Secondary mirror woes

[the big o]

Hi all,

Whilst using my celestron 76mm on Christmas night viewing Jupiter I kept seeing my secondary mirror in the image. Does this mean my telescope needs collomating?

Sent from my GT-I9300 using Tapatalk

[knobby]

If you can see the secondary that generally means you are very out of focus... Did it look like a donut?

[the big o]

It was strange, It seemed that when I first found jupiter and focusing in the secondary mirror appeared in the image and jupiter seemed very bright but seemed to disappear after a few seconds

Sent from my GT-I9300 using Tapatalk

[John]

If you can see the secondary mirror then it's out of focus and the disk of Jupiter will seem a large but featureless disk of light. When it's nearing being in focus Jupiter will appear smaller and smaller but should eventually be crisply defined with some of it's 4 brightest moons showing, depending on the eyepiece being used. You won't be able to see the secondary mirror then.

If you are using a high magnification and no drive system Jupiter will drift out of view quite quickly.

[the big o]

Cheers John! That makes sense. I feel I've just dodged a collomating bullet!

Sent from my GT-I9300 using Tapatalk