# Social space for birds

Birds, like us, seem to want to keep some social distance. Is there anything  complicated to it, or are they just leaving enough room to take off?  Why is the spacing wider on the neutral (top) phase than on the far phase?  What’s the story with the guy off by himself?

# Xsan 2.3 client won’t mount

I’m having a problem with clients dropping their  xsan volumes, usually on a restart of the client.  The fix I used is below, but  I’d live to have abetter method.  Here’s what I know:
The MDCs are running 10.7.4, as are the clients.
There is a ghost directory that I have deleted, but it returns from the dead, still x’ed out.
There’s been no change to fiber cabling.
The wwnn’s on the client match those on the qlogic switch for the client’s zone
All LUN’s are visible on the client via Disk Utility
Mount san volume fails from xsan admin and from Xsan in user prefs.
I’ve restarted the client
I’ve removed the client from the san and then re-added it
I’ve disabled the san pref and re-enabled it.

Both Xsan Admin and cvadmin act strangely.  (Note that I try not to run cvadmin and Xsan admin at the same time, and I don’t intentionally leave them running on both MDCs at the same time.  This has always been a recipe for squirrely behavior.) I believe there is a bug related to a disconnect between cvadmin and the Xsan Admin GUI.

In the Mount list, Xsan Admin shows all clients as “not mounted”

Here’s a terminal session showing cvadmin on the primary MDC:

>

Enter command(s)
For command help, enter “help” or “?”.

List FSS

File System Services (* indicates service is in control of FS):
1> Video[0]             located on ohaephqxs001.aepsc.meta:49257 (pid 232)
2>*Video[1]             located on ohaephqxs002.aepsc.meta:55017 (pid 35048)

Select FSM “Video”

Admin Tap Connection to FSM failed: [errno 54]: Connection reset by peer
FSM may have too many connections active.

Cannot select FSS “Video”
>

What fixes it is to force a failover of the MDCs.  This immediately mounts the problem client and  restores cvadmin to normal behavior; also Xsan Admin correctly shows clients as mounted.

# Hopes for Lytro

I was one of the ones who pre-ordered a Lytro pretty much as soon as the product was announced last year (http://blog.lytro.com/wp-content/uploads/2011/10/Lytro-Camera-Launch-Press-Release-10-19-11.pdf). I immediately took a bunch of shots, and immediately thought, “this is, right now, a one-trick pony”.   By the way, if there are big gaps in the post, the lytro plugin seems to be a bit unreliable…

I’ve found that in the shallow focus shots I end up taking with Lytro that the “best” focus is usually obvious, a choice you would make intuitively with any other camera.  And that the compositions one comes up with to show off the refocus feature look as contrived as a 1950s 3D movie.   Which may not be a criticism considering that 3D has come of age after many years of being a cheesy gimmick.

But Lytro is a gadget that is so brilliant in concept that I end up forgiving the silliness of the “Living Picture” marketing.  Here’s what the technology can do, and hopefully will do fairly soon:   instead of shallow focus, the software can, in theory make every shot a deep focus shot.  Or if you choose, make every shot a stereo pair.  When that’s accomplished in the current camera form factor, it will be be a short step to scale up to a larger format that could be of use to professionals.

For more on the Lytro camera, see http://www.dpreview.com/reviews/lytro. Or, what’s really cool, Ren Ng’s dissertation on light field photography is available on the Lytro site at http://www.lytro.com/renng-thesis.pdf

# Why collimate? And an excuse to try LaTeX

I’ve been enjoying a book i got on sale thru SPIE, Friedman and Miller’s “Photonics Rules of Thumb”.  Much of it is (literally) rocket science, but there are wonderful offerings for the advanced beginner, especially in the introductory sections.  One tidbit amateur astronomers may find interesting is a formula relating to the optical performance of a telescope.  The formula returns the angular diameter of the system’s blur circle:  $\theta=\sqrt{{\theta_D^2}+{\theta_F^2}+{\theta_A^2}}$  where  $\theta_D=$ diffraction effect; $\theta_F=$ figure imperfection; and $\theta_A=$ misalignment effect.  One immediately sees that an acceptable blur circle from diffraction and optical figure can be blown by poor alignment.  “Having an element with exceptional figure does not provide a smaller spot if the alignment can’t be done properly”

I also wanted an excuse to try out LaTeX in WordPress, using the built-in Jetpack dingus. It makes the math looks really great and obscures the fact that I’m somewhat math impaired. I found the site at http://web.ift.uib.no/Teori/KURS/WRK/TeX/symALL.html to be helpful, as was “The Short Math Guide to Latex”  at ftp://ftp.ams.org/ams/doc/amsmath/short-math-guide.pdf  I looked at many previews before publishing.  Here’s what the LaTex code looks like:

# A thunder storm

We did get an inch-and-a-half of rain and the landscape is greener.  During the storm, I tried out the video feature of the Canon 60Da because we were getting quite a lightshow.  The camera was running at 59.94 fps.  The CMOS sensor reads out from top to bottom,  so it records only partial frames of short duration events like  lightning flashes.

Here are 3 consecutive frames:

Apparently there are several flashes recorded.  A snippet of the movie is on YouTube.

# Weather radar suspense theater

Hope the we get the red stuff.

A light rain is falling, hopefully ahead of the much-needed downpour they’re getting to the west.  All Summer I’ve been eyeballing the radar and hoping the storm trajectory intersects our farm.  We’ll see a nice red blob pass just to the south, they get an inch, we get nothing