Time To Cast Another Mirror!

Polishing mirrors, particularly the behemoths we make at the Steward Observatory Mirror Lab is a slow, exacting process. While we work long hours, in fact, we're up to 3 shifts a day now, it still takes years to finish a mirror surface to the accuracy of nearly a glass molecule! But the casting of the mirror substrates is more a matter of engineering and science. We've got a fantastic casting crew that can push out the nearly 30 foot diameter substrates nearly once a year. Our last casting was a year ago January, and we're about to start another in a few days. This one is the 3rd mirror substrate for the Giant Magellan Telescope (GMT), and yesterday was the loading of the glass into the telescope mold.


Few things are more photogenic that watching the loading of 20 tons of gleaming glass chunks into the mold.  The E6 glass is a Pyrex equivalent, made for us from Ohara Optical in Japan.  They make it in small batches of a ton at a time, and cleave it into the chunks seen so that they will melt together in the substrate without trapping air bubbles.  And while these days we could obtain glass with nearly zero coefficient of thermal expansion(CTE), we use borosilicate glasses which become fluid enough to melt and run into the mold.  Ultra-low CTE glasses do not become fluid enough to do that.

The process started a couple weeks ago when the glass was brought in from our off-site storage.  Each block was inspected under crossed Polaroid filters to look for internal stresses.  While Ohara goes to considerable effort to maintain precise uniformity from batch to batch, occasional impurities result in internal stresses that do not get relieved by re-melting.  In the crossed-Polaroid test, stress birefringence rotates the plane of polarization allowing it to become visible.  In the photo at left, a seed, a speck of impurity introduces a high-stress point (circled at lower right).  If these are close enough to the block's surface, the glass can be re-cleaved to remove it and the rest of the block can be used.  Besides pulling out the small percentage that is rejected for high stress as above, it is also graded for quality.  The best glass is layered on top of the mold last so that the mirror faceplate will contain the highest quality.

The actual loading is a day-long Herculean effort by the crew.  They usually recruit a couple volunteers from other areas of the lab to lend a hand.  The shot at left shows a panorama of the operation.  A forklift brings up pallets of the inspected glass blocks at left, and a crew loads them into the inclined rollers to hoist them to the 3-man crew placing the individual blocks into the mold.  Another worker removes and collapses the empty boxes for recycling.  Peeking into the oven, you can see some of the resistive heater elements lining the oven interior, and the Inconel bands that encase the tub walls of the mold.  The crew had started loading about 5am and these pictures were taken about 6+ hours later.  It makes for a long, strenuous day, followed by the removal of the loading scaffolding.  Today after a final look around, they installed the top of the oven and make final preparations for the 3-month casting process.

Round about this weekend they will flick the switch and it will start the temperature ramp up towards the melting point of the glass.  It takes about a week to reach the high temperature of 1180C when the mold will fill with the molten glass as the oven spins at the correct speed to form the right curve on the molten surface.  This is scheduled to happen during the weekend of the 24th, after which it will cool slowly to prevent stress in the blank.  If all goes well, we'll get to open up the oven and take our first look about Thanksgiving.  If only we could pump out polished mirrors as fast!

My Favorite Galaxy!

Melinda was off last night, and the monsoon weather continues on hiatus, so we again headed to Kitt Peak National Observatory to catch some early Perseid meteors.  Since it was a "school night", we couldn't stay too late, but since she has to work on Monday night, the peak of the annual meteor shower, better to catch some than stay home and miss most if not all of them!

The Nightly Observing Program had been cancelled, since the forecast had called for a chance of rain, so we arrived to an empty parking lot, though all the "Big Boy" professional telescopes were open and working.  Like the other night we set up in the lot since it had pretty good horizons - not too much obstructions from the nearby trees or hills.  Melinda was only interested in the meteors, so set up a chair for visual lookin' and I again set up the tracking platform for some wide-field photography.  My hope, of course, was to capture a few meteors, but other than that, didn't have much of a plan. 

