Observing - Basics of Astronomy 2

A hand at arm’s length, a star chart, and recalling simple shapes and lines puts you right on target.

Now that we’ve explained how the sky is charted, the next step is in learning how to transpose information from the chart onto that big open sky above us.  I suggest you download and install Stellarium and explore it’s features. 

I also suggest you download and install One Minute Astronomer

These two programs provide virtually everything you need to find thousands of objects for observing.

Our eyes collect visual data, but the actual “seeing” happens in our brain where we perceive a real time image. Our brain retains a portion of the image in memory - (both conscious and subconscious) for subsequent use.  When we see a road marker on the highway, our mind automatically recalls a picture of the map.

As an experienced driver confidently navigates a road after studying a map, an experience astronomer leans to find celestial objects in space. Again - TOO COOL.


Observing Basics 1

Seeing the Cosmos

Weather / Moon Phases Observation Dates

E-Mail / Get on the List

Astro  Video LINKS


Earth - Pale Blue Dot

Oil Capital Astronomy Observing Center

Map and Directions

 Telescope Basics

Astronomy Optics and Systems

A key ingredient in finding objects that are either barely visible or invisible (hiding) to the naked eye is to use brighter identifiable objects for reference points.  For example:”Go about two thirds of the way past Walmart toward McDonalds and take a right at the phone booth; go down to the end and turn left at the Pink Flamingo.”

 1 - Learn Angular Size & Distance relative to the outstretched hand.

Angular Size & Distance is the length, width, and/or diameter of a celestial object as seen against the sky.  

Use your outstretched hand as the measuring tool!

Extend your arm fully and cover this image of the moon with your pinky. The ANGULAR size of the full moon is ONE HALF degree.

The Angular width of...     

...the tip of your little finger is 1 (one) degree.

... the span between outstretched pinky and index finger is15 (fifteen) degrees.

...your ring, middle, and index fingers is 5 (five) degrees.

...your fist is 10 (ten) degrees.

... the span between outstretched pinky and thumb is 25 (twenty five) degrees.

 I found this simple diagram at http://www.oneminuteastronomer.com

This is just another really good web site that will help you learn in short period what took years for many of us to learn.

2 - Transpose angular sizes and distances of objects from charts and lists

A  telescope with an eyepiece that yields 25 -30 X magnification has approximately a 2 degree field of view; a 8 X binocular or typical telescope finder scope has approximately an 8 degree field of view.  The greater the magnification, the narrower the field of view; and as power increases, the concentration of light diminishes as it is visually spread over a larger area.

It is important to understand why most astronomical viewing is done at low powers - well below the capability of the telescope.  The more you magnify an image, the smaller that field of actual view becomes.   Search for objects with low magnification eyepieces. Once you find and center an object you may increase magnification to reveal more details.

The angular size of the moon is 1/2 degree, so you can easily cover it with your pinky finger extended to arm’s length.  Many objects in the night sky have much larger angular size than the moon. A few galaxies in our local group and even more nebulae in the Milky Way galaxy are larger than (1) one degree. 

The Great Andromeda Galaxy - M31 is  three degrees long and one degree wide - 12 times the apparent size of the full moon.


The bright core of the Hercules Globular Cluster - M13 - is 1/4 degree or 15 minutes in diameter - 1/2 the apparent size of the full moon.

Your pinky may be smaller or larger but will vary in proportion to the length of your arm - thus the distance from your eye.

As you can see, I have little pinky drawing experience.

When I point out objects,  I use degrees and describe geometric shapes or imaginary lines which point to the object. I point out a star and say “go west 10 degrees and then 3 degrees south”, or “”those 3 stars for a right triangle; imagine a line between the two southernmost stars and look at a point 1/3 of the way along that line from the east.”

There is a member of the Astronomy Club of Tulsa - Steve C. - who is known by his friends as a master of this type of celestial “navigation”. Steve is “allergic” to fancy telescope controls; his brain is his computer.  Visit with him at the RMCC observatory and  you’ll end up smiling- perhaps laughing.  It is absolutely fascinating to see how years of practice using these simple methods allow Steve, James, John and others to navigate the sky as easily as they navigate city streets and parking lots.

If you don’t have someone to point things out, just remember what you see on your chart and then identify (within a few degrees) nearby stars. The wide field of low power binoculars and finder scopes makes finding objects invisible to the naked eye much easier. If you participate with any of these groups, someone will b e willing and happy to help you.

The Astronomy Club of Tulsa, and Star Corral are all about enjoying and sharing astronomy.

We enjoy helping others learn of basic astronomical terms and principles by sharing information and demonstrating simple techniques that allow anyone who is interested to catch on quickly.  



Pale Blue Dot

Observing Basics 1

Observing Basics 2

Seeing the Cosmos

 Telescope Crash Course

Astro  Video LINKS

Oil Capital Observing Center

Map and Directions



Weather and Moon Phases

E-mail us. / Get on the list.

Astronomy Optics / System