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Star Hopping

Summary: Star hopping is a process used to locate objects in the night sky. To star hop, the observer uses well known or well charted bright objects to find his/her way to a desired object. This is a good way to find objects in parts of the sky that are unfamiliar or to find faint objects.
Goal: In this lab, you will star hop to as many different stars and objects as you can. By doing so, you will quickly improve your skills with the telescope as well as become much more familiar with the stars and constellations in the sky.
Grading (ungraded): This is a skill building lab that should enable you to find fainter and fainter objects and prepare you well for your telescope practical. We hope you will be self-motivated and want to go as far with this as possible. Write down all of your observations in your observing log. There is no formal graded work or quiz for the Star Hopping lab.

Procedure: Star hopping is a process used to locate objects in the night sky. To star hop, the observer uses well known or well charted bright objects to find his way to a desired object. A predetermined path of bright stars is often drawn up before the observing session. First, you must obtain a star chart so that you can make accurate drawings that you can compare with what you see in the telescope eyepiece or finder scope (read the section on star charts below). The first object on your path should be a naked eye star (one that you can see without the aid of a telescope) near to the intended target. Then pick a number of other objects that provide a clear stepping path toward what you want to see. Things such as patterns of stars in geometrical shapes, pairs of stars that can serve as pointers in a particular direction, and different brightnesses to set off particular stars are acceptable steps to take. Galaxies and quasars are not acceptable as they will be too faint for you to find. When the observing session begins, locate the first star in the night sky. Center the main scope on this star. Then move the telescope to the next object by comparing the view in the eyepiece or finder with the drawings in the chart. This constitutes your first hop. Keep hopping until you get to the object under study.

Where to Start: Start with Polaris, the north star. Choose your hopping path from there, since you will begin your observing by polar aligning the telescope.

Star Charts: Here are some tips for painless star hopping. Each "hop" should move you in the general direction of the final object and should be relatively short in angular size. Hops, if possible, should be done in the finder scope since it provides a wider field and can thus allow a greater grasp of the orientation of objects. However, some objects may be too faint to pick up in the finder so the main scope is still important to use. Make sure that you do not bump your finder scope and cause it to become misaligned with the main scope. Another way to orient yourself if there are not enough stars in the scope to do so, is to remember your coordinate system. If you lock the RA wheel and nudge the scope in Declination, you will be moving either North toward Polaris or South. The stars, since they are fixed, will of course move in the opposite direction. So a nudge in the direction of Polaris will make the stars appear to move toward the South. To determine East and West you could turn of the tracking motor and watch stars drifting toward the West. Then it becomes easy to compare the view from the scope with the star chart.

Understanding Star Charts  Star Charts are pages in an astronomical atlas much as state and city maps are pages in a road atlas. The primary objects in a star chart are the constellations and the stars contained within them. The constellations have boundaries as well as unique names, much like counties on a road map. In addition, a grid is normally superimposed on the constellations that shows the equatorial coordinate system (RA and Dec).  The RA will be marked of in hours from 0 to 24 mostly along the bottom and top of the graph and the Dec will be marked off in degrees from -90 to +90 mostly along the left and right edges of the graph. Most of the objects placed on the chart will be stars of different sizes representing different brightnesses. Other objects such as nebulae and galaxies will have their own symbols. There might also be a few additional lines showing the apparent path of the sun over the year (the ecliptic) and the plane of the Milky Way galaxy.  A few of the objects will have numbers and letters that serve as identifiers for those objects. The brightest stars will have Greek letters that represent Bayer catalog identifiers. They are placed such that an earlier letter represents a brighter star. For example, the second brightest star in the constellation Lyra is Beta Lyrae. Numbers next to a star are from the Flamsteed catalog. They represent an ordering of the stars within a constellation by increasing RA. Thus the bright star with the lowest numerical value of RA in the constellation Orion will be denoted 1 Orionis. The Flamsteed catalog includes fainter (and consequently more) stars, but there are still many more even fainter stars with neither identifier. Some of these will have other identifiers based on other catalogs. Non-stellar objects have two major catalogs to represent them. The first is the Messier catalog, denoted by a capital M follow by a number. For example, the Great Nebula in Orion happens to be M42. This catalog has 110 entries, which  are usually the brightests and more easily seen. A much more complete catalog is the New General Catalog with about 7800 entries.  They are denoted by a capital NGC followed by a number. Some charts leave out the letters "NGC " to minimize clutter.  So if you see and object that is not a star but has just a number next to it, it is almost always an NGC identifier. A particularly bright or interesting object may be included in many catalogs and thus have many identifiers, but, in general, the oldest identifier is the one that is most often displayed on the chart.
 

