Barnard's star

End of my summer vacation and perhaps the first good weathers (concerning astrophotography) after last winter. Even then it was mostly cloudy and the few cloudless nights happened to be when I was too tired or had something else to do. I look at the time stamps on my astrophoto directory and I see 2014-09-04, 2014-09-13, 2014-09-30 and 2015-02-10. I hope this season is a lot better.

I was anxious to go out as early as it was reasonable. First trying to remember how to align the EQ3, then taking some test photos of possible exposure times. I bought a new laptop a while ago. Before I had EeePC to control the camera, but its screen is quite small for it. Now with bigger screen it was extremely easy to focus the lens. Live stream from camera to computer and pointing to some bright star.

My plan was to take a photo of Barnard's Star. It's the closest star you can see on northern sky, just about 6 light years away. Alpha Centauri system is closer with 4.3 ly, but Barnard's Star is the second after that. What made it interesting to me is the stars proper motion. It moves 10 arcseconds a year making it possible to see it's motion in just the span of few years. I plan to take similar photos every year from now on and compare them when I have enough data.

Barnard's Star can be seen close to 66 Ophiuchi, which has magnitude of 4.8 and can be seen with naked eye. On my 200 mm lens I could fit magnitude 3.9 star 67 Oph on same view and that was even easier to locate on sky. Barnard's Star has magnitude 9.5 so it's not visible to naked eye. I took a couple of lucky shots of the area close to 66 Oph and 67 Oph and compared the photos to Stellarium charts.

Barnard's Star pointed out

No map comparison here, only a piece of the original photo. No stacking this time. Just a single 150 second shot. Brightest star on lower left is 66 Oph. A bit enlarged version of the same frame without pointy lines:

Not much to see actually. Colour is red as it should be on a red dwarf. That's about the science I can do with this data.

Then couple years of waiting with this project.

Mosstack 0.7 development and problems

After Mosstack 0.6 which I realeased last year, I've been writing a new command line interface for it and that development has been quite slow. Coding math related stuff is nice, but I don't like interfaces. That added to the fact that stargazing and photographing weathers were extremely rare during last winter made me concentrate on other things. First I thought I'd get more programming done with no photos to process, but the lack of photos seemed to make the programming quite pointless. I also started another open source project with SailFish OS, a gym logbook for Jolla phones...

Astropy got updated to 1.0 and that broke my program. I started getting error while reading a Fits file the program wrote itself:

ValueError: Cannot load a memory-mapped image: BZERO/BSCALE/BLANK header keywords present. Set memmap=False.

It took me a while to understand and fix. The files are quite big and there might be a lot of them in the memory simultaneously so memmap is an important feature and can't be set False. Internet wasn't helpful at first. I tried removing said keywords from header, but it didn't help. Finally I found something that said Fits format not supporting datatype uint16. That was what I was using. I changed it to int32 and everything works.

Another problem was a memory leak with my new C extension VNG debayering method. Each debayer took about 300 MiB of memory and that was never released. I hunted that leak for days with memory_profiler and finally located it to the C extension. Even then I didn't see it myself but someone else pointed out I allocating memory inside a loop but freeing it only after the loop. Perhaps I really should learn to code C before attempting anything with it...

The new CLI is perhaps half done. You can run a simple stacking process with it but many features are still to be implemented. My plan is to get 0.7 done before the stargazing season in Finland begins. That means about a month.

Planned features:

• New CLI
• VNG debayering with C extension and C binary debayer (done)
• Decoding DSLR raw photo to FITS with a C extension so decoding would work without dcraw and imagemagick (almost done)
• New GUI with QML (moved to next release)

Mosstack 0.6.1 released!

I didn't even have time to write a release post about 0.6 when already I was reported a bug that prevented loading anything but Canon's raw photos. That was fixed in 0.6.1 and now the release announcement:

Mosstack 0.6.1

What's new? As already posted in http://mikkolaine.blogspot.fi/2014/11/mosstack-06-release-candidate-1.html there's quite a lot of changes. Here's a short list:

