Friday, August 09, 2013

The Perseids Peak

The Perseids have been upon us now for a few weeks, and are due to peek this weekend, the nights of the 10th through 12th. The shower itself actually runs for a few weeks, starting usually the second week in July and then running through the third week in August. The peak is always near the second week of August.
Like most meteor showers, the Perseids are associated with another larger body, in this case Comet Swift-Tuttle. This comet last paid a visit to the inner Solar System in late 1992, and has since been heading back into the depths of space. 

Chart courtesy The International Astronomical Union Minor Planet Center
With an orbit that takes it out to a distance further than Uranus, Swift-Tuttle takes a leisurely 133 years to make a complete loop around. Its orbit, however, is steep compared to most of the planets.

The Perseids are the debris that Comet Swift-Tuttle left behind. This material spreads out along the comet's path, and starting in mid-July, the Earth begins encountering it. For the following few weeks, our planet passes through that path, and in doing so we get the Perseids.
In order to catch these little pieces of cometary debris, you need to stay up a little late, at least until after midnight local time. Look towards the northeast; after midnight, the constellation Perseus will begin rising over the horizon, and it is here that the meteor shower's "radiant" is found. If you follow the path of all the Perseid meteors, they should point roughly back towards this, even though they could be anywhere in the sky. This is also roughly the direction the Earth is moving. In a sense, the Perseids are akin to bugs on our planetary windshield.

Chart created with Home Planet
So, if you get a chance, try to stay up late and catch these little remnants of a comet that won't be in our part of the Solar System for another one hundred and thirteen years.

Wednesday, August 07, 2013

The Smaller Telescope, Pt. IV - Examples of Current Smaller Telescopes

There are plenty of small telescopes out there, but the buyer needs to beware; too many of them are really not good telescopes at all. It's not optics alone that make a telescope. There are two other items that need to be as important; the mount and the accessories, namely the eyepieces.
One of the most common telescopes is the 50mm. If you go to eBay, you will find hundreds of them, with a solid proportion of them being sold with the flimsiest of mounts. Even the big names, like Meade or Celestron, have been known to drop the occasional bomb.
What follows is based upon personal experience. 

  • Meade Jupiter Series 50mm - 

This telescope has been out of production for a few years, but there are still plenty of them around. Like most 50mm, its primary lens was just fine. The problems arise when we move beyond the telescope. The first big problem was the tripod. It was somewhat wobbly. Since the telescope had a threaded mount, one would expect that you could simply replace the tripod. That is where we make the discovery that not only is the mount "stepped', it isn't a standard 1/4"-20 thread, but something close. The diagonal and eyepieces were .965" standard. These days, I keep an open mind, as there are good .965" eyepieces available. These were marginal at best. You could purchase a hybrid diagonal and move to the more common 1 1/4" size for eyepieces, but then the problem with the tripod still exists. I did not keep the telescope long.
Conclusion - wasted potential.

  • Meade 60mm AZ-T - 

Another one from Meade, and again also out of production. This telescope is a short tube tabletop model. It has quite a bit of plastic, but is not that bad a little instrument. It comes with an erect image diagonal, two 1 1/4" eyepieces (a 20mm Kellner, and a 9mm MA; mine had a 17.5mm MA instead of the 9mm!), a Barlow and a tabletop tripod with standard 1/4"-20 threads.  Sold with a handy carrying case. This is one of my favorite telescopes. Some people have complained about the focuser, but I've not noted any difficulties with mine. A great little "grab-n-go" telescope, it provides really nice views. The included Barlow was the only fault I could find with this telescope. I normally mount this on a heavier, and taller, tripod. I have managed to get a fair chunk of Messier's list with this telescope, even with the modest 17.5x magnification the 20mm Kellner provides. These are still to be found online at reasonable prices, and is recommended.

  • Galileoscope - 
This is the much vaunted 50mm educational telescope. When you purchase it, you are provided with just a telescope, and its accessories, all of which you assemble. The main eyepiece is a 20mm Plössl-type design, which for having plastic lenses provides very nice images. The other eyepiece is a Galilean, that is to say, a single concave lens, which also serves as the base for the 2x Barlow. Both are 1 1/4". When this telescope was announced, the initial plans was for it to cost $15 USD. It has now more than doubled, but is it worth it?

In my opinion - possibly. As an educational tool, it's great. It provides the student with hands on experience of how refractor telescopes work in their most basic form. The telescope comes equipped with a 1/4"-20 thread mount (really, a nut which is held into place in the lower part of the optic tube), so commercial tripods can be used. The Galilean eyepiece allows the student to see the sky the way Galileo did. However, there are downsides to the design as well. The optic design is straight-through; it cannot take diagonals. Well, it can, but the resulting focus range is very tight, depending upon the diagonal used. So, the telescope needs a fairly high mount; most recommend a tripod that can extend to 60" (1.524 m), as well as a chair or seat of some sort to make viewing higher objects easier. Objects that are closer to zenith, though, will be extremely difficult. 
Optically, it is a nice telescope. As stated previously, the 20mm Plössl gives good view when combined with the 50mm primary, I've used other eyepieces, and objects closer to the horizon, and feel that the telescope works fine.
Recommended with caveats.

