Texas Star Party

April of 2009, I had the opportunity to go to my first Texas Star Party (TSP). The setting, as it has been in recent years, was the Prude Ranch near Ft Davis, Texas. I was working my day job the first part of the week, but I managed to take two days off. I hopped in my pick-up truck at the end of work on Wednesday afternoon.

My pick-up is set up with a simple camper shell. My Orion XT10 fits easily in its soft case on the right side of the bed of the truck and I fit nicely on a camping mattress on the left side. The arrangement lets me stop at a campground or a star-field and quickly set up my gear.

I drove west on I-10 for five hours and arrived at the campground at Balmorhea State Park. The sky was dark there, but it was completely covered by clouds. I slept well and when I got up the next day, I went to the famous spring-fed swimming pool and rinsed off before driving the 40 miles up to the Prude Ranch.

I got to the “center of the universe” at about 9 AM. I checked in and got my tent pass at the ranch-house/dining room. I found an open slot along the road side of the middle observing field. As I was setting up my equipment, I found out from the fellows on either side of me that this spot had been occupied until the previous day. The previous occupant had broken his leg walking to the bathroom in the dark. (He tripped over a tent guy rope.) They wished me a good stay at the TSP and hoped that I did better than the previous astronomer.

For the rest of the morning and early afternoon, I wandered around the observing fields. There were easily several hundred telescopes set up. Many were under shiny metallic covers. There were counterbalanced binocular stands. I greatly admired the Couch Potato Telescope (CPT) and was able to meet its designer, Sim Picheloup. (Before the end of the TSP I had bought a kit from Sim to build my own CPT)

After lunch, I wandered up to the vendor area and looked through the booths. I bought a book by O’Meara on how to approach the Hershell 400 List. The Hershell list is a group of 400 mostly-dim deep sky objects. All of them need to be found to get the Hershell 400 certificate from the Astronomical League. More than that, the Hershell 400 certificate is the hardest of the required certificates for the Master Observer certificate. Receiving the Master Observer award is a goal that I have set for myself over the next couple years.

I brought the book and some information about the CPT back to my truck and settled down to do some reading and napping for the rest of the afternoon. It was warm, but I was able to get in a couple hours of sleep.

Late in the afternoon, I went to the meeting hall where Mexico Doug (one of the guys I camped next to) was giving a talk on collecting the meteorites from a large meteorite that fell south of Dallas earlier in the spring.

After I came back from the meeting hall, Doug introduced me to a group of observers who were hanging out under a couple shelters under a shade tree about 40 yards down the field from where I was. They kindly offered me a cold beer and a chair. Before the end of the TSP I was a member of the TSP Shade Tree Gang. (http://tspshadetreegang.com) I think my membership was assured when I showed up on Friday with a couple cold six packs for the group.

That evening, the sky turned mostly clear. The photographers were not pleased with the conditions, but it was a fine evening to run the 5x5 list and the Globular Glory list with my telescope. After I got that accomplished, I turned in for a nice rest.

Friday was another day of discovery – seeing what sorts of equipment folks had brought. I bought a hardware kit for the CPT binocular chair from Sim Picheloup. I also persuaded him to let me use a chair with my binoculars that night to run the TSP binocular list. He was very gracious to agree to my request. I bought a silver colored cover for my telescope to keep it out of the sprinkles and the sun – both of which came through the ranch that afternoon. Just before setting out for the McDonald Observatory for a great tour, I got my 5x5 and Globular Glory pins from a legend at the TSP. John Wagnoner was sitting in a folding chair outside the Meeting Room at one PM and he wanted to see my log. There was not much conversation, but I felt honored to have him look at my logs.

Late in the afternoon, clouds rolled into the ranch, so I rolled into the meeting hall with the majority of the other observers. The place was packed. It was the awards and rewards part of the meeting that most people were there for. But we had a great talk by a former ISS crew member. He had some great pictures of cities at night. It reminded me how much problem we have with light pollution and how special a place like the TSP is. I stuck around the meeting, listening to really bad jokes, and without surprise left without having won anything.