The waxing crescent moon was still above the horizon, but with it only 4 or 5 days past new, didn't much diminish the Milky Way Galaxy transiting almost due south.  In fact, the little bit of moonlight lit up the domes on the south ridge of the Observatory enough to let them stand out with the galaxy center shining down.  The image at left is a single exposure with the Canon XSi and Nikon 16mm fisheye at F/2.8.  I used the tracking platform at the half-speed rate so that the blur would be spread out between star and horizon to allow a little longer exposure.  This one is 90 seconds at ISO 1600 with in-camera noise reduction on.  The dome to the left is the 2.1 meter, and at right center is the WIYN 0.9 meter telescope.  The row of red lights at the bottom are to guide NOP guests to the rest rooms.

While taking the above exposure, I got a wild idea...  With the ease of making the panorama the other night of the Prancing Horse Nebula, I wondered how wide-field shots of the Milky Way could be put together for a portrait of our galaxy.  I chose another Nikon lens, an older 20mm F2.8 from my film days, and started down near the southern horizon.  I shot 4 or 5 exposures of 3 minutes each to stack and reduce noise, then moved north a good part of the frame, allowing a little overlap for software to assemble the panorama.  Of course, with meteors whizzing across the sky, if I happened to catch any of them, all the better!  In fact, I caught only one - a pretty bright one we saw zipping just above Cygnus, shown at left.  Deneb (alpha Cygni) is the bright star just right of center, with the North American Nebula just below left of it.  While only capturing the one meteor, we saw 43 Perseids in 3 hours of looking, and also saw about a dozen from the Delta Aquariids and Anthelion radiants as well as some sporadic, random meteors that we didn't include in our totals.

So anyway, I ended up shooting 6 frames with the 20mm, 4 or 5 exposures of 3 minutes each.  Coverage pretty much went from the southern horizon to below Cassiopeia near the northern horizon, though some thin clouds or haze, lit up by Tucson and Phoenix had me cropping out some of that section.  Amazingly, Photoshop had no issues with assembling the star exposures.  My only issues were with data reduction...  I shot raws as well as jpegs, also took the occasional dark frame to subtract electronic noise.  I first reduced the raws, subtracted the darks, reconverted to color, then stacked and assembled the panorama.  Unfortunately, this version was difficult to make the Milky Way look realistic.  The fainter sections looked very much like the brightest sections, so I went through it all again with just jpegs, without dark subtraction.  Since the blog limits me to 1600 pixels wide anyway, you can't see any sign of the hot pixels anyway...  And this version looks much more realistic, and the dark nebulae structure scattered through the plane of the Galaxy looks quite amazing!  Absolutely click on the image to see the full-size version.  I've seen a few impressive pictures of distant edge-on galaxies, but here you can see my favorite galaxy, assembled from images taken with a 20mm lens in less than 2 hours of exposure! 

And while the pixel limit really cuts down on what you can spot, you can easily pick out the Andromeda Galaxy at the lower left corner.  Of course the Prancing Horse dark nebula is seen to the lower left of Antares at the far upper right.  And the Summer Triangle of Vega, Deneb and Altair can be seen near the center.  Perhaps I'll make an annotated version with labels, but it is a shame you can't see the 10,000 pixel wide image.  Anyway, enjoy!

Pipe or Horsie?

I spent a few hours on Kitt Peak the other night and posted the Iridium Flare shot that was my first exposure of the night.  The next couple hours was spent on a 3-panel mosaic near the center of the Milky Way Galaxy - one of my favorite fields, the Prancing Horse Nebula.  Shown here is a wide field shot from a couple years ago from an observing session with our friend Christian.  Regulars know I'm a fan of dark nebulae - clouds of dust and gas silhouetted against distant cloud of stars behind it.  The left side of the frame shows the network of dark clouds known as either the "Pipe Nebula" or the "Prancing Horse Nebula".  You've got to use your imagination, but both can be made out.