  • Celestron FirstScope 76mm "baby Dobsonian" - 

I purchased this telescope in the spring of 2013, and am really surprised by its performance. It is a small Newtonian in a one armed Dobsonian mount, comes with 1 1/4" eyepieces, and is one of the easiest telescopes to work with right out of the box; open it up, set it on, say, a picnic table, remove the focuser and dust cover, pop in an eyepiece, and you're set. 
It does have weaknesses. For one, the included eyepieces are not the best. Of the two, the 20mm MA is the more serviceable, while the 4mm Huyghens is really not that great at all. Lack of a finder scope might bother some people. The primary mirror cannot be collimated (adjusted). 
But, how does it perform?
Ignoring the 4mm  eyepiece, with the 20mm MA it performs fine. The focal length of the telescope is 300mm, so it is a true short tube Newtonian, and operates better at low power. Still, moving over to one of my other eyepieces (a 10mm MA) revealed a great image of the Moon. 
My recommendation - probably one of the better beginner telescopes out there (along with the very similar Orion FunScope, based upon reviews and comparisons written elsewhere). Just purchase some additional eyepieces, maybe a finder scope, and you should be set.

To close, just a thought. Occasionally, you can find cheap telescopes at thrift stores and yard/tag sales. If the price is low enough, don't be afraid to purchase the instrument and give it a shot. There are always diamonds in the rough. Just keep in mind that some work might be needed, but the process of making those improvements simply add to learning more about this wonderful endeavor we call astronomy, If, in the end, the instrument is still found wanting, at least that can be said.

Thursday, August 01, 2013

The Smaller Telescope, Pt. III - Resouces

A few of my resources, and perhaps the least I need many times.
As mentioned in part II, this part we are going to look at how some of the resources available for binocular astronomy can be applied to the smaller telescope. 
Elsewhere in this blog, I've mentioned Garrett Serviss and his pioneering "Astronomy With An Opera Glass", perhaps the first book written on the subject of small instrument astronomy. Not only was it pioneering, but it was also practical; Serviss spent very little time reflecting on the instruments themselves, instead choosing to concentrate on observations. Many of the books on binocular astronomy today are split between both, covering the tools and the trade, if you will. But Serviss' book laid out the format that many still follow. For the smaller telescope enthusiast, the technical aspects of working with binoculars are of no use. Instead, you need to look at the observing section. 
There are, of course, still plenty of star guides that will be of use. 
In my personal library, one of the best books to guide us along is the late Sir Patrick Moore's "Exploring The Night Sky With Binoculars". Once you get past the first two chapters, which, not surprisingly, deal with the instruments, you find page upon page of targets to choose from. Chapter three, for instance, deals with many of the basics of stargazing, covering subjects such as the Greek alphabet (which is crucial in the identification of stars, as well as explaining how color is an indicator of temperature. After that comes chapters covering a variety of targets, from individual stars to clusters, nebulae, constellations and even some of the brighter galaxies. Near the end of the book he covers observing the Moon.
Another handy book is "Binocular Stargazing" by Mike Reynolds. I will admit, I've had a personal hand in the creation of this book; I helped to do some of the illustrations. But like Moore's book, it covers the equipment aspects first, and then dives into observations. After covering lunar and solar observing, the book then goes into how one can use binoculars for observing some of our planetary neighborhood. There are sections that cover the sky by season as well. One feature I like about this book are that many of the finder charts are drawn within circles, fairly close to what one should see when looking through binoculars or a telescope.Or
There is a book that deals with the Moon alone, and covers both binocular and telescopic observations. Originally written in the 1960's, Ernest Cherrington, Jr.'s "Exploring the Moon Through Binoculars and Small Telescopes" covers the lunar surface features in a bit more detail than the previously mentioned books, and therefore is of more utility. While no longer in print, the splendid Dover edition can still be found in abundance.
You will need star charts as well. There are perhaps dozens, if not hundreds, of sources here. Many of the basic books by Sir Patrick Moore, Ian Ridpath, Wil Tirion et al are more than sufficient, but there is an online source that I've found so useful, I've printed them off and had them laminated. These are Tashimi Taki's star charts, found here. These charts have proven invaluable to me. While they do cover deep sky objects down to 11th magnitude, the stars go down to magnitude 6.5, allowing them to serve as guides in the pursuit of more distant quarry.
This is just a start, and here based upon personal experience. Just remember that when deling with smaller telescopes that they will not reveal the heavens like much larger instruments. But they will open your eyes, are easy to use, and are a great starting place.
Next time, we will look at some of my instruments as case studies, as well as discuss what can be had, what to look for, and what to avoid.