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ASH2162
2003-Nov-19, 10:41 PM
I bought a C8 and wanted to ask the advice those in the know. I used to use a 4.5" Meade Newtonian and changed to the C8 because I was told the larger the aperture, the more light enters the scope, henceforth, the bigger/better the image, however, when I look at Orion Nebula, Jupiter & Saturn, they are as small as they were in the other cheaper telescopes.

Does anyone know what I am missing or doing wrong here?

AusJosh
2003-Nov-20, 08:24 AM
Its because those objects are relatively close to us, the C8 would be better at deep sky images and gathering light from more distant stars and galaxies.


.....i think......



-Josh

Dave Mitsky
2003-Nov-20, 09:17 AM
Magnification is a function of the focal length of the telescope and eyepiece in use. Since a larger aperture "gathers" more light, it allows higher magnifications to be utilized before images grow too dim.

An f/10 C8 has a focal length of about 2032mm. Using a 10mm ocular will produce a magnification of about 200x (the moving mirror of a Schmidt-Cassegrain makes exact magnifications problematic), which should be plenty enough to see planetary detail. Most deep-sky objects (planetary nebulae being one exception) will look better at lower magnifications. The amount of magnification one can use is directly dependent upon how good the "seeing" (i.e., the steadiness of the atmosphere) is (see http://skyandtelescope.com/howto/scopes/ar...ticle_136_1.asp (http://skyandtelescope.com/howto/scopes/article_136_1.asp) ).

These web sites contain much useful information on telescopes and observing:

http://skyandtelescope.com/printable/howto...article_244.asp (http://skyandtelescope.com/printable/howto/scopes/article_244.asp)

http://skyandtelescope.com/printable/howto.../article_80.asp (http://skyandtelescope.com/printable/howto/visualobserving/article_80.asp)

http://www.spacegazer.com/basics.htm

http://observers.org/beginner/j.r.f.beginner.html

http://observers.org/beginner/buynoski.html

http://skyandtelescope.com/printable/howto.../article_81.asp (http://skyandtelescope.com/printable/howto/visualobserving/article_81.asp)

Dave Mitsky

vet
2005-Apr-25, 03:52 AM
Originally posted by ASH2162@Nov 19 2003, 10:41 PM
I bought a C8 and wanted to ask the advice those in the know. I used to use a 4.5" Meade Newtonian and changed to the C8 because I was told the larger the aperture, the more light enters the scope, henceforth, the bigger/better the image, however, when I look at Orion Nebula, Jupiter & Saturn, they are as small as they were in the other cheaper telescopes.

Does anyone know what I am missing or doing wrong here?
Mr. Mitsk's explanation is well-put---but i wonder about your 'light-polution' index---do you have dark skies? that may make all the difference. if not? then you get the best deal on a 'nebular' filter. they work.

a 4.25 not only gathers less light, it may be better at 'punching thru 'pollution', like 'bad-seeing'. if you're used to the 'pitch-black' background of 6" and smaller apertures? that goes down as larger apertures capture more 'air-glow'---by the time you're looking at a spectacular 20" view of M-13, the background almost looks as 'twilight'. if you're c-8 takes an f/6.3 converter, you might want to try that---and low-power euepieces. don't give up, please. as for the planets? you should be seeing a lot more, but then you want 100X+ eyepieces.