Sunday, June 18, 2017

bigger jupiter, saturn's coming

finally able to take advantage of larger aperture
for a higher magnification jupiter
Jupiter 5/28/17
still a bit mushy, but showing some promise

meanwhile saturn reached opposition this week
coming up on prime viewing season
here's a wide field with a few moons:
Saturn and Moons 5/14/17
a bit closer on another night:

Saturn 6/14/17

will get to higher magnification when it rises earlier in the evening

Imaging notes:
The larger f/8 scope allowed me to use a 2x Barlow on jupiter, increasing the magnification by a factor of 2 compared to my old system (C8).  
Several other issues were critical to getting the system to work:
1. internal thermal tube currents are a major problem with the new big scope, it takes hours to cool down.  a "cat cooler" made a huge difference.
2. dark subtraction.  this makes sense as i'm trying to minimize expsosure shooting at ~30% max histogram.  the love/hate issue with my ASA DDM 60 mount continues.  the issue here is that most mounts move around so much that the subtle grid pattern in the camera is dithered out.  my mount tracks so well that the planet sits dead center even at very high magnification, so the pattern becomes evident in processing.  this is actually a good problem to have.  for example last night i took a series of images of jupiter at this focal length over the course of an hour and didn't have to budge the mount, even though the pointing model was made with a much lighter scope 6 months ago.  
3. diagonal: didn't test that rigorously, but shooting through the diagonal didn't seem to make that much difference.  
4. made a bit of progress working on LD compensation in win jupos which is necessary with jupiter so far from opposition, you can still see a darker section at the limb on the left (might be processing artifact in part).  
5. more on the mount: the mount is very sensitive to weight changes, the act of switching from eyepiece to camera with barlow felt like this classic scene from raiders of the lost ark. the key is to balance the mount with the camera, not eyepiece.  forget about binoviewers.  

image details (jupiter):
Meade LX850 12" f/8
televue 2x Barlow
ZWO RGB filters
4x2 minute captures for each filter R G B
captures with firecapture @ ~140 fps
exposure 3-4 ms per frame
stacked in autostakkert, combined in WinJupos, sharpened in registax 6
5/28/17 (2017-05-28-0446_7)
Eastbluff, CA

Sunday, June 4, 2017

Jupter's out, IR test and a new scope

the bright star in the east after dark (which is pretty late these days)
is in fact Jupiter. 
seeing has been lousy this season, but i finally gave it a try on a night of mediocre seeing and got this:
Jupiter 4/11/2017

ran a few tests with an infrared (IR) pass filter to see if it would yield a sharper image.  In theory the redder the light (longer wavelength), the less it is distorted by atmospheric seeing, so images should be sharper, but...
the optical resolution limit of a telescope is defined by the wavelength of the light: longer wavelength reduces the theoretical limit of the telescope.  furthermore, the IR pass filter typically allows less light than a standard red filter.  therefore, exposures may need to be longer (leading to more atmospheric motion) and/or higher noise.  
so in practice is the IR image sharper than the others?
here's a blink comparing red to infrared (no contest comparing to blue and green):
red vs infrared
clearly sharper, but perhaps a bit more noise.  

However, for the combined image, it was difficult to appreciate any difference:
here's RGB vs IRGB (substituting IR for red):
the difference is very subtle, with perhaps a bit more detail in the short blue stripe just above the middle white band.  

lastly, i used IR as the luminance channel which changed the colors dramatically, but probably a bit too far from the RGB:

this, i think, is my first successful image with a new (used) larger scope
which i picked up on astromart almost a year ago
in order to catch saturn's hexagon,
explaining a year of poor seeing.
the new scope is pretty friggin' big and a PITA to haul around in the dark at 2 AM so i hope it works out

new scope specs
Meade LX850 12" f/8 ACF OTA + Feathertouch focuser
56 lb (25.4 kg) tube weight
UHTC coating
primary 12" (305 mm)
secondary 4.72" (120 mm) / 41%

image details:
ZWO RGB filters, Baader IR pass "685" nm
2x90 second captures for each filter R G B IR
captures with firecapture @ ~140 fps
stacked in autostakkert, combined in WinJupos, sharpened in registax 6

