Monday, June 24, 2013

The Alien Contact Probability Boundary

The Drake Equation, as we all know, purports to determine the potential number of intelligent civilizations that share our Milky Way galaxy. Obviously, it makes a number of far-reaching assumptions. But, upon hearing yet another reference to it again, one that indicated it predicts millions of other civilizations, I had to think - there has to be an upper limit, or boundary, to that number based on one sheer fact: we have not heard from any of them, at least not just yet.

Now, of course I'm not the first to proffer this question (why haven't we heard from anyone yet?). What I am suggesting is that the possible number of civilizations is bounded by our not having heard from them to date. And, as time goes by without a signal, that number declines. 

Now, by intelligent life, my only assumption is that it is one that is capable of communication and it only needs to communicate, say, the value of Pi, the ratio of a circle's circumference to its diameter, since that it a universal constant and it seems the most obvious one, to me. (I believe this was actually part of a 1950's era sci-fi movie.) Furthermore, SETI notwithstanding, let's say we've had radio receivers around for nearly a hundred years. Note that I will not be dividing this number in half since I'm not assuming a signal is in response to our own transmissions.

So, if we assume a sphere with a radius of a hundred light years, how many such spheres are contained within the Milky Way Galaxy? Perhaps we should exclude the central portion of the galaxy on the assumption it is uninhabitable. But, we could make any number of such assumptions. I think that is the question since if the population density of life (previously defined) is greater than that, we should have picked up a signal from them, intentional or not.

To make this calculation, we'll use an ellipsoid volume calculator , and eliminate the central bulge, assuming that is uninhabitable. 

For the outer ellipsoid, I very wildly assumed dimensions of 100,000 x 100,000 x 10,000 light years (major axis x minor axis x vertical axis). For the inner ellipsoid, I assumed 20k x 20k x 5k light years. The net volume of the supposed inhabitable zone is then 51,313 billion light years. Dividing that by our 100 light year radius sphere of communication yields 513 billion such spheres.

What that number then represents, fraught with the assumptions as it may be, is the number of civilizations in the galaxy there would have to be in order for us to have heard from them by now (the bottom line number of the Drake Equation).

Now, I'm certainly not saying there is no other intelligent life, however you wish to define it, in the galaxy. But whenever I hear the galaxy is "teeming with life", I have to wonder, up to what point? Oh, I suppose we will hear a signal at some point, say in a couple or three hundred years or so. But, I'm betting the message won't be, "We'll get right back to you".

William Shaheen
Superstition Mountain Astronomical League

Thursday, February 16, 2012

Rusty Mountain Observatory development


The development of Rusty Mountain Observatory is well underway and at this point I'm just waiting for the new mount (Software Bisque's Paramount MX) - hopefully early April. (Hopefully sooner.)

The photo to the left shows the permanent pier, sold by the same company, bolted to a concrete foundation.


See the continuing storyboard for ongoing developements and details: http://www.pbase.com/wjshaheen/rusty_mountain_observatory

Wednesday, February 8, 2012

Rusty Mountain Observatory development

Construction is underway with the pouring of a pier foundation for Rusty Mountain Observatory in Gold Canyon, AZ.  Visit http://www.pbase.com/wjshaheen/rusty_mountain_observatory for monitoring progress.

Friday, July 15, 2011

f-ratio myth - indeed

After reading of Stan Moore's "f-ratio myth"*, I decided to test the concept. And, I agree with him (that it is a myth). Afterall, when you adjust the f-ratio on a camera, all you're really doing is stopping down the lens - i.e., reducing the aperture. Makes sense - and I think this test supports his contention. 

Both images below were taken with an SBIG ST-8300M (monochrome CCD camera) on an 11 inch Celestron EdgeHD SCT using 10 minute exposure times. (The images were taken as part of testing the Optec Lepus focal reducer and the f/10 was a baseline.)

See individual images at: http://www.pbase.com/wjshaheen/fratio_myth__indeed

If f-ratio determined "brightness", then the f/7 image should be twice as bright as the f/10. As it is, the difference is simply in the scale (and resolution) of the two images.

