Among the milkweed

We have a horse pasture that’s occupied by a horse, Rose, and donkey, Midnight. They are both pushing 40 and have been together for most of that time. They actually came with the farm; the previous owners could find homes for one or the other, but not both, and they are inseparable. Well they are both pretty fat, and can’t nearly keep the pasture mowed by themselves, so we get a lot of weeds. There’s a milkweed patch at the west end that is doing pretty well; the ponies keep the grass down, but don’t touch the milkweed, since it has a profoundly nasty flavor, and this benefits the milkweed nicely.

We don’t see a lot of Monarch butterflies here, a few a day from late May. I think the main migration route is more to the west. Heres a map of sightings from Journey North, and you can see a gap that runs up through Central Ohio.

Journey North map of 2019 peak Monarch migration.

Anyway, I was hoping to see Monarchs hanging out around the milkweeds, and over about 3 hours, saw one, and then two working the milkweed flowers.

Monarch on milkweed blossom

I had assumed that Monarchs were important pollinators of milkweed, but they are not. Milkweed flowers don’t produce pollen grains like I had expected, but bundle their pollen in a little sack, called pollinia. Their nectar attracts many insects, but only a few have the anatomy to (accidentally) grab the pollinia and move it to another flower on another plant. (It needs to be another plant, because milkweed doesn’t do selfing.)

Honey Bee and Japanese beetles working milkweed blossom.
Honey Bee and Japanese Beetles

I snapped this picture of a honey bee busily pollinating while two Japanese beetles busily destroy blossoms. I didn’t know anything about pollinia until I was reading up on monarchs and milkweeds in a really good book on the subject appropriately entitled “Monarchs and Milkweed” (Anurag Agrawal, Monarchs and Milkweed, 2017, Princeton, NJ, Princeton University Press). Well. The wonderful thing about photography is that you will find things in the image that you never noticed in the object. In the picture above, the honey bee has a little gadget stuck on her back legs, which is, sure enough, a pollinium.

Honey Bee and milkweed pollen sac “pollinium

The honey bee is one of the invasive imported species that we actually welcome, so it clearly didn’t evolve with milkweed. So it would be interesting to identify native pollinators. There’s a really good article on the topic at http://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC13/reference/econatres.napc13.rbetz.pdf which suggest that honey bees in fact displaced the native bees that evolved with the milkweed.

I did see a variety of insects working the blossoms.

Great Spangled Fritillary

The wonderfully named Great Spangled Fritillary is very common around here, as is the Common Sooty Wing. I doubt either of these guys have the equipment to pollinate milkweed but they enjoy the nectar.

Common Sooty Wing skipper
Wasp mimic fly, genus Physocephala

I thought this guy was a wasp, as it turns out, it’s a fly that mimics a wasp. Worked for me. I also saw several bumble bees, and a pearl crescent butterfly.

You’ll also see various red insects with black markings, sometimes on the blossoms. This little guy is the Red Milkweed Beetle (Tetraopes tetrophthalmus). Not a pollinator, these beetles eat milkweed for breakfast, lunch and dinner. Like Monarchs, they have evolved to manage the toxic sap of the milkweed, which provides them with a terrible flavor that makes them very unattractive to predators.

The “Tetraopus” refers to their four eyes, arranged above & below the antenna.

Milkweed Bug

The Large Milkweed Bug also evolved as a pest to milkweed, and like the milkweed beetles, has aposematic coloration, a cool word I just learned, which refers to coloration that warns predators that they can eat you, but may not enjoy it.

Milkweed bug nymphs

I believe these are Milkweed bug nymphs, a juvenile stage of the Milkweed bug. There is also a Small Milkweed Bug and a Milkweed Leaf Beetle that I haven’t seen yet, but all have characteristic red and black coloration, and live exclusively on milkweed.

Ant tending aphids
Ant tending aphids

Here’s an ant tending aphids on the bottom side of a milkweed leaf. The aphids suck juices from the plant, and ants drink the sugar-rich excrement of the aphids, “honeydew”. If you look closely, you can see a drop of honeydew emerging from the aphid. It seems to have the attention of the ant.

