Astronomy (not astrology) is one of my favorite hobbies. There are a number of links on my Links page that go to astronomy web sites.
I have an Astro-Physics refractor telescope which I really enjoy using. It's a truly superb instrument. If you want to buy a telescope, you can't go wrong with Astro-Physics. It's the Rolls-Royce of telescopes.
Choosing a Telescope
I won't get into too much here on how to pick a telescope (click here for a long-winded version). I'll just say that the most important thing about any telescope is its quality--period! Not its aperture, which you may have heard a million times, and definitely not its magnification. Its QUALITY. You'll be far happier with a small, high quality telescope than you'll ever be with a big, low quality telescope. Like anything else, you get what you pay for. If you're considering buying a telescope and aren't sure what to buy, my suggestion is that you not buy one until you are sure. It's easier to make a mistake than most people realize. Go to a book store and buy a copy of Astronomy and of Sky & Telescope magazines and read the articles and ads.
Look-up your local astronomy club and see what they've got. Take advantage of their experiences--good and bad--so you won't make the same mistakes. Go to their "star parties" and look through the telescopes that they have. See what you think. If you're new to this, you'll probably be surprised.
People are often amazed at what they can see with ordinary binoculars or even with just their eyes. You don't need to spend a lot of money to enjoy looking at the sky. Go to the library and get some books and maybe some videos about astronomy.
A Good Book for Astronomy
A good book for looking at the night sky is the National Audbon Society Pocket Guide Constellations. It will help you find things to look at without wasting your time with endless prose. It's a paperback book that costs about $10. I got mine in 1995 and I wished that it had been available years earlier!
Light Pollution
One of the hardest things to overcome in astronomy is light pollution. If you've the opportunity to work on some outdoor lighting, please do it responsibly. Don't use a 100 watt bulb if a 25 watt bulb will do. Aim the light properly. Sending light up into the sky is a waste of energy and destroys the beauty of the night.
For more information, please check with the International Dark Sky Association. They can provide some very easy to follow advice.
Naming Stars
One of the most disturbing things that goes on is paying to name a star. There are a lot of companies out there that will tell you that, for a fee, they will name a star (a VERY DIM star) after you or anyone you choose. It's bogus. These companies have made tens of millions of dollars by preying on people who don't know how stars are named. This is heartbreaking when people think they've named a star after a deceased loved one, especially if it's a child.
The analogy that I use to explain this is naming hills. I could start a company in my garage naming hills. If you send me some money, I'll send you a map with your name written on it near a hill. Of course, if you get a map from National Geographic or from the U.S. Geological Survey, it won't have your name on it. Since I sent to you what I said I'd send (a map showing your name by a hill), have I cheated you? Absolutely! I convinced you that I could name a hill--which I can't do any more than anybody else can.
Incredibly, the star-naming charlatans have threatened lawsuits against some astronomers who've tried to tell the public about their shady business. Since universities and planetariums are often not financially able to endure even a groundless lawsuit, the astronomers are forced to stop telling people about this scam.
Few law enforcement agencies seem willing to go to the time and effort to thwart this nonsense. If you've been victimized by one of these companies, ask for your money back. If they won't refund it, file a complaint with the postal inspector, if appropriate, and the district attorney. It is my personal hope that the customers of these unethical companies will file class-action lawsuits against them.
Stars names are legitimately recognized by the International Astronomical Union. You can check their comments about paying to name a star at www.iau.org/IAU/FAQ/starnames.html. You can't have them name a star on request.
(I'd like to note that there is at least one star naming organization that does not charge and acknowledges that this is just for fun and not anything official.)
Looking at Solar Eclipses
Is watching a solar eclipse dangerous? My flippant answer to that is, "Only if you fall and hit your head!" Seriously, though, people are often over-warned about the dangers of this to the point of irrational fear. There's nothing special about the light from the sun during a solar eclipse. All that's happening is that the moon is casting its shadow on the earth. This, of course, isn't any more dangerous than any other shadow. It isn't that you shouldn't look at the sun during an eclipse. It's that you shouldn't look at the sun EVER! During an eclipse, people have a motivation to stare at the sun which a really bad thing and can result in blindness. And certainly don't use a telescope or binoculars to look at the sun without a proper filter.
Here are some pictures I took from my backyard and from a park: Click here.
San Mateo County Astronomical Society (SMCAS) Calendars
Here are some calendars about an astronomy club near San Francisco: Click here.
