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Posts Tagged ‘deepskystacker’

The Heart Nebula, IC1805, in Narrowband

January 27, 2015 Leave a comment

This is one of my favorite deep sky objects, especially for narrowband.  It just fits on an KAF-8300 chip at 350 mm focal length.  The small cluster in the core is Melotte 15.

I took three nights of exposures, which were spread over 41 days due to poor weather and holiday trips.  Maybe next year when Cassiopeia swings into view, I’ll make a similar project of the Soul Nebula nearby.

The Heart Nebula (IC1805)

The Heart Nebula (IC1805)

Image data:

  • Exposures: 32 hours total: 96 x 10 min Ha, 43 x 10 min OIII, 53 x 10 min SII
  • Telescopes: Two William Optics Star 71s (360mm f/5)
  • Cameras: SBIG ST-8300M and QSI 583wsg, 2×2 binned
  • Mount: CGEM
  • Guiding: QHY 5L-II mono, guided using PHD2
  • Conditions:  mild winds on two nights
  • Processing: DeepSkyStacker -> PixInsight -> Photoshop
  • Date: Nov 21 2014, Dec 31 2014, and Jan 1 2015
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NGC7000

November 18, 2014 Leave a comment

This is not exactly a shining moment as an astroimager, because I completely messed up the polar alignment routine, resulting in smeared stars.  (When the CGEM tells you not to pick polar alignment stars too close to the pole, it means it!)  But NGC7000, more commonly known as the North America Nebula, is such a compelling object, I’m posting the image anyway.  It also gives a sense of how wide the field of view on the Star 71 is.

NGC7000 "The North America Nebula" in Narrowband

NGC7000 “The North America Nebula” in Narrowband

Image data:

  • Exposures: 34 x 10 min Ha, 14 x 10 min OIII, 17 x 10 min SII
  • Telescopes: Two William Optics Star 71s (360mm f/5)
  • Cameras: SBIG ST-8300M and QSI 583wsg, 2×2 binned
  • Mount: CGEM
  • Guiding: QHY 5L-II mono, guided using PHD2
  • Conditions:  wind gusts over 20 mph, gibbous moon
  • Processing: DeepSkyStacker, PixInsight, Photoshop
  • Date: Nov 2, 2014

NGC 6888 Narrowband (plus some PixelMath)

September 29, 2013 Leave a comment

Finally, some color images!  (Or at least false color.)

This is one panel from my earlier Crescent Nebula 4-panel H-alpha mosaic, with OIII and SII data added.  The first version is in a slightly modified “Hubble” narrowband palette (R=70% SII+30% H-alpha, G=100% H-alpha, B=100% OIII).

NGC 6888 in Hubble Palette

NGC 6888 in Hubble Palette

Image data:
Exposures: 13 x 1200s Ha, 16 x 1200s SII, 18 x 1200s OIII (Total exposure time: 15 hours, 40 minutes)
Software: guiding by PHD, stacking in DeepSkyStacker
Processing: PixInsight 1.8
Telescope: Takahashi FSQ-106ED (530 mm f/5)
Camera: SBIG STL-11000M with Astrodon 6nm narrowband filters, 2×2 binned
Mount: CGEM
September 16, 17, and 28 2013

PixInsight allows you to easily blend and mix images or color channels to create alternate palettes, so let’s use this image as a simple example.  Consider the following simple PixelMath parameters.

PixelMath

PixelMath refers to the color channels in an RGB image as [0], [1], and [2] respectively.  So this tells PixInsight to create a new image with the:

  • red channel composed of the original green channel
  • green channel composed of 70% of the original red channel + 30% of the original green channel
  • blue channel unchanged

The result is a false color image with a different flavor.

NGC 6888 Red-Green Reversed

NGC 6888 Red-Green Reversed

Sh2-129, The Flying Bat Nebula

September 28, 2013 Leave a comment

This is another monochromatic image I captured while the moon was near full this month. Sh2-129 is a very dim, but very large H-alpha region at the bottom of Cepheus. It’s close to the far brighter and more famous IC1396, which explains why it is so often overlooked among the sea of emission nebulae in that area. I’ve seen it referred to as the Flying Bat Nebula, but it probably has more claim to be a “Tulip” nebula than Sh2-101. This is definitely a challenging object to capture.

Nicola Montecchiari recently captured a terrific image of this nebula with the OIII-emitting planetary nebula OU4 at its core.  Looks like I will have to go back and capture some OIII data here soon!

Sh2-129, The Flying Bat Nebula, H-alpha

Sh2-129, The Flying Bat Nebula, H-alpha

Image data:
Exposures: 19 x 1200s Ha exposures
Software: guiding by PHD, stacking in DeepSkyStacker
Processing: PixInsight
Telescope: Takahashi FSQ-106ED (530 mm f/5)
Camera: SBIG STL-11000M with Astrodon 6nm narrowband filters, 2×2 binned
Mount: CGEM
September 15, 2013

A note about saving 32-bit data from DeepSkyStacker

Let me start off by saying that I love DeepSkyStacker (here referred to affectionately as “DSS”).  I think Luc Coiffier is a hero to the astroimaging community for creating it and making it available for free.  DSS does 95% of everything you could ever want to do when calibrating, aligning, and stacking images.  The Drizzle algorithm is terrific. It has the most straight-forward, easy to use interfaces around.  Lately, I’ve been playing with PixInsight’s stacking tools, but I keep coming back to DSS for its simplicity and its image quality scoring, which makes determining which images to exclude from a stack so much less tedious.

