© 2000 BMAA, Inc

On Sunday, April 15, 2000 this year's Northeast Astronomy Forum was held in Suffern, NY. For those members who are not familiar with it, the NEAF is an annual gathering of amateur astronomers and vendors, along with a full day of speakers on the subject of astronomy. It is located near the home of Televue, Inc, and is an easy 2-hour drive from our area. This is the fourth year that my son, Phillip, and I have attended. (Oh by the way, Mom goes along also!). As usual, we all enjoyed ourselves quite a bit. We drive up the night before, check into a nearby hotel (usually the Holiday Inn) and have a relaxing dinner at the local Friendly's restaurant. While there we always run into several other amateurs, clearly noticeable by their astronomy related T-shirts, hats, patches, etc.

The morning of NEAF, we eat our breakfasts and head right on over as soon as we are allowed in. This year the sponsors of the event, the Rockland Astronomy Club, held the event at the Rockland Community College, as opposed to the previous versions held at the Holiday Inn. This change in venue made for a much more comfortable, open forum. There was plenty of room to walk around, looking at the tables and speaking with the many vendors about their products. As usual, for many attendees, the highlight of the day is the Televue sale. There, high quality eyepieces are sold at greatly reduced prices, usually 50% off. These eyepieces are allegedly "cosmetically" damaged, although I have yet to see any signs of damage at all. The sale is great because the products are brand new and work great! About the only negative to this is the fact that the Televue line is usually very long and can keep you off the floor for a good deal of time. I picked up a beautiful 32MM plossl, and I could not find any deficiencies in it. By the time I got out of the line, it was getting late and was time to head into the auditorium for the speakers. All of us thoroughly enjoyed the talk on the Hayden Planetarium. It was very informative and looks to be a tremendous show. (A hint to those looking to go: although most of the shows are sold out well in advance, if you get to the ticket window early, there will be some tickets that are held back. Also, the early shows are usually not sold out, as well as the weekend evening shows.) My wife and I have already agreed that we have to plan a trip to NYC this summer. Millions of dollars went into the revamped facility and it looks to be money well spent. Although many of the purists have voiced objection to the changes at the Hayden, after listening to its director, it is clear that this new approach is meant to entertain and teach at the same time.

Another interesting talk was given by the editor of Sky & Telescope magazine. Most people would probably never imagine the amount of work and preparation that goes into every issue. We also stayed for the final talk, given by Seth Shostak of the SETI Institute. I do not know if radio signals are really going to be the way that we connect with other civilizations, but it is a start. [See related SETI article later in this issue. -ed]

There were some great door prizes (Phil won a hat and a red flashlight...can't go wrong there!). The raffle prizes are always great and this year was no exception. In addition to a full set of Televue eyepieces, there was a Meade ETX, fully computerized GO-TO scope, and a host of other prizes. No, we did not win any of them. Too bad, there were plenty of things we'd have liked!

Although it is great to see the many new products out there, and great to listen to the speakers, it is also a treat to meet and speak to so many nice people. While in the Televue line I was able to meet a couple of guys from New England and passed on a website that has plans for upgrading a 60mm scope. One of the guys there has one and was hoping to improve it for his 6-year-old son. In addition, I was able to introduce our own Jim Shearer to a resident of the upstate NY area that I was standing next to for about two hours. She was standing in line for her husband, while he walked around the floor. Hey, why didn't my wife do that? And Marian, Jim was a perfect gentleman, gracious and friendly as usual, but not too friendly, if you know what I mean. One special treat was seeing the famous actor James Earl Jones, wearing those suspenders, walking inside a portable dome and asking questions about it. Yes, his voice really is that deep, and no, he did not zap anyone Darth Vader style with his light saber. Seriously though, Mr Jones is apparently a serious amateur, owning a fully motorized home dome unit to observe from.

All in all, it was a wonderful weekend and I urge anyone who has never attended NEAF to try it next year.

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Reprints of articles, or complete issues of the CONSTELLATION, are available by contacting the Editor at the address listed below, and portions may be reproduced without permission, provided explicit acknowledgement is made and a copy of that publication is sent to the Editor. The contents of this publication, and its format (published hard copy or electronic) are copyright © 2000 BMAA, Inc.

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This is the first of a series of articles. There is too much to cover in one month's page, so the next installment will cover aberrations and limits, while the final will be a description of types and brand names.

Our scope is a giant eye, doing three things for the user.

First, it is a light gathering device. The human eye has an opening of about 1/3" at maximum, while the scopes in common use by amateurs are up to 12" and larger. The light gathering power is increased by the scope in ratio to the square of the apertures. Thus, the ratio of a 6" telescope to the eye is about 324. That is, 36 (the square of 6) divided by 1/9 (the square of 1/3). This ratio is over 6 magnitudes, so a 6" scope will show stars of about 12th magnitude if the night shows stars of about 5.5 or 6 to the naked eye. We have seen before that this is not strictly true, but is fairly close.

Second, the telescope has a properly curved objective which brings the light to a sharp focus. Hopefully.

