Blured round the edges

Hi

A quick question for all the experts I was out last night observing (brrrr...) and I noticed that in some of the views the image seemed to be blurred towards the edge of the field of view and focused towards the centre.

When I focused in the edges, the centre then became blurred. Is this a normal thing in SCTs

Thanks

Hi Dave,
For SCTs, its more the eyepiece that is the problem.
This depends on the eyepiece used, low cost low magnification (high mm focal length) eyepieces are your usual culprit for this.
This is why eyepieces like naglers are so expensive, it takes alot of optical engineering to ensure perfect widefield images.
Using f6.3 focal reducers can worsen the situation.

This is a form of coma and/or field curvature and there isnt alot you can do about it with a given eyepiece.

David,
Sounds like the eyepiece that's at issue here. What eyepiece were you using? Also, have you recently collimated the scope?
Regards,

Im using the meade 4000 26' that came with the scope

No never colimated the scope before. Thats another nights work but it doesnt seem to be too far off as when you defocus on a star, the black circle sits nearly in the centre. I dont have a high mag eyepiece to test it more thoroughly yet so colimating may l have to wait a little while.

Interesting, I have the same eyepiece and havent noticed this.
How near the edge of the field fo view are you talking about, What is your scope aperture, is it a F10 or F6.3,
are you using a diagonal??