Aphids, Aphis asclepiadis, on milkweed

These are apparently various life stages of the aphids, Aphis asclepiadis, with nymphs and a winged adult. There are two other species of aphids specializing in milkweed that I will be looking for.

Monarchs begin their lives on milkweed. They lay their eggs on the underside of the leaves, in three or four days, a tiny caterpillar emerges. This guy is about 2″ long, maybe 4th instar?

Over the next 10 to 14 days, the caterpillar eats a lot of milkweed, and grows through 5 instars, or molts, until it is 2 to 3-1/2 inches long. Then it forms the chrysalis, and another 10 to 14 days later, an adult Monarch butterfly emerges. The butterfly can eat wherever nectar is served. I often see them working clover in the hay field, also butterfly bush, cone flowers, and the usual butterfly suspects. The adults will return to milkweed to mate and start the cycle over.

Lunar eclipse at moonset

We’ve had an inch-and-a-half of rain over the last 2 days, and when I got up at 4:30 to check the sky, we were still socked in.  Went back to bed, woke up a little after 6, and I’ll be darned if the clouds hadn’t cleared out and offered a beautiful view of the earth’s shadow just beginning to take a bite of moon.  The photo below is about as deep as the eclipse got for me.

lunar eclipse

The partially eclipsed moon sinks into the tree line shortly before sunrise. Nikon P510 at 180mm; f/5.6 at 1/100 sec. 20150404 6:02AM EDT.

Comet Lovejoy trials and tribulations

Friends have asked if I got pictures of the comet (Lovejoy C/2014 Q2) and I’ve been reluctant to admit, that, yes, I have, but that they are pretty bad pictures.

The first was a wide field shot in which I imagined seeing the comet’s tail streaming gracefully among the Hyades and the Pleiades. For tracking, I mounted the Canon 60Da piggy back on the Takahashi, set the camera’s intervalometer to take 60 1 minutes shots, and went in the house. About 10 minutes later, I let the dog out, and the sky had socked in, and was spitting snow!. So I shut things down, having got 5 minutes of usable exposure in. There’s the merest hint of a tail, if you look close, and really want to see it. I shot the images at 28mm, f/5.6. The comet is really small in the frame, although it would have worked ok if I could get more exposure. Actually I think the picture captures the impression you get with binoculars.

Comet Lovejoy Jan 14, 2015.  Canon 60Da; 28mm @ 5.6; 5 x 60 seconds.

Comet Lovejoy Jan 14, 2015. Canon 60Da; 28mm @ 5.6; 5 x 60 seconds. Click for larger image.

 

The next clear night I used the STL 11000, and was able to see really nice detail in the comet’s tail. Unfortunately, the camera was overdue for the annual regeneration of its dessicant plug, and the image is overlain by the shadows of tiny ice crystals. So I took a few pictures and set up for flat fields, hoping I could zero out the frost. The frost is a moving target, and the flats weren’t helpful. So the image below is 5 minutes, dark-subtracted and auto-background-extracted in Pixinsight. The black cuneiform is what frost looks like on a chip. You fix that by removing the desiccant plug from the camera, and popping it in the oven for 4 hours at 350 degrees, which I did the next day.

Comet Lovejoy Jan 15, 2015.  STL11000 on Tak FSQ 106. 5 min exposure.  With frost!

Comet Lovejoy Jan 15, 2015. STL11000 on Tak FSQ 106. 5 min exposure. With frost! Click for larger image.

The third try for Lovejoy was one of those completely abortive observing nights that nobody ever admits to. I planned to use the Canon at 100 mm piggybacked to get Lovejoy with the Pleiades, while exposing the STL11k for the coma and tail. First, the nut that holds the Canon to the mount had come loose and disappeared, and a spare was not immediately at hand. So, I scratched that part of the plan. Then, I could not find Lovejoy in the STL! I had collected coordinates in the house, punched them in, but no comet in the exposure. So I went online in the hut to get updated coords, tried them, and no comet. Tested the overall setup, and made a perfectly lovely, centered shot of Aldebaran. But I apparently had outdated comet info. It was around zero that night, and I was dressed for it, but my feet were getting cold and I was getting frustrated, so I hung it up for the evening with nothing to show for it.  That was about a week ago;  the forecast suggests that I may get another try on Thursday!