*( See http://www.stanmooreastro.com/f_ratio_myth.htm )

Wednesday, May 18, 2011

Horizontal blooming in the Kodak KAF8300 sensor, when binned

Referring to the image here: http://www.pbase.com/wjshaheen/image/134819312/large
it turns out that what was suspected to be tracking errors, resulting in the "protrusion", or bulging to the right in star images, is actually caused by a characteristic inherent in the Kodak KAF8300 sensor known as "horizontal blooming", when binned. See discussion in the QSI support group here: http://tech.groups.yahoo.com/group/QSI-ccd/message/8682

In the process of centering an object the other evening, I was taking 0.5 sec binned images and noticed that even that short of an exposure exhibited the smearing I've been wrestling with for several months now. See the examples in this album:
http://www.pbase.com/wjshaheen/horizontal_blooming_in_the_kaf8300_ccd

Note the 2x, 3x, and 4x images exhibit progressively larger "bleeding" to the right, whereas the 1x1 example show no anomolies, other than a misshapen star due to atmospheric turbulence.

To attempt to isolate the cause and rule out tracking errors, I devised a simple test:
I rotated the camera approximately 45 degrees. (I normally image with the camera x-axis aligned to the RA axis.) The resulting binned image still showed the blooming directly and solely in the horizontal axis.

I then took similar images using Nebulosity2 instead of ImagesPlus - same result. The next morning, I reviewed past images taken with the SBIG ST-8300M - same result. Here is an example showing both tracking error as well as horizontal blooming:
http://www.pbase.com/wjshaheen/image/134819488/original
Note the distinct oval shape more characteristic of tracking errors (in both axes) versus the bleeding into adjacent pixels caused by horizontal blooming.

After trying a different USB port and eventually a different computer, and still seeing the same, consistent results, I browsed the QSI support group and found this is a known and common problem.

The good news, however, is that the fine detail strucure in an image would not be affectd by this issue (I had been wondering why there was no noticeable "smearing" in my M42 and M16 images, when tracking went well). And, some have suggested this could be addressed in post-processing.

But, as the saying goes, "the proof is in the pudding". So, here's a sample unbinned 10 minute image, dust mote notwithstanding:
http://www.pbase.com/wjshaheen/image/134819756/large

The area is in the neighborhood of PGC54526, RA 15h 17m, DEC 07d 00m, just north of M5.

With the Optc Lepus 0.62x reducer due to arrive any day, I will be able to image unbinned, albeit at a less comfortable 0.58 arc-sec scale. But, I'm very pleased that I've finally gotten to the bottom of a long-standing issue.

Regards,

Bill

Friday, April 1, 2011

Testing the Optec Lepus 0.62x Focal Reducer

Testing the Optec Lepus 0.62x Focal Reducer with the 11" Celestron EdgeHD telescope and the SBIG ST-8300M (monochrome) CCD camera. The telescope's stock rear adapter (with SCT threads) was replaced with an Astro-Physics 2" Visual Back (AP part # ADASCTLC) in order to install the focal reducer as close as possible to the OTA, as recommended by Optec.

I'm pleased to report that, overall, I found the reducer to produce very satisfying images, resulting in a reduction factor of 0.69x. See http://www.pbase.com/wjshaheen/optec_lepus_062x_focal_reducer_testing for full scale test images as well as an f/10 baseline image.

Update 24-Apr-2011: I resumed testing after resolving several issues having to do with the baseline - i.e., SCT collimation, guide-camera flexure and focuser flexure (yes, the Feather Touch focuser resulted in a slight drift, which was not mirror shift).

Visit http://www.pbase.com/wjshaheen/optec_lepus_062x_focal_reducer_testing and see the 4 images of M57 (Ring Nebula) taken this date - on the bottom row.

Some coma is noticeable in the lower left corner only and may be due to a tilted plane, which itself may be the result of, again, the leading edge of the reducer stopping at the edge of the internal field flattener. This is being researched with the vendor.

On another note, I have a professional source whose contact at Celestron indicates they will be releasing a reducer this summer. It will have a respectable back-focus (90 to 110 mm) but may not have the coverage originally desired. It will however cover an APS size chip and certainly the 8300.

Update 11-May-2011:
Update on the question of the reducer possibly not seating squarely (the leading edge of the reducer stopping at the edge of the internal field flattener), I just received word from Optec that they "have developed a different mounting configuration for the Edge HD scopes. For the C11 HD and C9.25 HD scopes a spacer is required to keep the lens housing from touching the Edge HD retaining ring." . (At the time I ordered mine from OPT, they had the former version in stock.)

Optec is sending me the new lens and housing gratis and I will be testing it in about a week.
(Thanks, Jeff!)

As an aside, I've replaced the ST-8300M with a QSI-583wsg - solves a host of flexure issues up and down the imaging train as well as with any mirror flop or guidescope flexure. The Starlight Xpress Lodestar connects easily to the QSI's guideport, given the standard C-mount adapter) and so far I've had no problem locating a guidestar.