Eclipse Movie!

I had the Canon T2i / 200mm EF-L (with Baader Filter on the lens cap) ticking off an image every minute during the annular eclipse this last May 20.  The camera had 140 images on it by the time the sun set behind the eaves of the house.  I focused as well as I could by hand on sunspots but they were pretty tiny at this image scale.

When I had a chance to look at the images I realized I was in for the same spot of trouble I was in for the lunar eclipse movie.   Each time the scope was re-centered the image would obviously shift in the image frame.  This means they all required alignment.  I still don't know of any better way to do this than by hand ... there are no stars in the field to take advantage of normal image registration software.  

So each frame was lovingly nudged into alignment by hand (in PS4).  All 140 of them.  Then cropped in Lightroom, exported as jpgs, and finally sequenced into a movie with Quicktime 7.

It looks a bit nicer if you view it at youtube so you might want to click the link.  At the very end you can see the sun setting behind a tree and finally the edge of the roof cutting it off for a premature end.

I chose to run the movie at 10 frames per second so the motion seems smooth.  The whole clip is only about 14 seconds!  Almost 2.5hrs worth!  And of course much more than that to align all those frames! Ah well ...  I've done worse for less.

The Baader filter gives a neutral white light image.  I noticed many of the images and movies out there are colorized - on purpose or due to the type of filter used.  They are rather more dramatic but I chose to keep any artificial flavorings out of the mix.

It was a good dry run for the Venus Transit on June 5.  I learned I really don't have enough image scale at 200mm and if I don't use the refractor I'll have to get a tele-extender.  Experiments underway!

Processing Partners

I love PixInsight.  OK, perhaps I'm getting a bit ahead of myself - after all it is those heady and exhilarating early days of relationship.  Let's just say I think this just may be the one.  We are going steady right now and I plan to pop the question even before the trial license period expires on 07:45:33 UTC December 12, 2010. 

This will not be an exclusive relationship.  Right tools for the job and all that.  I am on very good terms with my previous [processing] partner (Photoshop) and hope we will remain close friends.  We can spend quality time together on my terrestrial photography and I am sure that there may a few tricks that PS can do easier.  For those tasks we'll just go out for coffee.  But for astrophotography PS could never kindle my passion like PixInsight does.  In her heart of hearts I'm sure PS knew this day was coming. 

Contrary to popular belief, PixInsight is not difficult to get to know.  Exotic and perhaps a bit dangerous but that is part of the allure.  Algorithmic and rational.  Holistic and deep.  She doesn't paint herself or your images.  Yet watch her reveal the inner beauty lurking just above your noise threshold.  There is no user manual (yet) but this helps forge a deeper understanding right from the beginning.  And there are many who know her mysteries and are happy to share their advice.

If you are looking for a superficial one button relationship - don't bother.  You will have to invest some quality time but oh so well worth it.  You will get to learn strange and foreign sounding terms like ATrousWavelets and HDRWTransform.  You will get frustrated. Yes you will even fight at times.  But oh so richly rewarding.  If you want to inject a some fun and excitement into your processing experience ... on the next full moon invite PixInsight out for a night on the town.  You won't regret it.

New Insight

It's been a while posting but that doesn't mean I've neglected wearing the hair shirt.

I went to the 2010 Advanced Imaging Conference which was held over the weekend of Oct. 22.  I wavered about attending.  On the positive side, it was local - and it had a really great line up of speakers. On the down side it was rather spendy and since my regular imaging pal wasn't going I wasn't looking forward to being the token "Novice Hair Shirt".

In the end it was a great experience.  Met some really nice people and the talks were entertaining and informative.  I'd recommend the conference to anyone interested in astro imaging no matter what your experience level.  Oh, and they have a nice vendor fair which was well attended - all kinds of cool toys to look over.

Rogelio Andreo (see his Deep Sky Colors web site at right sidebar) gave a fabulous talk on his imaging techniques as well as some food for thought on image composition and goals.  It was the latter that made the biggest impression on me but I'll save those thoughts for another post.   On the technical side he talked about processing images with PixInsight in which he described some of the workflow and concepts.  As he said over and over again ... "not better, just different".

A week ago I finally downloaded the trial license of PixInsight and have been slogging my way up the learning curve.  I had been working in photoshop on an image of the Pleiades I took at Calstar, so chose that as my first go with PixInsight.  Below is a comparison of the same data - preprocessed in Nebulosity and the post-processed with PS and PI.

I know if I had worked a bit longer on the PS version I would have done significantly better than the above attempt - which admittedly kind of stinks.  And the PI version is stretched till the pixels screamed and bled noise all over the image.  But I could, in a rather short time - maybe a couple hours working through some of the tutorials -  come up with a result in PI that bettered my PS attempt.

Being relatively new to image processing I haven't yet locked down my synaptic pathways in the ways of PS.  This is one of those rare situations when not knowing much may be an advantage.  I can learn a new way of accomplishing something without having the disadvantage of going through a translation step.

 So I've put aside PS for now - and decided to spend some time learning a completely new processing methodology - before becoming proficient at the one I've put months of learning into.  Beautiful.  How hair shirt is that?!

How hot is *your* camera?

Story time ... but with charts and graphs and stuff near the end!

