21 May 2013 – Telescope Update – Thoughts & Impressions So Far
OK, everyone probably knows about my telescope by now, but if you’re new or haven’t been following too closely lately, a couple of previous posts (here, here and here) will get you caught up in no time Just to be sure, I’ll start over from the beginning and give a bit of background.
I was perusing Walmart’s Black Friday (really Thanksgiving night) sales circular when I saw a deal which was just too good to pass up. They had a Celestron PowerSeeker 70AZ telescope package for $37.86 which is about $60 or so less than I’d ever seen anyone ask for a scope like it. A few quick searches for reviews satisfied me that it wasn’t complete trash and was worth the very reasonable cost. I grabbed the nicest box I could and excitedly assembled everything once I got back home.
Here’s a promotional video for my scope from Celestron
I pointed my new telescope at the moon the night after I purchased it and I liked what I saw! The detail was so much better than anything I’d seen since I’d used a very cheap telescope my brother had a few decades ago and it was significantly better than I remember seeing through that instrument as well. I pointed the 70mm objective lens at Jupiter a few nights later and was captivated by the sight of that gas giant with visible bands of color and the four Galilean moons – Io, Ganymede, Europa, and Callisto – which appeared like bright diamonds suspended in a line bisected by the planet they orbit.
I was (and still am) hooked!
The coming nights brought me images of the Pleiades, Sirius, Bellatrix, Betelgeuse, Aldebaran, the Orion nebula, and more wonderful views of Jupiter just because it’s there and so cool to look at. Last night I saw the rings of Saturn without looking at a picture! To say I’ve enjoyed using my telescope would be a gross understatement. I’ve had a freaking blast!
While there’s been a tremendous amount of fun and discovery with this instrument, I’ve also started to notice some faults and I’m finding out where the limitations lie as well. Before I go into detail, I want to emphasize that I knew there would be faults and limitations with this scope and that I recognize that it’s built to a price point with plenty of corners being cut to reach that financial goal.
The first item to give me trouble was the tripod and mounting system and it’s done it in several ways. The first problem is that even with the azimuth lock knob screwed out so that it should have no effect, the scope is extremely difficult to move horizontally and doing so smoothly has been impossible for me so far. I’m going to try spraying some white lithium grease in a few places to see if this frees things up a bit, but I’m not all that hopeful. Looking up into the bottom of the tripod head it doesn’t look like it can be taken apart, either. Most of the time I just move the entire tripod – it’s easier.
Adding to the frustration generated by the sticky horizontal movement system is the altitude slow motion rod assembly. In theory, you can loosen the nut which allows the telescope to move freely in the vertical, but then you’d lock it down and use a knurled nut to screw the back into and out of the front allowing for slow and precise adjustment. The free moving part works as intended. The problems come when you try to use that knurled nut. There’s enough play in the system that a simple bump can move the scope out of alignment. Another problem I’ve had is that the knurled nut is a two piece assembly and it has become disassembled while I was trying to use it. It can be put back together in a few seconds, but it’s still annoying.
My gripes don’t end with the tripod. Not by a long shot. Saying the eyepieces aren’t the greatest is kind of like saying a sundial isn’t the greatest way to tell time. Both will do the job they’re intended to do, but not much more than that. The supplied eyepieces are Huygens design (click here for more info on eyepiece designs). This design dates from 1654 and is noted for a narrow field of view, chromatic aberration, and minimal eye relief. That pretty much describes the way my eyepieces perform. The field of view is very narrow, the chromatic aberration is very noticeable, and the eye relief is so short that I have trouble seeing the entire (very narrow) field of view while wearing my eyeglasses.
All of the above observations hold true for all three eyepieces, but I’m going to ding Celestron for something with one eyepiece in particular that seems quite ridiculous. The maximum magnification of any telescope will depend on its aperture. The aperture is the diameter of the objective (front) lens in a refracting scope or the diameter of the primary mirror in a reflecting scope – the larger the aperture, the more light will reach the eyepiece. The higher the magnification you want to use, the more light (larger aperture) you’ll need. If you try to use too much magnification with too small of an aperture, the image quality will suffer severely. Celestron lists the maximum useful magnification as being 165x, yet they supply a 4mm eyepiece which yields 175x. I’ve tried this eyepiece out while observing Jupiter, but it just can’t seem to find focus and the image looks horrible overall. I’m lucky I got the Walmart version of this telescope (more info on that here) because it came with three lenses – 20mm (35x – good for large things like the Orion nebula and the moon), 10mm (70x – decent medium power and useful on Jupiter and lunar craters), and the galactically useless 4mm. The normal version of this scope only comes with the 20mm and 4mm. A much better option would be to include a 25 mm (28x) eyepiece for wide field views that would actually be useful instead of the 4mm.
Continuing with the supplied optical accessories, we’ll look at the 3x Barlow lens Celestron included in the packaging. The Barlow lens triples the power of any eyepiece it’s used with. The 20mm becomes 115x, the 10mm becomes 210x, and the 4mm becomes 525x. That might sound great until you remember that Celestron themselves say that the maximum useful magnification for this telescope is 165x. I tried using the supplied Barlow with the 20mm eyepiece and diagonal (more on that diagonal in a minute) last night and could not achieve focus. I might try again tonight, but the problem is that if I’m trying to observe anything near the zenith (straight up overhead) without the diagonal, I’ll likely end up laying on the ground because of the height of the tripod etc. I’m OK with laying on the ground, but the short eye relief of the included eyepieces means that I might have to do a partial sit-up just to get my eye to a point in space where I can see anything at all. Assuming the Barlow will give me a usable image, it would only be limited to use with one of the supplied eyepieces. I would suggest that they supply a 1.5x Barlow. That would make the magnification 52.5x for the 20mm and 105x for the 10mm. This would be useful.
My favorite included accessory so far has to be the correct image diagonal. This is a little piece that goes between the telescope and the eyepiece and allows the eyepiece to be oriented 90° to the telescope so I’m not laying on my back when looking at something directly overhead. The diagonal Celestron included with this telescope also corrects the image so that it looks right side up and left to right aren’t flipped. It also allows the eyepiece to be rotated 360° for user convenience. The diagonal loses a little light, but I’m willing to deal with that if it means more viewing comfort.
I’m conflicted about whether or not I would recommend this telescope. On the one hand, it’s incredibly affordable. It does do what one would expect a telescope to do. On the other, there are some serious shortcomings. I knew about the deficiencies going in and was willing to deal with them. A beginner who didn’t know much about telescopes could very easily be seriously frustrated.
My plans are to keep using this current telescope until I can afford something better. It’s let me see quite a few wonders of the night sky, so it’s not all bad. I just can’t help but think of how much better my viewing experience would be with some better equipment
2 comments to 21 May 2013 – Telescope Update – Thoughts & Impressions So Far
126 queries. 0.506 seconds.