Cocoon Nebula (IC5146) Widefield

January 24, 2016 1 comment

I used the snow day here in the northeast to get started on the backlog of raw data from the fall that I haven’t processed.  This is the Cocoon Nebula, with its dark nebula friend, Barnard 168.

Cocoon FINAL v2

I actually took a full night’s worth of H-alpha data, but decided to use only the RGB data here, as a slight misalignment of the telescope shooting the H-alpha would have required a different cropping of the image.

Image data:

  • Exposures:  15×10 min R, G; 18×10 min B (2×2 binning) – total exposure time:  8 hours
  • Telescope: William Optics Star71 (360mm f/5)
  • Cameras: SBIG ST-8300M
  • Mount: Takahashi EM200
  • Guiding: QHY 5L-II mono, guided using PHD2
  • Conditions:  good transparency, calm winds
  • Processing: DeepSkyStacker -> PixInsight -> Photoshop
  • Date: Sep 14 and 17, 2015

Evaluating the full-frame performance of the William Optics Star71

January 23, 2016 1 comment

I’m excited to start imaging with my new Canon EOS 6D.  Having a full-frame chip will allow some very widefield shots that would require mosaics with a 4/3 sensor, like the KAF-8300 cameras I use most of the time.  Since conditions were less than ideal, I used the first couple of nights out to run some tests.  First up is a test of the 6D with the Star71.

The obvious target:  M42.  Below is a very brief exposure (17 min total, in 15s subexposures).

M42 17 min

That is a very wide field.  5.8 x 3.8 degrees.  I didn’t even intend to include the Horsehead Nebula when I pointed the mount at M42, but the field is so wide, I accidentally captured most of it.

Are the stars sharp out to the corners?  Yes.  The image below is a crop of 100 pixel squares from each corner of the above image.  No star reduction was done in any of these images. The performance is really good.  A little distortion on the right side, but quite tolerable.

Corners

What about vignetting?  I estimate less than 10% light falloff between the center and the corners from the flat frame analysis below (the image is highly stretched to reveal vignetting).  Note that there is a dark band across the bottom.  This was consistent across my images, and I’m not sure of the source, but I suspect something to do with dcraw (this image was imported into PixInsight, which calls dcraw for conversion).  DeepSkyStacker seemed to have trouble with some of the 6D’s images too.

vignetting

The 6D and Star71 are a good pair, and it’s nice to have a DSLR again for simple one-shot color imaging, especially for wide fields.  Once I get some adapters, I look forward to running the same test with the Takahashi FSQ-106ED.

The Pleiades (M45)

January 10, 2016 Leave a comment

Somehow, I’ve never really captured an image of The Pleiades (M45). Such a bright target directly overhead, but I was mostly looking for narrowband objects instead, I suppose.

Pleiades final 8x10 crop

This image was processed entirely in PixInsight, except for the final rescaling and jpeg conversion.  I’m moving more in that direction. Frustrating and unforgiving it is, but powerful.  For such a bright object, the dust makes it more challenging to process than I’d expected.

Image data:

  • Exposures: 20×10 min L (1×1 binning), 8×10 min each R, G, B (2×2 binning) – total exposure time:  7h 20m
  • Telescopes: Two William Optics Star71s (360mm f/5)
  • Cameras: SBIG ST-8300M and QSI 583wsg
  • Mount: Takahashi EM200
  • Guiding: QHY 5L-II mono, guided using PHD2
  • Conditions:  fair transparency, calm winds
  • Processing: DeepSkyStacker -> PixInsight
  • Date: Jan 2, 2016

Comet Catalina (C/2013 US10)

January 3, 2016 Leave a comment

Comets are difficult objects to capture and process, but the good ones are worth the effort. Catalina sits in the pre-dawn skies right now.  I’ve gotten up at 4am two mornings in a row to get this shot.  Yesterday, I captured it with Arcturus in the same frame, but I underestimated the comet’s dimness, so the final image was fairly dim and noisy. This morning, I doubled the exposure time with better results.

Catalina LRBG 3

LRGB imaging is not ideal for comets: even with 2-minute exposures, there is shift between them.  DeepSkyStacker comet alignment mode is great, but the color channels don’t quite line up perfectly. Next time, I’ll use a DSLR.

Image data:

  • Exposures: 52×2 min L, 18×2 R, 16×2 G, 17×2 B
  • Telescopes: Two William Optics Star 71s (360mm f/5)
  • Cameras: SBIG ST-8300M and QSI 583wsg, 2×2 binned
  • Mount: Takahashi EM200
  • Guiding: QHY 5L-II mono, guided using PHD2
  • Conditions:  light wind, nearby moonlight
  • Processing: DeepSkyStacker -> PixInsight -> Photoshop
  • Date: Jan 3, 2016

The Astrophotography Sky Atlas

November 22, 2015 Leave a comment

TASA Cover 500px

The Astrophotography Sky Atlas is now available at Amazon!

I spent two years coding, researching, and writing this book with a simple goal:  to create a compact, reasonably-priced atlas designed for the imager. Over 2000 deep-sky objects are plotted in their correct size and shape, including many faint nebulae not shown in other atlases. Stars are shown down to 9th magnitude.  The entire sky is covered in 70 full-color charts.

A tabular index contains important details on each object, including a description, the best time of year to capture it, and the required field of view.

What’s shown:

  • 416 emission nebulae and supernova remnants, including the complete Sharpless (Sh2) and RCW catalogs.
  • 171 reflection nebulae, including the complete van den Bergh (vdB) catalog.
  • 146 planetary nebulae, including the complete Abell catalog
  • 52 dark nebulae and molecular clouds
  • 792 galaxies (larger than 3 arcminutes)
  • 38 galaxy groups from the Abell and Hickson catalogs
  • 108 globular clusters (larger than 5 arcminutes)
  • 309 open clusters (larger than 5 arcminutes)

Keeping a focus on what is important to imaging, sparse open clusters and galaxies smaller than 3 arcminutes (unless part of a group) were left off the maps.