The sky was covered from one horizon to the other with clouds when I got out of the meeting hall. I went to bed and checked the sky about 1 AM. It was remarkably clear. Almost no one was observing. A couple guys doing astrophotography said that the sky was absolutely great for imaging. The cloudless part of the sky only lasted a couple hours, in which I was able to run the TSP binocular list from Sim’s chair. It was handy that the list only required finding half of the objects – because about half the objects were hidden by clouds.

By the next morning, the sky was mostly cloud covered and the forecast was for continued cloudy conditions through Sunday. Most of the folks that had vehicles began packing up. I was packed and on the road by about 10 AM. I stopped again at Balmorhea to take a dip and wash off sweat and dust. I was home by mid afternoon.

I unpacked my truck and sent John Wagnoner a letter with a copy of my binocular log. He was nice enough to send me a pin in the mail. These few days ended up being a simple, inexpensive trip that pegged my fun meter for astronomy for about a month.

I will be going back to the TSP. It is a nice time to get to know others, learn new tricks, and have fun observing in a great dark sky site.

Moon Questions

A week or two ago, one of my friends in the San Antonio Astronomical Association asked some interesting questions about the moon. He wanted to know how the moon would appear from the poles, from the Arctic and Antarctic circles, from the Tropic lines of Cancer and Capricorn and from the equator. Here is my slightly edited answer. I am interested in comments, as this is just the result of a thought experiment on my part. I have no experience seeing the moon from those areas.

Hunter,

Not many have worked on your puzzle. However:

In Australia, which is about the southern hemisphere opposite of us here in Texas, I have posted previously that the moon (and the sun) behave pretty much oppositely to what we experience.

The moon still rises in the east and sets in the west, but as one looks toward the horizon under the moon, one is looking north. So the moon rises from the right and sets to the left. Here in Texas, it rises from the left and sets to the right.

When the moon is young, the left side of the moon is lit up down there, instead of the right side like we are used to seeing. And when looking at the moon with binoculars when it is at its highest (north), the South Pole of the moon is at the top of the field of view and the North Pole is at the bottom.

The next questions depend on a fact that the moon's plane of revolution is near the plane of the ecliptic, not the plane of the earth's equator. That is to say that the moon's plane of rotation is pretty much in the same plane as the earth's (and venus and Mercury and Mars...) plane of rotation. (It is actually about 5 degrees out of that plane, which makes all that follows an approximation)

Those circles of latitude you talked about are mainly used to describe the motion of the sun across the seasons. Because of the tilt of the earth, the noon sun is directly overhead at the equator on only two days a year. They are the equinox days in March and September. On all other days, a point either north (late March to early September) or south (late September through early March) of the equator has the sun directly overhead at local noon.

In fact, to a pretty close approximation, the entire equator has its local noon directly overhead on the equinoxes. A circle of points north (or south) of the equator has its local noon directly overhead on every other day. On June 21st or so (depending on how close to a leap year we are), that circle which has its local noon directly overhead is at the Tropic of Cancer - about 23-1/2 degrees of north latitude -- just a little south of us in San Antonio. On Dec 21st or so, local noon is experienced directly overhead along the Tropic of Capricorn. (Remember that Capricorn is south of Cancer in the sky).

Starting from the spring equinox, when the North Pole is tipped toward the sun, the sun never sets at the north pole until the fall equinox. As spring progresses, there is an ever larger circle of earth surrounding the north pole in which the sun never sets at any time during the day. It rises higher and lower, but never sets until about an equivalent number of days the other side of the equinox. The furthest south this ring works its way outward from the North Pole, on the day of the Summer Solstice is a ring of points that are called the Arctic Circle at about 66-1/2 degrees. The same sort of thing happens the other half of the year inside the Antarctic Circle around the South Pole and surrounding what we call the winter solstice.

The other half of the year, there is an equivalent area in which the sun never rises around one of the poles. It has the same area as the area in which the sun never sets on the other pole of the globe.

What does the moon do at the far north and far south? Assuming that the moon is really in the plane of the ecliptic (and that is off by a little bit) Then there is a point near the north and south poles for each day of the year where the moon does not set for the first time that year. That day will be the day that the sun first stays up all day and the day that the sun first stays down all day.

