Binoculars and telescopes and other astronomy equipment and accessories are the meat and potatoes of amateur astronomy. A good pair of binoculars is what introduced me to the pleasures of stargazing many moons ago and only after a couple of years scanning the skies did I graduate to a telescope. That was one of the department store 60mm telescopes we’re all warned about, but my folks didn’t know any better, and to a 12-year old kid, it opened up the universe.
While cheap (in every sense of the word) telescopes are still to be found, recent years have seen the introduction of small but very affordable telescopes from manufacturers such as Meade and Celestron and, despite their small size, these telescopes have excellent optics that far outperform the cheap optics in my old 60mm scope from so long ago.
Many of these small telescopes now come with GOTO features that allow you to select an object to view from an attached handset and the telescope will automatically slew to that feature in the sky. What the ads tend to forget to mention is that in order to use this facility, the telescope must be correctly set up and aligned beforehand. Many scopes, unfortunately, lie gathering dust in corners and wardrobes because their owners couldn’t figure out how to use the thing. It’s not their fault – better, and simpler, instructions should be supplied with the telescopes. But for those who can work with such an instrument, a wealth of celestial objects are available for viewing that would be quite difficult to find otherwise.
Some old hands in astronomy societies have welcomed the new technology openly, others have decried its introduction as it stops newcomers from learning their way around the skies using star-hopping . In some ways, they see that there must be a little pain in finding an object before you can have the pleasure of viewing it. I suppose it’s a bit like the difference between being bussed to Machu Pichu or going on a five-hour hike up the mountain to see it. Which would you choose? If the hike is your cup-of-tea, then star-hopping is for you.
Personally, I think the introduction of hopping s has been a very positive development and has made the hidden beauty of the night sky accessible to many more people. If you’ve bought a small telescope with an integrated GOTO mount yourself, but are unsure of how to use it or the best objects to view, go along to your local astronomy society or club and ask their help. They’ll be only too willing to lend a helping hand.
Read the Choosing a Telescope article if you’d like to know more about the different types of telescope that are available and what might best suit your needs.
You should have a selection of eyepieces to use with your telescope to allow close-up views or wide-field views. Planets require small diameter eyepieces to see surface detail whereas larger subjects, like the Pleiades and other large star clusters require wide-field views. Pretty much any eyepiece can be used to get a good view of the Moon or close-up views of it.
Eyepieces range from about 3mm to 40mm (i.e. the glass in them, not the diameter of the eyepiece itself!) and come in three fittings: 0.965″, 1.25″ and 2″ (for high-end telescopes). The 0.965″ fitting is seldom used these days but older telescopes may have taken eyepieces of this size. There are also different types of eyepiece: Plossl, Erfle, Kellner, Orthoscopic, wide-angle, etc. The magnification an eyepiece provides depends on the focal length of your telescope – divide the telescope focal length by the eyepiece size to get the magnification. A typical refractor has a focal length of about 900mm. A 26mm eyepiece would provide a magnification of 34x with this scope. Used with a telescope with a 200mm (8 inch) focal length the magnification is 77x.
There’s another feature of eyepieces called the Field of View. Basically, this is how big an area of sky is seen through the eyepiece. The bigger the field of view, the more can be seen. How much of the sky is seen depends on the eyepiece diameter and the focal length of the telescope. Wide-angle eyepieces (82 degrees field of view, for example) tend to be quite expensive. Average eyepieces, such as Plossls, have about a 50 degree field of view.
While this discussion has centered mostly on telescopes, binoculars have a role to play in astronomy as well. A quality pair of binoculars cost less than a telescope and is a good entry point for someone familiarising themselves with the sky. They don’t offer the same magnifications as a telescope (but magnification isn’t everything) but they do show a much wider field of view which makes it easier to navigate across the sky. Because of this wider field of view, you also get to see the ‘big’ picture. And, because you’re using both eyes, there’s less eyestrain. You can get binocular viewers for telescopes and those who use them (even though they cost a few hundred dollars and you need two of every eyepiece) swear by them (rather than at them!). A typical set of binoculars will be 10x50s (front lenses 50mm across, with a x10 magnification). More powerful models are available – 20x60s are available from $150 upwards and you can get 20x80s for as little as $100. These binoculars are quite heavy and you can tire easily pointing them skyward for any length of time. Also, because of their higher magnification, any shake in your hands will also be magnified and stars will dart around in the view. For long-duration viewing, you’d be advised to get a tripod and a binocular tripod adapter which lets you securely mount the binoculars on it.
