Pleiades Rising

Trying to make the best of a trip to New Mexico during the full moon and monsoon season.  Don't get me wrong - the skies are spectacular.  I'm just haven't learned how to best capture what I'm seeing and feeling.  I have plenty more day shots that I like but haven't decided if I want to "cross the streams" on what would otherwise be a astronomy centric blog.  If I did it would increase the rate of images I post given the glacial pace of astro-imaging this year.

Here come the Pleiades again.  click to enlarge

The moon is two days shy of full and is swinging low on the horizon about 30 degrees outside of the right side frame.  The full width is about 170 degrees but the above image is a little less than that since I cropped out my shadow which was on the left side of the frame.  Only the brightest stars are visible because of the short exposure and moonlight.  You can see the Pleiades rising just above Kitchen Mesa, the large rock face in the left hand frame.

I experimented with a number of ways to capture/process this.  It is a two frame mosaic with each frame processed with 4 different exposures using Photoshop's HDR function.  I certainly do wish for more tools in the PS HDR module but at this point I don't do enough HDR to justify a specialty package.  I stitched the two frames using PTGui Pro since PS couldn't figure out how to stitch this correctly.  After that I did some final tone/exposure/noise reduction in Lightroom.

Pleiades Rising

Taken at Ghost Ranch, NM   July 31, 2012
Canon T2i (stock), Canon EF-S 10-22mm @ 10mm  f3.5
Manfroto Tripod (stationary)
two frames, each frame with 1, 2, 4, 15 sec exposures @ ISO1600

no dark or flat subtraction
vignetting and lens correction in Lightroom 4
HDR combine in Photoshop
frame stitching in PTGui Pro

final adjustments and noise reduction in Lightroom 4

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

Learning from the Sisters

As you can tell from my previous posts I've been spending a lot of time learning the basic fundamentals of PixInsight.  Using the Pleiades data that I gathered in the October new moon cycle, I've come to the conclusion that the Seven Sisters are an ideal training ground for astroimage processing.  Nice color, detailed nebulosity without being overly tricky (ala M42), some star color, and brightness variations to throw a little challenge into the mix.  A zillion amateur and professional images available on the net are also a help.  In other words a little bit of everything and nothing too difficult.

The fact that there is a detailed processing example on the PixInsight website helped a bit too.  Here is my current, um, version.  As always, click to flickr.

Encouraged by my early progress (see a couple posts back) I subsequently languished in a discouraging cycle of dead ends and restarts.  Trying more sophisticated tools against my image lead to worse results.  I finally discovered the NoiseEvaluation script and found that I was inexorably raising the noise floor as I processed deeper.  Even though I was keeping the data linear for as long as possible things just plain got noisier.  My tendency was to overstretch and otherwise use too aggressive settings and got to a place where even the sophisticated noise reduction tools in PI couldn't compensate.

Eventually I tackled learning how to do all the calibration processing in PI as well.  This is an area where PI does need some workflow streamlining - not for the faint of heart.  Nebulosity is much much easier.  But the tools in PI are powerful.  After I plowed through it I was able to get my subs to about 5-8x lower sigma SNR.  Pretty cool.  So now I was able to start post-processing with more headroom.

And well, I did only have an hour worth of exposure time.  I really shouldn't expect so much.  Two minute subs too.  But I think it is a very worthwhile learning experience to work with the same data set over and over to see just how much you can squeeze out of the noise.  Experiment often. Reprocess much. You will learn a lot which you can bring to bear on your subsequent images.

I have about 4 or 5 other image sets waiting to be processed but I've patiently spent hours and hours of time with the Seven Sisters while I learn PixInsight fundamentals.  Oh so pretty and alluring they are.  Not entirely painful company!

Pleiades

Taken at Lake San Antonio, CA  October 8, 2010
Canon T2i (stock), Astrotech AT80LE, 480mm  f5
Astrophysics AP900 mount
Guiding: SSAG/50mm Orion finder, PhD
30 120sec exposures @ ISO1600
94 darks
14 flats (1sec ISO 100
128 bias frames
calibration, registration and post-processed in PixInsight

Warm ups

Calstar 2010 is one week gone.  I did spend the extra night this year.  Ah, the extra night.  The night you hear about from the lucky few who stay one night more.  Of course it is always "the best night of the entire star party".  Inky dark.  Sugary Milky Way.  Dry.  No twinkle twinkle little star.  Is this somehow the reward for staying the extra night?

