Eyepiece Advice

[Nightspore]

1 hour ago, Stephen Waldee said:

Thanks for your explanation; but -- unless I am mistaken -- you showed pics of the TMB type oculars with lens elements removed, not the Expanse, right? My two Expanse oculars with the Smyth lens (6 and 9 mm) are indeed NOT easy in any way to disassemble; perhaps they used some sort of adhesive in mine, that was not employed in yours.  (The products kept changing, constantly, as we had of course noticed in retail sales, dealing with these obscure issues with Asian fabricators, out of our direct control.) 

 

I should add that MY own Orion Expanse oculars do not have the internal flecks of detritus that appear in-focus against a bright field, such as the Moon's surface.  My Orion/Vixen Lanthanums (discontinued) DO; so did one of my Orion Q-70s; and I simply could not tolerate or use a brand-new Orion Stratus 24, which I returned (no replacements were at the time in stock.) The worst example of all was an Orion Epic (original, not Epic II) 3.7 mm model that was kept by me ONLY for facilitating collimation of my C-11 at ridiculously high power.  I did try to disassemble and clean it; a complete disaster resulted.  The end result was that I took it to the Cupertino store, and Ken Sablinsky and I used another one in stock as the reference source, in a scope to check field and magnification, and tried various ways to reassemble and correct my INEPT and foolishly incompetent order of the elements.  FINALLY we got mine put together properly: adding even more dust and fingerprints, which I had intended to clean off again, but chickened out and left as-is: as the deficient eyepiece, with the WORST kidney-beaning and blackout problems I have EVER encountered, was not usable for actual observing; rather only as a sort of 'test instrument'. That was my last foray into the thickets of amateur eyepiece cleaning, aside from merely dealing with the two outer-most exposed lenses on top and bottom. 

 

I even added this embarrassing episode to an old (humorous, I hope!) article called "Obsessive-Compulsive Personality Disorder and Telescopes --

"http://celestialregina.x10.mx/haggisizing/astro/oc-astro.htm

-- wherein I have not really divulged the awful details but glossed them over and generalized them, just to give a moral example to those of us who have no fears and forge ahead--where perhaps we shouldn't.

 

One final point: I have removed the very easily detachable Smyth lens from my Orion Stratus and Baader Hyperions that have the unit, just to see what the eyepiece would do, at lower power, without it.  GHASTLY!  That design has possibly not only used the so-called Smyth assembly not merely as a sort of Barlow element, but also must have incorporated some field-flattening too.  The added lens assembly is absolutely essential, for if it's removed you take a good, fairly high priced ocular and turn into a disaster.

Steve & Regina, Ivins UT
http://reginacelestial.byethost3.com
or 
http://celestialregina.x10.mx

 

 

AFAIK, the Smyth by being a negative element, ameliorates much of the astigmatism in many eyepieces. The Expanse focal lengths that do not have the barrel element show a lot of edge distortion in fast scopes.

 

 

My 9mm 'Expanse' is a few years old. I'm pretty sure these were made by Barsta. My newer 6mm may be made by a different OEM. These EP's are sold under a variety of brand names.

 

 

The chromed-brass barrel should unthread completely from the aluminium housing.

 

 

The Smyth retaining ring can often need tightening as it can become loose and rattle. I've had this happen on the TMB clones as well.

 

 

The same thing can happen with the ring holding the eye lens with the TMB's. I think they shake loose in the lorry or the slow boat delivering them from China or something lol. I've turned loads of eyepieces into paperweights by trying to clean them. I've returned as many for having visible debris. 

[Kevin17]

On 7/13/2021 at 5:17 PM, Sonyme said:

Hi Paul, take a look at the Explore scientific wide angle 2" lenses. the 82 degree options give a great F.O.V. and are easy on the eyes. They do 18, 24 and 30mm so pretty good for scooting around the solar system and beyond. they also offer 4.7 to 14mm at 1 1/4". The ultra wides are brilliant for the money. Looking through them is like having your head in a space helmet! Certainly worth checking out. Gary

 

i bought a full set of those and barlow and they weren't compatible with my WO 91 FLT, couldn't achieve focus so they had to go back.

 

i was told b salesman not to get anything wider than 80deg as the human eye cant see more than 72 deg without moving your eye.

 

i went for Baader Hyperon in the end, not the quality i wanted with the ExpSci ones but they're nice. With the addition of modular spacer rings they go from 3.2mm which gives me the highest mag my scope can provide so im happy with that.

 

 

 

 

[Nightspore]

Does anyone remember any of the rumours of a production run of the 14mm ES having field curvature problems?

 

 

The 14mm isn't my favourite of the range but I can't see any real problems with mine. The rumour was that a whole load had been assembled with the wrong elements or something. I'm a bit sceptical as this was from the Cloudy Nights forum and almost everything on there is either vitriolic bile or fantasy island.