Southern California

Thursday, May 11, 2017

starburst nebula NGC 1569, narrow band

Here's starburst nebula NGC 1569 in hydrogen (Ha) and oxygen (OIII)

this sat on my hard drive for a year as i was initially disappointed for 2 reasons:
1 there was little difference between the OIII and Ha at this resolution besides signal strength
2 the narrow band and LRGB (below) were so discordant, i couldn't imagine the combine working well.  the Ha didn't enhance the image, it overwhelmed it.

here it is in LRGB:

when i finally combined the narrow and broad band images i was pleasantly surprised to see the sum adding up to more than the parts, even though some details of each were lost in the combination.
the combined image gives the classic appearance of stars clearing out and illuminating the surrounding hydrogen:
in this case the two bright "stars" appearing to illuminate the surrounding nebula are unresolved globular clusters containing thousands of stars (anyone fooled?), making this dwarf galaxy the largest "nebula" i've ever imaged

here's an interesting slow motion blink of the two images
some structures disappear, others appear, and others seem to move (lower left) as if being illuminated by a nearby source:

lastly here's an annotated mosaic:

more details on dwarf galaxy ngc 1569 at this site including observations of the "elephant's trunk" to the right
hubble image resolving the star clusters and more details at wikipedia
interestingly, the galaxy is blue-shifted, which means it's moving towards us, rather than moving away with the expansion of the universe.  

thanks to rick johnson for pointing out this galaxy with it's extreme narrow band emissions.

image details:

8" LX200R, SX Trius 694 binned x2 to 0.8"/px,
astrodon 5nm Ha, 3nm OIII, LRGB E SERIES GEN-II
L 472x1 minute, 24x3 minutes, R 64x3 minutes, G 59x3 minutes, B 55x3 minutes (RGB included in luminance)
Ha 25x20 minutes, OIII 11x20 minutes.
1/29/16-2/8/16, bortle white skies
eastbluff, CA

Sunday, March 19, 2017

Abell 30, the born again nebula

March has been a difficult month for me in recent years, 
a number of events have prevented me from completing this project, but finally,
here is my image of Abell 30, a rare "born again" planetary nebula who's central star re-ignited after turning into a white dwarf,
creating a new system of complex knots of oxygen (blue-green)
inside a mature spherical shell of hydrogen (red) and oxygen:
Abell 30 in Hydrogen (red) and Oxygen (blue-green)

Here's a blink first in Helium showing no nebulosity, only stars, then hydrogen with spherical shell, then oxygen with complex inner knots:
Abell 30 He II, Ha, OIII

The O III signal was faint, Ha signal extremely faint, and He II nonexistent.  
I remain baffled by sources stating that the knots have strong He II emissions, e.g., 
Osterbrock's Astrophysics of Gaseous Nebulae and Active Galactic Nuclei p. 264.
My He II filter is spec'd at 468.6 nm with a 4 nm band width, but detects no signal, might have to confirm it with a spectroscope.  

A few findings regarding exposure variation and binning:
for OIII 3 nm 
40 min binned 2x not much deeper than 20 min binned 2x, if at all.
20 min binned 4x (4 subs) much deeper than 40 min binned 2x (2 subs)
though it was difficult to be sure conditions were identical.  

filter band width:
for 40 min binned 2x 3 nm OIII deeper than 5 nm or 8.5 nm; not much difference between latter two
older unbinned subs with my SX H9 (0.6"/px) were far worse than either, threw all subs out

8" LX200R, SX Trius 694 binned x2 to 0.8"/px, binned x4 to 1.6"/px, (final image at .8"/px)
astrodon 5nm Ha, 5nm, 3nm OIII, chroma 4 nm He; custom scientifics 8.5 nm OIII
OIII 10x 20 min bx4, 28x 40 min bx2, 44x 20 min bx2
Ha 2x 20 min bx2, 15x 40 min bx2, 60 x 20 min bx4
HeII 13x20 min bx4
eastbluff, CA

Tuesday, March 7, 2017

crescents and earthshine

what's missing from my previous crescent moon image is this:

no, earthshine is not a drink served at california dispensaries.

