blurred image with 10mm eyepiece

[simon]

hi everyone hopefully you can point me in the right direction.

i recently bought a 10" auto-tracking skywatcher dobsonian, which csme with 2 eyepieces 25mm and 10mm.

i had stunning views of jupiter and the 4 moons with the 25mm and a ×2 barlow but when i tryed the 10mm the view was shockingly blurred with and without a barlow?

is the i piece really Rubbish?

is it not suited to the task or even the scope?

have i collimated my scope wrong?

the fl is 1200mm.

any help would be great.

one other thing. what eyepieces and make would you recommend for my scope? and would a 6mm eyepiece with a ×2 barlow give me a clear image of a planet?

thanks.

[simon]

i think ive posted this in the wrong place. sorry admin.

[Stu]

The 10mm would be giving you x120 which is well within the capabilities of the scope. The possibilities are poor collimation, poor seeing, or the ep really is bad. I've heard many comments that the 10mm standard ep's are not good so this is possible. I would check your collimation and try again on a couple more nights to see if it was the atmosphere causing issues, then look at upgrading.

Initially I would look at x200 to x250 for planets, that is normally the maximum that you can get too in the UK (assuming you are in the UK). A 6mm would give you x200 but barlowed would be too high. Maybe look at a couple of ep's in the 7mm to 5 mm range to start with on planets.

What sort of budget do you have?

Cheers

Stu

[Ganymede12]

I don't know if it applies to the 10" but the 8" dobsonian (solid tube) has two adaptors. A 2" and a 1.25" and I have read that it can be impossible to focus when both are being used at the same time.

[simon]

The 10mm would be giving you x120 which is well within the capabilities of the scope. The possibilities are poor collimation, poor seeing, or the ep really is bad. I've heard many comments that the 10mm standard ep's are not good so this is possible. I would check your collimation and try again on a couple more nights to see if it was the atmosphere causing issues, then look at upgrading.

Initially I would look at x200 to x250 for planets, that is normally the maximum that you can get too in the UK (assuming you are in the UK). A 6mm would give you x200 but barlowed would be too high. Maybe look at a couple of ep's in the 7mm to 5 mm range to start with on planets.

What sort of budget do you have?

Cheers

Stu

hi BigMakStutov

the viewing was very clear , if it is collimation what could i have done wrong? i'm using a cheshire collimator from astro engineering.

i was looking at spending upto £100 max, less if possible on an good eyepiece.

the statistics on the scope say it is capable of x400 , is this not a practical power for planet observation?

[jonathan]

The maximum magnification stated for a scope is most likely only possible under laboratory conditions, real world factors normally make the real usable limit much lower.

[simon]

I don't know if it applies to the 10" but the 8" dobsonian (solid tube) has two adaptors. A 2" and a 1.25" and I have read that it can be impossible to focus when both are being used at the same time.

hi Ganymede12

do you mean the two adaptors 2" and 1.25" at the same time? or do you mean the barlow and eyepiece together?

[simon]

The maximum magnification stated for a scope is most likely only possible under laboratory conditions, real world factors normally make the real usable limit much lower.

hi jonathan

i see, so do you think about half x200 is more realistic?

[Lenny147]

Chances are its the EP, my SW 10mm was used once then upgraded, 25mm was fine.

[DirkSteele]

hi BigMakStutov

the viewing was very clear , if it is collimation what could i have done wrong? i'm using a cheshire collimator from astro engineering.

i was looking at spending upto £100 max, less if possible on an good eyepiece.

the statistics on the scope say it is capable of x400 , is this not a practical power for planet observation?

400x is rarely a practical power for any telescope. The rule of thumb of 50x magnification per inch of aperture only really applies to smaller scopes. Once a magnification of 200x is exceeded (regardless of scope size) it really comes down to the quality of the seeing and how tranquil the atmosphere is. I rarely go above 250x with any of my scopes. That is not to say that it cannot be done, or should not be attempted. I have heard of individuals with very high quality scopes pushing magnification to as much as 500x, but that is under very rare atmospheric conditions.

