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AnotherJohnH

Wider EP for a f/8 150mm reflector?

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I'd appreciate some thoughts on selection of a wider EP. My current eye pieces are...

  • cheap 10 mm Kellner - maybe it's just physics but always seems to disappoint
  • Vixen 15 mm Plossl - nicer to use and view through than the other two
  • cheap 25 mm Kellner - seems ok to my very inexperienced eyes

I am thinking a wider and/or lower power EP might be a good next purchase for the following reasons...

  1. When viewing DSOs and clusters I sometimes feel I would like to step back a bit a see a little more
  2. I wonder whether a wider view though an EP may present an alternative more comfortable way to find things than using the finder scope

Any recommendations? ... my budget would be up to about £80

Edited by AnotherJohnH
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You might consider a used item from other members.  I have just bought four eyepieces from members and found them to be in A1 condition, and as good as new in use. ( a secret... Shh...I got three wide angle eyepieces for around 100 quid..But don't tell anyone)?

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I think GSO superview erfles will work well on F/8 - but will need someone to confirm this.

https://www.teleskop-express.de/shop/product_info.php/info/p807_GS-SuperView-30mm-2--Wide-Angle-Erfle-Eyepiece---68-Degrees.html

Just also check secondary size - it might be on a small size, and might not illuminate 42mm of field stop.

For my F/6 8" Reflector I use ES68 28mm - might be a bit to expensive given budget, but second hand one?

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Does your F/8 150mm reflector accept 2 inch eyepieces ?

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14 hours ago, vlaiv said:

I think GSO superview erfles will work well on F/8 - but will need someone to confirm this.

https://www.teleskop-express.de/shop/product_info.php/info/p807_GS-SuperView-30mm-2--Wide-Angle-Erfle-Eyepiece---68-Degrees.html

Just also check secondary size - it might be on a small size, and might not illuminate 42mm of field stop.

For my F/6 8" Reflector I use ES68 28mm - might be a bit to expensive given budget, but second hand one?

Thanks Vlaiv I hadn't come across those, I have been looking at the OVL PanaView 2" 32mm, but those certainly looks like an interesting alternative.

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With an f/8 telescope, you could select a 2" Meade 56mm Plossl even, provided that the exit-pupil of your observing eye dilates to 7mm.  It does for many, including myself at 54 years of age...

https://www.harrisontelescopes.co.uk/acatalog/meade-series-4000-56mm-super-plossl-eyepiece-2.html

Here is a comparison of the Meade, and the  2" OVL 32mm and 38mm, and through your 150P...

https://goo.gl/HHxx1G

https://goo.gl/oKauU8

https://goo.gl/SMRKF8

Incidentally, that's a nice little calculator with which to experiment.

However, the lower the power you go, the less black the sky becomes; to greyish-black.

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When do my presentations with schools, scout group, I use a 17mm wide angle eyepiece

Gives good eye relief with 7-9 yo's, and ideal for viewing Jupiter and its moon, and rings of Saturn

 

 

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I bought a Meade 2" 56mm super Plossl for wide views with my 250PX. The 250PX's focus draw tube has a fairly short travel, and I found that I needed a short 2" extension tube to get out-focus (conversely, I need a x2 Barlow to get the in-focus with my DSLR). I also found that the weight of the extra glass made the overall OTA front-heavy, and I needed to add a balancing weight at the primary mirror end.

Most of the time, my 1.25" 32mm Plossl gives me wide enough views, is much lighter, and does not require an eyepiece adaptor change when I ramp up the magnification using my other 1.25" eyepieces.

Geoff

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You could almost max out your true field of view with a 30mm 80 degree Wide Scan III clone available direct from China on ebay for £63.59.  The inner 50% is very sharp.  From there out, astigmatism and especially field curvature ramp up.  If you strictly look in the center, it's quite acceptable on most targets.  Finding targets off center doesn't really work because everything looks like a comet, galaxy or nebula out there.  I compared it to much more expensive options in an 8" f/6 here and here.

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For that scope the Skywstcher Aero or even the William Optics SWAN are worth looking at. Personally though I think a good 32mm Plossl would be hard to beat.

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31 minutes ago, Moonshane said:

For that scope the Skywstcher Aero or even the William Optics SWAN are worth looking at. Personally though I think a good 32mm Plossl would be hard to beat.

Yeah go for the WO swans, great bit of glass for a F8 scope. The 40mm will give you x30 in your scope, a 5mm exit pupil so a pretty dark sky but more over a lovely 2.3 degrees of sky to look at. 

And I reckon it should be pretty tight across the field as well and would be a great low power eyepiece.

Sorry shane mate although a 32mm plossl will be cheaper, at nearly a full degree less tfov I wouldn't share your enthusiasm for one.  

Hey nearly forgot, if you cn get your hands one a Moonfish 30mm/80 degree fov that would also be a great eyepiece. http://moonfishgroup.com/catalog/product_info.php?products_id=50&language=en

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18 hours ago, Alan64 said:

With an f/8 telescope, you could select a 2" Meade 56mm Plossl even.

https://www.harrisontelescopes.co.uk/acatalog/meade-series-4000-56mm-super-plossl-eyepiece-2.html

Here is a comparison of the Meade, and the  2" OVL 32mm and 38mm, and through your 150P...

https://goo.gl/HHxx1G

https://goo.gl/oKauU8

https://goo.gl/SMRKF8

Incidentally, that's a nice little calculator with which to experiment.

However, the lower the power you go, the less black the sky becomes; to greyish-black.

Thank you for your analysis Alan that is a very useful calculator ... bookmarked! ... should have explored SGLs menus more ?

Meade 2" 56mm looks interesting too.

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I'd go for a 38mm Panaview or if you can push the budget a little, or get one 2nd hand, a 40mm Aero. Going  the other way the Revelation 42mm (65 afov) would be a nice affordable wide field EP.

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Another thumbs up here for the 40mm SW Aero ED - I've had one for the past few months and it works really well even with my F/5.3 12" dob (though the resulting exit pupil is a little large with that scope). Best corrected of the Aero ED range I reckon.

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