One way to improve an image is to expose longer, another way is to use a telephoto lens and assemble a mosaic of the field.  This has the advantage of improving the resolution of the target object.  Using the (relatively new) Polarie tracking platform, I shot the dark nebula with my Canon XSi and 20-200mm lens, set to 100mm focal length at F/3.2.  Starting with the rear leg of the horse, or the pipe part of the nebula, I shot 10 exposures of 3 minutes each, shifted northward and repeated the sequence for the center and head sections of the field.  I took a couple corresponding dark frames at the start, between fields, and after the sequence to subtract during processing.  One rule-of-thumb in processing is that you sit in front of the computer just about as long as you spend exposing, and it was true in this case too.  Of course, it would help if I did this more often and became a little more proficient...  Luckily the automatic "photomerge" function in Photoshop worked on these starfields and made the mosaic construction easier.

The image at left is the result.  Do click on the image to see the full-size version - reproduced here at the Blog maximum 1600 pixels across.  There are a LOT of deep sky objects contained in the field, including a dozen or so globular clusters, and likely more Barnard cataloged dark nebulae.  The one that is readily seen is B72, the Snake Nebula, located right about in the center of the frame.  Unfortunately, the scale of the image is still too small to resolve many more objects.  I've rotated the frame to better "see" the Prancing Horse shape.  And while the left side of the frame looks redder (and corresponds to the first frame), I've treated all the fields the same, so I believe it is real...

This is the same frame, cropped slightly and rotated back so that North is upwards to show the "Pipe" (as in smoking pipe).  The tendrils are supposed to be wisps of smoke emanating upwards from the pipe.  Let me know if anyone doesn't see the shapes, and I'll add an annotated pair of images...

About the only way to do better, in resolution and depth is to start zooming into the field, particularly with the 1600 pixel blog limit.  It is too late in this observing session to do much of that, but may take up the challenge in the future!

My God, It's Full of Stars!

A couple sayings seem appropriate for this post.  The first is that you gotta' "Make Hay While The Sun Shines".  In other words, if the weather is good, and you've got hay cut, put off the trip to town and bale your hay before tomorrow's storm ruins the crop.  Farmers say it, really!  The other that comes to mind is that "I'd rather be lucky than good", and the picture at left seems to prove that!

We're back in Arizona now and we find a break in the monsoon clouds, so after getting Melinda safely off to work last night, I headed up to Kitt Peak National Observatory for some photon collecting..  While checking weather conditions, I normally check Heavens-Above to see about satellites, and notice a rather faint Iridium Flare is better if you go west (towards Kitt Peak).  Switching to the Observatory for the observing condition, the flare is predicted to be -8.4, which is about as bright as they get and about 80 times the brilliance of Venus!  What makes it more interesting is that it happens a few degrees from the deep-sky object M27, the "Dumbbell Nebula".  I usually enjoy imaging flares near sky objects, have posted one or two in the past.  Leaving home in Tucson, I had almost 2 hours to flare - you can set your watch by these, so you can't be late!

No stops for gas, snacks or bathroom, I took the required 80 minutes to legally make the trip and parked in the public lot.  One of the perks of working there - no one would have hassled me setting up there, but no one even checked on me, though one or two of the observatory cars passed in the deep twilight.  It was an incredibly clear night - it had been 2 months since the Canyon star party that I've seen skies like this.  Driving up the western flank of the mountain, the skinniest crescent moon hung on the horizon, yet as clear as overhead it was so clear.  As I set up my new Polarie tracking platform and hooked it up, I still had 10 or so minutes to go.  Camera, telephoto lens, polar align the tracker, install camera, focus on star - PERFECT!  Went to the field, between Delphinius and Cygnus, check camera settings, turn on long-exposure noise reduction for this exposure.  Check the clock - still a couple minutes for a test exposure...  Push the shutter - nothing!  Drat, I know exactly what it is - I forgot to switch the telephoto lens to manual focus, so in the dark, it tried, but couldn't find anything to focus on!  And of course, it moved it off the perfect focus I had set...So, back to a brighter star, live view, focus star, reacquire field in the viewfinder...  Check the clock - do I have time to take a test frame?  No!  Get out the intervalometer, preset to 3 minutes exposure.  Look up - I see a satellite!  Moving towards the field, I think it has to brighten a lot to be the flare, but in a few seconds, I push the button...  Off to the left, suddenly I see the REAL Iridium satellite flare to its brilliant peak - I was watching the wrong satellite!  I wanted to catch some details of the Milky Way and M27 if they were even in the frame, so let it go 2.5 minutes before I finally chickened out and viola - the picture seen above left!  Lucky, lucky, lucky!  The entire frame is shown, north is approximately towards upper right.  An annotated version of the frame is shown at right.  the two streaks are the satellites, the one marked with question marks is the mysterious one I was watching that caused me to start the exposure...