• Manual. Written in LaTeX since I plan to include explanation of all the math here as well. For now it's only manual for the command line interface. Manual is included in distribution package.
• Speedup for OpenCL operations. (Actually I have no idea about this. Just noticed during tests that what used to take 5 seconds, takes now only 0.5 seconds. I don't know who or what to thank.)
• Cropping before stacking. Works on both GUI and CLI. This reduces amount of required memory and makes stacking a lot faster.
• Added support for any images DCRaw can open. There's only one Bayer filter programmed (RGGB) so any other images work only as monochrome. This should be enough for most consumer DSLR cameras.
• Better project management. Removing frames from project, selecting the reference frame, clean command to remove temporary files...
• Adding premade master frame so creating the calibration frames isn't necessary for several image sets from same photo session.
• Giving "Bias level" instead of master bias is possible from command line. This subtracts given number from every pixel on each frame.
• Maximum and Minimum stacks. Partially for testing, but I guess there might be uses for these.
• Kappa can be defined for Sigma methods. Sigma methods reject or replace values that differ amount of κ*σ (κ defaults to 3.0 and σ is standard deviation) from the median.

Web page

Until now everything has been on BitBucket, but that's not the easiest media to share tutorials or such. I also applied an open source license of PyCharm (and got it too!) and that required the open source software in question to have a proper web page. Hence: https://sites.google.com/site/mosstack

How to get:

• Download the latest source package from BitBucket and follow the instructions included.
• Use Ubuntu's PPA https://launchpad.net/~mikko-laine/+archive/ubuntu/pyastrostack. This might work on some other distros derived from Ubuntu.
• Install from Gentoo-science overlay. Ebuild is renamed from pyAstroStack to mosstack.

Mosstack 0.6 Release Candidate 1

This was supposed to be a quite small version bump. Originally the plans were to add a couple of stacking methods, trim the math, and fix setting the reference frame (so that cropping would some day be possible)... The some changes required quite a lot of rewrite under the hood and suddenly there was a huge update coming.

According to CLOC there is almost 1000 lines of new code compared to version 0.5.2, with the sum being almost 6000. That's Python and Cython code lines. Comment lines, blank lines and C generated from Cython are not included.

Download release candidate from https://bitbucket.org/mikko_laine/pyastrostack/downloads. Ubuntu, Debian and Gentoo packages will be done for the final version.

Highlights from changes:

Crop window

• Cropping before stacking. Set reference image and set crop area from Gui by rectangle selection and the images are cropped after preprocessing. This reduces amount of required memory and makes stacking a lot faster.
  Cropping also works on command line, but requires giving coordinates manually.
• Added support for any images DCRaw can open. There's only one Bayer filter programmed (RGGB) so any other images work only as monochrome. This should be enough for most consumer DSLR cameras.
• Removing frames from project works on Gui and Cli
• Adding premade master frame so creating the calibration frames isn't necessary for several image sets from same photo session.
• Giving "Bias level" instead of master bias is possible from command line. This subtracts given number from every pixel on each frame.
• Maximum and Minimum stacks. Partially for testing, but I guess there might be uses for these.
• Kappa can be defined for Sigma methods. Sigma methods reject or replace values that differ amount of κ*σ (κ defaults to 3.0 and σ is standard deviation) from the median.
• Added size and clean commands to Cli. These report the size of temporary files of a project and delete everything except master frames.
• ImageMagick affine transformations are disabled. Code still exists, but isn't supported at least at the moment.

What's still to be done before 0.6:

• Documenting. Both the code itself and also how to use the program. I started a manual written with LaTeX but there will also be a website.
• Debugging. I'm quite sure there are quite a lot of bugs left in the code
• Cleanup. Old names AstroStack and pyAstroStack are still everywhere in the code. I plan to change all those and rename some files in the process. Also huge chunks of code is now "documented out" with # or triple quotes. Delete all that. Leave only what's required.

Triangulum Galaxy and other shots from September 30th

I failed at shooting the Triangulum Galaxy the last time, but now I had a bit better conditions. Seems like the 150 second exposures before were result of a extreme luck with alignment. This time even 120 s seemed to trail a bit but 100 second worked.

Here's 10x100 seconds stacked with Mosstack. Full photo in https://flic.kr/p/pHia6c and Astrobin entry here http://www.astrobin.com/129577/. Seems like focus was off. I adjusted it after this stack so the rest objects are more sharp.

I'm actually a bit surprised to get that much color on the photo. Stacking with IRIS gives even more blue, but I'm trying to process all my photos with my own stacker. I use IRIS for comparison only. Here's what IRIS was able to do.

Post processing is done with Darktable so full processing with open source software only.

Something more...

I took couple of shots at Pleiades just to see if I can get any nebula visible. 

There indeed is some and it's blue. There always could be more so more photo sessions required with this object. Full photo here https://flic.kr/p/pr8VMw and Astrobin entry here http://www.astrobin.com/129580/.

