focusing issue?

[barry f]

i have just bought  ourselves a nexstar 6se  (s/h) we were looking at jJupiter the other evening and i noticed that is didnt seem quite as sharp as my older evostar 90. i have a celestron excell 12mm ep on it which seemed to be not as sharp as on the evostar 90 is this due to a higher manification with my new scope / atmospheric cond' or is there another reason or am i expecting to much as i am relativley new to all this and not really knowing from the nexstar would i get a better result from another ep 

[Tinker1947]

They do fit a very poor quality focuser to SCT's this could be the same unit on your Nexstar, and you say the "seeing, and longer FL" may not help...

[John]

The 12mm eyepiece gives 125x and is a nice eyepiece which should work very well with the 6SE. 125x is well within the capabilities of the scope even under modetate conditions and you should be getting a nice sharp image.

The SCT's do take a lot longer than refractors to cool down though and the image will not be clear and steady until that has happened. You probably need to allow 40 minutes or so if the scope has been kept in the house.

[russ.will]

Do you have any other EPs you can try?

Failing that and assuming the scope was reasonably cooled, plus you weren't looking through too much haze/cloud, it could be that the scope need collimating.

When you get a chance, point it at a bright star and defocus. If you don't get a bright ring with a central, perfectly concentric shadow from the secondary, then it's probably collimation.

Russell

[barry f]

The 12mm eyepiece gives 125x and is a nice eyepiece which should work very well with the 6SE. 125x is well within the capabilities of the scope even under modetate conditions and you should be getting a nice sharp image.

The SCT's do take a lot longer than refractors to cool down though and the image will not be clear and steady until that has happened. You probably need to allow 40 minutes or so if the scope has been kept in the house.

its kept in my conservatory where its usually cold during this time of the year so would that make a difference to how long i should keep outtside before i use it ? maybe it does need collimating? when the conditions allow i will give it a go  as since i have got it and had sufficient time to get outside its been cloudy as heck   

[Saganite]

Even in a conservatory the temperature will be higher than the outside where you are observing, and as John suggests the scope should be put 

outside for probably an hour.

[barry f]

Even in a conservatory the temperature will be higher than the outside where you are observing, and as John suggests the scope should be put 

outside for probably an hour.

thanks i will do that then