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  #21  
Old 28-04-2019, 10:57 PM
A1 (Jason)
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Hi Knigtrider,

I use the 2" 30mm GSO SV with 68 degree AFOV all the time as a finder and wide-viewer in my 10-inch and 12-inch f5 Dobsonians. The image quality is absolutely amazing for the price.

GSO also makes 20mm and 15mm versions of this SV (superview) 68 degree eyepieces in 1.25 inch.

Andrews sometimes sell them. About USD$45 each online at AgenaAstro (dot) com

This is the best bang for buck in the price range you indicated. GSO products seem optimised for fast Newtonians.

You can distinguish the difference between coma and astigmatism by rocking the focus. Astigmatism causes the oval shaped stars at the edge of field to change direction by 90 degrees when rocking focus from in-to-out.

Best wishes, Jason
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  #22  
Old 29-04-2019, 01:28 AM
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Ukastronomer (Jeremy)
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Have you sorted this now

What was wrong with this by the way

http://www.moonfishgroup.com/catalog...products_id=50
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  #23  
Old 29-04-2019, 11:19 AM
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mental4astro (Alexander)
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Hi Jeremy,

That particular EP is not an optical match with Newtonians, and it will show astigmatism and field curvature when used in Newts. I have looked through one of these EPs in a couple of different f/ratio Newts - the visble aberrations are pretty much as noticeable/prominent as those seen through a 30mm GSO Superview. So the faster the focal ratio the more significant the aberrations are. This EP will be fine for some people with Newts, if you are able to tolerate the visible aberrations Certainly an inexpensive option, but it WILL show aberrations in Newts.

The same EP in a refractor, SCT and Mak, the image is much better. Fast fracs do show some field curvature with this EP.

Alex.
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  #24  
Old 29-04-2019, 02:42 PM
knightrider
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Quote:
Originally Posted by A1 View Post
Hi Knigtrider,

I use the 2" 30mm GSO SV with 68 degree AFOV all the time as a finder and wide-viewer in my 10-inch and 12-inch f5 Dobsonians. The image quality is absolutely amazing for the price.

GSO also makes 20mm and 15mm versions of this SV (superview) 68 degree eyepieces in 1.25 inch.

Andrews sometimes sell them. About USD$45 each online at AgenaAstro (dot) com

This is the best bang for buck in the price range you indicated. GSO products seem optimised for fast Newtonians.

You can distinguish the difference between coma and astigmatism by rocking the focus. Astigmatism causes the oval shaped stars at the edge of field to change direction by 90 degrees when rocking focus from in-to-out.

Best wishes, Jason
Thanks Jason,

I actually had a 15mm SV that I sold earlier this year. I found it to be less tolerable in my scope than the 30mm. Distortions started at about 70% out for me, and just didn't look very good when being used on GC's. It performed a lot better F/8 than at F/4.7

Thanks for the tip. I'll give it a shot one the 30mm.


Thanks Jeremy also for the suggestion. I had a look at it, but aren't really looking for another 30mm. I ended up buying a Meade HD-60 25mm. It had plenty of good reviews for scopes similar to mine. I haven't a had a go at it yet though
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  #25  
Old 29-04-2019, 03:03 PM
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mental4astro (Alexander)
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Quote:
Originally Posted by knightrider View Post
It had plenty of good reviews for scopes similar to mine.
THIS IS THE SINGLE BEST PIECE OF ADVICE THAT CAN BE TAKEN FROM THIS THREAD!

When reading reviews, LOOK for reviews that mention the scope you intend to use THAT eyepiece in, and ONLY that focal length.

Do not base an EP purchase on reviews that discuss other focal lengths as there WILL be performance differences between scope designs and focal ratios.

This way you will be able to find and cherry pick those eyepieces that best suit YOUR requirements, YOUR preferences, YOUR scope & YOUR price range, and not someone else's prejudices as those are entirely that other person's own preferences.

And if you can, borrow a mate's eyepiece or two, and see how they perform in your scope. Experience is the best teacher. You may not be looking to buy a similar eyepiece, but the experience you gain will prove invaluable to your own knowledge base, and you'll be able to offer a better balanced opinion on that/those eyepieces for the scope/scopes you've used them in.

