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William optics planetary eyepiece


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I've got all three, and the 6mm is definitely my favourite. It feels the most comfortable to use for some reason, and 3mm is usually too much for anything but double star splitting. Contrast is good and there's plenty of eye relief. It's a good choice for the type of observing you mentioned.

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How often would you say that the 200x is viable? A 7mm ep would give around 170x is this more often useable? Tryin to find that sweet spot for planetary observing.

240x with my barlowed 10mm is really hard to use as the focus point is impossible to hit under my seeing conditions so i am lookin for somethin that will see more frequent use

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I have the WO 6mm and the 12mm.  The 6mm is absolutely superb for planetary, Moon and double stars.  One of the best ep's I have ever bought.  Very comfortable to use as well, even with spectacles.

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I chose a 6mm TMB Planetary II on the grounds that its small exit pupil would give me maximum detail on my Skyliner for the Planets. Well, the Planets have to be visible in the first place! (weather and terrestrial  obstructions),  they also need to be bright, but more of a let down for me was the tightness of the field of view, compared to my BST's that I was building at the time. The TMB just did'nt feel right. I returned the TMB in favour of the 5mm BST. So much better for me and much more comfortable to use.


The WO SPL's have good eyerelief, but at only 55°FOV that would bother me! I'm not sure how much better the WO glass is against my Starguiders, but it would'nt hurt to try them? If they dont work to your satisfaction, return them for a full refund (ask first!) They do a 5mm and 8mm and I believe there is now an eyepiece that is just branded 'ED 3.2mm'. Both the 3.2mm and 5mm will need the best/better conditions to be really effective, due to their magnifications on, say my Skyliner f/6.

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  • 1 month later...

........and now I own a 6mm WO SPL. What a nice eyepiece, and I've only had a few moments to test it, and through veiled clouds? Cant wait to give it a proper session.

A decent 6mm will go nicely inbetween the 8mm and 5mm BST's on the 200p dob.

I got a cheap 6mm to try out before going for the Delos - just to make sure that 6mm was the right size for me.

It was.

Sometimes 150-170x is all the seeing conditions would allow when it was poor.

Sometimes 240x is available near Zenith, or viewing the moon.

The 6mm fills the gap inbetween.

6mm will also pay dividends when viewing Jupiter, Mars, Saturn etc

150x / 200x / 240x is good spread of eyepiece magnifications to have.

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Reeny........When I use my EPs I dont bother to calculate the magnification, I just use the focal length as my guide, if it's framed well, its good enough, but I know where your coming from.

But I read an article that described choosing EPs based on the focal ratio. ( This is after choosing the BSTs) It says my focal ratio f/6 should indicate my lowest focal length EP so 6mm, then double the ratio to find the "sweetspot" so the 12mm fits that position, then triple for the next EP so anything from 21mm and upwards would be fine. Again the BST 25mm fits the bill, but the 32mm Panaview has lead role when it comes to wide angle. I tried the 6mm TMB PII but did not like, I subsequently bought the BST 5mm, and now just waiting for the night to properly test this 6mm WO.

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Goodness! Sounds like an intense article and a very convoluted way to work out eye piece selection.

Sounds a bit like these people who say you have to have an eye piece with a certain eye relief because anything else isn't perfect.

I wish my site was as dark as theirs and my seeing conditions less variable! :)

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Convoluted! not really. For your  larger-focal-length eyepiece simply  multiply the focal ratio  by 7. The Smallest focal length matches the focal ratio and the sweet spot is twice the focal ratio. In essence a simple formula for acquiring  three eyepieces to cover high, medium and low power.

Like you say, depends on who's formulae or guide you want to follow?

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The Moon was out last night so I had a peek with my  BST 5mm, 8mm, 12mm and the 6mm WO.

I found under the present conditions that I favoured the BSTs starting with  the longer focal lengths, as there is so much to see with the Moon, and Oh so bright.

The real test for me will be on Jupiter when the  opportunity presents itself . A  much smaller  target, and I know how long I had to wait for the perfect image the last time I viewed Jupiter. If the 6mm betters that view its a keeper?

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