such.

But wait!  There's more.  Down in the comment field is a link to the World Wide Telescope.  Click that and your image is overlaid on the whole sky map.  Bazinga.


How cool is that?  So for now Flickr gets the nod.   Now I'll have to figure out how to connect Flickr and blogger in a peaceful way.  Ain't technology great? 

M16 M17 region picture overlaid on World Wide Telescope celestial map

Broken chips at the bottom of the bag

I'm absolutely craving some potato chips.  Ruffles would be nice but I wouldn't be picky.  We usually don't keep potato chips in the house, and it is well after 12:30am, so I don't think there are any in my immediate future.

I was finishing up this image when I started to think about potato chips and I made a connection (ok, so cut me some slack - it's 12:38am Saturday night after a looooong work week).   I'm down to the crumbs at the bottom of the bag with the remaining images from my trip to New Mexico.  Flawed yet still flavorful.  I won't be embarrassed - I'm reaching in and licking my fingers.

This image of M16, M17 was taken on the very first night I had *any* clear skies.  I took 35 images before I was clouded out.  In the end I only had 18 minutes of usable sub-frames.  It was also the first image with my 100mm lens and I didn't quite hit focus - I was in a rush because of the clouds.  Pity.

I really like these wide fields.  Might have something to do with having done so much visual astronomy over the years where a 1 degree field is HUGE.  This image is like 7x10 degrees.

A forest for the trees kind of thing.  It looks much nicer if you click the image to get the full crop.

A forest full of stars.
M16, M17 region
Taken at Ghost Ranch near Abiquiu,  New Mexico August 3rd, 2010
Canon T2i (stock), 100mm EF-L @ f3.2
Astrotrac Travel System mount
Imaging temperature range:  61F
18 60sec exposures @ ISO3200
60 darks,  28 flats (1/5" ISO 100) 30 flatdarks
pre-processed and stacked in Nebulosity
post-processed in PS4

Tuesday, August 24, 2010

Godspeed Jack

`` `Keep Looking Up' was my life's admonition;
I can do little else in my present position.'' 


PBS's Jack "Star Hustler/Star Gazer" Horkheimer's self penned epitaph.  

He died last Friday, age 72.

You will be missed.


Monday, August 23, 2010

One of Four

The image below is one panel of a 4 panel mosaic.   Just wait until you see the full thing.

Well, take a seat because it's gonna be a while.

OK, so the image is one panel of a 1 panel mosaic.  If you have been following along at all you know that my time in New Mexico - as wonderful as it was in every way - only had one perfectly clear night.  That night I imaged M32 and M33 before the moon came to spoil the party.

The other nights, some of which were quite nice thank you, were only partly clear (or partly cloudy as the shift in emphasis might have it).  It was one of these other nights, when it was "oh man-o-man this is gonna be great" clear I decided to shoot a 4-panel mosaic of the Milky Way in Cygnus.  Oh, maybe an hour exposure time each.  Yeah - have to spread it out over two nights.  No problem. 

Forty-three minutes into the first panel ... clouds.  High, thin, and hardly noticeable by eye.  Through the camera lens it is like looking through a window pane smeared with Vaseline.

So, the mosaic idea didn't pan out.  A night or two later I decided against any ambitious plan that would hinge on the necessity of another clear night.  Too big a gamble.  However I did get 43minutes of the first panel ... and at least I did start with a frame that had a "marquee" object - the North American nebula (and Pelican to the right).

Came out OK I think.  Really wrestled with the whole  "what color should I make it" thing.  I settled on a more bluish purplish look.  Blown out, eye-popping reds are just so ... well, red  {you see, I'm just jealous of you narrow-band imagers}.  I didn't want to just make it red because it is supposed to be red (even though it is, kinda sorta).

Color is proving to be more of an issue for me than I thought.  There is science, art, what "sells", and what makes me happy on a given day.  The color palette might be the same or different for all of them.

In deference to my current situation I'm going to let the last option guide me.   

I'll finish that 4-panel someday.  I'd be thrilled if you were still here waiting for it.