A friend once told me that "Luck Rewards The Well-Prepared", but in this case, I think I was lucky!

Of course, the above picture is re-sampled mightily to make the file a reasonable size, so lots of detail is lost.  Shown here at right at full camera resolution is the section over in Vulpecula (the Fox) where Messier 27, the Dumbbell Nebula is located.  I usually find it (can be spotted in binoculars!) by the faint parallelogram of stars connected in the image.  The greenish disk just below the bottom point is the nebula.  Don't forget that the 70-200 Canon F/2.8 zoom was set to 70mm for a wide field, so few details can be seen other than it's overall shape and color, but still nice to see next to the flare.





While setting up in the twilight, there was sort of a blustery breeze, which I sort of forgot about in my haste to get going.  But it did affect the image.  Lost in the above low-resolution image, the wind was wiggling the camera enough to reveal its presence.  In the full-res image at left you can see the wind-induced wiggles.  While easily seen in the trail of Iridium 75, the wiggle can't be seen in the stars' images, but it does manifest itself by bloating the star images a little bit...


So this is just the first frame of nearly 2GB of data I took on the incredible evening!  The rest I'll save for a subsequent post.  And I was still home by 1:30 - not bad for a "school night"!

Highlights Of Our Summer Vacation!

Our Summer break at "Ketelsen East" in the western 'burbs of Chicago is winding down, but we've covered a lot of ground in just a couple weeks.  Time to review a few of the highlights, each perhaps not enough to fill out a post on their own...

Of course, the primary reason we come back is because we both have family here.  So we've spent time with both of Melinda's sisters, and seen most of my relatives in Iowa as well - a couple times!  Min and sister Maj travelled down to Saint Louis upon her arrival to visit an elderly aunt while I was still off on RAGBRAI and had a good time reliving the past with them.  The day she returned from that trip, I got back from the bike ride and we returned to Iowa the next day for great niece Alivia's 7th birthday party!  She is a ball of fire, and along with her cousin Mya (also a great niece - that we've not seen in what, over a year) made you tired just watching them!  If we could only harness their energy...  We figured the cool temps would keep everyone out of the pool (high about 70F), but the 2 girls alternated between pool and hot tub at brother Jim's house, all while keeping everyone entertained.  A week later, we returned to visit some friends, and join (Dean's sister) Linda and Lauren for their 35th anniversary (Alivia and Mya's grandparents).  We ate at a local pizza joint and got to hang out with the great nieces again (at right).

We did a lot of local activities!  I think we cooked at home only once, and that was while Melinda was out with her girlfriends and I was home alone to grill...  We ate out with friends pretty much every night.  I got in a pair of banjo lessons, and do well enough that Melinda can recognize the tunes.  We're going to try to get it to Arizona so I can continue to practice.  We saw the movie "The Way Way Back", which was very good...  I went to the "Flea Market", a first-weekend-of-the-month garage sale that fills up the Kane County Fairgrounds with what must be the largest garage sale around.  That is where I found the 'ole camera I first got as a teenager last Fall.  This year, while tempted by a collection of science books from the 1890s, I only spent money to enlarge my collection of astronomy-themed 3D stereo view cards that a woman had.  She specialized in vintage postcards, but had a few thousand of the Keystone View Company cards.  Otherwise, if one was in the market, you could find everything from an Indian totem pole, to unknown rusty farm tools to TV Guide magazine from the 1980s - pretty much anything and everything!

