Why are my pictures coming up small?

(THIS IS ON ASTROPHOT0GRAPHY)
Hi there, i was taking a picture of Jupiter through my Meade LX200GPS 12". I was please with the picture but when i compared it to other pictures on Google (taken with other LX200GPS 12"s Jupiter was 10 times bigger. I take about 30 second exposures and on ISO 800. If someone could please recommend a good camera setting for Nikon D3100 taking pictures. And also why are my pictures small and how can i make them bigger.

Due to the highly elliptical nature of Jupiter's orbit the planet was very probably 10 times closer to the Earth when it was photographed by those other LX200GPS 12" owners and thus the pics were 10 times bigger than yours. Tip - wait till Jupiter is closest to Earth before photographing it.

Jupiter is hardly 10 X closer to earth as sometimes - never happens. You need magnification and/or photo processing or both to get those large images. Your small picture should be bright and show high resolution for successful enlarging. Modern astrophotography cameras and programs make this easy these days - you can change the progams while the camera is hooked to the telescope to get what you want since you can see your results while you are photographing - Try a good DSLR camera

Are you using barlow lens or extention tubes or teleconverter lenses? I don't know much about astro photos but i used to do photos and these things go between the camera and scope. This may help or point in rigt direction-

http://books.google.co.uk/books?id=KuQErr3Olf0C&pg=PA78&lpg=PA78&dq=lenses+and+extension+tubes+in+astrophotography&source=bl&ots=DNc8GfhHs4&sig=zpZxcXCpSGXEJdFaP9zwY71hv70&hl=en&sa=X&ei=_4_nUKfhHImS0QX7uYCYAw&sqi=2&ved=0CEAQ6AEwAg#v=onepage&q=lenses%20and%20extension%20tubes%20in%20astrophotography&f=false