With information on nearly every possible photographic object in the night sky, The Astrophotography Sky Atlas will help you choose your targets and plan your imaging.

Haumea

October 10, 2015 Leave a comment

I took these images back in June, but have been too busy working on the new book to post anything.  I have literally hundreds of hours of exposures waiting to be processed right now.

This is Haumea.  It’s not a pretty image, but I still think it’s cool that you can image Kuiper Belt objects from your backyard.  In fact, the collimation on my scope was WAY out of line (long story) when these were taken, and I was still able to capture Haumea with 8 minutes of exposure time on two nights (6/6 and 6/9).  This was also first light for my SBIG STL-1301E.

Haumea’s angular motion is only about 2.5 arcseconds over three nights.  I compared the images with Wolfram Alpha’s predictions for where Haumea would be, and they agree within a few arcseconds.  The differences are probably more due to my measurement error using Aladin than calculation errors:

  • June 6th:  predicted RA: 13h 58′ 46″, measured RA: 13h 58′ 41″
    • predicted Dec: +18d 02′ 17″, measured +18d 02′ 32″
  • June 9th:  predicted RA: 13h 58′ 38″, measured RA: 13h 58′ 32″
    • predicted Dec: +18d 01′ 38″, measured +18d 01′ 56″
Haumea June 6-9, 2015

Haumea June 6-9, 2015

  • Exposures: 8×1 and 10×1 minutes
  • Telescopes: AstroTech AT8RC (1600mm f/8)
  • Cameras: SBIG STL-1301E, 2×2 binned
  • Mount: Takahashi EM-200
  • Guiding: Orion Starshoot through 50mm finder, guided using PHD2
  • Processing: DeepSkyStacker -> Photoshop
  • Dates: Jun 6 2015 and Jun 9 2015

Making an adapter box for a Takahashi EM-200 mount

April 13, 2015 Leave a comment

As much as I admire Takahashi for their dedication to quality products, some of their design choices can be frustrating.  Worse, the cost to accomplish even standard tasks with their equipment — connecting a camera to a scope, controlling a mount, etc. — are steep.  I recently acquired an EM-200 Temma 2 mount, and before I could autoguide it or connect it to my computer, I had to overcome the non-standard cabling.

While the rest of the world has standardized their autoguiding connections with the same RJ-12 cable and jack (though not always the same pinouts) as SBIG’s now-ancient ST4, Tak for some reason decided to go their own way.  The Tak connection on the Temma 2 is known as a mini-DIN-6.  A quick search on the internet revealed that this is the same connection used on the old PS/2 keyboard and mouse cables.  I had some of those laying around the house, so I my plan was to use one of those.  Alas, this was not to be, as you’ll see in a minute.

Communicating with your mount on a deeper level than “speed up” and “slow down” usually requires what’s known as a serial port.  Serial ports on mounts are a little less standardized.  No modern computer has a direct serial (also loosely known as RS-232) connection, so you typically need a USB-to-serial adapter.  The output of this is what’s known as a DB9 connector, which you then have to adapt to whatever your mount requires.  For the EM-200, it’s a mini-DIN-4 connection.  Again, a little internet research reveals that mini-DIN-4 is also the standard for S-Video cables.  Aha, I have one of those lying around too!

Which brings us to an important point:  you cannot use S-Video or mouse/keyboard cables for these connections.  Why?  The pins on the connector do not always reflect the wires in the cable.  S-Video cables have two pins tied common, since the standard has two pins serving as ground.  Thus, there are only three wires in the cable, and we four separate wires for four separate pins.  It’s a similar story with the mouse cables:  only four of the six wires are used.  (Perhaps all six are used for PS/2 type keyboards?  I only had a mouse on hand.)  In fact, the DB9 serial cable I had actually turned out to only be connecting four of the pins when I opened it up.

So I needed one cable for autoguiding that was:  RJ-12 Socket <———->mini-DIN-6

I also needed a cable for serial communications that was:  USB<———->DB9<———–>mini-DIN-4

So it’s off to DigiKey to order some parts, since mini-DIN connectors are not something Radio Shack stocks in store.    I ordered:

  • 839-1091-ND “CBL ASSY MINI DIN MALE R/A 4POS”
  • 839-1093-ND “CBL ASSY MINI DIN MALE R/A 6POS”

The DB9 connector I did have around the house (from Radio Shack, and commonly available).  I also ordered a USB-to-serial adapter from ebay that has the FTDI chipset, as I heard that is the best choice, and I got an RJ-12 jack from Home Depot for $1.99 that has convenient punch-down connections on the back.  Finally, I bought a project box from Radio Shack to house it all.

Thankfully, Takahashi has published the pinouts for their cables, so this was a straightforward project.  I’ve reorganized them here in table format with schematics of the connectors.

The autoguide cable

Autoguide

The serial cableSerial

Now there is only the matter of assembling it all. These steps look easy, but it’s fairly tedious and can take a couple of hours.  First, cut a hole in the project box to fit the RJ-12 socket:IMG_1840

Now cut holes in the box to accommodate the cables (provide strain relief via knots or glue if needed), and strip the ends of each wire:

IMG_1841

Using the tables above, solder the wires to each connector as appropriate.  Double check the connections with a multimeter. Epoxy the RJ-12 jack to the box lid:

IMG_1842The final adapter box has a USB cable coming from one end, and the autoguiding and serial connections coming out the other:

IMG_1844And here it is attached to the tripod, ready for use:

IMG_1843

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