Getting shadow on Jupiter image

[Whererthestars]

I've just invested in a Celestron Astronomical 130eq telescope, and tried it for the 1st time yesterday.

Jupiter was clear in the sky and after a bit of trial and error I finally got the Planet in my sights. When I looked at this through the telescope there was a shadow blocking the image, which looks like a shadow image of the inside makings of the telescope itself, which effectively covered the planet.

Any ideas on what went wrong?! and how to correct this?!

 

[JB80]

Sounds to me like a collimation issue and you will need to realign the mirror.

It seems daunting at first but really it can be quite simple if you follow some simple instructions. Astrobaby's excellent collimation guide is the first place I turn to when I collimate my scope. http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

[ronin]

If it is what I suspect it is in a way both wrong and correct.

Wrong in that it is not what you want to see, correct in that is how the optics work.

I would suspect that by one means or another the eyepiece is too far out from the scope, when this occurs the big thing in the middle, the secondary, starts to be seen - that is the optics. Put the longest focal length eyepiece in aim at Jupiter and wind the eyepiece in towards the main scope. The shadow should disappear and Jupiter will steadily become apparent - it will be SMALL. What happens is that the shadow becomes apparent and people try to get it in focus, so end up playing at the wrong end of the focuser travel.

Next: On some scopes they supply a 2inch and 1.25 inch adaptor for eyepieces, they ship the 1.25 inch one inside the 2 inch one. Since it fits well and looks correct people leave them both in - lets face it why would you take apart something that looks "right". This holds the 1.25 inch eyepiece too far out and you have the same problem. Check and if there are 2 adaptors, if there is then remove both and put only the 1.25 inch one back in. This then should hold the eyepiece where it should be.

 

[John]

This is nothing to do with collimation - please don't start fiddling with that at the moment.

The shadow is caused by the scope not being in focus. As you adjust the focuser knobs the image of the star (or Jupiter) will get smaller and smaller as it nears focus. The shadow will vanish as the scope nears focus and when the image is at it's smallest it will be at focus.

 

[Owmuchonomy]

As John says just make sure your eyepiece is fully secure in the focusser then rack the focusser in and out until Jupiter appears small but clear. The other obstructions should disappear. Also make sure your eye is in the best position for the eyepiece by moving slightly to check.

[laudropb]

When you focus Jupiter in your scope with your longest focal length eyepiece it will be very small with little detail showing, perhaps 2 bands. You should be able to see some of its moons. These will look like stars stretched out on either side of the planet.