For the north pole and the south pole, that day occurs only twice a year, on the equinoxes. For points on the Arctic Circle and the Antarctic Circle, it will occur only on the solstices. For the rest of the points on the pole side of the Arctic and Antarctic circles, that will occur 4 times a year. The places on which it occurs each day will describe two circles which are parallel to the Arctic and Antarctic Circles.

On the equator, something akin to the sun occurs regarding the moon. For an observer on the equator, and near the summer solstice, when the North Pole is tipped toward the sun, a full moon will appear to be nearer the north horizon than at any other time. During the rest of that lunar month, if one looks toward the north, the moon will rise in the east to the right. The left portion of the moon will be lit in the early evening when the moon is young and the moon's south pole will be up in a pair of binoculars. (In my original post I had some of this backwards.)

Near the day of the winter solstice, a full moon will appear to be nearer the south horizon than at any other time. During the rest of that lunar month, if one looks toward the south, the moon will rise in the east to the left. The right portion of the moon will be lit in the early evening when the moon is young and the north pole of the moon will be up in a pair of binoculars.

Near the day of the equinoxes, the moon will pass nearly overhead. If it is a full moon, at these times the moon may pass through the earth's shadow and a lunar eclipse may occur. If it is a new moon, and the geometry is just right, a solar eclipse may occur.

On other days, there is a circle of points on which a full moon will pass directly through the zenith, directly overhead. The furthest north this circle will move is near the tropic of Cancer, as the summer solstice approaches. The opposite is true as the circle approaches the tropic of Capricorn as the winter solstice approaches.

All of this is complicated further because the moon is not really in the ecliptic, it is in a plane slightly off set from it. That really messes up the eclipses, because the moon can be anywhere in a ten degree arc north or south of the positions I have described above as the “ideal positions” The movement of the moon up and down with regard to the ecliptic can be described in longer cycles called saros cycles. And that is beyond the scope of what I can do in my head.

Dark Skies,

Rick

Thanks to Matt Rottman for the photograph of the moon.

The Dance of the Bears - July

As we look into the sky tonight, we see the big momma bear chasing the little baby bear around the pole. The baby has its tail wrapped up tight and stays just a little ahead of his mom. What junior does not know is that a big dragon had worked its way between them and Mom has just finished driving it toward the hero, Hercules. He has his foot on the dragon's head.

But the dragon had its eyes on others. There is a king who is protecting his prissy wife. He’s below the belly of the dragon and Cassiopeia is just peeking over the horizon east of north. Fortunately the strong hero, Hercules, is not letting the dragon get loose. But Hercules is busy with another project too.

He is about to try to charm the dragon with his guitar that he calls his little Lyra. The strings have this cool pick-up microphone on them called the ring nebula. And two birds have gathered to listen to the music. The swan, whose name is Cygnus, is flying south and further East is the Eagle. Someone has let an arrow fly between them.

Look! It must have come from that farmer, Ophiuchus. But he has forgotten his arrow since he is now fighting with a giant snake.

Down toward the horizon, the farmer has conjured a teapot which is pouring hot water on the tail of a scorpion. The steam from the tea pot, as you might see if the sky is really dark, is blowing along the horizon and is getting in the eyes of the swan. Later on, you may see that it is messing with the vain queen’s hair. Seriously, that spot where the steam is rising from is the center of the galaxy we live in. Downtown Milky way is a hot-time-space place, so for steam to rise from there makes sense.

Near the top of the sky is a bright star that can be found out the curved arc of the Big Bear’s tail. Arcturus is the heart of the shepherd king Bootes. The Bible calls the shepherd king David. And his crown is right between him and Hercules.

If you speed over to Spica with me, you are looking at a pretty girl named Virgo. She is threatened by that Scorpion, but the scales of justice (Libra) will do their best to protect her. Below Libra is a great Centaur, right out of the Harry Potter series, and his heart is a great globular cluster called omega Centauri. We can see it in Texas, but northern astronomers cannot. It is a great secret. Don’t tell them about it.

