Blurry!

[StarryP]

Hi guys, not new to amateur astronomy but recently got a present of a celestron Newtonian telescope and it will not focus sharply on Jupiter or Saturn. It's like the focus dial isn't sensitive enough! Any ideas what might be the problem? Help would be greatly appreciated before I look to return it.

[MarsG76]

If you can rack past and before focus, ie rack past focus on both sides and still cant get perfectly sharp focus than make sure that the seeing is good for the night... that might be the reason why focus is out... I've had nights where planets were blurry as, but other ights, or even later that same night, where planets were just crisp and detailed. Here you just need to be patient and persevere.

The other problem, also as likely, is that you collimation might be out a lot... check you mirror collimation. When collimation is out of whack, than perfect focus is not possible.

[Louis D]

Point it at a high and bright star to see if you can reach sharp focus on it.  If not, note what it looks like when slightly defocused on either side of best focus and report back here what you saw.