Earthshine is a glow which lights up the unlit part of the Moon because the Sun’s light reflects off the Earth's surface and back onto the Moon, best seen during the crescent moon.  It is also sometimes called the old Moon in the new Moon's arms (or vice versa), or the Da Vinci glow, after Leonardo da Vinci, who explained the phenomenon for the first time in recorded history.

yes, i know this lies far in the realm of cub scout merit badges, but i was reminded of it when i tried to cut and paste an image of the first quarter moon for the eclipse test/comparison and could not define the edge of the moon.  i had to eyeball it by empirically fitting a circle to the part that was visible.

when the moon is a thin crescent, it means the moon is almost directly between the earth and the moon, so the part of the moon lit by the sun is mostly facing away from us, while the dark side faces us.  now from the lunar point of view, the earth is almost directly opposite the sun, so all the reflected light of the earth lights up the night sky (a full earth).  this light brightens the surface of the moon just as a full moon lights our nights, the "earthlight" makes the dark surface of the moon easier for us to see.

in an odd twist, astronomers have used earthshine to detect life on earth, testing a technique that could potentially be used to detect life on other planets.

while shooting this image, i turned my low power imaging rig on the "dusk star", the bright star visible at sunset this month:

caught a tiny crescent venus, matching the moon.

Technical notes:
web cam, DMK 51 and the tiny tak, Takahashi FS-60C, 60 mm aperture at f/4.2 with a reducer.  The field of view is approximately 96x72 arc minutes.  Each image is a one minute video capture at approximately 12 fps, aligned in autostakkert, wavelets in registax.

Sunday, February 26, 2017

crescent moon, hollywood style

What's wrong with this picture (click for full size)?

nothing really, except that the crescent is facing the wrong way. 

though few people can say which way the crescent moon should be facing

they have a visceral feeling that this isn't right.

when the moon is a thin crescent, it means that the sun is illuminating the side which is not facing us, so the moon has to appear very close to the sun in the sky: the crescent moon is seen just after sunset or just before sunrise, with the crescent facing down at the sun below the horizon (tips pointing up).  in the northern hemisphere it points down and to the right at sunset (looking west with sun setting in the southwest).  
you morning people may know that the crescent lies down and to the left in the east.  
it's the opposite in the southern hemisphere.
OK that was really confusing
here's a better description.  

for bad astronomy blogger Phil Plait, this knowledge turned his world upside down

he concluded that springfield must actually be in the southern hemisphere based on this scene from the elon musk episode of the simpsons.

the only way the crescent can be on the top of the moon is if you're standing on your head, or in outer space where up and down doesn't matter.  or perhaps some strange partial lunar eclipse.

i chose this orientation as the unnatural rotation gives it a spacey feel

kubrick was well aware of this:

by the way, here's one of the most over-the-top analyses of a movie i've ever seen
tons of fun

but for the clouds you may see the crescent moon in the next few nights
take a look and see what's missing from my image
to be continued...

-bill w

Technical notes:
web cam, DMK 51 and the tiny tak, Takahashi FS-60C, 60 mm aperture at f/4.2 with a reducer.  The field of view is approximately 96x72 arc minutes.  Each image is a one minute video capture at approximately 12 fps, aligned in autostakkert, wavelets in registax.

Sunday, February 19, 2017

testing 1-2-3, preparing for the eclipse

testing out my imaging rig for the 8/21/17 total solar eclipse.  there will be a range of exposures so decided to shoot filtered midday sun, twilight moon, full moon.  Here are a few images (click on image for full size):
Sun white light filter 2-4-2017

Moon 2-4-2017
Moon 2-12-2017

Moon at twilight 1-30-2017 grey scale

Just for fun, i decided to simulate an eclipse with the images.
I selected the image closest to full and superimposed it on the solar image.
To my chagrin, the moon did not totally cover the sun--that whole perigee apogee thing--I'd created an annular eclipse.
so i had to use an image from another day when the moon was closer to the earth and large enough to completely cover the sun.
Here's the comparison illustrating variation in the apparent size of the moon during its orbit around the earth:
Lunar images superimposed on solar

Technical notes:
decided to go with my widest field webcam and shortest focal length scope with a web cam, DMK 51 and the tiny tak, Takahashi FS-60C, 60 mm aperture at f/4.2 with a reducer.  The field of view is approximately 96x72 arc minutes.  Each image is a one minute video capture at approximately 12 fps, aligned in autostakkert, wavelets in registax.