A school of blackbirds

One of my favorite  sights is the crazy blackbird flight school offered each Spring as hundreds or thousands of birds launch into flight together, wheeling and turning in unison.  We have a very healthy stand of bamboo grown from a few starts given to us 20 odd years ago by our friend Joe.  That little patch has grown into a dense grove that now provides shelter for hundreds of birds all winter.

frosty bambooHopefully the bamboo has survived this particularly brutal winter.  As Spring approaches, the bamboo residents are becoming more and more noisy.  At night I think there’s a windstorm raging and realize it’s the birds rolling over in their sleep in unison. In the morning and evening they put on an airshow going about their business.  I believe these are mostly red wing blackbirds, since I hear their territory calls coming from the bamboo, but apparently flocks often contain starlings and other blackbirds as well.

There are two groups to begin with; they seem to coalesce into one, but then split again, with one group settling into roost.  It would be interesting to know, but I can’t tell from the video,  if the  group that peals off to roost first is made largely of members of one of the two original groups.

Flocking is mesmerizing to watch.. It was modeled in a classic artificial life routine called Boids by Craig Reynolds.  His flocking model defines only 3 steering behaviors:  “Separation –  steer to avoid crowding local flockmates; alignment – steer towards the average heading of local flockmates; and cohesion – steer to move toward the average position of local flockmates.. … Flocking is a particularly evocative example of emergence: where complex global behavior can arise from the interaction of simple local rules.”

Pixinsight workflow for annotation

Since I’ve been using the Takahashi FSQ106-ED with the STL11000, I’m getting wide field images, about 3.9 x 2.7 degrees.  So the fields contain numerous cataloged objects that would be nice to identify.

Pixinsight offers a workflow to “solve” the image which provides accurate WCS coordinates that are added to the FITS header; and an annotation script that overlays  grid, constellation boundaries, and objects from several catalogs.

Sagitarius region

A wide field shot made with Canon 60Da and 28mm lens, about 45 x 30 degrees. Annotated in Pixinsight. 15 minute total exposure at Rancho Hidalgo, New Mexico.

For narrow field images, the ImageSolver script should work, but it fails pretty regularly on my STL11K pix and really fails on wide field shots made with the Canon 60Da with wide lenses like the one above.  Located in the Scripts | Image Analysis menu, the script panel asks for the center coordinates of the image, with a search function so you can choose a known object in the active image.  If the script fails, as is likely with wide field images, it is still useful to improve the accuracy of the ManualImageSolver script.  To use the ManualImageSolver script is not straight-forward, but it does work pretty well.  It’s not straight forward, because, before running it, you need to use the CatalogStarGenerator script to build a synthetic star field image; then use the DynamicAlignment process to manually match stars in the reference image (the synthetic catalog star image) to the target image (your astrophoto).  After saving the instance of DynamicAlignment to the workspace, you can run the ManualImageSolver script to provide WCS coordinates to the target image’s FITS header.  Honestly, you have to really want it.

Here are more details.  Open the target image, the image to be solved.  It must be FITS format, because the FITS header is where the WCS coordinates will live.  Locate a named object near the center of the image, you will use it the generate a CatalogStar image. I used M8 (Lagoon nebula) in the example. CatalogStarGenerator PanelRun the CatalogStarGenerator  located in the Script | Render menu).  Search for your chosen reference object, which will populate the coordinates fields.  Fill in the Dimensions field (from your target image) and provide the Image Scale info.  In the Stars panel, choose a catalog, probably the Bright Star catalog. The PPMC catalog is more comprehensive, but is too big for to be practical for wide field images Click OK to run the script, and it will build a reference image of the field. I use the STF panel (‘screen Transfer Function) to adjust the screen stretch so the stars are more easily seen.
Once you have a reference image you’re happy with, you align your target image with it using the

Synthetic star field

Synthetic star field made with CatalogStarGenerator.