The experimentalist in me wanted to test the theory and I can say on the basis of one data point it is absolutely true.  By far the best night of the star party.  The half dozen or so of us that stayed over were spaced around the periphery of the Calstar field, guardians of our own peculiar good fortune.

My pals James and Dan close by enjoying crisp refractor views.  Rogelio and Eric at the far end creating their next masterpieces with deep, methodical expertise.   I'm there with gear akimbo intent on getting some serious time in the bank for M33.  It was a special night.

Over course of the star party I took wide fields imaged with my new 10-22mm EF lens as well as though my AT80LE refractor.  From 10 and 14mm to 480mm with nothing in between.  The EF-L lenses sat warm in the camera bag on this outing.

A week home now and faced with a few gigs of data to process I decided to warm up on what really amounted to some test exposures for the refractor.  First light for the refractor, first images with the T2i bolted onto the end, first images on the AP900, first guided exposures ever.  A lot of firsts.

 Double Cluster in Perseus.  click to flickr

There is a fair bit of curvature in the f5 field of the refractor - not surprised, I'll need some kind of field flattener.  The above is rather severe crop to make the worst bits go away.  I suppose I could have spent some more time making the stars prettier but mostly I wanted to start the processing queue with something easy.  I know I have some really challenging processing ahead.  Consider this some toe touches to get me started.

Double Cluster

Taken at Lake San Antonio, CA  October 8, 2010
Canon T2i (stock), Astrotech AT80LE, 480mm  f5
Astrophysics AP900 mount
Imaging temperature: 18-22C in-camera sensor temp
30 60sec exposures @ ISO1600
57 darks (sensor temps 18-22C to match imaging temp range)
14 flats (1sec ISO 100) 22 flatdarks
pre-processed and stacked in Nebulosity
post-processed in PS4

Dark helps, Darks help

I made it out to Montebello with my imaging pal last Saturday night. This would be my only chance to get out this dark cycle before being sidelined by minor surgery. I'll be back in action in October but at least I have two images worth of data to process while I sit around in my jammies for a few days.

It was the first trip out after the New Mexico vacation. Montebello provides some reasonable skies considering its proximity to the greater Bay Area but New Mexico it aint. Those of you who live in super dark skies ... count your lucky (bazillion) stars.

Confronted with skyglow again I had to decide on what ISO to image with. I haven't characterized the camera (and probably won't) and frankly get tired reading about S/N and gain vs. exposure time trade-offs. The experimentalist in me says, "just do the comparison yourself". Some day maybe I will, but in that moment I just decided to throttle back down to ISO1600.

I've processed one of the two images I snagged that night - NGC253/288 region with the 200mm EF-L.   I rather like wide field frames of objects normally imaged at higher focal length. Not as flashy but it does give another perspective.

NGC253 and 288.  Canon T2i full frame at 200mm f.l.

Wow ... do dark skies make a difference. Noise was not my issue in New Mexico, even at ISO3200. This image had all kinds of noise that I had to beat down. But dark frames do help, and the more the better. I took 64 darks to throw against this and I still had more noise than I expected.   I was also too lazy tired to re-adjust polar alignment and had some trailing so I shortened exposures to 30seconds each (I took 60 for 30minutes of accumulated exposure time).

Below is a MacBook Pro 17 crop of the galaxy and globular cluster.

crop to the good stuff.  click to flickr

Stare at the center of our galaxy and look between your feet.  This view is just about straight down out of the plane of the Milky Way and NGC 288, the globular cluster, is hovering nearby at 28,000 light-years distant.  The Great Sculptor Galaxy, NGC 253 is over 400 times further away at some 11.5 mega light-years distant - one of our "just down the block" galactic neighbors.  Nifty. Burnham says 253 was first observed by Caroline Herschel which makes that a double Nifty.

Perhaps under a darker sky in October I'll try this again and put a lot more photons in the bucket.  An hour to 90minutes would do this pair some justice.

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:
M27
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