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PostPosted: Thu Mar 29, 2018 9:33 am 
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Joined: Thu Jun 02, 2016 11:32 am
Posts: 320
Location: New Farnley, Leeds lat 53.8N long 1.6W
Hello,
some time ago I bought a short focus Chinese OTA (80mm F5) for quick views, variables and clusters. It cost less than £100 new. Yesterday I spotted a set of 3 new eyepieces for sale as a bundle, on the "yoursforever" Chinese internet shop. They are described as 62 degrees FOV aspheric. They come in 23, 10 and 4mm focal lengths. I made a bid.
This morning I awoke from a pleasant place where there was nothing but light on the yellow grass, wind, small insects and the presence of a cat. The eponymous Chinese shop had made a counter offer overnight - $23 plus p&p. It seemed like an auspicious start to the day so I accepted the offer.
When (do not think "if"!) they arrive - sometime between 13 April and 10 May - I shall post an update about them.
The Glenn Miller Orchestra is playing "In The Mood" and it's time to drive my wife to her appointment.
No sunspots today; I haven't seen any all month.
Bob :)


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PostPosted: Thu Mar 29, 2018 5:27 pm 
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Joined: Tue Dec 05, 2017 11:53 am
Posts: 143
I am glad you are happy, but you get what you pay for, and what you want and get depends on what you want to do.

My setup before Christmas for two scopes cost £8k

BUT I know where you are coming from

I TOO buy things on ebay from China (knowing what I am buying) and if cheap enough I don't care if they are carp.

In fact on every occasion, £18 for an illuminated reticule, £1.50 (A JOKE) ordered FIVE for friends each for RED head torches they have been GREAT

https://www.ebay.co.uk/itm/Headlamp-Han ... 2749.l2649

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Celestron 8" Edge HD Evolution, Esprit 120mm, Sky Tee 2, William Optics Binoviewer, LVW8mm eyepiece and Celestron 19mm Axiom, matched W.O 10 and 20mm, and a few others


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PostPosted: Wed Apr 18, 2018 8:53 pm 
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Joined: Thu Jun 02, 2016 11:32 am
Posts: 320
Location: New Farnley, Leeds lat 53.8N long 1.6W
The eyepieces arrived 10 days after the order was placed - from Germany. They were well packaged and in pristine condition. There is a thread on these Chinese aspherics on Cloudy Nights and I pretty much agree with the majority conclusions expressed there. I won't repeat any of that here.

I daylight tested the 23mm (x17.5) and 10mm (x40) oculars in my 80mm f5 achromatic. These are the theoretical magnifications. Tested against a good Vixen 22mm plossl the 23mm aspheric showed slightly poorer definition and an apparent field of view that was probably in the region of 58-60 degrees rather than the 62 displayed on the eyepiece. Still not far off. Tested against an 11mm TV plossl the 10mm aspheric showed poorer definition, though still reasonable and the AFV seemed to be around 52-55 degrees.

Tested tonight in the twilight on the crescent Moon and Venus (Venus was an unfair test really) in a 90mm f10 achromatic, these Chinese aspherics performed better than I expected and gave good definition and pleasing views of the lunar surface. For Venus, only TV plossls would produce anything approaching acceptable images.

I await the opportunity to see how they will perform on stars and clusters in the 80mm f5.
Regards, Bob


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PostPosted: Thu Apr 19, 2018 12:05 pm 
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Joined: Mon Jan 09, 2006 11:05 am
Posts: 4903
Location: Lancashire
Plossls are good with short f. ratios Bob. They are/were used as gunsight eyepieces and known as symmetricals.
I bought a secondhand MEADE Plossl 6mm for a couple of quid on a flea-market. It performs better than my new BAADER Genuine Ortho 6mm.

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PostPosted: Thu Apr 19, 2018 6:28 pm 
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Joined: Thu Jun 02, 2016 11:32 am
Posts: 320
Location: New Farnley, Leeds lat 53.8N long 1.6W
Tried out on Venus in daylight today, 1715 - 1755 UT in seeing conditions varying from Ant IV to III. Very surprised to find the 10mm performed well at x91 and x182 on the 90mm f10 Refractor. Used a cheap, short x2 barlow then switched to a long TV x2 barlow to give x182. With the TV barlow definition and achromatism was better. These 10 and 4mm aspherics do produce some false colour on bright objects (which I may be wrong in putting down to the "plastic" aspheric element) but the definition was quite acceptable and the hard limb of the planet could be clearly seen in contrast to the dusky terminator. This allowed a phase estimate of 92%, which I think is fairly reliable. The 4mm gave x227 and some "traffic light" colour but again not so obtrusive as to ruin the definition, although focussing was that touch more difficult than with my TV 8mm plossl and x2 barlow combination giving the same magnification.
Brian's comments (above) are spot on here. I think these cheap (less than £6 each) eyepieces are compromised in short focus instruments but they perform adequately in a long focus telescope. I wanted a cheap set for my F5 refractor, but I got a serviceable range that better suits my longer focus instruments and I am surprisingly happy with them for general planetary views. They also give a bit wider field of view than the plossls.


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