I bought a reflector telescope off of ebay.The focuser if it is a focuser moves on a slide not up and down but horizontal.The secondary mirror moves with it.Is this a focuser or is this just changing the focal length?And if is not can a focuser be mounted on top of the slide?I don't have any eye pieces for it so I can't drop one in to see if it will focus...any help will be great....thanks
2007-09-08 06:56:05 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
it has no brand or model on it anywhere
2007-09-08 07:09:28 · update #1
This sounds like a Vixen Newtonian, imported from Japan by Celestron about a decade ago. It focuses by sliding the eyepiece holder and secondary up and down the main tube. Despite the weird focuser , these were excellent telescopes, usually mounted on Vixen's fine Polaris equatorial mount.
2007-09-08 08:43:37 · answer #1 · answered by GeoffG 7 · 1⤊ 0⤋
i don't know of any reflector design that moves the focuser along with the secondary.
you can't change the focal length of an optical tube. you can change the 'speed' but not the focal length.
the small secondary mirror you refer to bounces the collected light from the main mirror and it is the job of the focuser to bring focal plane of the eyepiece so that you see a clear, sharp image .
movement of the secondary means that your telescope probably needs collimating in order for it to focus on a star so that you see a nice tight spot. badly collimated optics mean you will not be able to see nicely focused images of anything you look at.
if you have touched the secondary, it is already too late and you will need help from someone that knows what they are doing.
since you don't have eyepieces, how are you going to test and use your telescope? i trust it uses standard 1 1/4" size eyepieces.
best of luck!
if you want to e-mail me a photo, perhaps i could be of more help.
2007-09-08 08:46:19 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Sounds like a focuser to me. If you move the secondary and eyepiece nearer or further from the main mirror, you are doing a focusing action. The optics work out since the secondary is flat.
2007-09-08 07:24:07 · answer #3 · answered by cosmo 7 · 0⤊ 0⤋
It sounds like a kind of focuser to me, but rather unusual and
not commonly found. I would try getting an eyepiece and
putting it in and looking at things some time; I bet it works.
You can find eyepieces at various sites on the net and eBay.
2007-09-08 09:53:11 · answer #4 · answered by Reginald 7 · 0⤊ 0⤋
Changing the focal length IS focusing.
How else would you go about it?
2007-09-08 11:33:13 · answer #5 · answered by Irv S 7 · 0⤊ 0⤋
brand and model?
2007-09-08 07:08:13 · answer #6 · answered by Faesson 7 · 0⤊ 0⤋