Monday, December 27, 2010

Galactic distances - comparing M31 and NGC891

At a recent star party, we showed guests views of M31, the Andromeda Galaxy, and it was surprising to some just how big it appears to us (because it's so close, in terms of intergalactic distances). Now, earlier this week I published an image of NGC891. Well, two nights ago I photographed a portion of M31 (that's all that would fit in the field of view) and thought a side-by-side would make for an interesting comparison.

The field of view in both images is 26.4 arc-minutes, or, a little less than the
apparent width of a full moon.
Scroll down to find the links to the individual galaxies' images.

Sunday, December 26, 2010

NGC253 with the SBIG ST-8300M

I've been getting settled in with my new imaging platform: an SBIG
ST-8300M through a Celestron EdgeHD 925. The combination yields a 20x26.4
arc-minute FOV and a 0.95 as/p when binned 2x, which I feel is very effective.

Here's the latest result (NGC253):

And, the entire gallery to-date for this set-up:

I think it's a sweet combination but comments welcomed.

Monday, December 20, 2010

Testing the Antares 0.5x Focal Reducer

Testing has been completed for the effectiveness of the Antares 0.5x Focal Reducer on a Celestron 9.25 inch EdgeHD telescope. Please visit for the results and sample images. There may be extensions of the test as equipment is changed and will be announced here.

Resources in Astronomy

A compilation of astronomy related resources to educate, to participate in, or to just enjoy.

Professional and quasi-professional organizations
Amateur Observers' Program - Project to locate asteroids and comets:
APOD - Astronomy Picture of the Day:
APOD - Jupiter movie:
Arizona State University - Space Exploration Resources:
Astronomy Magazine - See also Sky & Telescope Magazine below
Atlas of the Universe - The Universe within 100 million lightyears:
Cornell University - Ask an Astronomer:
D.A.T.A. - Demonstrations and Animations for Teaching Astronomy:
Galaxy Zoo - Project to classify galaxies; open to the public:
Galaxy Zoo - Wikipedia:
Google Earth - Sky:
Heavens Above - Includes ISS Position:
Hubble Site - All things related to the Hubble telescope:
International Dark Sky Association - The Light Pollution Authority:
Microsoft's WorldWide Telescope - Software:
NASA Satellite Sighting Information - Identifies ISS sightings for Arizona:®ion=Arizona
NASA Television - Watch NASA TV on your PC:
NASA/JPL - Cassini-Huygens Mission to Saturn & Titan:
NASA/JPL - Saturn Observation Campaign:
NASA/JPL Home page - NASA/JPL News and links to NASA missions:
NASA/JPL Night Sky Network - Resource for Astronomy Clubs:
NASA World Book - Index of World Book @ NASA Articles:
Project HiRise - High Resolution Imaging Science Experiment:
Resources for Teaching Astronomy:
Royal Astronomical Society of Canada - Explore the Universe:
Science at Nasa - Headline News:
SEDS - Students for the Exploration and Development of Space:
SEDS.Org - List of Common Deep Sky Catalogs:
Sky & Telescope Interactive Star Chart:
Sky & Telescope Magazine - The venerable astronomy publication: - Amazing on-line sky map software: - Simple but effective sky charts: - A veritable space channel: - Daily space digest:
Stellarium - Free Planetarium Software:
STSci - Space Telescope Science Institute (note the Education Toolbox):
Universe Awareness - an inspirational program for young children:
University of Arizona - Mt. Lemmon SkyCenter:
US Naval Observatory - Data Services:
US Naval Observatory - Home page:

Below are vendors/suppliers of astronomy products and services
Anacortes Telescope & Wild Bird:
Astromart - website provided by Anacortes; includes classified ads of previously owned equipment:
Astronomics - Telescopes & Telescope Accessories:
Exploradome - A home observatory:
Global Rent-a-Scope - rent time on a telescope:
LifePixel - Infrared camera conversion services: Life Pixel
Oceanside Photo & Telescope:
Seasonal Star Charts - Waterproof, colorful star charts: - Control a telescope over the internet:
Software Bisque - TheSkyX, TheSky6, among others:
Starizona - Adventures in Astronomy & Nature, located in Tucson, AZ:
Woodland Hills Camera and Telescopes - Woodland Hills, CA:

Places to visit/stay (astronomy Bed & Breakfasts)
Arizona Sky Village - Portal, Arizona:
The Astronomer's Inn (defunct) - Benson, Arizona:
New Mexico Skies - Mayhill, New Mexico:

