Try increasing gamma if dark sections aren't distinguished

Try increasing gamma if dark sections aren't distinguished

Sunday, February 11, 2018

lunar libration

After the recent lunar eclipse, I attempted to line up a before and after image, superimposing the full moon from the night before with the eclipsed moon just before sunrise, and found something odd: they don't match.  it wasn't just a matter of lining things up--which i can correct, or size--which i expected to be minor, but the surface of the moon itself appeared to have rotated:

lunar libration, full moon at sunset to eclipsed moon at sun rise 1/31/18
In a moment of doubt, i feared that a processing bug was creating horrific artifacts, since i know that the moon is tidally locked to the earth (it doesn't rotate, the same side always faces us).  then i recalled the term lunar libration, referring to minor rotation in the appearance of the moon relative to the earth.  a number of factors contribute to this, but the easiest to grasp is that as the earth rotates, the observer's location shifts.  in this case, viewing the moon at sunset and then sunrise, i had moved by the diameter of the planet earth, explaining why the moon appeared to rotate slightly.  

Here's a really cool animation of lunar libration throughout a lunar month:
as well as a more in depth explanation of the causes of lunar libration:

imaging details:
close up:
ZWO ASI120MC, Takahashi FS-60C at native F/5.9, 355 mm.
skywatcher star adventurer tracking mount  
full moon .325 ms exposure 12 seconds captured at ~17 fps
eclipsed moon 152.6 ms exposure 68 second capture at 6 fps
13:24 UTS
Eastbluff, CA

abell 33, the diamond ring nebula

Here's a spherical planetary nebula with a bright foreground star conveniently superimposed on the edge, providing the "diamond" for the ring:

Abell 33, the diamond ring nebula OIII RGB
click on image for full size
The small blue star in the center is the white dwarf creating the nebula.  A close up of the RGB version shows a hint of a second star to the lower right.  This is likely another superimposed star or a "visual double", as a double central star should (in theory with rare exception) create a bipolar, rather than a spherical nebula.  
central star of Abell 33
RGB, upsampled 2x
apparently an open issue in astronomy is whether the percentage of planetary nebulae double central stars matches the percentage of doubles in the general stellar population.  there are several recent surveys which address this, and may confirm my supposition, but i don't have access to them.  

The binary fraction of planetary nebula central stars - II. A larger sample and improved technique for the infrared excess search

The binary fraction of planetary nebula central stars: the promise of VPHAS+

The RGB image shows two other things:
1. how faint the nebula is, as it was barely detectable on the RGB image, requiring narrow band filters to bring it out.
2. how bright the "diamond" star is as it created a "bloom" (bright white artifact to the right of the brightest star).  
should have shot the RGB unbinned to better resolve the central star and minimize blooming.  

I did take a few trial Ha shots, but got only extremely faint signal in a circle, matching the OIII, but without detail.  

Image details:
8" LX200R, SX Trius 694 binned x2 to 0.8"/px,
astrodon 3nm OIII, RGB E SERIES GEN-II
R 18x4 minutes, G 16x4 minutes, B 8x4 minutes
OIII 24x20 minutes.
4/14/17-5/1/17, bortle white skies
eastbluff, CA

Sunday, February 4, 2018

super blue blood moon

here's the rising full moon on the evening of 1/30/18 followed by the setting super blue blood moon from the next morning (click on images for full size):

darker version with a bit more detail:

The full moon above is sharper than the eclipsed moon for several reasons:
1. the eclipsed moon was lower in the sky, therefore subject to more atmospheric turbulence
2. the faint eclipsed moon required longer exposure (500x), also increasing the effect of atmospheric turbulence.  

shot this one in lazy mode.  my garage faces west, so i set up my imaging rig the night before, taking a quick image of the full moon to make sure everything was working.  then moved the equipment into the garage facing west, closed the door and went to bed.  
got up and 5 AM, opened the door to my "observatory" and voila super blue blood moon over my neighbors house:

I'd checked the framing with the setting moon the week before.  this image took a fair amount of work in photoshop as the street lights gave the house a strange green tint. there was also star trailing evident over only 20 seconds (seen below), so i pasted the telescopic version over the moon image in the wide field DSLR image.  

imaging details:
close up:
ZWO ASI120MC, Takahashi FS-60C at native F/5.9, 355 mm.
skywatcher star adventurer tracking mount  
full moon .325 ms exposure 12 seconds captured at ~17 fps
eclipsed moon 152.6 ms exposure 68 second capture at 6 fps
13:24 UTS
wide field:
Nikon D-60, AF-S DX NIKKOR 55-300mm f/4.5-5.6G ED VR, f/5.6 55 mm 20" iso 400

Eastbluff, CA

Sunday, January 28, 2018

Copernicus infra red

Here's a close up shot of copernicus, one of the most photogenic craters on the moon with its terraced walls and central peaks: 
Copernicus 9/10/16 infra red filter
click for moon-walk size

it's easily visible to the naked eye here:
7/8/17 IR/UV block filter

Interestingly, the crater was named by a jesuit at a time when church doctrine opposed the heliocentric model.  The crafty jesuit justified naming such a prominent crater after the father of the heliocentric model by noting that the astronomer was placed in oceanus procellarum, the "ocean of storms". wikipedia link with more information about the crater

The image of the crater was taken with an infra red filter and a telescope that is "mostly" a reflector (mirrors).  it was a test shot which proved that the IR filter was sharper than standard visible filters.  more on that in this post on jupiter.  
Interestingly, the full disk image was taken with a filter that blocks infra red.  why? it was taken with a refractor.  refractors use lenses to bend light.  since infrared light bends less than visible light (the same phenomenon that made it desirable in the previous image), it doesn't focus well in refractors, creating a blurry image.  

Technical notes:
Copernicus: celestron nexstar 8 GPS (8" SCT on a wedge)
captures with firecapture @ ~58 fps
stacked in autostakkert, Drizzle 3x, then reduced to 1.5x, sharpened in registax 6
Full disk: 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.  1 minute video capture at approximately 12 fps, aligned in autostakkert, wavelets in registax.
Eastbluff, CA

Sunday, January 14, 2018

Sunday Sundogs and a pillar

saw a pair of Sundogs while running in the back bay today.  pointed them out to everyone i passed.  most thought i was crazy, but one couple shouted a "thank you" after they found it.

Sundogs 1/14/18

Sundogs are caused by light refracting off hexagonal ice crystals.  if they are random a halo is formed, if they are horizontal, two spots are seen on either side.  Here's a nice explanation.  

Here's a phenomenal example of a double solar halo with sunddogs taken from a ski slope in sweden:

speaking of solar images, here's an Ha image of a "straight pillar"--a form of solar prominence:

Image details:
cellphone Droid turbo
Eastbluff, CA 1/14/18
Lunt 60 PT 
ASI 290 MM camera
20 second video 183 fps
Shutter=5.0 ms
Eastbluff, CA 1/4/18