blurry image with high magification lenses

[minks]

Hello! I own an Orion XT8 8inch dobsonian with 1200mm focal length... I just bought a 6.3mm eyepeice and a 3x barrlow as well as a 40mm eyepeice.. problem is that Jupiter looks quite blurry at high magnification.. with just my 6.3, it doesnt look clear, it looks like i took the same image of my 25mm and stretched it out... my scope should be able to handle a 6.3, no? I even tried putting my barrlow on my 25mm and i still get the same results! any advice?? I do not expect to see everything, just a little color and maybe a belt or two !]

Thanks!!

[Hypernova]

Hi there,

I would suggest that you are using too much magnification. Excessive magnification will darken the image and also blur it as you described.

Your 6.3 gives about 190x in your scope which is about the maximum on nights of average seeing. It might be worth trying a lower mag eyepiece such as a 8mm.

You should also check your collimation, if it is far out it maybe affecting the views you get, especially at higher magnification.

[Ben Ritchie]

You should also check your collimation, if it is far out it maybe affecting the views you get, especially at higher magnification.

This would be my guess too - 6.3mm shouldn't be too much unless the seeing is quite poor. I'm guessing it's a Meade Plossl or clone?

[Chris H]

Hi, I'm currently finding with my XT10 that anything above x150 and the image begins to look pretty poor. Your scope can handle the 6.3mm ep easily but you'll have to wait until the atmosphere is pretty steady. Also check collimation, if it's out this won't help your cause.

[Polar Bear]

I think with the 6.3mm EP it may be a case of too much expectation but not with the 25mm EP. Theoretical maximum magnification is rarely achieved and needs perfect collimation, perfect seeing and very expensive quality EP's.

I always use this N.A.A. Telescope Math Calculator to give a realistic idea of magnification and it shows your scope would perform the best between 50 and 100 x using a 24mm and 12mm EP. Your 6.3mm gives you an exit pupil of 1.07mm and 190x so that is pushing it a bit and would need the collimation and seeing to be spot on. Even a mediocre 25mm EP should give sparkling results so I would suggest checking your scope and your focuser to ensure everything is as it should be.

Paul

[brianb]

Jupiter does not stand magnification well, about x20 per inch of aperture is as much as is of any help, even then only when seeing conditions are unusually steady (which the current blustery airstream doesn't help at all).

[Chris H]

Have a look at this thread there is a discussion towards the bottom about the best magnification for Jupiter at the mo.

http://stargazerslounge.com/equipment-help/113178-help-me-choose-my-next-eyepiece.html#post1521888

[mdstuart]

With high power under normal UK seeing the stars at high power do go "slightly" blurry. If they have any level of brightness they no longer look like a point but a very small but fuzzy full stop. This is my experience over many eyepieces on a well collimated scope. Down to about 9mm on my 1200mm scope the stars are points but above that it starts to go "blurry"...

Apart from on good seeing nights like a few weeks ago when Uranus looked like a sharp disk and the stars looked like points even in the 6mm lens.

Mark