Telescope

Thanks solar eagle. I will give it a go and see what happens.

Yes I saw the ebay pic of the JAWA scope, that is exactly what I have.

Still would like to get an instruction booklet.

https://www.apm-telescopes.de/media/manuals/skywatcher/en/12.pdf

..."The magnification produced by a telescope is determined by the focal length of the eyepiece that is used with it. To determine a magnification for your telescope, divide its focal length by the focal length of the eyepieces you are going to use. For example, a 10mm focal length eyepiece will give 80X magnification with an 800mm focal length telescope.

Thanks solar eagle.

I'd take the scope out in the daytime and focus on distant objects. Sometimes, it's hard to focus on dim objects at night. Or at night, the moon is the best target to start with, to get the scope in focus.

If it's been banged around, it could well be out of alignment. It's easy to check. Just remove the eyepiece and look at the diagonal. If it's aligned, you should see an enlarged reflection of your eyeball in the diagonal mirror.

"...it provided no magnification"?

Do you mean that you could see an image but it was not magnified? Misalignment wouldn't affect magnification, it would just make a distorted or dark image.

You can calculate the magnification of a telescope as the ratio of focal lengths:

M = F_primary / F_eyepiece

where, in your case, F_primary would be about 18 inches and F_eyepiece is probably marked on the eyepiece.

Why would You see a reflection of Your eyeball? Your eye would have to be in front of the scope where the light gathering is and then reflected back into the eyepiece. Looking back into the eyepiece holder would just show You the primary mirror. Am I missing something here?

I did focus on the moon with a ten MM eyepiece and it did not magnify at all , in fact just looking at the moon with the naked eye looked the same as looking thru the scope.

I know the formula for magnification, there seems to be something else at play here.

I have not yet tried to realign the optics yet but I will keep everyone posted.

I have a 10" reflector scope in the garage. When I look through the open eyepiece hole at the diagonal mirror, I see the magnified reflection of the diagonal mirror and my eyeball reflected in reflection in the diagonal mirror. The reflection of the diagonal mirror in the primary mirror should be centered. (You probably have to shine a flashlight sidewise on your eye to illuminate it.)

Sorry, if I didn't accurately describe it in the last post.

I can't understand how you would see an unmagnified image. Could you take a picture of the telescope through the front side showing the mirror in the back?

... there was no eye piece but I did have an extra eyepiece from another telescope that would work...

Is this eyepiece a positive (convex) lens or a negative (concave) lens. To tell, hold it out at arms length and you should see a small image of what's behind it. If the image is inverted, it's a positive lens and if it's right side up, it's a negative lens.

From your description, it sounds like your eyepiece could be a negative lens. Simple telescopes (Galilean telescopes) have a negative lens for an eyepiece. It gives an upright image but doesn't provide much magnification.

What you need is a positive lens eyepiece (Keplerian telescope).

(These diagrams show a refracting primary lens, but the principle is the same for a reflecting primary mirror.)

https://brunelleschi.imss.fi.it/esplora/cannocchiale/dswmedia/esplora/eesplora2.html

Just a thought...

https://www.telescope.com/Choosing-Eyepieces/p/99803.uts

The eye piece i used was from My 8 inch Newtonian reflector so it is the correct eyepiece.

Here is the best pic I could get of the primary mirror. sorry it does not show much.

Remove the eyepiece and shoot a pic looking into the telescope, as centered as you can get it....

Okay, Here it is.

Looks pretty close...maybe a bit off...

From your picture, your scope looks like it's in alignment to me.

I'm still puzzling over "no magnification"...

The full moon is pretty bright and your scope very fast (f/3.6). I'm wondering if you were catching a reflection off the inside of the scope tube and not the actual moon. Just a thought...

Maybe try looking at something distant in the daytime. You won't have the high contrast of bright moon - dark sky.

Thanks for the pic. I wanted to see the magnification of the primary, and it looks OK to me.

I'm still hung up on "no magnification". With a 10mm eyepiece and about 18" prime focal length, the magnification should be about 45X. For the moon, that is about 22 degrees, roughly equivalent to a 7" diameter disk held at arm's length.

If you can shoot a picture through the eyepiece hole at the diagonal mirror as SE suggested, that might help. You should see the diagonal mirror reflected in the primary like this one that I took...

I am going to give it another shot outside on the next clear night. Maybe I had to many beers that last night I took the scope out.

Thanks for Your help and thanks Solar Eagle also.

oilcan13

Okay; Last night was clear so I got the scope out and put in a 16MM eyepiece zeroed in on Jupiter and behold I was able to see three of the Galilean moons. Switched to a 10 MM eyepiece and was just able to make out a few bands on Jupiter. I was going to try for Saturn but without a finder scope it was kind of difficult.

Evidently I was doing something wrong when I first tried the scope.

So thanks again to You guys for Your input it is appreciated.

oilcan13

Well done...

Case closed....

The inner 3 moons, Io, Europa, and Ganymede are in a 4:2:1 orbital resonance. The 4th large moon, Callisto is in a resonance of 5:12 resonance with Ganymede.

So after 83.5 days, Callisto orbits 5 times, Ganymede 12 times, Europa 24 times, and Io 48 times and the 4 moons are back in their original positions. (I guess we would have to wait 167 days to see that, since every other one would occur in the daytime.)

https://www.space.com/40659-jupiter-moon-optical-illusion-music.html

(I guess we would have to wait 167 days to see that, since every other one would occur in the daytime.)

OK, that's about 1/4 year later, so you could see it 87.5 days later...

This actually has a practical consequence or, at least, it once did. Before the development of an accurate chronometer, latitude could be easily determined by ships at sea by shooting the pole star with a sextant, but without accurate time, longitude could not. This was referred to as the "Longitude Problem".

There was a contest offering a prize to solve the problem of getting the accurate time a sea.

"Interestingly, it was a British churchman and astronomer, Dr. Nevil Maskelyne (the gentleman responsible for the first Nautical Almanac in 1767) that resurrected Galileo's idea. Maskelyne attacked Harrison's atempts to create an accurate mechanical timepiece for navigators as not worthy of serious consideration, especially since God had already so thoughtfully supplied humanity with the master clockwork of Jupiter's satellites. While he was an intelligent and gifted scholar, Maskelyne was no sailor. He failed to appreciate the impracticality of aiming and keeping a 3-foot telescope trained on Jupiter in anything but a flat-calm sea. When that tiny flaw was pointed out to him, he proposed an unsuccessful gimballed "marine chair" for shipboard observations, which was supposed to allow the observer and telescope to remain horizontally stable in much the same way a gimballed ship's compass negotiates the yawing, pitching and rolling motions of a vessel at sea."

http://www.oceannavigator.com/May-June-2004/Longitude-by-Jove-navigating-with-Jupiters-moons/

Great, glad to hear you're up and running.

Dear Sir

I design Optical systems and have complete knowledge of Optics and telescopes. If u need any technical information, u are free to discuss with me.

My Name

Prakash Borole

Pune India

Thanks, I think I'm all set for now but will keep You in mind.

By the way have you had any experience or know of "JAWA" scopes? I understand they are made in India.

oilcan13

No, i am not aware of this firm