From Binoculars to Telescopes: A Personal Journey

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Από τον Richard "Doc" Kinne είναι το παρακάτω άρθρο που δημοσιεύθηκε στην ιστοσελίδα της AAVSO στο E Y E P I E C E V I E W S - May 2008.

 

 

FROM BINOCULARS TO TELESCOPES: A PERSONAL JOURNEY

By Doc Kinne,

 

Observing variable stars, as we all know, can be an increasing challenge. That's part of the fun, in fact! Some of us rise in several levels during our variable star observing career - from naked eye observation to binoculars to telescopes to CCDs.

 

Due to the similarity with how our eyes and binoculars work there is usually not a great amount of problem moving from naked eye observation to using binoculars. Yes, you do have to learn your way around the sky (which can be great with binoculars), and you do have to go through learning about differential photometry with comparison charts, of course. But you have to do that with naked-eye variable star astronomy as well. Given all of that, the nice thing about observing with binoculars is "what you see is what you get." There is no confusion about the star field being in the "wrong" orientation, and the field you see in your binoculars is usually large enough that you can recognize it in the sky.

 

This is how I started, and my first recorded observation was via 7x50 binoculars of Z UMa. My Z UMa observation simultaneously showed me both the thrill of variable star observation, and the limitation of binoculars.

 

The limitation with binoculars, of course, is their light gathering ability. I would look at star after star and a vast percentage of them were either below 7th magnitude in brightness, or at least has a minimum that went significantly below that. I wanted to follow the more numerous fainter stars, and that meant a telescope. Telescopes offer more challenges to the beginning observer, but the increase in light gathering power is worth it.

 

The first challenge I found myself dealing with was a greatly reduced field of view. With binoculars you can see almost half of the bowl of the Big Dipper. With that kind of a large field to see "guide stars" in, you can usually zero in on your star without too much trouble. With a telescope and its greatly reduced field of view I found myself developing expertise in an activity called "star hopping." Star hopping is when you acquire an easily found star in the general area of your target. From that initial star you "hop," or "walk," your scope's field of view to your desired star. You find the initial star, then move the scope slightly to the direction of the next nearby known star, then again, and again, until you find yourself at your target. Star hopping will not only enable you to find your targets, but I found it really acquaints you with your star's area of the sky.

 

With most people using reflecting telescopes of one kind or another, including myself, the next challenge in making the leap form binoculars to telescopes was dealing with "flipped fields." In this instance, with telescopes, what you see is not what you get. Even more disconcerting, until you get used to it, is that the telescope field moves exactly in the opposite direction that you'll expect. This motion is probably the largest difference between binoculars and telescopes. Once you get used to this, the rest will be significantly easier. This, I think, was my biggest challenge.

 

With telescopes you'll be using AAVSO charts of "B" scale or higher. You must remember that the "B" charts and higher are made to show you how your field will look in your telescope - flipped over and turned around from the actual sky. This is where your brain must be backward because the challenge here it to remember that if your target star in your field of view is above and to the right, you need to nudge your telescope down and to the left.

 

If you have a Cassagrain telescope you'll be using the "reversed" charts. Here, in your field of view, the sky has been turned around, but not flipped over.

 

No matter what your scope, I found that if I always made a point of nudging my telescope slowly I could evaluate if the movement I was making was really in the direction I wanted to go.

 

Remember that magnification is a non-consideration with variable star observing. It's all about the mirror size in this game. When I got my telescope a few years before I got into variable star observing I never thought that I'd go for lower magnification, but I keep looking at those super-wide field of view eyepieces every time I look at an Orion catalog. The bigger the field you can see, the more valid comparison stars you'll be able to use.

 

Finally, as you are beginning your transition from binoculars to telescopes, make your first several telescopic observations outside of the galactic plane. Stay away from the Milky Way. I was surprised how many additional stars the scope picked up, especially in those environments, and until you get used to your new field of view and the orientation of your telescope, you won't want a whole forest of stars confusing you.

 

Variable star astronomy is a journey. Some may elect to stop at binoculars and with appropriate stars there is nothing wrong with that. Good work can be done with binoculars. However, most of us bitten by the variable star bug will, sooner or later, find ourselves moving a bit further down the road and starting to observe from a telescope. I found that they are very different instruments, but mastering the telescope for variable star observing will give you benefits both for your variable observations in particular and your knowledge of the sky and astronomy in general.

 

 

 

 

 

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