Yes, there are some telescope experts in here who will undoubtedly be able to solve your problem.<br /><br />What is the make and model of your telescope?<br /><br />Are there any undesirable light sources where you are viewing, such as a street light, that could be illuminating the inside of the tube?<br /><br />Describe in a little bit more detail the "Shadow" you are seeing.<br /><br />Does this shadow appear with all your eyepieces and also when using a Barlow lens?