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Upgrading your eyepieces - The first step

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Let's Talk Astronomy."Introductory To Eyepieces"


Credit rvoptics

Starting with the moving of Venus and Jupiter towards one another in the night sky, Dennis Ashton goes on to talk to Ian Littlewood about the different magnification power of Eyepieces to be used with Telescopes.



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The Plössl is an eyepiece usually consisting of two sets of doublets, designed by Georg Simon Plössl in 1860. Since the two doublets can be identical this design is sometimes called a symmetrical eyepiece. The compound Plössl lens provides a large 50+ degree apparent field of view along with relatively large FOV. This makes this eyepiece ideal for a variety of observational purposes including deep sky and planetary viewing. The chief disadvantage of the Plössl optical design is short eye relief compared to an orthoscopic since the Plössl eye relief is restricted to about 70-80% of focal length. The short eye relief is more critical in short focal lengths below about 10 mm, when viewing can become uncomfortable especially for people wearing glasses.
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Enhanced Moonfish® 30mm 80° ULTRAWIDE

30mm Ultrawide 80° 2" Eyepiece - Enhanced

Main features
Focal length: 30 mm
Apparent Field of View: 80°
Fully multi-coated
Barrel: 2" / 50.75 mm
Rubber eyecup
M49 camera thread
Elements: 5 elements in 3 groups
Eye relief: 22 mm
Field stop: 40.8 mm
Weight: 570g (1.2lb)
Length: 114 mm (4.5")


Other
Blackened lens edges
Threaded for 2" filters
Rubber grip
End cap & bolt case

The Enhanced Moonfish® 30mm 80° ULTRAWIDE is a very serious wide-angle 2" eyepiece, at a very affordable price. Contrast and correction is good for very low powered wide-angled viewing of those larger deep sky objects.

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kidney bean blackout effect
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Simpler eyepiece designs such as Plossls and Orthoscopics become progressively more difficult to use as the focal length decreases. By the time they get to 8 or 10mm designs, the eye lenses for these types of eyepieces are tiny and looking through them is like peering through a keyhole. The UWA designs with their integrated Smyth (barlow) lenses change all of that. The eye lens on this 8.8mm UWA is over 20mm across which is about the size of the eye lens on a 25-30mm Plossl or Orthoscopic. This makes the 8.8mm a much easier eyepiece to use. While the UWA designs still have issues with the dreaded "kidney bean" or "blackout" effect, I found that with the 8.8mm, this is relatively easy to avoid since your eye is closer to the eyepiece and overall this is much preferable to the tiny eye lenses of other designs.
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1.25" 5mm BST Explorer Dual ED eyepiece

The eyepiece uses two separate ED (Extra-low Dispersion) glass elements of different glass types in its optical system to provide exceptional colour fidelity (with astonishingly low levels of chromatic aberration) so that the true colour differences between binary star pairs and planetary surface details are easily visible. It has a  60° field of view which is very flat and it is particularly recommended with telescopes with a f/5, or greater, focal ratio. It is uniformly sharp edge-to-edge, with markedly low astigmatism. Barrel distortion is essentially non-existent, eliminating the annoying "goldfish bowl" effect of distortion of the image which is often seen in some eyepieces when panning across a star field.
Each air-to-glass surface in the eyepiece is fully multicoated for high light transmission and exceptional contrast.  This high contrast makes it a good choice for splitting close binary stars, for examining low contrast lunar and planetary detail, and for finding small and faint planetary nebulae against a truly dark sky background.  The lens edges are blackened to eliminate internal reflections and further improve contrast.
As you would expect, the chrome barrel is threaded for standard 1.25" filters and has a capture ring to help reduce the chances of accidentally dropping the eyepiece out of the focuser.  Explorer eyepieces are parfocal, minimising the amount of refocusing needed when changing eyepieces within the series.
The eyepiece is set in a heavy rubber cladding which is grooved for easy grip.  It has a soft rubber twist up eyecup which will make it unbelievably convenient to those of us who wear spectacles. The colour coded body rings and clear lettering print will help you find the right one in the dark.
The eye lens is large in diameter and with 13mm eye relief this makes it very comfortable and easy to look through.  It weighs 7.4 ounces.

Coating: FMC fully multi-coating
Focal Length: 5, 8, 12 15, 18 &  25mm
Lens Structure: 6 elements 4 groups
Price: £41.00

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SkyWatcher 25mm Super-MA Eyepiece (1.25"/31.7mm)

The modified achromat series of eyepieces offer a good standard of performance in a very affordable package. Designed for telescopes with mid-range to long f/ratio, these oculars have features usually found only in more expensive designs. These Super Eyepieces incorporate a fold-down rubber eye- shield, fully coated optics and outstanding field correction.
Design: Modified Achromat, fully coated
Focal Lengths: 25mm, 10mm & 3.6mm
Eyepiece Barrels: 1.25"/31.7mm Format
Apparent Field of View: 52° (20mm and 10mm), 50 degrees (25mm and 4mm), 40 degrees (3.6mm).

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SkywatcherMA.jpg
£14.99

Ed ~ These eyepieces can be picked up second-hand for a few pounds.  But, as a new product, it is worth considering the slightly more expensive Plossl design.



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Sky-Watcher 'SP-Series' Super Plossl Eyepieces

These standard 1.25 inch/31.7mm eyepieces set high performance standards for modern telescope oculars. The proven 4-element Plossl designs display edge-to-edge pinpoint imaging across their panoramic 52º fields. Utilisation of top quality optical glass, superior multi-layer coatings and edge-blackened elements deliver superb high contrast images.
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skywatcherSP.jpg
£19.99



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When choosing a telescope eyepiece, remember that more space between the eye and the lens allows for more adjustment possibilities. Compare different styles of eyepieces for telescopes with the shopping tips in this free video on home astronomy from a telescope salesperson.

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