Internationally known amateur astronomers and astrophotographers ("today's heroes")
Anthony Ayiomamitis - Astrophotography and exoplanet research:
Bernard Hubl - Astrophotography:
Christopher Go - NASA Link:
Christopher Go's Jupiter site:
Ginger Mayfield - Sample tripod photo - good for students interested in photography:
Jerry Lodriguss - Catching the Light - Astrophotography by Jerry Lodriguss:
Johannes Schedler - Panther Observatory:
Nicholas Outters - Astrophotography from France:
Robert Gendler - Whose many photos are featured on APOD:
Russell Croman - Astrophotography:
(And, many more)

Astronomy Clubs
Amateur Astronomers Assoc. of Pittsburgh:
East Valley Astronomy Club (EVAC) - Gilbert, AZ:
Saguaro Astronomy Club - Phoenix, AZ:
Superstition Mountain Astronomical League - Gold Canyon/Apache Junction, AZ:
Tacoma Astronomical Society:

(The list is still growing. Contact the author to add your organization to this list.)

Friday, December 17, 2010

De-Mystifying Star Drift Alignment.

Over the years, there has been a spate of messages vilifying the star drift alignment method of polar aligning a telescope mount. Part of the problem, as I see it, is that in attempting to explain it, most actually complicate it. What gets lost is the simple notion that what you can use to align the mount is the very effect you want to avoid in your images in the first place - objects drifting in declination. And even if you don't bother to determine which direction to adjust the mount to correct the drift, all you have to do is make an adjustment and determine if the drift increased in speed, decreased in speed or, better yet, reversed direction, from which you could extrapolate the appropriate adjustment. In fact, with the neat tools available to us today, such as DSLR Focus or ImagesPlus, or even a web cam, within a few attempts you gain a terrific feel for the process. Part of the difficulty has been that at one time you needed to use an illuminated reticle eyepiece and after making an adjustment you had to re-acquire a star, all while bending your neck...well, you've been there and don't want to go back.

So, without any equations or ditties to remember, let me relay two variations on the method I used recently. (Although, I do use an exercise to determine the correct movement - later below.)

First of all, from where my telescope is set-up, I cannot see the pole - so I don't use a polar alignment scope. Not that I have anything against them, I just feel it is just as easy, and more direct, to simply monitor the effect that I want to correct for in the end product - declination drift in the final image. Once you have gained even a rudimentary familiarity with the sky, a rough aligning to the north celestial pole becomes second nature. (If you see Orion, say, or Perseus, you have a very good idea where the NCP is located.) And the beauty of it is, the farther off you are, the more quickly you will see that show up in the drifting of a star.

To illustrate, just the other evening, I used ImagesPlus in its focus mode, along with the camera I image with, to align the mount. Again, this could be any image capture program. The advantage here is that once you select the region of the initial image for focusing, you can enlarge that portion and see any movement at the pixel level. Then, manually "release" (trip the shutter), wait a few minutes, perhaps the length of your sub-exposures (sometimes more quickly than that depending on how far off you are) make an adjustment and repeat the process. Actually, you'll see the movement show up pretty quickly since it is magnified.

And perhaps an even easier method is to use a web cam (or the guide cam you use in a separate guide scope but installed in the main instrument) and monitor the drift. I tried this last night using Craig Stark's PHD Guiding program. And, since PHD now includes a grid overlay as well as a bulls eye option, it's a matter of placing a star conveniently on the screen and watching the drift in real time, as opposed to snapping pictures with the DSLR.

And, of course, another advantage to using a camera, of any type, is you can rotate it within the focuser to get the movements to parallel the mount - i.e., north is up, etc.

As far as the general process, here is a technique I find helpful to understand the mechanics of what is happening with respect to the movement of the mount versus the path of a star across the sky. Imagine two circles, such as two hula hoops, overlapping and lying in the same plane. The outer circle is the earth's equatorial plane. The inner one is the equatorial plane of your mount. Now, imagine tilting the inner circle backwards (say, below the pole) and envision the effect along the meridian versus at the horizon. The arc formed by each circle/loop is nearly parallel close to the meridian. But, near the horizon (either east or west) the arcs of the two loops form an angle where the two circles intersect. That is why altitude adjustments are to be made with a star near the horizon. And if you picture the two intersecting circles and imagine a star moving along from left to right, you will see that they diverge on the eastern horizon and converge towards the west. So, with a star tracking along the true equatorial plane and your mount tracking along the inner circle, the star will "fall" when pointing east. Now, put the circle back in the same plane and then imagine rotating it (turning the base, say, towards the southeast). Now you see a similar effect - near the meridian, the arcs will intersect, one rising, the other falling. In fact, when I see the star drifting northward, (I don't like remembering ditties), I stand with my arms outstretched and my body tilted back, facing what I believe to be south, then I turn slightly southeast and rotate my body and notice the arc formed by my arms (representing the equatorial plane of the telescope) versus that of the supposed equatorial plane. In this case, my arms will trace a falling arc at the meridian. So, a star moving along the true arc will appear to rise in the field of view. And if you turn towards the southwest and rotate, your arms will trace out the reverse pattern, your arms crossing upward and the star falling. So I must be west of the pole and adjust accordingly. (This really needs a graphic, but, try to visualize it, which in itself will reinforce your understanding.)

