Try increasing gamma if dark sections aren't distinguished

Try increasing gamma if dark sections aren't distinguished

Sunday, July 23, 2017

Solar rotation Active region 2665

like the earth, the sun itself rotates.  its period is once every 24 days at the equator, but only once every 35 days at the poles.  this was determined by watching sunspots rotate across the surface.  
This animation shows a group of sunspots (AR2665) rotating across the disc of the sun over the course of 9 days, from July 8th to the 16th 2017: 
Sun 7/8-16/2017, AR 2665
interestingly, today (7/23/2017) this "active region" lived up to its name and spat a gigantic coronal mass ejection out into space.  fortunately, it's facing away from us, though apparently right at mars, potentially affecting satellites there.  more at spaceweather.com
a few wacko preppers are predicting earthquakes as a result.  a more balanced perspective can be found here.  In any event, if a really big one of these things hits earth, our electronics are fried.  the active region should be rotating back towards us in about a week, hopefully bringing nothing more than a few auroras.   

Hydrogen alpha versions of this region at the beginning of the rotation can be seen in a previous post:
http://astrowhw.blogspot.com/2017/07/big-prominence-this-weekend.html

Image details:
DMK 51 web cam, Takahashi FS-60C, 60 mm aperture at f/4.2 with a reducer.  Baader solar film, Tiffen 77 mm green and IR ND.6 filters.  The field of view is approximately 96x72 arc minutes.  20 second video capture at 12 fps, aligned in autostakkert, wavelets in registax.

Tuesday, July 18, 2017

jovian animation

on 6/17/17 Jupiter put on a show:
both io and ganymede transited jupiter's face while the great red spot was showing.  unfortunately, the seeing was not great.  here's what i salvaged:
Jupiter Ganymede, Io's shadow
6-18-2017 05:23 UT
the animation shows ganymede (upper left) rotating across the face of jupiter and then fade from view.  io has already begun its transit, but is lost in the northern equatorial belt.  just as ganymede fades from view, io's shadow races across from the left side.  towards the end you can again see a hint of ganymede again, (brownish spot) rotating across the surface up top.

here's shot from the night before with a bit better seeing, but no exciting events:
Jupiter
6/17/2017 05:28 UT
imaging notes
Poor seeing on the night of the animation
combining all the images in winjupos smoothed things out dramatically, 
but required way too much time in photoshop combining the win jupos and standard versions.  
The mono camera/filters do seem to give better color (previous night).  

image details:
Meade LX850 12" f/8
televue 2x Barlow
FocalLength~4100mm
Resolution~0.19"

for animation:
ZWO ASI120MC (color camera)
approximately 40x1 minute captures spaced by a minute
captures with firecapture @ ~134 fps
exposure 5 ms per frame

for still image:
ASI120MM-S mono camera
ZWO RGB filters
3x2 minute captures for each filter R G B
captures with firecapture @ ~190 fps
exposure 5 ms per frame
stacked in autostakkert, combined in WinJupos, sharpened in registax 6

6/17-18/2017
Eastbluff, CA



Tuesday, July 11, 2017

big prominence this weekend

variety pack of images:
solar prominence 7/8/17 (occulted)
Hydrogen alpha
H alpha composite
Ha exclusion
Ha colorized composite
full disk, full spectrum

image details:
full disk:
DMK 51 web cam, Takahashi FS-60C, 60 mm aperture at f/4.2 with a reducer.  Baader solar film, Tiffen 77 mm green and IR ND.6 filters.  The field of view is approximately 96x72 arc minutes.  20 second video capture at 12 fps, aligned in autostakkert, wavelets in registax.

Eastbluff, CA 7/8/2017

Ha:
Lunt 60 PT double stacked
manually guided on a shaky alt-azm mount
ASI 120 MM-S camera
20 second video 57 fps.

Sunday, July 2, 2017

testing 4-5-6: summer sun, salvaged sunspot.

in testing a tracking mount for the eclipse, i encountered an unpleasant surprise: the sun is brighter in the summer!  so bright that the sun is now completely overexposed, blowing out any sunspots and surface detail.  a few more filters and voila granulation and a few small sun spots (click to see surface detail at full size):
Sun 6/24/2017
click for full size
Here's an image of the monster sunspot of October 2014 showing a close up of surface detail (click this link for more info on sunspots and granulation):  

AR 12912 10/25/2014
click for full size
salvaging sunspots:

A monster sunspot stole the show during the partial solar eclipse of 10/23/14 (see this link, and this link for more details on sunspots and granulation).  The sunspot was so big that i couldn't capture the whole thing in one frame except at a slow frame rate so i kludged together a mosaic.  several days later i imaged it again with the full field at slow frame rate, but for some reason the software wouldn't let me process it after i extracted the green channel (best contrast, see below).  gave it another shot with updated software and was able to pull out a nice image despite the low frame rate (12 fps).  

full disk filter discussion:
potential solutions to overexposure on the full disk:
1. additional filter in front of camera--too hard with takahashi adapters
2. stop down aperture--worked provisionally, but hate to throw out light
3. neutral density gel film in front of telescope--not optical quality so blurs image
4. larger filter in front of objective--an opportunity to test more filters :)
tested two types of filters: 
-0.6 neutral density IR blocking
the advantage of this is that IR is poorly focused by refractors so it blurs the image a bit, so blocking IR should give a sharper image.
-green filter
why green? turns out the solar granulation has the highest contrast with a green filter.  furthermore, refractors tend to handle green light best.   
fortunately, the 77 mm filters fit perfectly on the dewshield of my takahashi FS-60, though it's not threaded. 

results: both filters blocked enough light to prevent overexposure.  hard to say whether the ND or green filter gave a better image, but stacking the two gave the best results in terms of granulation contrast (subtle difference).  

Technical notes:
full disk:
DMK 51 web cam, Takahashi FS-60C, 60 mm aperture at f/4.2 with a reducer.  Baader solar film, Tiffen 77 mm green and IR ND.6 filters.  The field of view is approximately 96x72 arc minutes.  20 second video capture at 12 fps, aligned in autostakkert, wavelets in registax.
Eastbluff, CA 6/24/2017
sun spot:
camera ZWO ASI 120 MC, telescope Celestron Nexstar 8 GPS (8" SCT), Baader film and IR/UV block filter.
20 second video at 13 fps, 5 ms exposure.
green channel extracted with PIPP, aligned in autostakkert, wavelets in registax.
Eastbluff, CA 10/25/2014

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
FocalLength~4100mm
Resolution~0.19"
ZWO ASI120MC/ASI120MM-S
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):
RGB vs IRGB
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:
RGB vs IR-IRGB

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
2438mm
0.38"
56 lb (25.4 kg) tube weight
UHTC coating
primary 12" (305 mm)
secondary 4.72" (120 mm) / 41%

image details:
ZWO ASI120MC/ASI120MM-S
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
4/11/17







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
ASA DDM60
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