Binoculars are also great for looking at large scale celestial objects such as comets. Looking at the Moon through 20x binoculars brings it close enough to see topography but also, you’ll see in three dimensions, something lacking when looking through the eyepiece at a telescope. You can whip out a pair of binoculars much more quickly than setting up a telescope so if you have very changeable weather where you live, they might be a better option for sky viewing. Of course, you can throw a pair of binoculars into your luggage very easily and view the sky from your holiday destination with ease.
One problem that besets telescopes is the set-up time. If all you’re interested in is casual observing, then this isn’t much of an issue. But if you’re into astrophotography or imaging, the set-up time is increased as it needs to be more accurate and on top of that there’s the additional time involved in preparing the camera and possibly an associated laptop or PC. If you live in an area where the weather changes at the drop of a hat, by the time you’ve set up, the clouds have rolled in and you’ve got to disassemble everything again. Actually, what I found was that the take-down time was the hardest; at the end of an observing or imaging session, when you’re tired and cold and all you want to do is go asleep, that 20-30 minutes of taking everything apart, packing it away and storing it can seem like a lifetime.
After many a session like this, I decided that I needed an observatory. If it’s clear, I can be set up for observing in about 3 minutes. Setting up for imaging takes a bit longer due to the more accurate setups and alignments required. Finishing up for the night takes about 5 minutes. There are now many observatories commercially available – there’s plenty listed in the back of the astronomy magazines. But they are expensive, running to several thousand dollars. In my case, I decided to build my own, for a variety of reasons.
If you own a large telescope (8″ or larger), an observatory is probably a good idea. These scopes and their mounts can be on the heavy side and if your have a disability or a medical condition (like a hernia), moving heavy weights in the dark (when accidents are more likely to happen) may not be an option. Get your observatory and a few helping hands to place your telescope in it and you can view the stars at your leisure whenever you want. If you’re any good at DIY, SkyShed provide plans for building a roll-off roof observatory, one of the most common types of amateur astronomy observatory, and the type I built myself.
Astrophotography is simply taking pictures of the night sky with a camera of some description. Up until the last decade or so, all astrophotos were taken with film-based cameras. Then CCD cameras started appearing, small ones at first until now we have megapixel colour CCD cameras available as well as simple webcams and electronic eyepieces. Imaging is the term that’s used to define astrophotos taken with an electronic camera rather than a film-based one.
These days, it’s a fairly simple matter to take astrophotos. Using a piggyback mount, you can mount an SLR type camera on top of a telescope that has a tracking drive and take long duration exposures of the stars (up to a few minutes duration; longer if your telescope is very accurately aligned). Cameras can be connected to telescopes with adapters that turn the scopes into huge telephoto lenses – great for taking photos of the Moon. You can also do long-duration exposures, but there’s little room for error when setting up your telescope as any inaccuracy will show up as star trails. jumps or jags on your photos. With film based cameras, astrophotographers had to select what film to use (different emulsions respond differently to light), the film speed and whether to use slide or negative film. If negatives, then they’d have to give very specific instructions to the photo labs in order to get decent prints back (the negatives themselves would be fine). And there was the wait of at least a day before they could see their results.
Now, with the advent and popularity of the Canon EOS Digital Rebel cameras, astrophotographers can see the results at the telescope. If it’s a lousy image, delete it and take another one. Then, because the image is digital, it’s already in a format that’s easily processed with the likes of Adobe PhotoShop or PhotoShop Elements. So, by the end of the night, you could have a stunning image just waiting to be printed out. Nikon also have a range of digital SLRs, but I haven’t come across any opinions as to their usefulness for astrophotography, whereas the Canon EOS Digital SLRs seem to be the cameras of choice (I use one myself).
Webcams are a cheap way of getting into imaging. These cost a few tens of dollars but typically have CCD chips with a resolution of only 640×480. They’re best used for imaging the Moon rather than stars or nebulae. Still, some superb images have been taken with them. Final images are prepared through software such as Registax. The camera basically takes a movie of the subject and software is used to analyse each frame in that movie. Substandard frames are rejected and all good quality frames are stacked and averaged. This has the effect of removing any noise from the image and what you end up with is a single high-quality image of the subject, like a Moon crater. Autostitch lets you combine overlapping images into mosaics and panoramas (you can use it for ordinary daylight photos) and blends images together seamlessly. It’s completely automatic. You just tell it what images to combine and it does the rest.
If you’re serious about imaging, then you need to think about getting a dedicated CCD camera. There are several manufacturers out there but the two best known are the Santa Barbera Instrument Group(SBIG) and Starlight Xpress. These both offer a selection of cameras ranging from several hundred dollars to several thousand, depending on your wallet! [Night Sky Observer]