Now, you might be tempted to simply let the auto guiding program eliminate any drift, or at least any residual drift. True, but you will still have field rotation to deal with later in post processing. And, true, some amount of misalignment at least enables applying declination corrections in one direction, thus avoiding over-correcting in declination, what with backlash and all. But, only enough to overcome variations in seeing.

Obviously, this entire area can be treated much more technically (and turn more novices off). Based on factors such as your focal length and amount of movement in the guide star over a period of time, the exact correction to azimuth and altitude can be determined mathematically (just as programs such as Gemini do). The point of this exercise is to lend a natural understanding of the fundamental process/geometry at work and provide a simple method for achieving very accurate polar alignment based on the very problem it is meant to cure - drifting stars.

William J. Shaheen
Superstition Mountain Astronomical League
Gold Canyon, AZ USA

Thursday, December 16, 2010

The World of Astronomy

Welcome to the wonderful and wonderous world of astronomy. Too few of us are aware of the enormous yet free treasure that lies in the canopy that is just overhead. To remedy that missed lifelong opportunity, this is the first of what will be several articles that will delve into specific areas about astronomy and astronomical objects. My own particular area of interest is in "astrophotography", the practice of photographing celestial/astronomical objects. To aid in illustration, I maintain a photographic website at: Specifically - . Feel free to visit. I also teach a course which I title, "Astronomy Without A Telescope", so-named because it is important, and possible, to enjoy the celestial wonders without the aid of a telescope. The course covers the following areas:
(1) Orientation - Our place on the earth and the resulting motion of the night sky. Visualizing the celestial plane (demonstration using an simple umbrella); Zenith versus celestial north; Celestial versus geographic coordinates versus altitude and azimuth; Discussion of local and prime meridian.
(2) The Earth-Moon System Phases of the moon - Why? Demonstrate moon orbiting the earth - "Moon Eclipses Saturn"; Why isn't there an eclipse every month? Why can I see the moon in the daytime? Why is the moon higher in the sky in the winter than it is in the summer? The 5 degree tilt; The Lincoln story (Demonstrate Virtual Moon Atlas) (Sun/earth/moon side view diagram).
(3) A Sense of the Solar System - The plane of the ecliptic Inferior vs. Superior Planets; Why can't you see Venus at midnight? Retrograde motion of superior planets. Why is Jupiter low in the summer sky but high when it’s in the winter sky? (Use TheSky6 (tm) to compare altitude of Jupiter on 7/21/2007 @ 9 pm to position on 2/21/2014 @ 9pm.)
(4) It's About Time - What is time? ("That which marks the passage of events.") Measurements of Time - Local Mean Solar Time; Universal time (UT); Sidereal (Star) time.
(5) Our Galaxy and Beyond - Earth's Annual View of the Sky. Demonstration using placards with constellations. The First Point of Aries Parallax – parsec = 3.26 lightyears. Celestial coordinate system – Right Ascension and Declination. (Use TheSky to illustrate the difference in RA/DEC between 1950 and the present, to demonstrate precession.)
(6) Astrophotography Without A Telescope - Using a camera with a standard or telephoto lenses.
(7) Resources in Astronomy - RASC Observer’s Handbook; Norton’s 2000 Sky Atlas; 2000 Uranometria2000.0; Burnham’s Celestial Handbook; Binocular observing; TheSky6 (planetarium software provided by Software Bisque -; Virtual Moon Atlas. See also:
Please contact me for further information or to register for the course, held at the Superstition Mountain Campus of the Central Arizona College in Apache Junction, Arizona.
Thanks for reading and I look forward to hearing from you, either comments or questions.

William J. Shaheen
Superstition Mountain Astronomical League®
Gold Canyon, AZ USA