And speaking of friends, we met Mary and Dave, organic farmers west of town here...  She was recently given a telescope that her sister was throwing out from their Wyoming ranch.  Mary didn't know if it was functional, but it also had a thick layer of dirt and dust on it.  We retired to their place after dinner and it was a decade-old Meade telescope of fine quality, though only 3.5" in diameter.  I wiped the dirt off as best I could and was able to show them Saturn - this while set up on the hood of our car since it lacks a tripod.  She was certainly impressed by the view and promises to keep it going after I found her the manual on-line.

And speaking of friends, we spent time with Carolyn a few times - she even joined us in Iowa for Alivia's birthday.  I came home from the Flea market to find her and Melinda down at our micro-beach on the Fox River with her grandson Colin.  They wouldn't let him into the water, but he had fun running and jumping on what little sand there is.

In the 3 weeks I've been here, it is interesting to watch the progression of flowers, both native and cultivated, as they come and go.  When I arrived in mid-July, the plot next to the house was all about the tiger lilies, now there is no trace of them, but the phlox are now filling it with white and lavender.  The sunflower at right is from the back yard of Sharon, a friend over in Davenport, Iowa.  It was backlit and striking, so captured it with the macro...

And while I enjoy stalking the various bugs and insects of the region, you already saw the highlights, but have a couple more to show you.  I spotted a common whitetail dragonfly in a prairie walk at our nearby forest preserve.  Easy to spot, but harder to stalk and sneak up on!  And at right is a katydid spotted in the little jungle adjacent to our house...

And of course, RAGBRAI is always a highlight.  While I've made some posts about it already, indulge me for a few more pictures!  First up is from our camp in a backyard in Harlan Iowa.  After a warm trip across the state, and a hot first day's ride, a rainbow over riders Sue Ellen and Terry portend nicer weather for the rest of the week.  This frame is actually a "High Dynamic Range" (HDR) image assembled from 3 exposures with slightly different exposures to maintain detail in shadows as well as highlights.  We actually had just about the coldest weather we've seen on the ride in my 20 years, hitting 50F for a low on Friday night!

As driver, I don't get on the route very often, but while picking up riders in Pella, I spent some time hanging out in the Dutch capital of the state!  They are quite proud of their heritage, and have the largest operating windmill in the country (135 feet tall) that is actually used for grinding grain.  On this breezy day it was putting on quite a show.  This vertical panorama was able to get it all in with all the bikers in the foreground.  The museum and store in the adjoining building was pretty neat too.  You could even buy your own wooden shoes, including some pretty ornate ones for special occasions!  On my way out I ran into a couple local residents dressed up in traditional garb.  The one on the right admitted she was actually of German descent, but for a crowd of this size, all the locals were Dutch!

Well, those were the highlights of our Summer trip.  What was perhaps the most amazing is that after last Summer's drought and hot temperatures, other than my first few warm days in the mid-nineties, it has rarely gotten over 80F the last couple weeks.  It has been great, though a little on the rainy side.  Given the choice, I'll take rain and cool!  Until next time...

An Odd Visitor!

Just south of our house in Illinois is a jungle of bushes and shrubs.  I hadn't looked around in it this trip, so took a break from yesterday's blog post and brought along the macro lens, just in case anything interesting came along.  Boy, did it! 

I've never noticed these fellows before, but one species of bush had about a dozen or more on it.  They looked amazing - like a headless beetle!  They are about 5-8mm long, lacked antennae or a head, and walked, if not looked, like a crab in a shell.  Of course, a Google search with similar keywords turned up nothing, so I sent the picture at left to  "Bug Man" Carl Olson, an entomology expert at the University of Arizona.  In a former life, we played volleyball together (he was on a different team) in City League play.  The last couple decades, we was well-known locally in all-things-insect, from being interviewed on TV to various press releases from the University of Arizona.  While he retired from teaching at the beginning of the year, he continues to curate the insect collection of the UA, with nearly 2 million specimens, as well as answer the 4,000 requests for identification that they get a year!

