Any ideas folks why Celestron Xcel LX is poor?

[Welrod50]

Hi folks,

I'm after some advice or reasoning from the forum please...

Just recently purchased a 5mm Celestron XCel LX eyepiece and tonight was the first opportunity I've had to give it a whirl. I bought it as my highest mag EP so as to replace the x2 Barlow and std 10mm EP that came with my SW Explorer 130. I've found these to be fairly poor even in good seeing.

This evening, seeing here in Staffordshire pretty good and not really any atmospheric turbulence. The 25mm EP is, as ever, relatively sharp. The 10mm EP actually pretty sharp too tonight. I didn't bother with the barlow though as I know it's not really worth using.

Enter stage left - the lovely new 5mm XCel LX. On it went, everything cooled down nicely and my eyes tuned in!

It's terrible! I can get it to focus ok, although it is a very fine line indeed between focussed and blurred. But when it is in focus, the sharpness and contrast are worse than the 10mm with the Barlow.

Is this EP going beyond the capabilities of my SW 130 or is it something else? I have not checked my scopes collimation (yet!) but if the 25mm and the 10mm are sharp, surely this should be?!

Any thoughts please?

Scott

[Thirdway]

Well, tonight did you try the Barlowed 10mm to compare? 5mm lens in a 130 is a tall order. I rarely get beyond 9mm on a 200.

Contrast disappears as you swap magnification for aperture. You can only get so much light so the more you convert into a larger image the less sharp and contrasts it becomes.

I am usually happy with 8mm or 9mm using the Baader Zoom. Can't see much point going beyond that. I would have bought a lower mag lens such as a 14/15 and a high quality Barlow to go with it. I'm presuming your using the new range of Xcel lenses and not old stock?

[E621Keith]

It's best to check collimation first. Miscollimation will affect high magnification more than low magnification.

[iwatkins]

Would have thought 5mm was pushing it even in good seeing conditions.

With a front just gone through in your part of the world although seeing looks good it won't settle for a few hours yet.

Give it another go when things are settled but even so I think 5mm will be pushing it.

Cheers

Ian

[Welrod50]

I have just tried the barlowed 10mm and it's pretty much the same as the 5mm XCel LX. The LX is darker and less reflective inside and is a wider view also, but the contrast and sharpness are as poor as the 10mm with the Barlow, albeit with less CA than the barlowed image.

I'm beginning to think that going beyond 10mm with my scope is largely pointless. I now intend on buying a Baader 8-24mm zoom. I've toyed with the idea for a while and had initially elected to go for several fixed EP's but this has made my mind up. I also intend on getting a collimator and having a crack at doing this myself.

If it is out, I doubt it's by much as the std EP's actually aren't bad at all this evening.

Oh and yes, the LX is a new one.

Thanks for the quick replies guys

Scott.

[Thirdway]

There have been some reports of the Baader zooms sticking or failing. I have only had mine for a month or so and it's been fine, just very stiff at low temps.

I might be tempted to get Xcel in 25, 17, with an Ultima Barlow so that gives 25, 16, 12.5, 8 and get something around 32mm in ultra wide for DSO, if you can send the 5mm back then your only buying one lens and a good Barlow and gives a similar range as the Baader but a wider view and probably slightly better clarity and field flatness.