And now something without any nebulosity: the Double Cluster.

I had shot this one before as well and my idea was to compare these two to see the development of my gear and me. The previous photo is here and full version of the new here.

Dumbbell nebula, Ring nebula and exposure tests

The sky was clear on September 13th and I planned to shoot some stars before Moon rises. I thought I had prepared everything, but turned out I hadn't charged cameras battery. Luckily there was enough power to last until Moon lit up the sky. Maybe 15 minutes more had been possible but nevertheless... everything went better than I expected.

First some more tests about exposure times. 80 second was easily possible the last time, now I tried some more.

100 second exposure (left) and 150 second exposure (right)

100 seconds looked good so I took 150 second. When I look at the photo on computer screen I'm not sure about 150s. Most stars look ok, but maybe some show some trailing. I have to run final tests about this on a better ground. This time the mount was a bit unstable. So I'm not sure whether the trail is caused by mount shifting on ground or incorrect alignment.

Result was something between 100 and 150 seconds so I chose 120 as exposure time for shooting the Triangulum Galaxy.

Triangulum Galaxy M33

This failed. Moon was rising and it's glow had lit the eastern sky. Air humidity was also quite high and some fog did form a while later so all that made Triangulum a wrong target for that night. Still I spent 10 x 120 seconds worth of time and battery on what you see above. Also I managed to tilt the camera couple times so only seven photos were usable.

Well... You can see it and maybe even recognize it as M33. Bigger photo (if really necessary) in https://www.flickr.com/photos/96700120@N06/15063242487/

Ring nebula M57

After the Triangulum failure, I realized the sky was more clear of light pollution right in zenith. Lyra and Ring nebula was the first thing that came in mind. Couple of photos there and only one of them was not tilted during exposure. I really have to stay away from the mount during shooting...

This is a single 120 second exposure. Quite nice. Although focal length of 200 mm is quite short for M57. Bigger photo in https://www.flickr.com/photos/96700120@N06/15063241107/

Dumbbell Nebula M27

Battery indicator was blinking red but I thought I'd use all the remaining power to shoot the Dumbbell nebula. It was also in a dark spot of the sky. Now the exposures are only 30 second and I took 10 of them but still this is what I got:

I'm impressed. Last time I tried M27 was with my old 75-300/4-5.6 zoom lens. I got a faint gray smugde. Now the aperture was 2.8 and my faint smudge has some real color! Can't wait to take some longer exposures of this.

Here's one a bit zoomed to show in the preview on Facebook or G+. :)

Bigger photo in https://www.flickr.com/photos/96700120@N06/15048413067/ and one with more stars around it in https://www.flickr.com/photos/96700120@N06/15047931927/. There's also open cluster of NCG6830 on the bottom if this image.

Proper alignment of EQ3-2 and first photos of the season

I've had problems with aligning the EQ3-2 even though I have a polar scope. For some reason I misunderstood the instructions totally. I always assumed the scope shows some kind of fish eye view and the constellations visible should cover the real stars. Nope.

View from polar scope. Image linked from
http://stargazerslounge.com/topic/158612-is-there-an-eq5-pro-synscan-goto-manual/#entry1602579

The scope shows Big Dipper and Cassiopeia from northern hemisphere and Octans from the south. Place polaris here circle is exactly as it says, but the rest are just directions where the constellation should be. This was the information I was lacking.

Now I made a somewhat good alignment and started to look through the scope. Polaris was by chance quite close to the circle. With couple of minutes of screwing and unscrewing the legs I got Polaris right where it should be. Now the tests...

With rough alingment I got maybe 20 second exposures with 200 mm optics without the stars trailing. Once or twice 25 to 30 seconds was possible close to celestial pole. Now I tried 30 s, 45 s, 60 s, 70 s and when that worked I took 20 exposures with 80 second time.

Here's an single shot to how the stars don't trail with 80 second exposure.

The Moon was up and almost half so sky was kind of lit. Before this it has never bothered me too much since my exposures were so short, but now it was a problem. I tried to stack my Andromeda photos and the result was worse than my previous best one (with 25s exposures). There's really no point of posting that image here.

After Andromeda photos were shot I decided to try the Whirpool galaxy. I knew the Moon makes that difficult so the result won't be good. Before this I haven't had any image of it. Now I got this

From nothing to this. Now I'll just wait for a better conditions (no Moon) and try again.