North American Nebula
Taken at Ghost Ranch near Abiquiu,  New Mexico August 4th, 2010
Canon T2i (stock), 200mm EF-L @ f2.8
Astrotrac Travel System mount
Imaging temperature range:  58-62F
43 60sec exposures @ ISO3200
60 darks,  21 flats (1/5" ISO 100) 21 flatdarks
pre-processed and stacked in Nebulosity
post-processed in PS4

Sunday, August 22, 2010

Sometimes you just got what you got

I'm pretty slow sometimes but processing this image of M33 taught me something.  You can spend as much time as you want processing an image hoping to stumble across some arcane photoshop command-alt-clickery that will extract ever fainter photons that just aren't there.  Yeah, sometimes you just got what you got.  Be satisfied.

I learned a lot this time around.  Blue-Red channel trickery to kill the green weenie.  Color halo reduction. All kinds mask selection/load/subtract-ery.  Good stuff - and absolutely no way to reproduce how I got to the endpoint.  However ... I am repeating to myself ... be satisfied.

At 200mm the image scale for M33 isn't all that great.  At least compared to M32.  It's smaller than I remembered :).   I was also a bit surprised that 60 min didn't pull out more.  A late rising moon just below Kitchen Mesa accounts for the still persistent gradient in the lower right corner.  The presentation could be improved but dear reader ... there simply ain't no mo' photons.  I give you all I have.

You know what?  I'm satisfied.  Mostly :)    Hanging up the hair-shirt for a bit before I tackle another set of data from the New Mexico trip.  Click for larger image.

M33  Macbook Pro 15 center crop

Taken at Ghost Ranch near Abiquiu,  New Mexico August 6th, 2010

Canon T2i (stock), 200mm EF-L @ f2.8
Astrotrac Travel System mount
Imaging temperature range:  52-54F
60 60sec exposures @ ISO3200
64 darks,  21 flats (1/5" ISO 100) 21 flatdarks
pre-processed and stacked in Nebulosity
post-processed in PS4

Sunday, August 15, 2010

M31 ... now in Color!

I spent a couple, a few  5 hours today trying to get a handle on the color image of M31.  First I had to figure out the best settings in Nebulosity for the debayer step.  There are no default settings for the T2i - the camera is still rather new.  While I could have chosen just about any setting and done the color correcting later (in Nebulosity or PS) my previous attempts were rather garish.

To get a handle on this I took a RAW picture outside in sunlight that included a gray card.  Verified in PS that the RGB values were the same (check).  Then I opened the file in Nebulosity and debayered with every setting possible (hair shirt?  check).  Then I wrote down the RGB values reported by Nebulosity for the same spot on the nominally gray card and selected the conversion profile that gave the "most gray" (equal RGB) values (double hair shirt, check).

Next I proceeded to reprocess all the images with the new setting.  Which, by the way if you are reading this and happen to be in same situation and don't want to spend 2 hours going through the exercise the answer is ... ta-da ... straight color scaling (not a specific camera like stock 40D or unmodded 300D or whatever).

After all that I cropped and did a Auto Color Balance.  Saved every file en route.  Then I post processed the image in Nebulosity.  The spirit was willing but the body was too weak to start postproc in Photoshop.

The image is still too pale, greenish bluish or something.  And I have orange star halos, some noise to bang down and so on.  After some well deserved rest I'll tackle the image again in Photoshop to see what I can do about color issues.  In some sense I like the more muted colors.  Going forward I'll have to think about how I will use colors in these images.  But, for now, here is M31 in all it's Ghost Ranch glory.

As for all images ... click to see a larger version.
M31 processed entirely in Nebulosity

Taken at Ghost Ranch near Abiquiu,  New Mexico August 4th and 5th, 2010
Canon T2i (stock), 200mm EF-L @ f2.8
Astrotrac Travel System mount
Imaging temperature range:  52-58F
87 60sec exposures @ ISO3200  (taken over two evenings)
64 darks,  21 flats (1/5" ISO 100) 21 flatdarks (still not sure about needing these)
pre and post-processed in Nebulosity

Drive that Spike

Remember that post about making the bobby pin Bahtinov mask ... the "Happy Face"?  I ended up using it only once.  Well, there was only one night worth using it but that is beside the matter.  On *that* night I wanted everything to be as good as I could make it so I figured since I spent so much time making the blasted thing I might as well use it.