 Using the RA dial to find objects (a shortcut) Instead of going through the sometimes time consuming task of star hopping, a dedicated observer can often locate an object more quickly by properly aligning the RA dial on the telescope. The RA dial is simply a piece on the telescope near the base that has the 0 to 24 hours of subdivided RA printed on it. It is adjustable because the motion of the stars necessitates changing it every time the telescope goes for more than a minute with the motor off (i.e., every day at least). To use the RA dial effectively, polar alignment must be very accurate. A small error in polar alignment will make it nearly impossible to use this technique without further effort. The advantage is that this further effort can still be less than star hopping on some occasions. To align the RA dial, simply center the scope on a bright star near your target for which you know the RA. Then move the RA dial (not the scope) until the pointer on the scope is lined up with number on the RA dial that matches the star's RA. You can check the Dec. of the bright star against what the Dec. is reading on the scope to see if you are correctly polar aligned. (If not, use hte offset method: calculate the difference in RA and Dec between the star and target and apply these differences to both axes.) Then, leaving the RA dial in place, move the scope until the pointer matches the number on the RA dial that corresponds to whatever object you are looking for. Then line up the Dec. the same way and presto, you should see the object. If not, then you can use a technique called sky sweeping to, hopefully, find the object. Simply lock the Dec. and move back and forth in RA around the value you started with. If you don't see the object yet, unlock the Dec., increment it by about one-half degree, lock it again, and sweep in RA. Keep doing this until you find the object or move more than 5 degrees in both directions from the original Dec. setting. This method can be very quick, but it can also be very frustrating if you do not take the time to polar align reasonably well.


Object List #1: The ALPHA LIST

Note: There's no need to "star hop" to stars this bright! These are starting points for star hopping!  Look at 8 to 10 of these stars,
choosing a variety of spectral types.  In your observing notes, remember to comment on the color of each star and see if you can relate the color and the spectral types of stars.
 
 
Name Constellation Right Ascention Declination Visual Magnitude When to View (Fall / Spring) Distance Sp.Type Comment
Dubhe 
Ursa Major 
11h 04m 
+61d 45'
1.8 
Early / Middle 
105 LY 
K0 II 
34th brightest 
Spica 
Virgo
13h 25m
-11d 09'
1.0
Early / Late
275 LY
B1 V
16th brightest
Arcturus <
Bootes
14h 16m
+19d 11'
0.0
Early / Late
37 LY
K2 III
4th brightest 
Rasalhauge 
Ophiuchus
17h 35m
+12d 34'
2.1
Middle / ---
60 LY
A5 III
55th brightest
Vega 
Lyra
18h 37m
+38d 47'
0.0
Middle / --- 
27 LY
A0 V
5th brightest
Altair 
Aquila
19h 51m 
+08d 52' 
0.8
Middle / --- 
16.5 LY
A7 IV
12th brightest, 64th closest
Deneb 
Cygnus
20h 41m 
55d 17'
1.3
Middle / --- 
1600 LY
A2 I
19th brightest
Alderamin 
Cepheus
21h 18m
+62d 35'
2.4
Middle / Early
52 LY
A7 IV
86th brightest
Fomalhaut 
Pisces Austrinis
22h 58m
-29d 37'
1.2
Middle / --- 
23 LY
A3 V
18th brightest
Markab 
Pegasus
23h 05m
+15d 12'
2.5
Middle / Early
110 LY
A0 III
30th brightest
Alpheratz 
Andromeda
00h 08m
+29d 05'
2.1
Middle / Early
120 LY
B9 IV
... 
Schedar 
Cassiopeia
00h 40m
+56d 32'
2.2
Middle / Early
150 LY
K0 II
65th brightest
Hamal 
Aries
02h 07m
+23d 27'
2.0
Middle / Early
75 LY
K2 III
48th brightest
Polaris 
Ursa Minor
02h 32m
+89d 15'
2.0
All / All
300 LY
F7 I
49th brightest
Menkar 
Cetus
03h 02m
+04d 05'
2.5
Middle / Early
150 LY
M2 III
91th brightest
Mirfak 
Perseus
03h 24m
+49d 52'
1.8
Middle / All
570 LY
F5 I
33rd brightest
Capella 
Auriga
05h 17m
+46d 00'
0.1
Late / All
45 LY
G5 III
6th brightest
Aldebaran 
Taurus
04h 36m
+16d 31'
0.9
Late / All
68 LY
K5 III
13th brightest
Betelgeuse 
Orion
05h 55m
+07d 24'
0.5
Late / All
520 LY
M2 I
10th brightest
Sirius 
Canis Major
06h 45m
-16d 43'
-1.5
Late
8.6 LY
A1 V
1st brightest, 8th closest
Castor 
Gemini
07h 35m
+31d 54'
1.6
--- / Middle 
49 LY
A2 V
23rd brightest. double star, 3" sep.
Procyon 
Canis Minor
07h 39m
+5d 14'
0.4
--- / Middle
11 LY
F5 V
8th brightest
Regulus 
Leo
10h 08m
+11d 59'
1.5
--- / Late
...
... 
...