DynamicAlignment process (located in Process | Image Registration menu).  When the process panel opens,  click the reference image (the synthetic star field); this defines the reference image for the process.  Then click the target image (your astrophoto).  Now click a star in the reference image that is obvious in the target.  This will place an X in the target that you will drag to the corresponding star.  The first few alignment points can be surprisingly painful, but once 2 or 3 points are correct, the rest are (usually) placed pretty accurately.  However, you MUST check each point since there is generally some distortion  in the field.

dynamicAlignment_screen

Screen shot of DynamicAlignment showing first alignment point.

The other pain point is that for best results, you really need 40 or so points spread over the target. (A shortcut is to use 4 or 5 alignment points and then run ManualImageSolver  followed by ImageSolver, which should run happily and produce a pretty good result.)  Ok, so you when you have enough alignment points, drag an instance of the DynamicAlignment to the workspace.  The instance is represented by the little triangle at the lower left of the process window; when you drag it to the workspace it creates a savable icon with all the details of the alignment session.  You need that when you begin ManualImageSolver. located in Script | Image Analysis menu.

ManualImageSolver script panel.

Manual Image Solver script panel.

Select your DynamicAlignment instance with the Control Points icon, and the catalog star reference image as the Reference Image.  You can improve accuracy by raising the Polynomial degree to higher numbers.  The residuals image provides an accuracy check; the distortion map shows optical distortion, and the distortion model provides a way of modeling the system to simplify solving other images with the same optical setup.  Anyway, now that you have manually solved the image, a set of WCS coordinates have been inserted into the FITS header.  And you can run the AnnotateImage script in the Script | Render menu.

Annotate Image script panel.

Annotate Image script panel.

The script panel provides an essential preview tool which lets you play with settings without rendering the whole image.  You will want to try different settings on labels and markers, but a tip is to use the Graphics Scale slider at the bottom to change everything at once.  You can render to a new annotated image, or a transparent overlay.  There are issues with label crowding, and it is easier to edit an overlay than the rendered image.  It’s still not easy.  You could render the grid and the labels into separate overlays which would make the text labels easier to work with.  I guess I prefer the transparent overlays, and accept that labels will be crammed together.  When you have your overlay, you can apply it with PixelMath.

PixelMath setup to add overlay to background image. I guess I normally would check  "generate new image" instead of "replace image".

PixelMath setup to add overlay to background image. I guess I normally would check “generate new image” instead of “replace image”.

All you need to do is add the overlay image to the background image.  Use the Expression Editor to select images from the workspace.  Here’s a detail of the result. detail_sag_annoteation

Accuracy is pretty good. I fear the label crowding is inevitable with this wide of a field.  Manual Image Solver is one of the tools in Pixinsight that is actually really well documented, as is Image Solver.  For the straight poop see http://pixinsight.com/doc/scripts/ManualImageSolver/ManualImageSolver.html

 

 

It’s cold.

It’s -13 outside.  I was trying to make snow;  I poured boiling water in a mister and was spraying it around outside.  I think the droplets were too small;  what came out looked like white steam and rose quickly out of sight.  Bigger droplets were definitely frozen.. Anyway it was inconclusive.  morning_moon_DSCN1165I checked the WoodMaster, which needs a lot of attention when it’s this cold, and the controls were dark!  After checking switches & breakers, sure enough the power was out.

I can heat with wood or propane, but without power, I have no blowers or pumps, so we’re really screwed with a major outage.  There was no weather happening, other than unusual (um, record breaking) cold, so I didn’t think it would be long before the heat came back on.  It was about an hour, and the house only lost a degree or two.  I had laid out the Mr Buddy heater and the Coleman lantern, figured I’d wait till 50 degrees in the house before lighting a match.

In the plan is a standby generator.

