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JimBobs63

Advice on buying a low power wide field eyepiece

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Posted (edited)

Hi,

As you will see from the signature below, I have a 150P (f5) scope with a range of X-Cel LX eyepieces from 25mm to 7mm, and two Powermates at 2.5x and 5x.

So now I want to choose a wide angle low power 2" (or 1.25") eyepiece to suit my scope.  I recognise that for exit pupil limitation I can only go up to 35mm.

Given that the Tele Vue Naglers and Panoptics and other such quality eyepieces at £300 to £600+ are out of my league cost-wise, I would seem to have two options:

I could pay for an eyepiece in the same sort of cost bracket as the ones I have - I could get a OVL Aero ED / TS UFL 35mm 68-69degree (I think these are essentially the same eyepiece re-badged), or a William Optic 33mm SWAN 72degree, which are all available in the range of £95-110.

Or I could stretch (and perhaps sell the Ultima 2x Barlow) towards buying an Explore Scientific 34mm 68 degree eyepiece, or perhaps a Celestron Luminos 31mm 82 degree, at double the price - around £210-230.

What are your thoughts on the difference in quality for my relatively fast f5/6" scope?  Is it worth the extra cost to go for the ES or Luminos eyepiece?

Any help and advice gratefully received!

Jim

 

Edited by JimBobs63

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For widest field, but not the best correction at f/5, I would go with the 35mm Aero ED.  It nearly maxes out the field of view possible in a 2" barrel.

For best correction at a reasonable price, I would go with the 30mm APM Ultra Flat Field (or Altair UFF).  It has nearly the same true field as the 35mm Panoptic with more magnification, less field curvature, and less distortion.

The 31mm Luminos has SAEP and EOFB to deal with.

The SWAN eyepieces won't do well at f/5. The Aero EDs do better for similar money.

The 34mm ES-68 is decent, but is regarded as the weakest of all the ES-68s.

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Pretty good summary of the options there from Louis :thumbright:

A 35mm would give you a 3 degree true field compared to the 2 degrees that the 25mm X-Cel LX delivers. Quite a gain.

 

 

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Hi Jim, you have some good advice above.

I’d like to add that I once owned a 33mm Swan and with my Dobs it was only sharp in the centre of field of view and deteriorated rapidly towards the edges.   Probably much better in something like an f10 SCT but that’s not what you have......

Ed.

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Great Advice by Louis. I had the TMB Paragon 40mm (the Aero EDs are clones) and that was stunning, but the 35mm isn't considered as good as the 40mm. I used the Paragon at F/6 which was fine, but it would give rather a large exit pupil at F/5.

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Posted (edited)

I will definitely agree with @Louis D. I purchased an APM 30mm UFF on his recommendation. I find it a mind blowing experience looking through it. That said, I've never looked through a Aero or Luminos so can't compare but I certainly wasn't disappointed with the APM.

Al

Edited by Ally8446
Correction of info

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As I have advised someone else recently with the same scope, I would avoid trying to go too wide, unless that is you are young and live in a date site. The main reason is exit pupil, for people over 50 it rarely exceeds 5mm, and any light source may affect dilation as well. As such I would go for a good quality wide angle eyepiece between 25 and 30mm max.

Another benefit is that you are less likely to have problems with astigmatism. And finally whilst you will have a wider field, your limiting magnitude will be lower (increasing magnification means you see fainter stars, up to a point that is, being dependant on seeing and optics).

i hope this helps.

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With F/5 scopes I rarely use anything longer than 31mm in focal length. More often it's a 21mm which seems to do better on DSO's from my back garden.

 

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Thank you everyone for the replies.

I think I will spend the extra and go for the APM.

Jim

 

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