By the way, did I tell you that the strong man, Hercules had a globular cluster for a heart as well?

Under the Virgin girl is a square of stars called the crow. It is raising its voice to try to scare off the big water snake which is about to be swallowed up by the western horizon.

More directly West is Leo the Lion. This month he is standing on Saturn which is brighter than his regal heart, Regulus. Both Regulus and the lion’s eye star (Algeba) are pretty double stars.
And that takes us pretty much right-around to where we started with the dancing bears.

I hope your dreams are pleasant tonight as you think about these beasts and heros dancing over your heads. Maybe you will fall asleep thinking about the bears chasing each other round and round and round...

Messier Marathon - Late March 2009

After the practice all-nighters I had in January and February, and the “Third Quarter” practice two weeks before the club’s Messier Marathon, I felt ready to tackle the challenge of my first Messier Marathon. I felt some outside pressure, as I had given a talk at the San Antonio Astronomical Association “Beginner’s Forum” in March. In that talk I had explained my approach to the marathon – everything from charts to naps to timing. So it felt like some people were watching me to see how I actually did on my first marathon.

The field was open on Friday night, even though the marathon was going to run on Saturday night. Friday afternoon was cold and windy, temperature in the high 40s and expected to go down to about freezing overnight. I was set up with my pick-up next to my scope and with a camper shell on the back of the pick-up. I would have a retreat from the wind, if not from the cold.

The sky was severe clear all afternoon, but as the sun set, the few of us that had chosen to spend two nights at the star party saw a bank of clouds in the west under the thin crescent moon. These clouds continued to advance toward us, and by the time it was beginning to get dark enough to see stars, they had covered all of the difficult western objects. It was disappointing to not have a chance to identify these, since it had been a month since I had the opportunity to do so and they were now 30 degrees closer to the horizon than when I had last practiced on them.

The rest of the sky was nice and clear, and I was able to easily see the 5.6 magnitude stars in the Little Dipper. I found a number of galaxies, starting with the Leo triplets and the Big Dipper and moved on to the Virgo cluster of galaxies.

But the cloud bank continued to roll in from the east, and by 2330 the sky was mostly covered by clouds. I decided the best thing was to get into my down sleeping bag and see what the sky looked like later. When I awoke about 1:30, the sky had cleared. But oh! Was it windy! And it was cold!

I rolled out of my sleeping bag and spent an hour with the middle of the night objects, following them down to the top of Sagittarius and Cygnus. I had a cup of hot chocolate in the warming booth that Hunter Scott, our host had made available in the tree line surrounding the field. (By the way, he did an incredible job preparing the field and making snacks and hot drinks available for the event.) And then I went back to bed to wait for the pre dawn hour and a half .

The pre-dawn went well. The season had progressed and more of the constellations were available in the East than the last time I had practiced a few weeks before. I saw all those Messier objects that I had not been able to see in the preceding months.

After a nap that lasted until the need for a late breakfast woke me up, I got up and commiserated with the others that had spent the night on how cold and windy it had been. Some wondered, as the day progressed and it got no warmer, whether many folks would come out for a cold night of star watching.

However, as the afternoon wore on, the field filled with cars and scopes. One estimate made before the sun went down was that we had 40+ scopes on the field and over 70 folks using them. We had Rudy’s BBQ catered, which probably increased the crowds. But it was still windy. The prayer over the food included a supplication that the sky stay clear and the wind die down. (And that is what happened.)

The sun set as anxious astronomers sat down at their scopes to take a look at the thin crescent moon 30 degrees above the horizon. When the stars began to appear, I worked hard to try to find the evening objects in the glow of the sun set. I was able to find most of the sunset objects quickly. M78 was not easy, but I finally spotted it as the sky grew darker. M74 turned out to be too hard to find. I had a pointer star to give me reference, but it was almost lost in the warm red of the fading sunset and I could see nothing above it at all – above in my eyepiece, which was closer yet to the horizon.

The night proceeded, pretty much according to plan. I was able to see all the other Messier objects, including the nasty hard ones in the early morning. Added to this, I saw several comets, several planets, and was able to stay warm all night. Compared with the night before, Saturday night was easy as far as the weather was concerned.