 

Object List #2: DOUBLE STARS

Notes: Position Angle refers to the location of the secondary (the fainter of the two stars) with respect to the primary (the brighter member of the double). Astronomers measure angles counterclockwise from north (the 12 o'clock position). Separation refers to the angular distance between the pair, in units of seconds of arc. You should be able to estimate the separation in your field of view, since you should be comfortable by now with the angular field of view of your 25 mm and 10 mm eyepieces. Magnitude is the apparent magnitude of the two members of the binary, at visual wavelengths.

 

 
 
 
 
 

Name of Primary Constellation RA Dec Position Angle Separation Visual Mag. Comment
Beta 
Cepheus 
21h 29m 
+70 34' 
249 
13.3" 
3.2, 7.9 
... 
Alpha
Cassiopeia
00h 41m 
+56d 32'
282
69.5"
2.2, 8.9
... 
Eta
Cassiopeia 
00h 49m 
+57d 49' 
293 
12.2" 
3.4, 7.5 
... 
Alpha 
Canes Venatici 
12h 56m 
+38d 19' 
228 
19.3" 
2.9, 5.5 
... 
Epsilon 
Perseus
03h 58m
+40d 01'
10
8.8"
2.9, 8.1
... 
Eta
Perseus
02h 51m 
55d 54'
300
28.3" 
3.3, 8.5
... 
Gamma
Aries
1h 53m 
+19d 17'
0
7.8" 
4.5, 4.5
... 
Alpha
Hercules 
17h 15m 
+14d 23'
110
4.6" 
3-4, 5.4
... 
Gamma 
Leo 
10h 20m 
+19d 51'
125
4.6" 
2.6, 3.5
... 
Alpha 
Ursa Minor 
02h 32m 
+89d 16' 
218 
18.4" 
2.0, 9.0 
Alpha Ursa Minoris is, of course, Polaris 
Theta 1 
Orion 
05h 35m 
-5d 24' 
--- 
13"-16" 
5.4, 6.3, 6.7, 6.8 
Quadruple system known as "the Trapezium," at center of Orion Nebula. 
Zeta 
Ursa Major 
13h 24m 
+54 56' 
152 
14.4" 
2.3, 4.0 
Zeta Ursa Majoris is a wide double with the brighter separated into two, i.e. a triple system. It is the closer pair that is given here. 
Gamma 
Andromeda 
02h 04m 
+42d 20' 
063 
9.8" 
2.3, 4.8 
... 
Beta 
Cygnus
19h 31m
+27d 58'
054
34.4"
3.1, 5.1
Notice the nice color constrast between the two stars in both Gamma Andromeda and Beta Cygnus. Why?
Epsilon 
Lyra
18h 44m
+39d 40'
+173
207.7"
4.7, 5.1
Epsilon Lyrae's stars are both doubles themselves (a double double). The separation is very small (2.5 arc seconds) and is best viewed in the 10mm eyepiece.
Zeta
Lyra
18h 49m 
+37d 36'
150
43.7"
4.3, 5.9
... 
Nu
Draco
17h 32m 
+55d 11'
312
61.9"
4.9, 4.9
Notice the lack of color contrast between the two stars in both Zeta Lyra and Nu Draco. Why? 
61 
Cygnus
21h 07m 
+38d 44'
144
31"
5.3, 5.9
Famous nearby double, 11.1LY away. 4th nearest naked eye star, first star with measured parallax (by Bessel in 1838). 
Omicron 2 
Eridanus 
...
... 
105 & 347
89" & 8"
4.5, 9.5, 11
Unusual Triple system. Primary is a K1 V star; secondary is a white dwarf; third and faintest companion is a low-mass M5 V star. 
Iota 
Cassiopeia 
2h 29m 
+67d 24'
241 & 114
2.2" & 7.3"
4, 7, 8
Triple system. 

