I have a makusutove 150 1800 telescope and I cant seem to get it to focus correctly - it seems as though the mirrors are focussing the light behind the viewing lens. I can get a focussed image if I hold the viewing lens about 4 inches behind the telescope. how can I adjust this telescope to enable a focused image with the viewing lens in the holder?

The mirror is the BOTTOM of the scope -- the focuser is on the UP end of the tube. Put the eyepiece with the largest number written on it into the focuser. Practice turning the focus knob during the day time until you get a sharp image in the eyepiece.

Put the eyepiece with the largest number written on it into the focuser. The FOCUSER END of the tube is the UP end the mirror is the bottom of the telescope.

Practice focusing on a distant object during the day time.

If this is a reflector telescope, did the small secondary mirror located beneath the focuser hole fall out?

This mirror sends the light from the main primary mirror out through the focuser. Watch this video to get an idea of how this works and how to replace it.

http://www.andysshotglass.com/Collimating.html

The secondary mirror is a small tilted mirror near the front end of the telescope mounted on what's called a "spider". It reflects the light from the large mirror in the bottom back out through the hole in the focuser.

Usually these are already assembled and in place when you buy a reflector style telescope.

See this web site and watch the video:

http://www.andysshotglass.com/Collimating.html

If you have a telescope with a MIRROR then the end with the focuser is pointed UP.

If you have a telescope with a lens in the front and and the focuser on the end, then the end with the lens is pointed up.

Read this and look at the pictures that show which end is UP:

http://www.texasastro.org/telescope.php

You can buy a new focuser here:

http://www.telescope.com/control/category/~category_id=focusers

You probably don't have the focus right. Just turn the focus knob until you see something. It can take anywhere from 70-80 turns from full extension to compression. Careful not to force it when it stops turning.

Not upside down---

The eyepiece and focuser is on the FRONT of the telescope. Light enters the tube-- hits the mirror on the bottom-- and bounces back up to the small secondary mirror which reflects it out to the eyepiece.

It's called a Newtonian design--

All of Tasco's manuals are on this web site-
http://www.tasco.com/pages/instruction-manuals/

Put the eyepiece with the largest number written on it into the focuser-- do not use the 2x barlow if you have one. Practice focusing with this eyepiece during the day time on a distant object like a telephone pole or a building.


www.telescopeman.org
www.telescopeman.us

Try tightening the grub screw that fastens the knob onto the shft that it turns.

Better still, buy a flexible extended focusser which makes focussing much easier. Check on eBay for "Meade flexible focus"