I felt like my preparation time for the marathon was just right. I was disappointed at missing M74, but in that I did not feel alone. Many astronomers better and more experienced than I am have had the same problem. I came in second for points for manual scopes in our club – I did not get as many of the extra credit comets and asteroids as Mike did. I had not planned that part of the marathon very well and only had large scale charts of the position of those objects.

Would I do this again? Sure! Getting ready for the Messier Marathon taught me a lot about the sky. It trained my eye to see faint fuzzies quickly. It helped me to organize my observing time. It helped me to grow in my appreciation of dark sky sites and as the months rolled around the sky, I learned even more about the progression of the sky through the year.

What’s next? I think I might be headed toward a binocular Messier Marathon in the future.

Observing Neptune and Uranus – July 2009

I woke at 0430 in the early morning of Friday the 3rd of July and thought of a recent post on the Starynights Yahoo group on observing Neptune. I dug the page out of the Sky & Telescope website that shows where Uranus and Neptune are for 2009, and went out into the front driveway. Venus and Mars were down the street to the East and Jupiter was above my neighbor's house across the street (south). The lights of nearby San Antonio did not obscure the majority of the stars in Pegasus, but none of the stars in the circlet of the fish between the square and Jupiter were visible by naked eye.

I pulled my XT10 out of the back of my camper shell covered pick-up and set it up with a 10x50 finder scope. Before long I had identified Neptune just to the north of Jupiter as a blueish dot in my 10mm Radian eyepiece (120X).

I then set about finding the circlet in my finder scope. Before long I had it identified and two of the stars led me to the pale green disc of Uranus.

It was the second time I have seen Uranus and my first sighting of Neptune. I put the scope back in its case and dropped back into bed at about 0545. Great morning! It will be fun to show these off at star parties as they get closer to evening events as the summer moves into the fall.

White Light Solar Filter

I mentioned to the San Antonio Astronomical Association that if anyone had any of the filter film, I would like to make a solar filter. This last week, my friend Keith Little gave me a gift. He is making several solar filters and had purchased a sheet of Baader filter film. He was able to cut me a 4 inch diameter disc.

I obtained a couple sheets of foam core board for this project. I cut two pieces about 3 inches bigger in diameter than my scope’s opening, and then a couple pieces that would make up a stack of rim pieces. I cut an opening 3-1/2 inches in diameter and situated as close to my secondary mirror as I could make it without the secondary blocking the circle cut.

I taped the piece of Baader film to one of the large discs across the cut-out. Then I taped the second disk to the first and the rim pieces to these two pieces.

I used a piece of malleable wire to create a safety device to assure me that the filter cover cannot blow off my scope while I am looking at the sun.

All together this project took about 2 hours and it works great. If we ever start having sun spots again, I’ll be able to look at them now!

A Simple Dobsonian Telescope

In the late months of 2008, I bought the telescope I should have bought first. I bought it for the right reason. I wanted to know about the sky.

All my telescopes have names. Maybe it comes from the habit of all my sailboats having names, but it was influenced by David Levy’s writing about his scopes having names. That first Meade SCT is Virginia. She is a refined package and was purchased when my family lived in that state. The Celestron 4se is “GT” which is short for GoTo and seems like the sort of name that a computer with a telescope strapped onto its frame should have. The Orion XT10, a ten inch commercial version of John Dobson’s volkscope, is Texas. It is big and it was bought in San Antonio.

As the summer and fall of 2008 marched along, I learned about the deep sky from little GT. I reacquainted myself with celestial mechanics when I refurbished Virginia. With Texas, I fell headfirst into the inky black sky of southwest Texas. During the winter months of 2009, I began to prepare for the Messier Marathon to be held in the last weekend of March. Texas was just what I needed for that task.

A Dobsonian scope is a very simple version of a Newtonian reflecting telescope. It is characterized by a large primary mirror near the ground and an angled secondary near the top. The mounting system is super simple. There is a central pivot in the base which allows the scope to be rotated in azimuth and there are large bearings on each side of the optical tube assembly which allow the scope to be moved in altitude.