Object list #3: CLUSTERS AND NEBULAE

Notes: Most of these objects are challenging when seen from a large city. You may experience difficulty seeing them even if the telescope is pointing in the right spot! They are nevertheless among the most beautiful objects in the night sky and quite interesting to look at. As an aside on light pollution, you should know that while faint, several of these objects are visible to the naked eye under a very dark site.  Always start with the 25 mm eyepiece to locate the object.  For th esmaller ones (planetary nebulae), you may have to switch to the 10mm to clearly distiguish the object from the surrounding stars.  In all cases, use both magnifications (eyepieces) when making your observations as one may reveal something the other doesn't.  If you have difficulty finding these objects with the star hopping method, you may have more luck using coordinate offsets from a nearby star you can locate easily (such as in the "alpha list" above).  This will work best if the star is close to your final target and if you did a good job at aligning your telescope to the North Celestial Pole.
*** = extra challenging. Good luck!

 

 
 
 
 
 

Name Constellation RA Dec Size (arcmin) Distance Comments
M42: Orion Nebula 
Orion 
5h 35m 
-5d 27' 
10'
1600 LY
Region of Star formation. Surrounds multiple star Theta 1 Ori.
M34 
Perseus 
2h 42m 
+42d 47' 
30'
1500 LY
Bright galactic cluster. Age = 100 Myr.
NGC 884/869 
Perseus 
2h 20m 
+57d 09' 
29' / 29'
7400 LY
Famous Double cluster. 
Age = 11Myr / 6Myr. 
M45: The Pleiades
Taurus
3h 47m 
+24d 07' 
100'
400 LY
Very bright, very large galactic cluster. Age = 70 Myr.
M41 
Canis Major 
6h 47m 
-20 44' 
38'
2400 LY
Galactic cluster 4d south of Sirius.  100 Myr old.
M44: The Beehive 
Cancer 
8h 41m 
+19d 45' 
80' 
520 LY
Very large galactic cluster.  660 Myr old.
 *** M13
 Hercules
 16h 40m
 +36d 33'
  10'
 22000 LY
 Globular cluster framed by 2 stars of 6th mag
 *** M92
 Hercules
 17h 16m
 +43d 11'
  8'
 25000 LY
 Globular cluster, compare with M13
 M11
 Scutum
 18h 48m
 -6d 20'
 13'
 5600 LY
 Very dense galactic cluster.  224 Myr old.
 M57
 Lyra
 18h 52m
  +32d 58'
 70''
  2300 LY
  Famous Planetary Nebula ("Ring nebula").  Neb is 3900 years old
 NGC 6826
 Cygnus
 19h 43m
 +50d 24'
 25''
 2300 LY
 "Blinking " planetary nebula.  Look for central star! Neb. is 5200 years old
*** M15 
Pegasus 
21h 30m 
+12d 10' 
5' 
32000 LY
Globular cluster.
*** M36 
Auriga
5h 36m 
+34d 08' 
12' 
4100 LY
25 Myr old galactic cluster
*** M35 
Gemini 
6h 09m 
+24d 20' 
25'
2200 LY
107Myr old galactic cluster.

Object List #4: STARS KNOWN TO HAVE PLANETARY COMPANIONS

Notes: This is a list of several solar-type stars known to have planets in orbit around them. The planets themselves are hopelessly beyond the reach of amateur telescopes (in fact, they have not yet been seen directly, even with the most advanced telescopes used by astronomers), but it is interesting to see what a starlike Sun looks like from afar and think that it has planetary companions, some perhaps similar to those in our solar system. These stars are not visible to the naked eye from campus, but can be glimpsed in the finderscope. They are an easy sight through the telescope. What would the Sun and its family of planets look like to an alien civilization living on a planet orbiting such a star? How hard would it be to identify the stars worth investigating for signs of (perhaps intelligent) life?

 

 
 
 
 
 

Name RA Dec Sp. Type Distance Visual Mag. Planet Mass (Jupiter = 1) Orbital Pd. Comment
51 Pegasus
22h 57m 
+20d 46' 
G2 V 
44 LY 
5.5 
>0.5 
4.25 days
... 
47 Ursa Major
10h 59m 
+40d 26'
G0 V 
45 LY 
5.1
>2.4 
3.0 yr
... 
upsilon Andromeda
1h 37m 
+41d 24' 
F8 V 
54 LY 
4.1 
>0.6 
4.6 days
System of 3 planets!
rho 1 Cancri
8h 52m 
+28d 20' 
G8 V 
44 LY 
6.0 
>0.8 
14.8 days
Northernmost of a pair
tau Bootes
13h 47m 
+17d 28' 
F7 V 
62 LY
4.5 
>3.9 
3.3 days
...
16B Cygnus
19h 42m 
+50d 31' 
G2 V 
96 LY 
6.0 
>1.6 
2.2 yr 
Wide double star. B is to the SE (PA=135)
rho Corona Borealis
16h 01m 
+33d 19' 
G1 V 
55 LY 
5.4 
>1.1 
40 days
...