6SE Collimation problem?

[baggywrinkle]

I have noticed that I am finding it hard to focus my Celestron 6SE with any EP of 18mm and less.

Sharp at 24 and 20mm but below 18mm it starts to go fuzzy....

If this were a collimation problem surely it would be throughout the range?

With a focal lenght of 1000mm a 9mm EP should not be over the top.

Any ideas?

[faulksy]

hi, it does sound like colimation, have you done a star test to rule this out. regards mike

[ronin]

I would have said something wrong wih the mirror assembly. They focus by moving the mirror up and down the tube. So if that gets restricted then the mirror will not travel and you lose focus somewhere.

Is the focuser on it standard or is there anything absent or added that would alter where the eyepiece sits?

[Joe_L]

Sometimes I've had a similar problems - the stars gave a good doughnut out of focus but in focus looked like fuzzy balls when using higer powers. In the end I put it down to seeing conditions or dew as some days were worse than others. Since then I've sometimes seen sharper stars so this confirms it. Do you get a good doughnut on both sides of best focus?

[Peter Drew]

Most likely seeing conditions in view of the recent hot weather, Schmidt-Cassegrains are particularly sensitive in this respect. No harm in checking the collimation as already mentioned.

[Peter Drew]

Oops!, just noticed your location.

[LukeSkywatcher]

Strange because SCT's are known to keep their collimation very well. How old is the scope? did you drop it on its head as a baby?. Have you been tinkering with the focuser when you shouldnt have been?. I doubt its a collimation issue because that would be apparent across any EP size. Maybe there is a bit of slipping between the focuser and the whatever part it connects to to move the mirror. Maybe it needs greasing?

[baggywrinkle]

It is 8 months old and never dropped.

We are in winter down under and for WA it is Siberian (2-3C at night), and yes we have had dew, but not on the night I noticed the problem. It is now raining (has been for a day or so) so I will have to wait until it clears or try some terrestial looks.

If it is clear next Thursday I will take it to the shop I bought it from, they have viewing evenings so people can test scopes.

[LukeSkywatcher]

2-3C at night during winter is fine. The grease (if any) will not be frozen. Its good you can take it back to where you bought it. That should give you solutions and solve the problem.

LOL@2-3C being "Siberian".

[baggywrinkle]

2-3C at night during winter is fine. The grease (if any) will not be frozen. Its good you can take it back to where you bought it. That should give you solutions and solve the problem.

LOL@2-3C being "Siberian".

Yeah OK....

I am setting up at the moment to have a peek...there might not be rain tonight.

[Markinaboat]

Hi - it's 3 motnhs further on now. Was this issue resolved? If so, it would be extremely valuable information.

Many thanks