Should I buy this telescope I saw at a thrift?
July 15, 2017 9:59 AM   Subscribe

I found a Celestron Astro 114 at a thrift for $40. How can I tell if it's in good condition?

I spotted this telescope yesterday at a thrift on a 50% sale so final price is $40. It has the stand and the scope together. I see the same scope on Amazon for around $178.

In looking at it I thought it would be cool to be able to take some up close looks at the moon or planets. I don't have an ongoing astronomy hobby, so purchasing this implies an ongoing learning curve of how to use it.

It appears to be in good condition though I have no experience in understanding whether it is or not. That's my real question. How would I figure out in 5-10 minutes standing in a thrift whether the scope has a fatal problem, missing pieces or other deal breaker. Once I buy it, it's mine, no returns.

My only goal here would be to have a decent piece of optics to look at the sky occasionally on clear nights. What should I look for in terms of potential problems or should I even buy it at all or perhaps save my $ for some other instrument.
posted by diode to Technology (7 answers total)
You can call the folks at Celestron and they will talk to you at length about every little detail. However, if it seemed unblemished, I would buy now and ask questions later!
posted by jbenben at 10:09 AM on July 15, 2017 [1 favorite]

I'm not particularly fond of this style of telescope as a beginner's or introductory scope, they are a bit fussy to set up & aren't particularly easy to aim. That said:

- first you need to know that this is a reflecting telescope, meaning that instead of a big lens (like you'd see at the front of binoculars) it's got a big mirror, near the back, something like a shaving mirror. Unlike a normal mirror, however, the reflective coating is on the front (exposed) side of the glass, so the first thing I'd do is shine a flashlight down the tube to see if the mirror looked intact and clean. dust can be cleaned off with difficulty, but any sort of spots or stains would be a no-go.

- second, it should come with one or (preferably) two eyepieces, they should fit in the tube at the side, and when you look through them (maybe out a window?) at something pretty far away, you should be able to focus on it. If the eyepieces are missing, don't buy it, replacing them will cost a lot more than your $40. If the focusing mechanism doesn't work, don't buy it. If you can't look out a window, at least try looking across the room, you may not be able to focus but you should at least see a blurry image.

- third, make sure the mount is OK. I'm not talking about the tripod, but the bits between the tripod and the tube, with all the knobs. The two knobs are for fine adjustment, and turning them should move the telescope a little bit. There should also be some sort of quick-release that lets you swing the telescope around and point it in the general area you're interested in. Nothing should be wobbly.

Odds are this was a gift somebody never figured out how to use, so it could be in very good shape. My biggest worries would be (a) dirt on the mirror, because it was stored poorly or (b) missing eyepieces, because they're easy to misplace.
posted by mr vino at 10:18 AM on July 15, 2017 [9 favorites]

From my recall, the two eye pieces were in place on the scope, one for sighting and one for the reflector. There was a 2" rubber cap on one side of the main tube that you can pull out and inspect the interior. Looking through the scope's eyepiece, I couldn't see a clear field of view, it had some circular obstruction. In other words, when I took off the cap and looked into the eyepiece as you would normally do to see a remote object, there seemed to be something in the way that was part of the scope, not a fragment or broken bit. Best I can explain it. I wouldn't know how to inspect for dirt on the mirror.
posted by diode at 10:49 AM on July 15, 2017

You should be able to look straight down the open end and see. There will be a "spider" structure in the tube that holds the mirror that sends the image from the main mirror to the eyepiece.
posted by Huffy Puffy at 11:49 AM on July 15, 2017

it had some circular obstruction

That's normal. This image might help you visualize what you're seeing: you're looking down the eyepiece tube, into the secondary mirror, and seeing the secondary itself (and its supports) reflected in the primary.

The bad news: if you can see a clear view of the secondary mirror, instead of a blurry view of whatever the telescope is aimed at, it means you probably aren't looking through an eyepiece. The eyepiece is a separate part that looks like this and fits into the eyepiece tube. The telescope isn't usable without an eyepiece, so if it doesn't come with one, that'll cost you at least another ~$50.
posted by teraflop at 11:57 AM on July 15, 2017 [1 favorite]

Thanks teraflop. That about tears it for me. I might print this page up and put it on the telescope so other people can know what they are buying. My spidey sense was tingling that something had to be off, I think the missing eyepiece is what it is. Best to wait until the right scope, ready to go, comes along.
posted by diode at 12:12 PM on July 15, 2017

Uh, you're not in the DC Metro area are you? I'll take that scope for $40. I'm sure I have an eyepiece around here somewhere.
posted by runcibleshaw at 1:08 PM on July 15, 2017

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