Focusing is a hard.  Like real hard.  Especially with a short focal length camera lens at wide open f-ratio. The slightest touch of the focus ring (no - autofocus doesn't work - too dark even on a bright star) is enough to make your stars look like they have had nothing but Micky Dees super-sized combo meals for a month.  That and surrounded by halos of all colors.  Bah!

For this trip I mostly just used live view on the Canon back mag'd up to 10x and tried to make the stars as tiny as possible.  Worked well enough for the conditions.

Here I took a picture at ISO3200 for 5 sec then reviewed on the camera back (blown up 10x) and by the tiniest touches tried to get that middle spike in between the X.  Back and forth.  Nudge, shoot, review, nudge, shoot, review (say naughty word), nudge, shoot, review (say naughty word), nudge ... you get the picture.  I kept the last picture, said "good enough", resisted the temptation to touch focus again without the mask and carried on with imaging.

Handy tip ... remove Bahtinov mask before imaging run.  Yeah.  Wouldn't that be something.

Fortunately I had to frame my shot with test exposures and noticed the stars were all dim and funny looking.  Yikes.
Center the Spike!  Bahtinov focus on 200mm Canon EF-L at f/2.8

I only just now thought to take a look at that image under the light of day.  Much easier to see on the computer screen than while on your knees craning your neck to see the camera back.  Looks pretty good - just a touch off - but it would have taken luck to place that spike any better.  The only way would be to use a fine motion focus ring attachment - something I have been working on.  More on that another day.

I'm happy with the focus on the Andromeda shot - don't really think I could have gotten it any closer.  The Bahtinov mask is cool and a real savior for those imaging with telescopes.  I'm not sure it is of much help with 200mm or smaller camera lenses, but it was fun to make while the storms rolled by.

Friday, August 13, 2010

The Abscence of Color

It would appear the imagers job is never done.  All images are a "work in progress".   You just know you can add some more data ... process a little more ... learn some secret dark art that will make the image pop.  I'm not immune.

Friend(s): "So!  Did you get any pictures of the sky?"

Me: "Ah, yeah, a few.  But there were clouds ... had one good night ... will take me a while to process them"

Friends(s):  (losing interest quickly) "oh, ok ... let me see something when they are done then".

What they don't realize is they will *never* be done!   sigh.  So in order to combat this illusion of progress through motion I will post up what is likely the only good image from the trip ... in B&W.  I gray-scaled the image because I am having a nasty time trying to get the colors figured out.  All RBG debayering channel sensitivity hoo-ha.  Really starting to get me PO'd.

M31, M32, M110  (Andromeda galaxy and companion elliptical galaxies)

Canon T2i, 200mm EF-L @ f2.8
Astrotrak Travel System mount
87 60sec exposures @ ISO3200  (taken over two evenings)
64 darks,  21 flats (1/5" ISO 100) 21 flatdarks (still not sure about needing these)
preprocessed in Nebulosity
post processed PS4

Color will follow when/if I get that figured out.  Just hate throwing away all *that* data.

Sunday, August 8, 2010

Expectation Management

hmmmm ... now that didn't quite go as anticipated.  I look at the date of the last post and it was a full 8 days ago.  Storms, aging hardware and people not quite so sure how to cycle a router (or if they should even trust a guy who looks like he just wandered in from the outback to do it) all conspired to keep me off the net.

So here it is a full week later and we have arrived back home.  Home where the signal is strong and bandwidth abundant.  Somehow the trade doesn't seem even.

No, my heart is still on that mesa.  Sitting on a cold folding chair, my tracking mount and camera ready for any break in the clouds.  Hours out there.  Everyone else asleep.  Hour after frustrating hour.

I loved every minute of it.

