TRG – Telescope Review Guide

Orion’s Skyquest XT4.5 is the smallest in their Dobsonian line of telescopes that includes the XT6 , XT8 , and XT10. Newcomers to the hobby are always surprised at how large amateur telescopes are, but to experienced observers, this XT4.5 is considered a very small scope. Tiny, in fact (It’s so small, astronomers are buying them just because they think they’re so cute). Make no mistake, though–the XT4.5 is a full-fledged telescope, and is a serious observing tool that could last you for years.

Your money buys you a lot in this case. Included are a good-quality 4.5″ f/8 primary mirror, two eyepieces, a finder, and a CD-ROM with a stripped-down version of The Sky, a software guide to the sky. The scope comes in two cartons. One contains the optical tube, and the other is a flat-packed box containing the base, which you assemble yourself. Orion includes all the hardware and tools you need, and the instructions are well written. Allocate about 30 minutes to assemble and align everything.

There are a couple of cost-cutting measures. The primary mirror is spherical, not parabolic (this is not likely to affect the views, however). Also, the focuser is plastic. Plastic focusers are naturally less robust than metal ones. Finally (and this may be the most serious concern of all), the scope is a little short for an adult. The eyepiece is only 3 feet off the ground, which may force you to stoop over (hint: try sitting on a short chair or stool while observing). On the other hand, the height is ideal for a child, making this a great telescope for kids.

Under the stars, the XT4.5 exhibits excellent performance. Once properly collimated (aligned), the optics give clear, sharp, contrasty views.  Jupiter’s cloud band and four moons are no problem to see, nor are Saturn’s rings. The Orion Nebula is a glowing fan of green gas, with a quartet of tiny stars at its core. Under dark skies (and with some diligence) the XT4.5 can even pull in some of the fainter deep sky objects, like the brighter galaxies in the Virgo Cluster.

As recently as a few years ago, the old adage regarding telescopes was that you must spend at least $300 to avoid buying junk. While this is still mostly true, Orion’s little XT4.5 breaks the price barrier in a big way. As long as you can deal with the short eyepiece height, it’s a great starter scope.

What can you see this month? A lot! So get out your best telescope or best binoculars and get to viewing!

May Sky on YouTube

Jupiter becomes more easily visible this month as its elevation in the pre-dawn sky is getting higher – about 23 degrees above the horizon by month’s end.   During May its separation from the Sun increases from 77 degrees to 101 degrees, and its magnitude slowly increases from -2.3 to -2.5.   It will lie just below the the last quarter Moon on the 17th in the pre-dawn sky.

Mars still remains low in the pre-dawn sky this month, but as it rises increasingly earlier than the Sun as the month progresses will become easier to spot.   It has a magnitude of +1.2.   By the end of the month, the angular separation from the Sun has increased to 40 degrees. We will have to wait a month or so until it will be seen easily in the pre-dawn sky.

Venus passed betwen the Earth and Sun in March so is now visible in the pre-dawn sky.   It will only lie 12 degrees above the horizon as the Sun rises on the first of May, so will be easier to spot later in the month.   It is at magnitude -4.4 at mid month, up and to the right of Mars.   In the middle of May, a small telescope will show a crescent phase equivalent to just before a first quarter Moon.   An interesting fact about its brightness is that it stays pretty constant at about -4.4 for most of the time that it is visible even though the apparent phase changes greatly.   When the phase is thin, Venus is nearer to us and the effective reflecting area of Venus as seen from Earth remains pretty constant.

Saturn is now high in the southern sky after nightfall in the constellation of Leo.  It lies well below the body of Leo.   It starts the month at magnitude +0.8 with an angular size of ~18.8 arc seconds and these fall to +0.9 and 18.1 as the month progresses.  Saturn is significantly less bright this year than it sometimes is: the rings are very close to edge on (as shown in the Hubble image of Saturn) and thus there is less apparent reflecting area.   During May they are at an angle of ~4 degrees from the line of sight.   The rings will be seen (or rather – not seen) edge-on later this year and it will not be until 2016 that they will be at their widest again.  A small telescope will easily show its largest moon, Titan, and show some bands around the surface.

Venus is getting close to the Sun and is hard to spot right now. In  about a week it will become a morning object. Early risers can witness Venus in all of its glory for most of the rest of the year.

Saturn has just passed opposition but is still near its brightest for the year. Unfortunately the rings are nearly edge on right now and so are not very visible. Disappointing as that is, Saturn is still an impressive target and you should be able to pick out some of its moons even with a smaller telescope.

Mars and Jupiter are close together in the early morning sky with Jupiter being the far brighter of the two. A good

Jupiter and the Galilean Moons

telescope should pick able to image the Great Red Spot as well as at least four of the 63 known Jovian moons. The four largest moons are called the Galilean moons as they were first observed by Galileo on January 7, 1610 when he trained his home made telescope on Jupiter.