I started with a simple, unmagnified finder, the Telrad. That meant that I needed to learn where something was in the sky and point the scope by hand at that area. For almost all the objects I was interested in observing, I could not see the object with my unaided eyes. That meant that I needed to learn about the constellations. Then I needed to find some relationship between the stars that I could see and the object I could not see.

I use two major techniques for finding objects in the sky with a Telrad.

- The first is to use the concentric circles in the Telrad. They have diameters of 1, 2, and 4 degrees. If an object is near an easily observed star, perhaps within a degree or two, I can place the correct Telrad circle on the star and have the central circle oriented toward another star. Then looking through a low power eyepiece (I use 32 mm for 38X magnification) I find the object of interest.

- The second is to use two stars and to imagine the object of interest as part of a triangle of a certain shape (right, isosceles, equilateral) or if the object is directly between two stars, I estimate the position as half-way, 1/3, ¼ etc of the way between the stars. An example of this last technique is in finding the ring nebula, M57, between two stars in Lyra. A second example is M13 in Hercules.

Those techniques are sufficient for double stars and Messier objects. For the Hershell list that I have just begun working on, I have added a finder scope to refine the area of interest after initial pointing with the Telrad. The spotter allows some initial star-hopping across dim stars.

The medium aperture “dob” is a great scope for many purposes. There is no scope which can so quickly teach an observer about the sky – to learn where objects are and how they are related to the stars around them. A dob with a primary mirror between 8 and 12 inches in diameter is reasonably easy to transport, not prone to going out of adjustment, and requires no on-site calibration or alignment. (When I pull my truck up at a public star party, it takes me about 2 minutes to pull the base out and place it on the ground and then the scope goes right on the base. I have a stool which is good for sitting on for prolonged careful observing or for kids to kneel on if they are not tall enough to see in the eyepiece.) I am often showing folks the wonders of the sky well before some of my friends are able to see stars to begin their alignment.

A dob, especially at a power between 40X and 50X. is intuitive for beginners or children to use. When they point it somewhere, that’s what they look at. No mystery, no gears, no computers, no alignment. A dob teaches folks that the stars have a constant and incessant travel from east to west. A dob is perfect for hunting for pretty objects, scanning for comets, finding Messier objects, and with investment in a good 8-10mm eyepiece, for looking at planets and the moon. It is short enough for many children to use on their own. It is easy to transport in the back seat of almost any car. It’s not perfect, but it is pretty close.

I have begun to recommend a scope like this as the best family telescope. It is heads above the scope I bought for my family in the 1980s and a lot cheaper. I will probably begin to look for a dob with a larger mirror, that’s called aperture fever. But it will take some looking to find a scope that I like better than Texas.

Setting Circle Telescopes

The first telescope I bought, 25 years ago, was a setting circle telescope. It was a Meade 8” LX and was built about 1983. This scope folded the light in mirrors twice and then through a diagonal. The light entered the front of the telescope through a plate of glass, bounced off a curved primary mirror at the back end of the scope, which focused the light on a curved secondary mirror in the center of the glass plate. After reflecting off the secondary mirror, the light passed through a central hole in the primary mirror, reflected off a diagonal and then into an eyepiece.

This type of design is known as an SCT, short for Schmidt Cassegrain Telescope. Another design, the Maksutov Cassegrain has a more radically ground corrector on which the secondary mirror is mounted. The Celestron NexStar 4se scope that I have written about in another blog is a Maksutov scope.

What I really want to get around to talking about here is the mounting that my scope had, because that has something to do with learning about the sky. But first I should mention a couple other mountings that scopes I had played with as a young teen were fitted with.

The table-top refractor my parents brought home had a swivel and a fork. This type of scope is still sold in grocery stores just before Christmas. Such scopes are bought by the thousands and most of them are carefully packed in the back of a kid’s closet until they move away for college. They are cheap. They are hard or impossible to use for any real astronomy purpose. They are the equivalent of the $20 guitars which are sold in the grocery stores next to the telescopes. They are guaranteed to frustrate the kids who receive them. But I digress… The swivel and fork mounting is formally called an altitude/azimuth or alt/az mounting. Such a mounting allows the telescope to be swung in a circular direction to every part of the horizon (azimuth) and to be raised to some portion of the sky (altitude).