When I was out imaging last week I decided to shoot 30 second sub exposures for the image in the previous post.  The other image (still processing, up soon) used 60 second sub exposures.  So that decision meant that I would have to shoot two complete sets of darks as they must match the exposure time, ISO, and temperature of the light frames.  Typical hair-shirt move.

So at 3:30am I start shooting my darks.  At least it doesn't take a lot of skill.  Block the lens, check the ISO,  set the interval timer, sit back and ponder life's mysteries.

I said it doesn't take a lot of skill, not zero.  I still had to change the exposure time and interval for the two sets.  Thought I did, but hey, it was now after 4am.  Yes, I came home with 2 sets of 30sec darks.  Sigh.  Well, at least I had a lot of 'em.

I knew it was roughly 60F out there so my plan was to shoot my 60sec darks in the garage when the temperature was about the same.  Done.

*Insert LOST backstory sound effect*

Previously I had discussed the idea of a dark library with my imaging pal.  He thought it would be cool if one could measure the temperature of the exposure, bin them by temperature and exposure conditions and then match them to the temperature of the light frames.  Cool Beans. I knew that many DSLR's had temperature sensors from past experience shooting Giga-pans in the hot sun.  Ever see that "your camera is getting too hot" icon?  But how to get at that temperature?

Some searching led me to exiftool - a wonderful utility to extract *all* the hidden goodness from your camera image headers.  A command line utility to boot (a GUI is available for the less righteous - windows only).  But for us Mac and Linux folk it is full on shell time.  Pull up that terminal get crackin!  Some thrashing around and sure enough, with the right incantation I got it to spit out...

28 C

Time to get real sweaty and pull on another hair-shirt.  Some hours later - with shell script higgledy piggledy- a file including a table for each dark exposure was mine for the taking.

*Insert LOST return from backstory sound effect*

I knew that using Live View and heck, just shooting images, would heat up the camera (why have a "too hot" warning otherwise) but I was quite surprised by what I found.  The results are shown in the graph below.

First just follow the blue diamonds.  Start with the camera turned off and equilibrated out in the garage.  Ambient temperature steady at 60F.  Set timer to expose for 60seconds, wait 15seconds, take another.  Wash, rinse, repeat.  See temperature climb.  See temperature rise to over 90F!  Yikes.

OK.  Say you are willing to put in a 60sec delay between exposures to give the sensor time to "cool down".  Follow the red diamonds.  Better, but hey, still pushing a 20F rise in 45minutes.

Even a two minute interval doesn't buy much and I'm not waiting around that long.  An ambient temperature of 38F allows for shorter intervals and the temp levels off quicker.  But instead of a brisk 40F you are actually imaging at a balmy 60F.

A check of my light frames shot in the field show the same effect.  Only difference is the camera *starts* warm since I have taken test exposures, focused with Live View and whatnot.  Those first few shutter clicks get you warmed up in a hurry.   Guess we know where all that energy stored in the battery goes.  Huh.

The bad news is self-evident.  The good news is that it is at least possible to know the temperatures of your frames and match darks accordingly.  The not so good news it that doing that is a bit of a pain.  The great news is that one can get just fine images not worrying about this.   More shooting, less fussing = more fun.  But for those of us with a closet full of hair-shirts ... no rest for the weary.  Dang, yet another advantage those cooled-CCD folks have.

How does one use exiftool to get at all this?  I'll post what I've learned later.  For now I leave you with this handy tip.

If you are ever caught out lost and freezing in a forest ... just curl up around your DSLR and hit the shutter every minute or two until help arrives.   You heard it here first.

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

Dark Side of the Moon

I wanted to try and make good use of the time before the moon gets out of the way.  I figured I would start in on my dark frame library.  Now dark frames are used to pound down the noise inherent in any long duration exposure at high ISO.  The noise increases with temperature as well.  So a dark frame library has to involve separate sets for each exposure/ISO/temperature combination.  Yikes.

This can all be done in the field right after the exposure run but that doubles the time (each dark must be the same duration as the "lights").  Not to mention that you gotta take your flats and flat darks as well.  So a library is appealing.

I've read that a common practice is to bin your darks in 10deg F increments so that any given run of light frames is within 5deg F.  Next would be to decide what your most common exposure durations will be.  For this trip I expect to be shooting 30sec, 60sec, 120sec for sure.  Next ISO.  Most likely 800 and 1600. See how this rapidly gets "hair shirty"?  Not to mention keeping the storage business alive and kicking.

I am limited by whatever the ambient temperature is on a given night and that has had me come to grips with a looming specter.  It's hot here.  Like glorious shorts and tee shirt in the middle of the night hot.  A fertile hothouse for noise.  It is just a limitation of DSLR imaging.  I suspect that this is the main thing that drives people to a dedicated cooled CCD camera.

Undaunted I proceed.  Marek and I discussed just how many dark frames to take for a library master dark.  The noise decreases as the inverse sqrt of the number of exposures so at some point taking more reaches diminished returns.  We agreed that "many tens" would be a good target.   Last night I shot 32 60sec ISO800 images and tonight I'm shooting 64 30s ISO800 images (why 64?  because I can.  because I can while I am writing this blog entry).

Last night it was 68F.  Tonight ... 74F!  And of course when and if I get to actually take some lights it will be 55F and will have to take my darks in the field anyway.  No mind ... I will have some hot darks to take home as souvenirs.  I only hope that they are not the only astro images I take while here.  Very very hair-shirt.

No, not stars.  Noise.  A hot dark frame.