James Paulson's roll off roof observatory at the Sunridge Observatory site, taken in the summer of 1986, housing a 10 inch f/5 Cave Astrola Newtonian reflector telescope

Saturday, August 29, 2009

Aligning a GoTo Equatorial Mount

The above diagram indicates the general layout of the mechanics of the night sky. If you projected a line through the Earth from the south pole to the north pole, and on into space, that line would appear to point directly at Polaris, or as we commonly call it, the north star.

All of the stars in the northern hemisphere rotate around Polaris during the course of the evening due to the Earth's rotation. To counteract this, one needs only line the Right Ascension axis of the equatorial mount at this magical center point, and all movements can be counteracted by turning the telescope on one axis. The Right Ascension axis is the one that is connected to the tripod. The one that is connected to the telescope and the counterweight shaft is the Declination axis. Every object in the sky has a co-ordinate given in hours, minutes and seconds of Right Ascension, and degrees, minutes, and seconds of Declination. Objects above the celestial equator have positive degrees of Declination and objects below have minus degrees of Declination. You go from 0 to 90, and 0 to -90 degrees going north of the celestial equator and then south of the celestial equator respectively. There are 24 hours of Right Ascension in a full circle.

You can do a simple alignment of your astronomical telescope's mount by placing the mount with the counterweight down, tube up. Now rotate the telescope until the tube is exactly in line with the Right Ascension, or polar, shaft of the mount. You can turn the base of the telescope in azimuth until it is in line with Polaris, and then finally, adjust the latitude setting on the equatorial head until the telescope is directly aimed at Polaris. This is the most simple method of polar aligning a telescope, and is sometimes called the home position on GoTo equatorial mounts.
Once you have roughly aligned the scope, you can use the hand controller to pick two stars, center them in the field of view, and hit enter to tell the electronics that you are pointed at them. Aligning a GoTo mount is really this easy, and once you've done it once, you can remember how to do it time and time over.

Another far more precise method uses the declination drift method, where you choose stars near the celestial equator both at the meridian, and at the eastern horizon. I first discovered this method in a 1977 Sky and Telescope article by Robert Provin on doing precision astrophotography. It has never let me down. You need a reticle eyepiece to do this, and you only move the telescope in Right Ascension to do this. The longer you can keep the star from drifting, the more precisely aligned your telescope will be. This method works great in an observatory, even when you can't see Polaris.

First, choose your star near where the celestial equator (i.e. at or about 0ยบ in declination) and the meridian meet. The star should be approximately 1/2 hour of right ascension from the meridian and within about five degrees in declination of the celestial equator. Center the star in the field of your telescope and monitor the drift in declination.
•If the star drifts south, the polar axis is too far east.
•If the star drifts north, the polar axis is too far west.
Using the telescope's azimuth adjustment knobs, make the appropriate adjustments to the polar axis to eliminate any drift. Once you have eliminated all the drift, move to the star near the eastern horizon. The star should be 15 to 20 degrees above the horizon and within five degrees of the celestial equator.
•If the star drifts south, the polar axis is too low.
•If the star drifts north, the polar axis is too high.
The closer those stars are to the celestial equator, the more accurately your mount can be aligned. For long term use in an observatory, I will let it drift for 90 minutes, but you can speed this process up a lot by using a barlow lens because it really amplifies the drift. Remember to only make corrections in Right Ascension while doing this.

Some people like Dobsonian mounts. I have only ever used equatorial mounts, first without tracking, then with tracking, and finally with GoTo, which I absolutely love. Doing this simple procedure can let you see thousands of objects without frustration, and let you focus on enjoying your scope, rather than tracking it around the sky. I don't find an equatorial mount confusing in the least, either to operate or find objects with. Merely using one can teach you how objects appear to move in the night sky, much like the drawing above depicts. So before you go out and buy that big yard cannon that everyone recommends to newcomers, you might consider the convenience of having and using an equatorial mount. If you are going to do any kind of astrophotography, it is the only way to go. My blog's record is proof of that. If an 8 year old can use one without tracking, you can learn too. It really can deliver you a lifetime of amateur astronomy.

Monday, August 24, 2009

Touring the Galaxy with GoTo

Tonite I decided the sky conditions were superb for a last summer blast of some of the finest objects in the Milky Way galaxy. I headed out a little after 8 PM and set up the scope to give it a little time to adjust, which it has little problems with. The night was cool and bug free, and clearer than I have seen it since I got my telescope. After I got it aligned, I worked on a small list of objects that were unfinished from my last dark sky evening. I viewed M22, M25, M28 and M70, all globular star clusters. The area around the heart of the galaxy, the halo, is rich with these old objects, and each one is slightly different. I used only one eyepiece tonight, the 18mm Ortho delivering approximately 42x.

I went on to view a variety of objects including M92gc, M13gc, M7oc, M8 (Lagoon), M15gc, M27 (Dumbell), M20 (Trifid), M17 (Swan), M11 (Wild Duck), M31 (Andromeda galaxy), M16, and M32. I also pointed the scope at Neptune and could pick out it's color, and took a look at Jupiter, which was unusually crisp this evening.

All in all it was a good Monday evening, and I am inside and heading to bed at a reasonable hour.

