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Glom
2003-Jun-24, 11:08 PM
Okay, so I've been reading up on telescope a lot lately and I just wanted to try out evaluating some telescopes. Here goes...

Astro-Telescope 300X Refractor (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3229892863&category=3636)

:( Advertised in terms of magnification.
:( Has 0.96'' barrel diameter.
:( Says it is standard.
:( Says the tripod is light. In other words, rickety.
:( Gives the aperture at 60mm, which means that by aperture rule (2Îmm or 50Îinch), maximum practical magnification is 120X not the 300X advertised.
:( "Effective operating aperture f10" That's not an aperture, that's a focal ratio.
:) Right angle finder.

Meade Model 4501 Telescope (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2936317345&category=28181)

:) Advertises in terms of aperture, focal length and f-stop.
:) Doesn't mention magnification anywhere.
:( "Adjustable 3-vane diagonal assembly" Does he mean an equatorial mount?
:) Gives the types of eyepieces.
:( Gives the types of eyepieces as Huygenian and Ramsden.
:( Describes the eyepieces as high resolution.

BUSHNELL DEEP SPACE SERIES 420X TELESCOPE (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2936320339&category=28181)

:( Advertises in terms of aperture.
:( Doesn't given any other details about optical specs but 450X wouuld require an aperture of over 8'', which doesn't seem likely from the photo.
:( Doesn't even say what kind of telescope it is.
:( "Full Length Variable-Height Hardwood Tripod" And what's half length?
:( Doesn't give eyepiece types.
:( "Diagonal Mirror" Star diagonal in other words.

KONUS 4.5" REFLECTOR TELESCOPE! FREE RA DRIVE (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2936351124&category=28181)

:) Advertises in terms of aperture.
:) Knows the term wide field.
:) Uses focal ratio.
:) Accurately describes some common benefits of reflectors over refractors.
:) 1.25'' barrel diameter.
:) Uses Plossl eyepieces of not too short focal length.

Dickenmeyer
2003-Jun-25, 04:30 AM
Given the information listed the Konus and the Meade are the only ones even worth considering and the eyepieces listed with the Meade are junk. I know the Konus scopes may be purchased through the Edmund Scientific catalog, but I've never read anything about them or used them. Meade has unfortunately entered the race to become the Tasco of the 21st century by launching a whole line of department store scopes. They can move a whole lot more marginal 114mm reflectors and 90mm refractors through Wal-Mart than they can 14 inch Schmidt-Cassegrain roboscopes through mainline telescope dealers. I have examined some of their department store scopes in the stores and there is a vast gulf of quality easily seen between them and Meade's higher end scopes. (or midrange scopes like mine)

Kaptain K
2003-Jun-25, 10:50 AM
"Adjustable 3-vane diagonal assembly" Does he mean an equatorial mount?
No, the "diagonal assembly" is the apparatus in a Newtonian telescope that holds the secondary mirror in position to intercept the light cone and deflect it to the eyepiece.

Glom
2003-Jun-25, 11:59 AM
"Adjustable 3-vane diagonal assembly" Does he mean an equatorial mount?
No, the "diagonal assembly" is the apparatus in a Newtonian telescope that holds the secondary mirror in position to intercept the light cone and deflect it to the eyepiece.

Of course. :oops:

gethen
2003-Jun-25, 02:19 PM
So what do you say to the relative who bought one of those Walmart Meades for her son, and wants you to come help because "we can't see anything?" I've been stalling because I know nothing about the telescope (she wasn't sure if it was a refractor or reflector) and am not sure I can help. After I get a look at it I may check in here for help. For all I know, it may just need collimating, but I really don't know what they should expect to see with it.

SkyEyeGuy
2003-Jun-25, 03:38 PM
Gethen,

Ouch. My only suggestions would be that they start by trying to observe large, easy targets -- the Moon, Jupiter, etc.

I received just such a scope for Christmas last year. Its biggest problems were:

1) Horrendous mount. Shook like, um, something that shakes a lot.
2) Plastic optics. 'Nuff said.

As an experiment, I beefed up the mount a bit, and bought a cheap adapter that allowed me to use 1.25" eyepieces, rather than the abyssmal plastic .965" units supplied.

I wasn't willing to try replacing the objective, or anything like that. I set a $50 limit on this little jaunt, and I did manage to turn a junk 2" refractor into useable, if still inferior, telescope.

Follow this link to the narrative:

https://www.sff.net/people/frank-tuttle/telecomp.html

Maybe something there will help. Good luck!

gethen
2003-Jun-25, 04:14 PM
Thanks for the great link! At least it gives me (and the relatives) somewhere to start. :)

SkyEyeGuy
2003-Jun-25, 05:57 PM
You're quite welcome, Gethen. Good luck.

I did forget to mention exactly what I did to the mount.

Telescope owners -- please remember that this was a *junk scope* as you read.

I used a powerful, fast-setting expoxy to glue the telescope tube directly to the tripod mount head. Originally, the scope was secured to the mount by means of a single screw, which connected plastic to plastic with enough shake and play to render the whole works the telescopic equivalent of a bobble-head toy. By glueing the scope to the mount, and leaving it taped together overnight, I was able to reduce the shakes by about half. And since I didn't figure I'd ever want the mount for anything else, I felt okay in doing so.

I had planned to mount the telescope on a spare camera tripod I had lying around, but the threaded insert on the scope was a nonstandard size, so I just got out the glue.