Home Observatory: Background

After 11 years of visual astronomy, traveling to darker skies and hoping for good weather were yielding too few actual nights under the stars. It was time to build a home observatory: The Robservatory was born.

By far, the biggest challenge for amateur and professional astronomers worldwide is the rapid and relentless disappearance of dark skies as a result of light pollution. To counter this effect, the imaging of certain objects which transmit light at special frequencies (typically emission nebula, planetery nebula, and some galaxies) can be done through narrowband filters, which transmit light only at these very specific, narrow wavelengths, while blocking broaderband light from sources such as streetlights, house lights, and even the moon.

All images on this site have been captured at The Robservatory, located 12 miles west of Manhattan, under some of the worst light pollution on the planet.

Monday, December 23, 2013


NGC 281 is an H II region in the constellation of Cassiopeia and part of the Perseus Spiral Arm. . Colloquially, NGC 281 is also known as the Pacman Nebula for its resemblance to the video game character. (Wiki).  Total exposure for this image was 42 hours through narrowband filters.
(Click to ENLARGE)

Saturday, March 16, 2013

The Monkey Nebula

NGC 2174 (also known as Monkey Head Nebula) is an H II[1] emission nebula located in the constellation Orion and is associated with the open star cluster NGB2175.  This image is a composite of 3.5 hours of Hydrogen-alpha, 4.5 hours of Oxygen-III, and 4.5 hours of Sulphur-II.

Saturday, December 15, 2012

The Heart Nebula

The Heart Nebula, IC 1805, Sh2-190, lies some 7500 light years away from Earth and is located in the Perseus Arm of the Galaxy in the constellation Cassiopeia. This is an emission nebula showing glowing gas and darker dust lanes. The nebula is formed by plasma of ionized hydrogen and free electrons. (WIKI)

Click image to enlarge, X upper right to close. 


Tuesday, August 7, 2012

Pelican and North American Nebula Mosaic

The last three months have been spent learning how to use PixInsight, a powerful new image processing platform.  One of its features is the capacity to stitch together individual images into a mosaic.  Normally, a given image only accesses a relatively narrow cross section of the night sky, the dimensions of which are determined by the size of the camera's ccd chip and the optical characteristics of the telescope to which the camera is attached.  (The equipment in the Robservatory captures a slice of sky roughly the size of the full moon.)  The mosaic capability removes this constraint.  The image presented here is a two frame mosaic.  Each frame consists of about nine hours of exposure, three hours each shot through Ha, OIII,and SII filters.  These two composite frames were stitched together so well by the program, that the "seam" between them, which runs vertically down the image's midline, is virtually invisible. While the mosaic feature is not unique to PixInsight, it is one of many features of this new and exciting program that has given imagers more sophisticated processing tools specially designed for astrophotography.

(Click Image to Enlarge, X upper right to close:)

Image information:
This emission nebula on the left is famous partly because it resembles Earth's continent of North America. To the right of the North America Nebula, cataloged as NGC 7000, is a less luminous nebula that resembles a pelican, and is thus dubbed the Pelican Nebula. The two emission nebula measure about 50 light-years across, are located about 1,500 light-years away, and are separated by a dark absorption cloud. This  image captures the nebulas, bright ionization fronts, and fine details of the dark dust. The nebulae can be seen with binoculars from a dark location. Look for a small nebular patch north-east of bright star Deneb in the constellation of Cygnus. It is still unknown which star or stars ionize the red-glowing hydrogen gas. (Source: NASA APOD).

Saturday, June 2, 2012

NGC 6543: "The Catseye Nebula" (Click image to ENLARGE)

 Total exposure time, 7.5 hours, bicolor image composed of Ha and OIII.  The OIII data comprises most of the structure seen in the image.

"The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its more familiar outlines are seen in the brighter central region of this impressive wide-angle view. But the composite image also combines many short and long exposures to reveal the nebula's extremely faint halo. At an estimated distance of 3,000 light-years, the faint outer halo is over 5 light-years across. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. More recently, some planetary nebulae are found to have halos like this one, likely formed of material shrugged off during earlier episodes in the star's evolution. While the planetary nebula phase is thought to last for around 10,000 years, astronomers estimate the age of the outer filamentary portions of this halo to be 50,000 to 90,000 years. Visible on the right, some 50 million light-years beyond the Cat's Eye, lies spiral galaxy NGC 6552. "  (Source: NASA APOD)

Sunday, May 13, 2012


Over two years have past since the last image was posted.  Two issues have been at play: image quality, and automated imaging.

Image Quality:
As other astroimagers have found, there is an inherent paradox in what we do: the better one gets, the worse the outcome.  What is gained with experience is a more critical eye--since images are comprised of lengthy time exposures, and the Earth is in the habit of rotating, blurred (oblong) stars in astroimages, at first overlooked,  become the nemesis. The tracking mechanism in the telescope mount that moves the scope and camera in synchrony with the earth's rotation (and thus rendering still the object being imaged) is a metal part with manufacturing tolerances (i.e. error tolerance) of approximately the width of a human hair. More error than that, and oblong stars are the result.  This mount element has been replaced by a high quality custom part provided by Ovision (get the subtlety in the name?), located in France.  Tracking error has been thus significantly reduced and is now within acceptable limits.

Automated Imaging:
There are literally dozens of ministeps as one travels from Point A (locating an object to image) to Point B (imaging the object).  Little by little, increased intervening complexity has been layered in.  Each element was fine tuned.  Here's a verbal schematic of the steps involved in taking astrophotographs:

  • Select an object to image
  • move scope to the object
  • take a test shot
  • compare the test shot to a skychart to make sure the object is centered
  • correct the position of the mount
  • take another test shot>iterate this sequence until the object is in fact centered
  • focus the telescope using a focus motor
  • activate the filterwheel to choose a special filter which selectively passes light of specific wavelength of interest
  • have a second scope track a nearby star and send tracking corrections to the mount which itself is already tracking at the rotation speed of the earth
  • stop after 30 minutes and download the image
  • repeat the cycle for a specified number of images
  • move to the next object
  •  repeat all of the above
  • stop at dawn
Needless to say, the above can keep one up all night.  The latest step, however, has been to add executive software that controls and implements ALL of the above.  At this point, except for opening an closing the dome, The Robservatory is now completely Robotic.

Below is is the first, successful, completely automated image. 

For this automated image, I opened the dome and pushed one computer button.  Fifty five minutes after sunset, the equipment came alive, located and tracked the object, did all the filtering/focusing/tracking/imaging, and downloaded the images to the computer while I slept through the night.  All of the fine tuning has paid off as well: my image keep rate started at about 20%; tracking or focusing errors used to cause the remainder to be rejected.  For M97, the keep rate was virtually 100%. I'm pleased that with extensive tinkering and some relatively minor upgrades, my mid priced mount is delivering a level of precision comparable to premium mounts that typically exceed 3x the cost of mine.

The image below  is of M97, the "Owl Nebula". M97 is the exploded gas shell of a very old star. The green gas is ionized hydrogen; the blue gas is ionized oxygen.  Total exposure time was 18.5 hours.

 (Click on image to ENLARGE): 

Sunday, January 17, 2010

The Soul Nebula (Click to Enlarge)

The Soul Nebula is an active region of star formation, located 6500 light years away in the Perseus Arm of the Milky Way galaxy. Ionized hydrogen gas is represented by the reddish tones, and ionized oxygen is depicted in cyan. Total exposure time consisted of 30, 30 minute images captured between October 2009 and January 2010 and combined into a single, 15 hour image. North is up.