Image is M20 - the Trifid Nebula - courtesy of Gemini Observatory/AURA

Tuesday, August 18, 2009

A Trek in Sagittarius

My binoculars have sat alone in a corner for a couple of months now ever since I got the scope. But last Friday night, and again Saturday I went out with them not wanting to pack the scope out in sub-seeing conditions and have been rewarded with some spectacular views in Sagittarius, including at least M25, M24, M7, the wild duck cluster and the butterfly cluster. It is very relaxing to take the tripod mounted 15x70's out and pan the lower portions of the milky way without having to crane my neck, seated in a chair with a comfortable height. I have the red dot finder spot on, so I turn it on dim and pan, and after finding something I can correlate it with my planetarium software and confirm what I am looking at with the reticle on the starfield. I am going to coin this as non-targeted astronomy, as opposed to doing deliberate targeted astronomy.

I was honestly wondering if I would use my binoculars much after getting the scope. But nights like these have reminded me that if I treat it as a specialty instrument and use it the way it was intended, it can be an excellent addition to doing GoTo/Telescope viewing and imaging. 15x70's are spectacular for browsing the milky way but I wouldn't want to hold them in my hand.

An earlier post alluded to using binoculars to view the Milky Way's finest objects and I have not been disappointed. This is really the first time I have experienced Sagittarius at latitude 36 degrees, the last time having optical assistance I was at latitude of 50 degrees, and the 14 degree difference is stunning.

Use everything you have....just enjoy astronomy.

Friday, August 14, 2009

A Beginning with Jupiter

I've been experimenting with the Meade LPI and thought I would make a second attempt at Jupiter with some adjustments. I believe that my focus is a little off, and I lack the focal length to really increase image scale. Jupiter was a bit low in the sky when I shot these and I did not stack them myself, but rather let Envisiage do the stacking setting the quality up a bit higher. The seeing was not really great visually either.

You can see 3 of Jupiters moons, and these photos were taken on the evening of August 13 at approximately 11:00 PM EDT. It's going to be a lot harder to image Jupiter than I've seen in some photos. Especially at a focal length of 762 mm and f/5. I may experiment and mask the scope down a bit to see what I can do to sharpen the image. I hope to have better photos down the road.

Saturday, August 8, 2009

What Happens at Astronomy Club Meetings

Last night a club that I belong to held an astronomy club meeting. For the second time in 2 months I decided to skip the meeting.
For many years I have been in an astronomy club of one form or another. They are a great place to get out and meet people with similar interests and share ideas. What usually does not happen however is a lot of common observation time. Often times there are fundraisers, public open houses, tour groups, not to mention the countless hours of volunteer work maintaining a facility.
So I've decided to forgo the groups for now. My interest is in observing. I don't need the headaches of dealing with all the extras required to keep everyone happy. Our club is small, and meets in the basement of a members house. Our time is occupied watching TiVo'd reruns from the Discovery channel. I can do that at home, and save the gas. I think with a group like this, the best thing we can do is have a montly agreement to meet in a field somewhere if it is clear and bring our telescopes. There is no facility to maintain.
I'm open to new ideas for how to improve an astronomy club, and make meetings more meaningful. I'm at the point where I don't even want to go anymore, but my interest in astronomy is stronger than ever.

Monday, August 3, 2009

Ex Luna Lux LPI

"From the Moon, Light via LPI"

This image is my first ever digital image, taken with the Meade LPI. It shows Mare Imbrium and Plato, Archimedes and Aristotle (craters). I shot this 2 days from full and was trying to capture the terminator, always a challenge when the moon is this bright.

Imaging with Envisiage is completely different from using 35 mm film, which was how I used to do this. Before we would bracket our exposures and wait days, and be at the mercy of the labs chemistry and density selections, that is, if the camera remained stable when the shutter opened. No more "hat tricks." Now with the PC, we have complete control over how the end result appears. I processed this a little using JASC Photo and cropped it a bit at the same time. I have tons to learn and lots of time to do it all.

It's not much, but I did it myself. It's good to be back in the imaging field again.

Sunday, August 2, 2009

Law of Universal Expansion

One of the most interesting things about this forum is watching people grow, from asking that first question, to getting a new scope that they have chosen based on advice, to asking more questions, to the frustrations and the joys alike, it's just awesome to watch people grow. I've been around this hobby for a lot of years, and at one point I actually was bored with it, I had flatlined so to speak. But I think that CN has rekindled my interest a lot and the friendships I have made with people here are so invaluable. Where else can I go and talk with so many like minded people about things as mundane as mesquitos to scope selection, the joys and frustrations of the weather, a good nights viewing, etc.

I think when you really begin to appreciate the people here and the good advice that they have you begin to learn and develop that brain/eye/affective connection, new things open with the hobby and there is no room for boredom. When I am not working I live, breathe and enjoy astronomy in so many ways beyond just getting out under the night sky. I can see all of you with your scopes doing likewise, the variation between each instrument, and almost half-predict your frustrations with some things at times. To me, that is the ultimate appreciation of the hobby.

I don't recommend one scope over another for any reason than the individual using it. I think picking a telescope is a very personal decision. I think we all learn from our joys and frustrations alike and use that to learn from. I think I could do astronomy with ANY telescope, but doing astronomy with the telescope that minimizes all of those frustrations should be an important goal. How ambitious are you? How willing are you to endure the frustrations to achieve said goal? And when you do go through it, and get to the other side, are you willing to experience that feeling of this all being worthwhile? For me, it certainly is.

One of the reasons I write this blog is to share those personal experiences with you all, so that you can see what this is all about. You can see that there is no prize at the end, it just keeps growing and growing. It is the law of universal expansion in action.