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Something to be said for parfocal eps


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My ep box has generally been a bit of a mix, with a barlow thrown in. Until today if conditions were good I would go from a 6.5mm Meade to a barlowed 8mm radian. Although I really like the rad, there isn't much in it when viewing the planets or moon. I've now got a 4.5mm Meade and it is nice to not mess about with refocusing or barrows when you are at high powers with a dob.  

With planets I never use the low powers, so usually only use 2 eps - medium to determine seeing and a higher one depending on how steady it is. Perhaps I should ditch the Barlow and pick up an old 4mm rad    too.  

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Somehow, parfocality is way at the bottom of my list of important eyepiece properties.

I do have a few that are parfocal with each other, but even those require small amounts of refocusing. And the other ones ... once you get to know them, they end up in your muscle memory and you kind of automatically know which  require a bit more in- or out-focus.

It does take me a while though to get familiar with a new eyepiece. Fortunately I don't buy a new one every month.

 

 

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28 minutes ago, Ruud said:

Somehow, parfocality is way at the bottom of my list of important eyepiece properties.

I do have a few that are parfocal with each other, but even those require small amounts of refocusing. And the other ones ... once you get to know them, they end up in your muscle memory and you kind of automatically know which  require a bit more in- or out-focus.

It does take me a while though to get familiar with a new eyepiece. Fortunately I don't buy a new one every month.

 

 

None of mine were until recently. At low powers I'm not bothered, but at the high end I would rather use parfocal.

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I used to like the parfocal properties of the T6 range I had, though I didn't have all of them, the lions share of the Delos range too. The Ethos collection seem to be all over the place but now more manageable when used in the Paracorr. As said it is nice but never really gets to me, being able to see anything would be nice at the moment.

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  • 4 weeks later...

I parfocalized all of mine using rubber o-rings. Next to no re-focusing required now! Note the o-rings on the 34mm and the single o-ring on the adapters and barlow. On the right is a metal parfocalizing ring on the housing of the original 2" barlow piece. My barlows are also parfocal.

 

Cheers!

EPs 2016.jpg

P1440321.JPG

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I've given up worrying about parfocality as well now - even though my main eyepieces are Tele Vue and Pentax the focal planes are all over the place. I like their other characteristics though so I'll put up with tweaking the focus a bit.

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Parfocal seems to work well when synced with A DSLR focus. Bearing in mind that focussing on a dim object through a camera screen is not a lot of fun. I used to do this before using a laptop. The eyepiece I used was 20mm with a parfocal ring added to give the same focus as the camera focal plane with consistent results.  A flip mirror with a synced eyepiece ? but I found this arrangement with the camera rather heavy.......................Dave

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