- For rise, set, and Jupiter information, star party dates, and older calendars: Click here.
Small and Cheap Table
Before I had a real table, I needed a small platform to hold my eyepieces, filters, etc. while observing. After some thought, I recalled a brief article which appeared many years ago in, I think, Modern Photography. A 1/4 X 20 "TEE" nut can be put on a piece of wood so it can be attached to a camera tripod (I think the idea was to provide a platform for a slide projector). I used an old wooden office "in" tray. The sides prevent things from rolling off-- which is a very important feature! The tripod makes height adjustment easy and the tilt adjustments of its head permit easy leveling of the surface. The three-point support means I don't have to worry about finding a piece of flat ground as I would for a four-legged table. Since I already had the camera tripod and the old wooden tray, the cost was almost nothing. It's important to keep in mind that this platform is only as sturdy and solid as the tripod. Don't lean on it unless you've got a really heavy duty tripod or you may spill your things onto the ground!
Polar Alignment Without the North Star
Background:
Polar aligning my telescope was a problem. It seems that just about every article or book starts out by telling the reader to point the telescope mount's polar axis at the North Star which is fairly close to the north celestial pole. That wouldn't work for me because I couldn't see the North Star from my backyard! I found a few published techniques for polar alignment with a star other than the North Star by sweeping the telescope and adjusting the mount at the same time or, of course, by adjusting the mount to my latitude and then trying to level it and then trying to find true north (without the North Star!). I didn't like any of this. I rarely tried alignment beyond just a guess.
The method described here was suggested by my brother after I overheated my brain trying to reinvent spherical trigonometry in an effort to find a better way. Despite appearances, the method is quite easy after you've done it a couple of times and will provide good accuracy if you work carefully.
The goal:
It's always a good idea to keep an eye on the goal: the mount's polar (right ascension) axis needs to be parallel to the earth's axis. Note that it is not necessary for the mount to be level! This may be a surprise to you but it really is true. The celestial coordinate system is only two-dimensional so the mount need only be aligned in two dimensions: altitude (the latitude adjustment) and azimuth (getting it pointed to true north). Rotation on the third axis has no effect on polar alignment. Mounts that have a latitude scale need to be level so that the scale will be accurate not so that the polar alignment will be accurate. It should be possible to make a latitude scale that does not require a level mount but I have never seen one. You may also be surprised to learn that to use this method you need to know your longitude instead of your latitude.
The method described here does not require a level mount but it will be easier and faster the closer your mount is to being level.
The concept:
If you can see the celestial pole, alignment is fairly easy. At a declination of 90 degrees, right ascension is not important because right ascension is undefined at the celestial poles. Setting the telescope at 90 degrees declination or using a polar axis sighting scope and then finding the celestial pole is all that's needed to get the mount's right ascension axis parallel to the earth's axis.
However, with a little work, almost any star (or planet or any other celestial object) can be used for polar alignment. It's just that with a star that's away from the celestial pole, right ascension can't be ignored.
A telescope with an equatorial mount has a total of four adjustments. Two of them are for the telescope: right ascension and declination. Two of them are for the mount: altitude (latitude) and azimuth (north/south). Some mounts can be rather difficult to adjust while others are easy. If you have a mount that is difficult to adjust using the celestial pole, this technique won't make it any easier.
In a nutshell, what we will do is:
1) Rotate the telescope in right ascension so the declination axis is horizontal (or so that the telescope is pointing straight up if that's easier to determine),
2) Set the right ascension circle to read the current local sidereal time,
3) Point the telescope so that the right ascension and declination circles read the coordinates of a known star,
4) Adjust the mount in altitude (latitude) and azimuth until that star is centered in the field of view.
5) If your mount is level, you're done. If it's not level, repeat the above steps until there is no more error.
Decide on a star:
Pick some visible star that meets the following conditions:
1) you can see (!),
2) you know you can identify,
3) you know the coordinates of,
4) is not at the celestial pole,
5) is not on the mount's azimuth axis,
6) is not on the mount's altitude axis.
To minimize error, the star should be as far away from the celestial pole and the mount's axes as possible. Stay away from the pole because right ascension loses its meaning near the poles (this affects accuracy). Also, stay away from a star that is near the mount's axes because you want a star that will move around in the field of view as the mount is moved on either axis. A star that is on or near one of the axes will have little or no movement when the mount is rotated on that axis. Also, although it has no effect on accuracy, you may find that the adjustments will be a little more intuitive the closer the star is to having a right ascension that is the same as the local sidereal time (which we will address presently).
