TRG – Telescope Review Guide

Yes, it’s only July but it’s not too early to start thinking about what to buy for that astronomer on your Christmas list! But what would be the best telescope to get? The choices are almost endless! Here then is a short list. You can’t go wrong with any of these:

Orion Skyquest XT4.5

Celestron CGEM 800

Orion Skyview Pro 127

Orion SpaceProbe 130

Orion SkyQuest XT8

Keep checking back as I’ll be continuing my research into great Christmas telescopes and publishing my findings here!

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.

For long-exposure, deep-sky astrophotography, the most important things to look for in a DSLR camera are low noise, high sensitivity and a good signal-to-noise ratio in the final output data.

Usability features, like live-view focusing, dust-reduction technology, and single-cable operation are also very attractive features to consider for astrophotography when choosing a camera.

I recommend Canon DSLR cameras over Nikon because of Canon’s proven performance, low-noise characteristics, and ease of use.

The Canon 50D is my top rated camera for it’s balance between performance and usability. It offers good signal-to-noise, live view focusing, one-cable operation, no amp glow and 14 bits of tonal depth.

The best entry-level DSLR for astrophotography is the Canon 1000D (Digital Rebel XS). It hits a very sweet spot in terms of its price-performance ratio.

In making your decision, you will have to choose between price, performance, and features. Older cameras have excellent price-performance ratios and larger pixels that yield better signal-to-noise ratios, but many suffer from amp glow, a red glow in the corners and edges of a long exposure image caused by electronics associated with the camera’s sensor. Canon now turns these off during long exposures in their latest cameras (Canon 400D, 450D, 40D, 50D, 1000D). Amp glow can be removed in older cameras, however, with proper dark-frame calibration.

Newer cameras have reasonably good signal-to-noise ratios and also have very attractive features like live focus, but are more expensive.

Both Canon and Nikon offer very inexpensive entry-level DSLR cameras such as the Canon 1000D and the Nikon D40 that work remarkably well for astrophotography.

For general daytime photography and some fun astrophotography, try an unmodified stock camera. If you get really serious later about long-exposure deep-sky astrophotography of red emission nebulae, you can have your camera modified then.

Based on this analysis, if price is your primary consideration, the Canon 1000D is the camera you want. If you can afford the Canon 50D, it is an excellent camera with great usability features. If you want a Nikon system, then pick up a Nikon D40, or, if money is no object, a Nikon D3 or D300.

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.