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svbony 68° eyepieces

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#1 bananas

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Posted 13 October 2018 - 12:27 AM

I'm a noob with an Orion Starblast 4.5, F4, 113mm aperture, 450mm focal length.  I found it at a thrift store for $30 without eyepieces.  So I bought a used svbony 68° eyepieces in 20mm and 9mm because I'm cheap.  That  gives me 22x and 50x magnification.  I also got a Meade model 140 barlow to pump it up a bit.  The eyepiece coatings look good.  They're only multicoated so that means at least one lens surface has no anti-reflection coating.  

 

I anticipated a poor performance with an F4 scope from what I've read in this forum.  I tested in daylight first.  Well, the 20mm was an OK performer.  Not a flat field.  There's just a hint of blackout at the very center that distorts the image as your eye moves around.  I found myself shifting the object off center just to get a clearer view. The 68° AFOV is acceptable than I thought. Probably more than I needed. The 17mm eye relief is a welcome.  Barlowing produced an image similar to the 9mm.  The blackout diminished significantly if not disappeared.  The eye relief didn't really extend as I anticipated.  Night views was great.  Makes searching easier but not much else to see at such low magnification.  The moon looked pleasantly sharp.  I can almost discern saturn's ring.

 

The 9mm in daylight was also OK.  Sharp center and no blackouts.  It kidney beans easily if the entire field is not in view.  Your eye also have to remain centered.  It states a 17mm eye relief but I feel it's shorter than that.  The Expanse Clone equivalent states 15mm eye relief. My eye glasses hits the lens before the full field comes into view and the beans disappear.  That didnt happen with the 20mm.  Barlowing was a blur.  The image was bigger but no additional resolution.  A disappointment.  I saw saturns ring for the first time so that was good.  Mars was just a flared blob. The eye relief also did not extend with the barlow as anticipated.

 

I will adjust my review as I do more viewings in the coming days.  I wonder if getting the 6mm is worthwhile. 

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Edited by bananas, 13 October 2018 - 01:55 AM.

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#2 Miranda2525

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Posted 13 October 2018 - 01:30 PM

Same eyepieces as the Orion expanse, Owl, Antares W-70's, etc which are really 65 or 66 degrees. The 9mm was drift timed at 70.5 degrees. The 20mm isn't good at all even at F/5, but the 9mm is ok with some edge of field brightening. Not only are there clones out there. Now there's clones of clones!

 

Jon Isaacs did some digging and found this below.

 

https://www.cloudyni...tion/?p=8798605


Edited by Miranda2525, 13 October 2018 - 01:45 PM.

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#3 bananas

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Posted 11 November 2018 - 10:54 PM

After more daylight testing the 20mm center is really not great with the F4 scope.  The secondary mirror shadow is just too noticeable and distorts the center image.  With the 2x barlow it becomes much better than the 9mm.  Instead of seeing a faint shadow of the secondary it is now slightly brightened, but no big deal.  Center is now sharp. No diminished brightness due to barlow. No edge brightening. 

 

The 9mm would easily blackout the edge of field but comes and go for some reason and less problematic at night. Center sharpness and clarity is comparable to the barlowed 20mm.  Barlowing the 9mm is horrible, resulting in dimming and fuzzy image.


Edited by bananas, 11 November 2018 - 10:57 PM.


#4 Usquebae

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Posted 12 November 2018 - 12:04 AM

That's a great scope, I think.  I would suggest getting the 6mm and keeping the 2x barlow permanently in place.  The three EPs on barlow then would yield 45x, 100x, and 150x.  A good spread, with improved correction.




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