When are You Setting up:
When are you going to set up? This matters because you need to know the local sidereal time at that moment. (The local sidereal time is equal to whatever right ascension happens to be straight up at any particular moment.)
There are web sites that you can use to determine the local sidereal time at your location. Be sure to use your correct longitude. The longitude of a nearby city may not be accurate enough. You can use this web page to compute local apparent sidereal time: United States Naval Observatory Local Apparent Sidereal Time Calculator
If you set a clock or watch to the local sidereal time, it will keep sidereal time for several hours with enough accuracy for our purposes so you may want to set your watch to the result of the calculation--just remember to use 24 hour time! After 6 hours, your watch will be about 1 minute slow.
Telescope Set Up:
Try to get your telescope reasonably close to being polar aligned and as level as possible when you initially set up. Although it's not necessary to do this from a purely technical standpoint, in practice it will make things easier later. If the "coarse" adjustments are far off, the "fine" adjustments will be more difficult--perhaps substantially.
In all of the following discussions, it is very important to keep in mind that "adjusting the mount" means moving the mount's altitude (latitude) and/or azimuth without disturbing the telescope's right ascension and declination. "Adjusting the telescope" means moving the telescope in right ascension and/or declination without disturbing the mount's altitude and azimuth. (The telescope's optical axis will certainly move in right ascension and declination when you adjust the mount's altitude and azimuth. It's just that you don't want to rotate the right ascension and declination shafts in their bearings.)
Using a level, adjust your telescope in right ascension so that the declination axis is exactly horizontal (east or west doesn't matter although you may have preference because of accessories getting in the way) or, if your mount makes it difficult to determine this, use the level to point your telescope exactly straight up. Precision here is crucial. Accurately set the right ascension circle to read the current local sidereal time. (Because it's not always possible to set up before dark, you should try to obtain a level that's easy to see in dim light. Some of them can be nearly impossible to see--especially if you're using a red flashlight.)
If your mount has a clock drive, make sure it's on and you can take your time with the next step. Note that you do NOT engage the clutch that actually drives the telescope. You just want the right ascension circle to be driven which should happen just by turning on the motor. If your mount does not have a clock drive, try to work quickly as you won't have a motor compensating for the time you use making adjustments.
Accurately adjust your telescope in right ascension and declination so that the setting circles precisely read the coordinates of the star that you picked. If your initial polar alignment was reasonably accurate, your scope should be pointing in the direction of that star. If you have a clock drive, now is the time to engage the telescope's right ascension drive clutch.
Adjust the mount in altitude (latitude) and azimuth until the star is centered in the field of view. Depending on how your mount is made, you might have to move or adjust the support (a tripod, for example).
Repeat the above steps until there is no error. How many iterations this requires depends on how close your mount is to being level. If it is precisely level, you shouldn't need to repeat the above steps unless you want to verify that things are ok--which is probably a good idea.
Your telescope is now polar aligned with more than enough accuracy for visual observing and enough accuracy for short exposure photographs.
In Conclusion:
Although this procedure may sound complicated and the first couple of times that you do it may be awkward, with only a little practice it will become a lot easier. After a few times you'll find that it takes a lot longer to describe it than it does to do it! I find this much more precise than trying to adjust the mount to my latitude and then leveling it and then hoping to find true north (without the benefit of the North Star!).
Note that even if you can see the celestial pole, because the North Star is never the first star visible after sunset, you can be polar aligned much earlier by using this method. You should also note that this procedure can be used to align your telescope during daylight hours by using the sun (with a filter, of course!) or, if you know where to look, a bright star or planet that may be visible during the day.
Abbreviated Version:
If your mount is precisely level and your mount is precisely set to your latitude, you should only need to adjust the mount in azimuth (point it to true north). If this is the case, the alignment will be quite quick. If you can do it this way, it is certainly worthwhile.
Declination Setting Circle Alignment:
You should probably verify that your mount's declination setting circle is correctly aligned before trying to use it. It probably is adjustable so you should check it (some mounts hide this fact with decorative hardware). Even if it isn't adjustable, you should check if it is properly aligned and note any error so you can correct its readings.