The second scope I got to play with had a “german-equitorial” mounting. This was a much more complex mounting, and I had some idea of how to use it back when I was in high school. (The problem with that scope was not so much the mounting as the optics.) To set up an equatorial mounted scope, the direction north needs to be known in azimuth, as well as the altitude of the north celestial pole. Just like the alt/az mounting, which rotates in two planes and can point in any direction, the equatorial mounting can move in two planes and point in any direction. The difference between the two mounting systems is that in an alt/az mount, the pivot rotates around a vertical pole, as though it came from the center of the earth and aimed toward the highest point overhead (the zenith). An equatorial mount has that pivot rotating around the line that connects the north celestial pole and the south celestial pole – and that is a line that is very close to the line formed when I point a laser pointer at the north star. Rotating around that line, the 360 degrees of rotation are measured NOT in degrees, but in hours!

I know. Those astronomers are crazy. But there is a method in their madness. Describing the circle in 24 hours makes sense, because the sky actually moves around that circle in … 24 hours. We call it a day. Before you get all excited, let me deflate your expectations some. The 24 hours in the sky have almost nothing to do with the time on your watch either where you are or at Greenwich or anywhere. An hour and minute of Right Ascension (RA) simply marks out a north/south line which starts at the north celestial pole and ends at the south celestial pole. All the stars on a single RA line stay there, month after month and year after year, for all practical purposes. It is like knowing the longitude of a city on the earth.

Since RA is like longitude, there has to be something like latitude to give an address for a star. That second number is declination (dec) and it is measured in degrees north and south of the “celestial equator” which is the circle equidistant from the two celestial poles.

So do I have your head spinning yet? It was a big concept for a 16 year old kid to figure out before the days of the internet. Back then we had encyclopedias for that purpose, and I am sure that I spent time with the Encyclopedia Britannica and a lot of pacing to figure this all out.

Well, it was one thing to see how it works, and another to get it to work. Like I mentioned, the first thing one needs to do is to aim the pivot axis toward the north star. (Actually a little off from the north star, but for a 16 year old the north star was pretty close.) The required pointing north and adjusting a joint to the latitude of Cincinnati, Ohio – about 39 degrees. That accomplished, a kind of magic could now operate. When I pointed the scope at a star, and the star began to move west out of the field of view, all I needed to do was to very slowly turn a gear that drove the RA adjustment in order to follow the star.

I saved that for the last – maybe to surprise some of you. The only reason to have an equatorial mounting is that wonderful advantage. If a scope has an alt/az mounting, the observer needs to constantly adjust both the altitude and the azimuth as the object moves through the heavens (well… as the earth rotates). If you have ever been to a star party and the scope host needed to readjust the scope to point at an object you experienced this. But with an equatorial mount, only one axis, RA needs to be adjusted. Dec for the star stays the same all night, all month, and all year.

Fast forward to my first purchased scope, the pretty Meade 8 inch SCT. It had an equatorial mounting and a super cool new feature. The RA adjustment had a clock driven motor that kept an object in the center of the field. Now that was the height of cool! It required that I set up the scope near an electric outlet or next to my car, but I was free from having to constantly correct the RA adjustment. Maybe I would even be able to take a photograph as the scope body stayed locked to a particular part of the sky.

In the end, that scope was both a great piece of optics, with lots of light gathering power (4 times as much as my 4” computerized scope) but it also taught me the celestial mechanics of how the stars move in the sky and why.

When I got interested in astronomy in the summer of 2008, I took that Meade telescope out of the closet, had a little work done on the secondary mirror (it had begun to lose its coating) and still use the scope occasionally. I was able to find dozens of Messier objects in it once the computerized scope showed me what I was looking for. I will probably have it forever. It is practical and it has sentimental value.

But my SCT is not my favorite telescope and it is not what I would recommend that a new astronomer buy. That story will need to wait for another blog entry.