little gem nebula NGC 6818, planetary primer I

Planetary nebulae are clouds of glowing gas surrounding a “dying” star.  Visually, many are relatively bright grey patches (by deep sky object standard, though very faint compared to an actual planet).  Spectrographically, they typically have very strong doubly ionized oxygen (OIII) emissions compared to other nebulae.  An OIII filter is a handy tool for the amateur astronomer, enhancing these nebulae and confirming their identity.  Though not detectable visually, they also tend to be relatively strong in singly ionized Nitrogen (NII) and singly ionized Helium (denoted HeII, which I may avoid going forward due to the unfortunate confusion). 

NGC 6818 aka the little gem is a small bright planetary nebula in sagittarius.  Roughly planet sized and near the ecliptic (path of the planets through the sky) one can see why it gets the moniker “planetary”, but at roughly 6,000 light years away it’s 1/2 light year across.  The blue/teal in this image is due to OIII emissions and red due to NII emissions. 

Here’s the OIII

NII

Blink

8" LX200R, SX Trius 694 0.4"/px

astrodon 3nm NII, 3nm OIII

ASA DDM60

NII 19x20 min OIII 24x5 min

7/26-8/21/2015

planetary nebula Abell 72

Abell 72 is a faint planetary nebula

It's weak signal is almost all (teal/blue) OIII (doubly ionized oxygen)

the blue central star shows nicely in this image:

the other interesting structure in the field is the small faint galaxy pair just below the nebula.

at 979 million light years distant, the pair is quite far in the background.  it took 7 hours of exposure with a narrow band oxygen III filter to bring out the faint planetary nebula. an additional 9 hours of broad band exposure were required to bring out the faint galaxies.  interestingly, the nebula was barely detectable in the broad band image, showing the power of narrow band filters in light polluted skies.  

8" LX200R, SX-AO, astrodon 5nm OIII filter, chroma LPR filter, SX H9c/H9, ASA DDM 60
8/2014

luminance 56x5 min, RGB 14x20 min, OIII 22x20 min

super blood moon

while it was a super moon (moon at closest point to earth in it's orbit during full moon) 

and a blood moon (red due to atmospheric refraction of red light during an eclipse), it was not the best eclipse experience from southern california.
why?
the eclipse occurred just after moon rise, so the dramatic darkening which occurs during an eclipse was lost as it was still twilight when it rose.  add to this light clouds and haze on the horizon and you've a less than super eclipse.
fortunately, i had a spectacular lunar eclipse experience last april, blogged here.  

what today's eclipse did offer was an opportunity for widefield/landscape shots capturing the blood red moon as it rose...
so i took my gear on the road to a south facing beach hoping to catch it rising over the rocks in corona del mar, but it was rising too far north (i'd seen the moon rise over the rocks in mid summer)...
so i drove to the mountains (ok a hill in newport coast, but it sounds better)...

here's my attempt at a landscape wide field of the moon.  A car pulled up just in time to illuminate the foreground trees and fence in this shot (must have been Wally Pacholka's):
closer:
closest:

wide field:

nikon D 60, AF-S DX NIKKOR 55-300mm f/4.5-5.6G ED 

close up:

ZWO ASI120MC, Takahashi FS-60C F/5.9

cheers

still more summer sun: filaments, proms and spots

used a variety of cameras telescopes and filters to capture a range of solar activity last Sunday 8/23/15.

sunspot grouping AR 2403 in hydrogen alpha compared to broad spectrum (white light):

Ha single stacked, large chip camera full disk:

the prominences projecting off the edge out into space are much more faint, so i created a composite of this and a longer exposure which burns out the center (color version):

double stacked Ha for better contrast, capturing  the filaments and prominences smaller chip camera which has a faster capture rate:

closer view of filaments and prominences upper right:

negative:

prominence only with over-saturated pixels blacked out:

Hydrogen alpha activity around sunspot grouping AR 2403:

close up version in white light showing the sun spots

Imaging details/discussion:
full disk Lunt 60 PT single stacked, on grab & go alt-azm mount, DMK 51

i switched to 60/50 double stacked as i thought higher contrast would make it easier to capture the prominence/filament juxtaposition upper right.  The single stacked Ha band width is .7 anstroms, double stacked narrows it to less than .5 angstroms.  this makes the surface filaments stand out more.  since the double stack leaves a bit of a gradient with full disk anyway, i switched to my new planetary camera ASI 120 MM-S which isn't big enough for full disk, but it has a much higher frame rate--10x faster than the DMK when cropped.

the white light capture was done with an 8" SCT, baader photographic film an IR/UV cut filter and a 550x10nm filter with the faster ASI 120 MM-S camera.  i tried 4 different filters: 540x10nm, 550x10nm, 8.5 nm OIII, 10 nm Helium.   On quick switching with a filter wheel the 550x10 seemed slightly better than the 540x10.  i then took a series of 6 20 second captures separated by a minute with the 550x10 filter hoping to capture some sort of motion.  what i found was huge variation in seeing with 4 of the 6 captures showing mush and two showing some detail, making it difficult to really conclude whether one filter was better than the other.

Sunny Sun Day

Sun showed a lot of activity on Sunday so I took a quick full disk shot with the lunt 60 on my grab and go alt-azm mount.

Hydrogen alpha


composite:


exclusion:

the exclusion seems to bring out the very long serpentine filament mid/upper left

colorized:


Lastly here's a close up of the prominence to the right:

Lunt 60 PT single stacked, DMK 51


tried the sun spot grouping in WL, but failed miserably on saturday