Brand new cria

We have a new addition!

stardust_IMG_1239

Brand new Stardust and mother Izzie. The gnarly pink blob is placenta.

Baby Stardust was born last Sunday.  She was born healthy around noon, and immediately started exploring the pasture.  Unfortunately, she and her mother Izzie didn’t connect in the nursing department.  We gave the baby a colostrum supplement, but true alpaca colostrum products are not available.  Izzie’s teats were soft, and she wasn’t producing milk, so we started bottle feeding with Ultra24 milk replacer.   We gave Izzie a shot of oxytocin in the evening, and she was almost immediately producing milk.  So between Ultra24 milk replacer and what we could get from Izzie,  we got Stardust on a bottle immediately.  stardustIMG_1270But it was touch-and-go for a while if she would make it.  Without colostrum from the first nursing, alpacas don’t develop an effective immune system.  Even though Izzie was making milk, they still weren’t making the connection.  She developed pneumonia, but the vet  blasted her with antibiotics, which helped a lot.  In fact, after the antibiotics, they connected on the nursing thing!

On Friday we took baby Stardust into the vet clinic for a plasma transfusion, which supplies the specific alpaca antibodies she would have gotten from colostrum, and now she seems to be doing great.  She’s nursing regularly, and adamantly refusing the bottle.

We keep an eye on her with a cheap outdoor X10 Airsight wireless IP webcam (see X10 homepage ).  I bought on sale for $69 (I also got one for the Hut).

Image of baby alpaca nursing

BarnCam snapshot of Stardust nursing, and Izzie.

The webcam works ok via a Linksys network extender, but either the extender or the camera occasionally needs to be manually reset.  The webcam does not have wide enough coverage, so sometimes the beasts are out of the shot.  The webcam has IR LED illumination for night.  It’s been in the 50’s in the evening so Stardust is wearing her jacket and hanging out under a heat lamp.

Day of Rest

I need to do some painting.  Not the creative kind, but the Hut is showing wear, and the Scope Shed is still wearing its original brown.   This occurred to me at maybe 4:30 am after getting up to pee, and before falling back to sleep.  So it made sense to get the painting stuff laid out this morning.  Thinking about painting reminded me I have a window to replace in the barn, which has been boarded up since winter, and I should really paint the window before replacing it.  It would be best to lay it out on the picnic table.  IMG_1056The picnic table is currently loaded up with a pretty cool, very heavy cast iron sink that until we re-did the kitchen last year was, in fact, our kitchen sink, since probably about 1924.  It’s something that is actually desirable for a person wanting a funky antique update to a modern kitchen, but whatever, it’s a cragslist thing as far as I’m concerned.  And it’s tying up the picnic table.  So I’m going to hook up the trailer to our Craftsman garden tractor and move the sink to the barn with other flea market stuff.  The trailer is pretty old, and the tires don’t hold air.  IMG_1057I have some Green Slime — you know Green Slime?   It’s an eponymous product that you pump into iffy tires and it generally plugs up slow leaks.IMG_1069 I pump slime into the trailer tires, and pump them up.  The tiller also has a leaker tire, so I slimed it as well. I get the sink loaded; it’s about 120 pounds of cast iron, but I can horse it around and get it loaded.  Ollie, the labrador interrupts, demanding a Frisbee  break.  IMG_1059 The sink accumulated a lot of debris sitting there for months, so I run it over to the hydrant, and see the tire looks low, but the sink cleans up okay, and I run it to the comoressor and put some more air in.  Meanwhile the male alpacas are mowing the back yard, and Express, who seems to have more testosterone than he strictly needs, is running down Ferb, biting and generally harassing him.  Ferb is making an alarming noise that is unequivocably a scream.  You can’t really separate them when they’re doing this; you just end up chasing them around uselessly.  But they react well to being hosed down.  It distracts them, cools them off, and they forget they’re mad.  In fact they love being hosed down. They’re like city kids on a hot day; cracking a hydrant does wonders for everybody’s attitude.  I got pretty hot too, and take a break for a dip. IMG_1064

IMG_1068

This can’t be good.