I was talking to a woman while waiting in line for lunch a few days ago.  She was relaying her disappointment of a hike canceled due to lightning but instead she got to spend a few hours connecting and talking with her grand daughter while watching the weather pass.  Understanding, I told her that Ghost Ranch is all about "expectation management".  She said "oh, I have the remember that ..." and pulled out a pen and began scribbling in a notepad.  Having someone write down something I say at a place where world famous writers, poets and artists hang out was amusing to say the least.  But the more I thought about it the more I could see it for myself.

I didn't get 13, 7, 4 or even 2 incredible nights to image the heavens.  I did get some quality time on a cold rusty folding chair with views like this to keep me company.

Sunday, August 1, 2010

Storm Chasing Astrophotography

I also imaged Sagittarius with the 50mm lens and no tracking.  This was a stack of 16 10sec images at f/1.4 and ISO3200 using the same master dark frame as the Cygnus shot.  I stopped because the clouds were rolling in faster than I could take pictures.

The cloud moving through the image was illuminated by lightning in 4 of the frames giving it the feel of a new nebula moving into the neighborhood.  I think it looks kinda cool.

I have birthed a new discipline ... wide field astro/storm chaser imaging!

Hey, with good focus and some flats this might have amounted to something!

Stacking no Tracking

It might seem strange but honestly I never considered that there would a condition somewhere in between Raining Like Cats and Dogs and Darkest Skies You Have Ever Seen.  Not only is there such a condition it is by far the most likely one I am going to experience if there is any break in the seeming perpetual cloud-out.

Actually it happened last night.  It was raining at 9pm.  By chance happened to look up at 9:40pm and ... "that's a funny cloud".  Yeah.  It's commonly known as the Milky Way.  Now mind it is still partly cloudy but I was still elated to see a "poke your eye" out MW.   It takes me 20minutes to get back to our hovel and decide that it is not worth it to pull out the Astrotrac and go full-auto.  Instead I just grab the tripod, a 50mm f/1.4 lens and figure I take some short duration shots under various conditions so I can say that I at least took some kind of image of the stars.  Basically I was going out with not one piece of equipment that I so painstakingly shipped out to New Mexico.  No mind ... I'm on it.

About 45min later the sky was extinguished and the rest of the night was full of lightning and heavy rain. None-the-less I got a couple images and learned some lessons.  Lessons first - images later.

1.) The 50mm f/1.4 lens is cool (so much freaking light) but it is no red-stripe.
2.)  It is near impossible to focus at f/1.4 while looking at a live view screen.
3.)  Plop down some $$ for a nice carbon fiber tripod.  Cheapie tripods, well, lets just say some language that I wouldn't use around the girls was spoken into the night air.
4.) In a serious pinch ISO3200 will do.  A serious pinch.  Noisy but OK if you downscale.
5.) Don't panic and shoot wide open.  The lens can buy you a lot even stopped down a notch or two.
6.) Acceptable trailing is in the eye of the beholder.  My eye didn't like anything more than 10sec with a 50mm lens.
 7.) Trying to frame a shot near the zenith while mounted on a tripod is desperation in action.

Never shy to try something completely new and abandoning my detailed planning (read making stuff up on the spot) I thought I might shoot a bunch of short duration frames, shoot some darks, and try to stack 'em.  While my images look like crayola (bad focus, jumpy tripod, lens not set correctly) I think this idea has merit (I'm sure others have tried this).

So ideally one would:
1) shoot as high an iso as acceptable
2) lens as wide open as acceptable (but probably stopped down a bit)
3) turn off in camera dark frame
4) shoot a bunch of darks to bang down the noise
5) shoot flats (I didn't and wished I had)
6) stack lights with translation and rotation settings and let software take care of image shift
7) process to your hearts content

With some practice and experimentation I think some very nice wide field images could be had with no tracking mount at all.  The below is a stack of 25 10sec exposures at f/1.4 and ISO3200.  Same number of darks.  All on a static tripod - no tracking!

Cygnus near Deneb with a tiny teeny North American nebula below.  Wish I had come at least somewhere near focus and shot some flats.