The best way to check the declination circle's alignment depends on how your mount is made. Hopefully, the instruction manual will tell how to do it. If not, the following method can be used with many mounts.
You will need to set certain things level. You may have to adjust what you are doing depending on how your telescope and mount are made. For example, if you need to set the telescope horizontal, it may be easier to check if the primary cell is vertical.
1) With the level, adjust your mount's altitude (latitude) so that the polar (right ascension) axis is precisely horizontal (latitude=0).
2) Adjust the telescope in right ascension so that the declination axis is approximately horizontal (this step is just to make the next one easier).
3) Adjust the telescope in declination so it is precisely horizontal.
4) Set the declination circle to read exactly 90 degrees.
Your declination circle is now aligned. It is essential that this be done precisely. You may want to place some kind of indexing mark on the circle and mount so you can realign it easily if necessary. It's a good idea to check this once in a while.
Preliminary Latitude Adjustment:
You should also set the mount to your latitude. Extreme precision in this latitude adjustment is not necessary if you use the polar alignment procedure that I've described because you'll make-up for it when you do the polar alignment. In fact, from a purely technical standpoint it is not necessary to set the mount to your latitude in advance if you use this polar alignment technique. In practice, however, it will make things easier if you do this first and try to be reasonably accurate. You can use any technique that is convenient. The one described below works well enough for a preliminary adjustment and doesn't require any special angle measuring tools.
1) With the mount reasonably level, adjust it in altitude for a latitude of 0 degrees (polar axis horizontal). Note that if you just finished with the declination circle alignment as described above, it's already set for a latitude of 0 degrees.
2) Adjust the telescope in right ascension until the declination axis is approximately horizontal.
3) With the telescope initially pointing in the same direction as the skyward end of the polar axis, adjust the telescope in declination, pointing it down, until the declination reads the compliment of your latitude, that is "90-latitude" (always consider your latitude positive).
4) Adjust the mount in altitude (latitude) until the telescope is horizontal.
The mount is now adjusted to your latitude.
Sources of Error:
There are several things that can frustrate your attempts at polar alignment. They are:
1) Misidentification of the target star. Bring a planisphere!
2) The coordinates of the target star were misread from the star catalog or the catalog has an error.
3) The setting circles were misread. Be sure that you're using the correct index/numbers for right ascension and that you are using the correct north or south declination.
4) The wrong local sidereal time was used.
5) The accuracy and resolution of your setting circles provide a limit on the accuracy of the alignment regardless of how carefully you work.
6) The wrong longitude was used.
7) The declination circle is not properly calibrated. Some are made in a way that makes it very easy for them slip out of alignment.
8) Your leveling of the declination axis (or pointing the telescope straight up) was inadequate. It's essential that you do this precisely.
9) Your level isn't accurate.
10) The right ascension axis and declination axis are not at exactly 90 degrees to each other. The telescope's optical axis is not at exactly 90 degrees to the declination axis. There's probably not much that can be done about these problems although with some mount designs you may be able to shim some components to reduce the error.
11) Experience has shown me that three iterations will get the alignment fairly close. If this isn't happening for you and you're sure that you aren't doing anything wrong, pick another star. I have not analyzed the possibility of a mathematically unstable solution (oscillation instead of convergence). If that happens, you will go back and forth with the adjustments trying to get the object to stay centered.
Notes:
If you're in the market for a watch, you might want to consider one that lights-up in the dark, has two time zones, and works with 24-hour time. You can keep one time zone set to "regular" time and set the other one to local sidereal time for the evening. Note that some dual time zone watches will not let you independently set the minutes which makes using the second time zone for sidereal time impossible.
Why is it necessary to do iterations if the mount isn't level? If the mount is level, when the declination axis is set to horizontal (or the telescope is pointed straight up), rotating the mount on its azimuth axis won't have any effect on the declination axis having been set horizontal (or the telescope having been pointed straight up). However, if the mount is not level, rotating the mount on its azimuth axis will cause the declination axis to not be level anymore. This partially rotates the right ascension index on an axis that has a component that is parallel to the right ascension axis, changing the setting of the sidereal time. This means that, in effect, the right ascension circle wasn't really set to the sidereal time. If the mount isn't level, you have to "sneak-up" on the correct right ascension setting by iteration. If you work carefully, this is no more or less accurate than having a level mount, it just takes a little more effort. The closer your mount is to level, the fewer iterations you'll need to perform.