By the time we got back from our evening activities last night I had an answer - they do in fact, have heads - you can see their little brown eyes just in front of their legs.  These are Enchenopa binotata, the two-spotted treehopper.  They have evolved to take on the appearance of thorns or leaf stems to avoid predators.  I also had an inkling that they were hoppers of some sort - after e-mailing Carl the picture, I touched one and it jumped a good foot and a half!

Of course, now that I've seen them, they stand out like a sore thumb and wonder how I've missed them in the past.  They are rather smallish and my 100mm Canon macro didn't do an outstanding job yesterday, as the wind was frustrating my efforts.  Today I did slightly better, getting the shot at left, but still, for a quarter-inch across bug, it is about the best I can do...  And of course, the search continues for the unusual...

New McDonald's Menu Item - A Blog Post!

As I said in my last RAGBRAI post, after the bikers take off in the morning, I like to linger over breakfast and read the paper.  In Omaha, where the bike ride originated this year, after doing my cooler and snack shopping, I stopped at the McDonald's at 40th and Dodge.  Breakfast was uneventful, but as I was gazing out the window, I saw a blog post!

Even regular readers of this blog likely don't realize it, but at the bottom of the page, there is a link to "FEEDJIT", which tells us who is reading the blog and what they are looking at.  Of course, there are limitations, it identifies not actual readers, but lists the city where their ISP is located, and how they got to the blog.  Interestingly, one of the most popular posts I've ever written is the one on Moiré patterns!  For some reason, the patterns created, usually from a pair of overlapping screens, stands out and yells to me!  In this case, from inside McDonald's, it was caused by the overlapped screen patterns of window advertising!  The view from the outside is innocent enough - shown at left.

But the view from the inside, to someone who (at least sometimes) notices the little things, was very different!  Shown at left is above's left window from the inside.  The Moiré pattern I noticed is in the overlap areas - note that the overlap pattern at right is different from the overlap at left.  Click the image to see a larger version.  What causes it?  Well, the advertisement is not a solid graphic - it has little holes in it...  I know that Tucson has requirements for convenience stores to unblock windows so that the inside can be seen from the outside at night - a theft deterrent.  By putting the little holes in the graphics, they become at least partially transparent to see inside at night, and like these pictures show, you can see outside during the day.

The key for the present experiment is that when the holes are put into the graphic, or if they exist in the substrate before processing, they come out with different hole spacing!  As a result, when they are overlaid on each other a Moiré pattern results.  In fact, when you click and load the left image you may get a checkerboard pattern on your screen as the hole pattern interferes with the pixels on your viewing monitor. The picture at right and near left show the overlapped areas with more resolution so that you can spot both the hole pattern in the graphic and the resultant Moiré pattern.  While the pattern on each of the graphics looks identical, if you look at the full-size version and put a ruler up to the screen you can see that the patterns have slightly different spacings.  Because the Moiré patterns are different, we know that all three of these graphic screens are slightly different in size or frequency.  Even though the 2 outside graphics don't overlap, we can tell that if they did it would result in a different Moiré pattern!

Going back to the very top picture of the
advertisement from the outside, the right hand part of the graphic has a totally different look from the inside.  The main reason is that the graphics have no, or almost no overlap.  However, there is a window sun screen that is used to block part of the incoming light.  The screen, as shown at left, has a regular pattern that hangs down over the graphics.  The resultant set of Moire patterns between graphics and sunscreen is shown at right.  It is quite intricate and again, is different over different graphics showing that the hole spacing differs slightly.  At least to me it is very eye catching, though most people would likely not see the patterns, let alone realize what causes it or knows its name!  I would file it under "frequently seen but rarely observed" - my moniker for details from everyday life that few ever notice.

And while not listed on the menu at McDonald's, I got a big kick out of it.  And after seeing this my first day of the ride, I went looking at other outlets for similar effects, but never saw it again.  Keep your eyes out!