It looks like the tires are holding air, and the sink is put away.  I’m ready to put the tractor away, but it doesn’t start, it makes an alarming grinding noise but doesn’t turn over.  The solenoid?  I am constantly struggling with the various  small motors that run things around here.  I get the cover off the engine; need to replace the air filter, how does this poor thing breathe?  And, um, it’s way overdue for an oil change….

Once I get it opened up, there’s an obviously broken bendix gear, at least I think it’s a bendix….  Bendix? Nope, I think it’s broke-ixs.  So now I’m inside surfing for parts.  PartsTree is my friend.  But I have to go back out to get the model number off the engine.  I get the number, but it doesn’t come up!

Part Number 501!

Part Number 501!

I dig thru the yellowed pages of the tractor manual, and get an entirely different model number, which does come up in PartsTree, and I will be trying to install this thing in 3 to 5 business days.

Meantime I need to put the dead tractor away. It’s 3:30 now.   I rig a tow strap to the zero turn mower, and drag its ass to the barn .  On the way, I see some mulberries coming on. IMG_1063They’re not quite there yet, but actually mulberries are best when they’re almost but not quite ripe.  In the barn, I lay out the covers and bolts so they’re ready to go when I get the parts.

It’s time to get a brief dip in before the afternoon thunder storm arrives.

I need to do some painting.

Visit to Sleeping Bear Dunes

On a lovely but chilly May morning I arrived at Sleeping Bear Dunes National Lakeshore and saw this marvelous mountain of sand that begged to be climbed.

The Dune Climb

The Dune Climb

I was glad it was chilly because the Dune Climb is steep, and, well, sand is a bitch to walk thru.  Once at the top, there is a dune trail is marked by posts and levels out somewhat.

Grasses colonize the sand wherever it holds still long enough.

Grasses colonize the sand wherever it holds still long enough.

It’s about 3 miles to the lake, and I believe I went about a mile and a half before thinking I didn’t want to be too tired to get back.

A Google Earth view of the area.  1 is the parking area, 2 is an area of outcrops.

A Google Earth viewshowing the Dune Trail.   1 is the parking area, 2 is an area of weathered sand dunes that expose cross bedding “in action”.

I found the traverses down and back up the dunes to be brutal.  And not knowing what I was getting into, I hadn’t brought any water (always take water!).  But what a place!

Grass and the invention of the circle.

The invention of geometry.

Grasses, especially beachgrass, grab any opportunity to thrive; they slow the wind, making deeper sand downwind.  The increased sand load can then bury neighboring plants.  But in windy corridors (or along trails), plants can’t get established, and the sand and wind express themselves in complex ripples.

Differential drying adds to the complexity of ripple development.

Differential drying adds to the complexity of ripple development.

Here’s how I understand the formation of the dunes at Sleeping Bear.  The last ice age delivered vast moraines of sand and gravel to Michigan.  The glaciers were pretty much gone by 8,000 years ago, and as the ice load came off, the land rose (“isostatic rebound”), and blocked the North Bay drainage pathway to the east through what is now Lake Huron.  The new drainage pattern created the Lake Nipissing Great lakes, with a proto-Lake Michigan.  With lots of sand, and wildly fluctuating water levels, prevailing winds from the West began building the dunes we see today.  These are called  “perched dunes”; old, high dunes made of sand deposited on top of glacial moraine. The highest elevation of the dunes, Sleeping Bear dune itself, is about 450 feet above Lake Michigan, but the sand is not that thick.  The park also has plenty of lake-level beach dunes

The sand itself comes from glacial deposits near the lake shore, or that have washed into the lake from inland deposits.  Then during periods of relative low water, the sand is blown on shore by prevailing winds.

About a mile from the parking lot there’s a notch between the dunes.

Google Earth view of location of sand outcrop. Click for larger.

Google Earth view of location of sand outcrop. This is location 2 on the overview aerial.  Click for larger.

The formation is probably encouraged or created by by trail erosion,  but it has beautifully exposed layers of sand showing bedding and cross bedding structures.