Alex.
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  #26  
Old 09-05-2019, 08:54 PM
knightrider
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Alright, so the skies cleared and I got to try it out.

Used in: SW Dobsonian/Newtonian 10" F/4.7 without a coma corrector.

My impressions: The HD-60 25mm performs excellently. It shows a nice flat field with the quality of the image (to my eye) edging just ahead of the SW super plossl.
It's nice and sharp across almost the whole field.

Distortions....which I will call coma from the education in this thread, start at about 95% out, where it appears like a fishbowl lens effect at the very outer edge of the of the field. HOWEVER, it is not deterring and is honestly minimal compared to the rest of the field. It can only be seen if you're trying to fault the eyepiece.

The image appears brighter (observing the Orion Neb), but this could be because of the extra AFOV.

It resolved the spattering of stars at the centre of Omega Centauri @ x48.
And for the first time, with this lens I discovered for myself the Homunculus Nebula in Eta Carinae, I had never spotted it before even though I'd observed the Carina Nebula on quite a few occasions. It appeared as a planetary nebula would except much brighter with a transparent oval shape.

It's certainly nice to have the extra AFOV over the Plossl, and is definitely a step up from the Plossl.

Even though the performance of the Plossl is actually quite close, I felt the plossl wasn't as well corrected, and the narrow AFOV feels a little too claustrophobic when viewing some nebula's. But I will still keep it as it is certainly not a useless lens.

Hopefully someone will find this review helpful, as it's been difficult dredging through countless reviews of different eyepieces that make no mention of the type & F/L of scope they're used in.

Thanks for reading everyone.
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  #27  
Old 10-05-2019, 07:05 AM
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DeWynter (ILYA)
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Originally Posted by knightrider View Post
- Budget of $50-$130...?

- 26mm ES62 - Probably out of my price range... I haven't done any digging on these yet.
I cannot comment on ES in fast Newt, but in terms of pricing... For $144 AUD you can get 24mm ES68 at https://www.aliexpress.com/item/Expl...885867117.html
$155.42 - $7.28 (seller's coupon) - $4.37 (new user coupon) = $143.77
If you do that in AliExpress app on mobile phone it will be even cheaper - something like $141. These ES eyepieces are not fake. They are the real one.

Food for thoughts.
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  #28  
Old 10-05-2019, 09:06 AM
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mental4astro (Alexander)
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Knightrider,

There is something to remember about plossls - it is a nearly 160 year old design optimized for slower Newts than available today, and it does not use the same exotic glass types available today - there will be some performance "difficulties" compared to many contemporary designs, including modestly priced ones. Even those plossls made to higher standards with really good quality optical glass and the very best coatings, you may notice some aberrations.

Your review of that 25mm HD-60 is a very good one! You've come to recognize the difference between coma and astigmatism, and by your account astigmatism is really well controlled. Coma is not a flaw in the eyepiece, so don't think it is something to dismiss the eyepiece over.

I have no experience with the HD-60 line. But your review is an excellent help if I was looking for info on how that particular 25mm performs in a Newt.

Only other way to round off your review is to try out the same EP in a refractor, namely an apo, as these will be best corrected for chromatic aberration. If you have a friend with say a Skywatcher ED80, that would be good enough. AND if you could also test it in an achro (fast and slow) and an SCT or Mak, then you've hit the review jackpot in covering all the major scope designs. I guess I am fortunate in that I do have samples of most of these scope designs, or easy access to friend's scopes, and this is something I try to do to become familiar with the EPs I use. This experience is what I look to share, or those reviews carried out in similar ways, and never hear-say. Hear-say only fosters ignorance and brand prejudice.

The HD-60 line may be designed optimized for a convex focal plane (refractors, SCT's and Maks), I don't know. Yet your review of the 25mm IN A NEWT is ONLY for that 25mm in a NEWT. Do not make performance calls about THIS 25mm in other scopes, nor assume that the other focal lengths in the HD-60 series will perform the same in a Newt or in any other scope. Contemporary EP design is much too complex for such simple assumptions. Thinking carefully about what you read in reviews can open up a world of really good EPs that are best suited to the scope/scopes YOU HAVE, and that will cover a modest budget all the way to the most exotic.

Alex.
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