I am a beginner and I am using a Celestron AstroMaster 114 telescope. Whenever I try to view distant planets such as Jupiter I am presented with a black circle that has black lines leading from it. In between these lines is a white blur. When I focus the telescope using the focus knob, the black circle along with the white blur shrink to the size of a star in the night sky before becoming larger. I don't have this viewing the moon and in fact was able to see a very breathtaking image of it. I am using the star finder with the red dot and I have aligned it during the day so my star finder and my telescope are looking at the same thing. Any help would be greatly appreciated.
Jupiter and the four largest moons are easily viewable with 8x to 10x binoculars, so I think the first step is to read the manual to learn how to set the focus to infinity. I'm rather surprised that there's much change in the focus knob between lunar and Jovian observation in the first place!
I agree with the other answers that you are somehow seeing the secondary & its mounting "spider", which suggests that you either have a significant misalignment or more likely are massively out of focus.
What I can understand is, you are seeing the secondary mirror and the vanes while observing Jupiter, it is not a big problem since it arises only in you are not having the Jupiter in focus. In fact those "black lines" and "black circle" will help you collimate your telescope for better viewing experience. And if you want to see Uranus with a 114mm aperture telescope, I won't say you can't see it, but what you will see will be a dim star like object which may actually be Uranus. I don't know if you can see the greenish-blue colour. Sorry to have a pessimistic view. Good luck!
Is it four black lines at right angles from each other? Perhaps the black circle is the secondary mirror, with the unfocused target making the white blur. If so, first try focusing on something fainter, perhaps a double star or a cluster. Then swing back to Jupiter without changing focus. Also try varying the distance between your eye and the eyepiece lens.