Third, the telescope has a local magnifier, the eyepiece, to enlarge the image.

So lets talk about the eyepiece and what it does.

The image of the target is a real image, with real size, in the focal plane of the objective. The eyepiece works on this image and transmits it to the eye, after doing it's optical magic. Unfortunately, it has aberrations and errors which can cause problems. No eyepiece is ideal, and even among the highest quality, the eyepiece an observer likes best may not be the one you like best. It seems to enter the realm of personal preference.

Anyhow, let's explain some of the terms and characteristics. Some of this information may come as a surprise.

An eyepiece has two main lenses, being the field lens at the scope end and the eye lens at the eye side. Other lenses are added in more exotic types for correcting various aberrations.

FOCAL LENGTH- is determined by the curvature and separations of the lenses in the ocular. Short and long focal lengths are relative terms, loosely meaning the power they provide with a given scope. Shorter focal length yields higher power. The focal length is the distance from the principle plane to the object which will yield a parallel beam.

POWER- is determined by dividing the focal length of the scope by the focal length of the eyepiece. An eyepiece of 1/2" focal length will yield 60 power if used with a scope of 30" focus. This is based on the eye being focused for 10", as in reading a book. If the eye can focus closer the power will be slightly higher. Really.

APPARENT FIELD- is the width of the field seen by the eye through the ocular. The real field is the apparent field divided by the power. So if you have two eyepieces of the same focal length, the one with the larger apparent field shows a wider real field.

EXIT PUPIL- is the size of the focused image, and is the light cone entering the eye. It can be seen by aiming the scope at the sky or a lit wall, and will appear as circle of light floating above the eye lens. Its size is determined by the diameter of the objective divided by the power. Thus, a 6" scope at 60 power will yield a 1/10" exit pupil. This is what limits the minimum power a scope can use. If the power is too low, the exit pupil will be larger than can enter the eye. The minimum is usually given as 3X to 4X to the inch of aperture. The fully open pupil of the human eye sets the limit, and becomes less as we age. A young person can use a scope at lower power and still have a fully illuminated field. The exit pupil can be limited by the type of scope, the size of the eyepiece lenses, and the size of the secondary in a reflector.

The exit pupil is very small at high powers, so only a portion of the human eye's lens is used. For those suffering astigmatic problems in the eye, high powers will use only a bit of the eye's lens and may make it unnecessary to wear glasses. This small eyebeam is also the reason why "flies" or "motes" in the eye are more troublesome at high powers.

EYE RELIEF- also called back focal length, is the distance from the eye lens of the ocular to the focal plane. A large eye relief allows the user to keep his glasses on and still see the entire field. The eye relief is usually longer in low power oculars. Some sets of eyepieces have been designed to give 20 mm or so of eye relief at all powers. I have a 6.5 mm Konig with a huge apparent field that is not usable because I can't get my eye close enough to the eye lens to see the whole field without actually bringing my eye into contact with the lens. This is not good for the eye, needless to say.

TRANSMITTANCE- is the ratio of light getting through. The more elements in the eyepiece, the more absorption and reflection. Multi-coated lenses allow more light to get through, but there is no way to prevent absorption in lenses. Better quality glass transmits more light. In cheap or poorly designed eyepieces, the lenses are too small and will limit transmission; also, this will limit the field of view.

EFFECTIVE F NUMBER-is the f ratio of the telescope at which the aberrations of the eyepiece become objectionable. Simple Huyghenian eyepieces perform poorly below about f/12, and Ramsdens below about f/8. These simple oculars perform well with my f/14 refractor, but will cause color and clarity problems in your f/5 Newtonian.

SOME QUALITY NOTES- the more elements, the more scattered light along with absorption and reflection. The better quality eyepieces have higher transmission due to superior coatings, less scatter due to imperfect polishing and figuring, less aberrations due to optical errors or poor design and use full size lenses with good mechanical design and close tolerances of machine work. Add in quality control and cosmetics.

As you can see, there is a lot of design necessary to produce a good eyepiece, and consequently good ones are not cheap. However, price alone does not determine quality.

Advice - try as many as you can on YOUR scope before buying on the advice of others. My personal preferences are the mid priced Plossls of Televue and Celestron. I'm sure you have your own preference, and do not let anyone tell you differently without a trial at the telescope. Many claims of superiority are made. Each eye is different in its color sensitivity and tolerance of aberrations. One person's eye may like the image in a Televue better than a Meade, while the user of the Meade swears you are not seeing what he is.

Good eyepieces bring out the best in the scope and the observer, but a good eyepiece with a poor scope will obviously not improve what is already a bad situation.

In closing this section, let me add this.

The best eyepiece for planetary and critical contrast applications is most likely not the best eyepiece for wide field or photographic use. The simpler eyepieces perform splendidly on the narrow field needed for Jupiter, and scatter less light, but they tend to have narrower fields of view. Only by trial can you find the best combination for your application.

