nexstar 90 mak focus problem

[nightpie]

hi all new to this so please bear with

we have recently bought the above scope,and we seem to have a problem with focusing

we got this model as we were told how good it is and all that you can see is amazing,however everything we look esp jupiter is like a pin ***** and when we zoom in or out to focus it goes black in the middle and bright edges that are not the rings

if you need any more info please ask and we will give as much as we can

thanks for any advice

[umadog]

Welcome!

Just so you know the lingo, the focus knob doesn't "zoom" since twiddling it doesn't alter magnification.

Jupiter doesn't have rings but you will see its 4 largest moons. If you're far out of focus you will see the shadow of the secondary mirror, which appears as a black disk in the middle of the object. This is normal. It's not visible when you're in focus.

Can you be a little clearer what it is that you're expecting to see or trying to see? What eyepieces have you tried on Jupiter? It sounds to me like you may have unrealistic expectations. Jupiter will always look small, but you will be able to make out the two major cloud bands and the polar regions. Deep space objects such as galaxies will look like faint smudges and you will not see colour in these. Particularly with a smaller scope, going to dark skies is very important for deep space objects. Some stars will appear coloured (generally reds or blues). Jupiter will show some colour contrast. Saturn possibly will in that scope. Mars will look obviously red.

[michael8554]

Set up the focus during the day, pointed at a distant object such as a chimney stack or TV aerial.

The focus range on a Mak is large so many turns of the focus knob may be required.

Make a note of which eyepiece you used because you may find any other eyepieces you have may be out of focus when substituted.

If you can swap eyepieces without refocusing then you have "parfocal" eyepieces.

As Umadog says, jupiter will still look very small despite the magnification of the telescope.

Good luck

Michael

[nightpie]

thanks for the reply guys

advice appreciated and taken on board

but be prepared for more queries and advice

thanks