[Lenny147]

I bought a 9mm Celestron X-cel Lx EP to replace the 10mm, works well

[simon]

400x is rarely a practical power for any telescope. The rule of thumb of 50x magnification per inch of aperture only really applies to smaller scopes. Once a magnification of 200x is exceeded (regardless of scope size) it really comes down to the quality of the seeing and how tranquil the atmosphere is. I rarely go above 250x with any of my scopes. That is not to say that it cannot be done, or should not be attempted. I have heard of individuals with very high quality scopes pushing magnification to as much as 500x, but that is under very rare atmospheric conditions.

thanks DirkSteele

[simon]

hi all ,

do you think the 25mm + X2 barlow should have been blurred as well as the 10mm, if the collimation was wrong somehow ?

[simon]

Chances are its the EP, my SW 10mm was used once then upgraded, 25mm was fine.

hi lenny147

i was sort of thinking this, its a super plossl 10mm multi-coated 52* . i think there about £20 to buy . im sort of hoping your right.

[crazyjedi]

The stock 10mm EP that came with my SW newt is not good I never use it. The view through it was always a little blurred and dim

[simon]

The stock 10mm EP that came with my SW newt is not good I never use it. The view through it was always a little blurred and dim

thanks crazyjedi

[Stu]

In theory it should have been, although it does not give as high a magnification. As I mentioned, the 10mm doesn't have a good reputation so that is probably the problem.

The other thing is cooling. How long did you leave the scope to cool for? I would think it would need 45 mins to properly stabilise, unless you have cooling fans. This makes more of a difference at high powers ie you can start observing at low powers sooner.

I mentioned x250 as a maximum as there is normally not much to be gained in terms of detail above this due to the atmosphere, unless you are under very stable skies, or at altitude. That said, I have used x300 and more on very good nights or on the moon or doubles.

Others probably have more suggestions on ep's, but I do think the Celestron XCEL-LX are very good, as are the Baader BGO's for planetary work, where field of view is less important.

Stu

[crazyjedi]

What sort of budget are you thinking of to replace the 10mm?

[Lenny147]

You will find when you upgrade the EPs the views will be very much improved, although the 25mm served me well in the beginning, like others have said the 10mm is blurred and even worse with a Barlow

[Stu]

Just to clarify on magnifications for planetary observing. Jupiter has lots of quite low contrast features and doesn't take magnification as well as others. I tend to use x180 to x200 on Jupiter if conditions are ok. Saturn has higher contrast in the rings so takes more magnification and Mars its relatively small and tricky so if the seeing is good I tend to throw as much as it will take at it, x250 say maybe more.

Stu

[simon]

In theory it should have been, although it does not give as high a magnification. As I mentioned, the 10mm doesn't have a good reputation so that is probably the problem.

The other thing is cooling. How long did you leave the scope to cool for? I would think it would need 45 mins to properly stabilise, unless you have cooling fans. This makes more of a difference at high powers ie you can start observing at low powers sooner.

I mentioned x250 as a maximum as there is normally not much to be gained in terms of detail above this due to the atmosphere, unless you are under very stable skies, or at altitude. That said, I have used x300 and more on very good nights or on the moon or doubles.

Others probably have more suggestions on ep's, but I do think the Celestron XCEL-LX are very good, as are the Baader BGO's for planetary work, where field of view is less important.

Stu

thanks :-)

[simon]

What sort of budget are you thinking of to replace the 10mm?

around £100

[simon]

Just to clarify on magnifications for planetary observing. Jupiter has lots of quite low contrast features and doesn't take magnification as well as others. I tend to use x180 to x200 on Jupiter if conditions are ok. Saturn has higher contrast in the rings so takes more magnification and Mars its relatively small and tricky so if the seeing is good I tend to throw as much as it will take at it, x250 say maybe more.

Stu

thanks :-)

[simon]

You will find when you upgrade the EPs the views will be very much improved, although the 25mm served me well in the beginning, like others have said the 10mm is blurred and even worse with a Barlow

thanks :-)

[Astrosurf]

I found the 10mm with my Skywatcher was pretty pants. I love my Hyperions as they're excellent quality with great eye relief. They also do zooms (expensive!) - can someone advise on these?

http://www.firstlightoptics.com/baader-planetarium/baader-hyperion-68-degree-eyepiece.html

I'm sure someone will suggest something cheaper!

Alexxx