Normally this once-a-year column that I write is titled "Astronomer of the Month". Every year after our annual Stella Della Valley campout/convention in Ottsville a drawing is made from a list of all the volunteers that helped out at that event. The winner (or loser, depending on your point of view) is declared "Astronomer of the Month" and interviewed for publication in our newsletter. But Scott insists that "I am not an Astronomer", although he has attended star parties, SDV, Astronomy Day, and other club related activities. If he isn't one of "us", then who is this mystery man?

Scott is a long-time member of BMAA, having first joined our club back in 1988. His interest in science, astronomy and other space related events goes back a long way as well. Back in 1957 Scott actually saw (after his dad pointed it out) the Russian artificial satellite "Sputnik" cross overhead; the beginning of the Space Age. Wow!

In the mid-eighties, Scott had wanted to attend an Astronomy course at the Churchville Nature Center, taught by none other than Artist/Amateur Astronomer Bob Oughton, co-founder of our club. The problem was that Scott was teaching a course in photography the same night and time at Churchville, and so he was unable to attend. Later, Bob Oughton and a few of his "students" decided to form an astronomy club. Scott got the word and subsequently joined the newly formed Bucks-Mont Astronomy Association.

Having done more than a few of these interviews on occasion, I can attest to the fact that we have a considerable percentage of our membership who are originally from other parts of the country. Scott, however, grew up in this area, Richboro, graduating from Council Rock High School in 1963, followed by two years at Trenton Junior College (now Mercer County College) in commercial art. His skills as a photographer are self-taught, along with film/TV courses he later took at Bucks County Community College. I found that he was Peter Kostmayer's congressional photographer in Bucks County from 1982 to 1988. I was also surprised to see Scott one night supervising the sound system for an event at The Philadelphia Museum of Art. "Just another gig" he says, "I get involved in all that kind of stuff". Mercer Folk Fest, Philadelphia Folk Fest and many other festivals around the northeast are examples of where you could find him at work with sound. A self-employed entrepreneur, he also does live recording, sound design and editing. Scott gets into sound contracting and other systems installations as well. One of the more unusual jobs that he occasionally encounters is working on tower-type exterior clocks. "Just about anything electro-mechanical" he laughs, "to make a buck".

During the course of one of these interviews I usually ask the question , "What other hobbies do you have besides Astronomy". However, in Scott's case I was worried that he might respond by saying , "Well I do some Amateur Astronomy on the side". The most that I could get him to admit to was that he has the club's refractor at home, and a pair of binoculars that he purchased from BMAA member Bob Post. With his commitment to the boards of four other non-profit organizations from Churchville to Wilkes-Barre, he doesn't have a whole lot of time for hobbies.

Finally, I asked this Non-Astronomer how he got involved in becoming editor of our club newsletter. As it turns out, back in the early 90s Connie Beck was both the newsletter editor and president of our club. "I took on the newsletter because that (president and editor) was too much for just one person to do". And so, ever since then at club meetings when the president asks for a status report on the newsletter, Scott inexorably replies with a slight grin, "Need articles".

I have set up a Group account for BMAA in the SETI@home project. This is a very clever way to provide much-needed computer time for a scientific research project, and to involve the general public as well. So far, about 1,500,000 people have at least tried it.

SETI@home uses idle time on home and business PCs to analyze data from Arecibo. Once your computer is set up, it periodically downloads a data file to your computer and processes it when a screen saver is activated. When analysis is complete, the results are uploaded back to SETI@home and another data file is downloaded. This can be completely automated, or if you prefer, SETI@home can prompt you when it's ready to connect again.

In addition to running as a screen saver, SETI@home can also be configured to run as a low priority process that is always active. This is recommended only if you have spare memory (15MB) that other applications won't need.

The analysis is very time consuming, but since it happens in the background, you're not really aware of it. On my 400MHz Pentium II, it's averaging 10.5 hours per datafile, and on my 133MHz Pentium, about 55 hours. This is how often my machines need to connect to the Internet, which is not very often, especially on the slow machine!

To join the project, visit the following site:

You'll need to download a modest installation program and run it. You'll then need to log on for the first time, giving your e-mail address as an account ID, and then choose some simple configuration settings.

Once this is done, join the BMAA group by visiting the SETI@home Group's page:

and searching for "BMAA". Once this page comes up, click on "Join this Group" and enter your SETI@home account name (e-mail address) and password (which you can have them e-mail you if you haven't jotted it down earlier).

That's all there is too it, and it's kind of fun to do.

One thing I've noticed: the screen saver does a lot of fancy graphics, which actually take up about 50% of the running time. If you turn the graphics off after a few minutes and go to a blank screen, SETI@home gets a lot more done. In Windows, you do this by bringing up the Display Properties screen, switching to the Screen Saver tab, and click on Settings. In Settings, put a check mark in the 'Go to blank screen" box and choose the number of minutes you want to see the fancy graphics before you blank the screen.

On the SETI@home web site you'll find lots of information about the program and about the screen saver's display. Some of it is a little dense, but most of us will understand some of it.

So far, only three people are in the BMAA group, and one isn't even a club member. Still, between us, we've accumulated 2 years of CPU time - computer time that otherwise would have been completely wasted by Windows.