I have been having an issue with it recently that I’d like to highlight to other users, though.  This could be user-error on my part, and I’d like to hear what I’m doing wrong if that’s the case.  Googling for similar issues, I think Jerry Lodriguss posted a similar issue to the DSS Yahoo board last February.

The issue I’m seeing is this:  if you save images (“Save picture to file”) with “Apply adjustments to the saved image” setting selected, the data are limited to a 16-bit resolution, even if the file is saved at 32-bits.  There is no problem if you use the autosave.tif file or save the image with “Do not apply adjustments to the saved image” setting selected.  I didn’t notice this issue until I started focusing more on narrowband imaging, where even 20-minute exposures are exceedingly dim.  I don’t usually use DSS for stretching my images, but at some point I experimented with it, and I left the “Apply adjustments…” box checked.  Even though I haven’t used DSS’s histogram tool in months, the setting remained in the “Save picture to file” dialog box, and I was getting a lot of posterization in my final images.

Below is a screenshot from PixInsight of a DSS-stacked image of IC 2177 (12 10-minute exposures taken through an H-alpha filter), saved with the “Do not apply adjustments to the saved image” setting selected as a 32-bit integer FITS. Note the smooth histogram.

IC2177 Do Not Apply

And here is a screenshot from PixInsight of the exact same image saved in DSS with the “Apply adjustments to the saved image” setting selected, also as a 32-bit integer FITS. Nothing was actually done with DSS’s histogram tool (“Apply” was never clicked, though it appears to apply the default stretch without clicking it).  Note the posterization and combed histogram.

IC2177 Apply

Once I get a free weekend, I need to go back through some of my recent images that show significant posterization and re-process them.

Again, DSS is amazing software that deserves to be on every imager’s computer, but this post is just a word of caution about what settings you use when you save your files.

IC 2177, The Seagull Nebula

April 16, 2012 Leave a comment

This is a narrowband image of the nebula IC 2177, known as the Seagull Nebula.  Frankly, I think it looks a lot more like a parrot, even a phoenix (which would be a more dramatic name), but it’s hard to deny that it looks like a bird of some kind. It’s just a terrifically photogenic deep-sky object.

Also going for it is the fact that it was discovered by an amateur, Isaac Roberts, who published what Wikipedia calls ” the first popular account of celestial photography of the deep sky” in 1893.  I was going to complain that it took me four nights to collect the data for this image, but I’m sure Mr. Roberts had it a lot tougher than me back in the day.

Click to enlarge

Image data:

Exposures:  28 x 600s Ha , 23 x 900s O-III, 17 x 900s S-II (14h 40m total), all binned 2×2

Software:  guiding by PHD, stacking in DeepSkyStacker, processing in Photoshop CS3

Telescope:  Borg 77EDII 330mm f/4.3

Camera:  SBIG ST-8300M with Baader standard narrowband filters

Mount:  CGEM

Taken March 17, 18, 19, and 22, 2012 from Whitehouse Station, NJ.

IC405 and IC410 in narrowband

March 17, 2012 Leave a comment

This image represents four nights of exposures, including plenty of human errors and adjustments along the way.  Ultimately, 11 hours of exposures went into the final image, though I took about 20.  This became more of a project than I thought it would!

IC405 (right) is known as the Flaming Star Nebula.  I don’t know if IC410 has a nickname, but people call the two little gas squiggles near the top The Tadpoles (not to be confused with the interacting galaxies with the same nickname).  I wanted to capture both in one frame, which is just barely doable at 330 mm with the Borg 77EDII.  In H-alpha, these are both reasonably bright, but the O-III and S-II data are very dim.  In fact, I took two nights of exposures, split equally among the three filters, before I realized that 10 minutes binned 2×2 wasn’t giving me enough O-III or S-II to stretch.  The histogram was so narrow, the nebulosity pulled into a few discrete levels, even at 16 bits.  So I went back and took two more nights of just O-III and S-II, but binned 3×3.  This sacrifice in resolution was less than ideal (it’s a ridiculous 10″ per pixel), but I drizzled the resulting frames to pull a little more detail out, then combined it back with the H-alpha at the original resolution.  I don’t even want to talk about the night of data I lost because I forgot to check the “autosave” box in CCDSoft.  Then I processed the heck out of it, and though I’m less than thrilled with the final result, it’s time to let this one go until next year.

Image data:

Exposures:  23 x 600s Ha binned 2×2, 23 x 600s O-III binned 3×3, 20 x 600s S-II binned 3×3, a total of 11h 0m

Software:  guiding by PHD, stacking in DeepSkyStacker, processing in Photoshop CS3

Telescope:  Borg 77EDII 330mm f/4.3

Camera:  SBIG ST-8300M with Baader standard narrowband filters

Mount:  CGEM

Taken March 5-6 and 13-14, 2012 from Whitehouse Station, NJ.

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