Crossbed formations.

Cross bed formations.  Image from #2 on the map.

I found this area oddly exciting, like seeing sandstone come alive in these delicately patterned layers of sand.  The structures are fragile.

Bedding and cross bedding.

Bedding,  cross bedding and ripples. Image from #2 on the overview.

What preserves the distinction between layers?  The sand is pretty thoroughly unconsolidated, but apparently there is already enough structural variation between layers for them to erode at different rates.  Presumably layers represent episodes of various wind

Cross bedding.  Rusty beer can for scale.

Cross bedding. Rusty beer can for scale. Image from #2 on the overview.  Click for larger size.

conditions; the cross bedding occurs on the lee side of the dune with the maximum slope corresponding to the wind direction. This was bothering me, so I consulted Arthur L. Bloom’s Geomorphology – Systematic Analysis of Cenozoic Landforms, which has a really good discussion of aeolian processes.  The threshold velocity for erosion is related to grain size, so the layering  reflects sorting during deposition.

Cross bedding.  Image from #2 on the map.

Cross bedding. Image from #2 on the map. Click for larger.

The gravel is “lag” gravel, and is left behind as sand blows away.  Still a bit curious that there’s so much of it this high, about 300 feet above the lake, and pretty much local high ground.

Lag gravel.

Lag gravel.

The Sleeping Bear Dunes Website  has a website at http://www.nps.gov/slbe/index.htm and good geology field notes at http://www.nature.nps.gov/geology/parks/slbe/; there’s also a good explanation of ancient shorelines of the Great Lakes at http://www.nps.gov/piro/naturescience/upload/August_2009_PIRO_Resource_Report_Blewett.pdf Also, I’ve learned much from Raymond Siever’s Sand, a Scientific American Library mongraph that is about a lot more than just sand.

M64’s unusual dust feature

We had a really clear night June 3rd, following a cold front, so I set up an imaging run on M64, the descriptively named “Black Eye” galaxy.  I got a good hour of luminance data, but only about 15 minutes each of RGB.  I haven’t made anything acceptable with the color data yet, but the luminance is ok.  M64 (aka NGC 4826) is a crowd-pleaser  for amateurs because it shows visible structure in modest scopes due to its startlingly obvious dust lane.

M^$

M64 (NGC 4826), exposed 6-3-2013; luminance 12 x 300 seconds. 12″ LX-200 at f/10 with SBIG ST-10XME, resolution .47 arc-seconds/pixel. Click image for larger size.

But the dust lane wants an explanation.  It’s located at the inner third of of a broad disk, and is obvious even at the fairly broad angle at which the galaxy presents itself.  The outer disk has suggestions of spiral structure, but the details have apparently softened over time.  The explanation is probably related to the observation that the outer part of the galaxy includes a gas disk rotating in the opposite direction of the stars and gas in the inner disk, presumably from accretion or collision at some time in the distant past.  From  a paper by Corsini, E. M.; Bertola, F,  “The Phenomenon of Counterrotation in Galaxies” (http://adsabs.harvard.edu/abs/1998JKPS…33S.574C):

This galaxy contains two nested counter-rotating gaseous disks.  Radio and optical observations revealed an inner disk of about 1 kpc radius containing ~107 solar masses in HI and  ~108 solar masses in H2 and a counter-rotating outer gas disk extending from 1.5 to 11 kpc and containing ~108 solar masses in HI.

 

They are coplanar to the stellar  disk. Stars co-rotate with the inner gas  but beyond the dust lane less than 5% of them (~108M ) co-rotate with the outer gas.  The kinematical features of NGC4826 are interpreted considering an original gas-poor galaxy with prograde gas which slowly acquires a comparable mass of external retrograde gas.  The new counterrotating gas settles in the outer parts of the stellar disk,leaving undisturbed the galaxy morphology.

The galaxy is now relatively isolated, so there is no obvious smoking gun.  The culprit may have been a counter-rotating dwarf galaxy in orbit around M64, which has now completely lost its identity, and is suggested only by the Black Eye.