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What site do you use to purchase APM HDC eyepieces?

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31 replies to this topic

#26 sixela

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Posted 31 July 2020 - 09:43 AM

I don't think the EOFB is just the barrel distortion, frankly.

Someone posted a comparison with a Docter, which shows no EOFB even though it's got quite some barrel distortion.

#27 Starman1

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Posted 31 July 2020 - 10:27 AM

I have had two overnight outings with the 12.5mm APM.

In one overnight, the skies were clear, very dry, and dark, with no haze at all in the air.  I noticed no EOFB.

[12.5" with Paracorr @f/5.75]

In the other overnight, the skies were clear, not dry, and with a little more haze in the air.  I did notice EOFB.

But that night I also noticed it in about a half dozen other eyepieces not known to have any EOFB.

So is the EOFB environmental, or intrinsic to the eyepiece?  The jury is still out.

My next time out, I will make a point to look specifically for it in every eyepiece I use.



#28 SeattleScott

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Posted 31 July 2020 - 10:34 AM

I don't think the EOFB is just the barrel distortion, frankly.

Someone posted a comparison with a Docter, which shows no EOFB even though it's got quite some barrel distortion.

I think Don said maybe it was the combination of two types of distortion that seemed to cause EOFB in light pollution. The distortion on the APM is partly similar and partly different from what I understand.

Scott

#29 Starman1

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Posted 31 July 2020 - 10:47 AM

Yes, but EOFB isn't fully understood.

 

it seems to vary with f/ratio of scope, for example 

   so the angle of incidence matters

it definitely becomes more visible in less transparent air or where more atmospheric light scatter occurs.

   so there are environmental factors involved.  Perhaps the eyepiece characteristics magnify the atmospheric issues.

it is also a different % of the field in different eyepieces

   so the focal length and internal construction have something to do with it.

it can be reduced with baffling, lens edge blackening, barrel darkening, etc. in eyepieces that have it, but not eliminated entirely.

   so at least some of it can be blamed on the internal construction of the eyepiece.

it is visible in eyepieces with pincushion distortion and with barrel distortion

   so it is not simply due to the distortion characteristics of the eyepiece.

it is only an edge of field issue, so something is going on optically that enhances light scatter at the edge of the field but not the middle.

 

If it were completely understood, it would become common knowledge how to avoid it.  That it isn't avoided says it is not yet understood, or even acknowledged.


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#30 Tacosauce

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Posted 31 July 2020 - 03:29 PM

If it is a scam site it is a really good one. Unfortunately no address on website so you can’t go to local BBB to verify the company. But with the SSL and foreign currency conversion, it feels too polished to be a scam site. However I haven’t ever heard of it before so it is possible.

Scott

Thanks for checking it out :) 

After 4 or 5 eyepieces, the cost savings is significant. 


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#31 Voyager 3

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Posted 01 August 2020 - 08:39 AM

I have had two overnight outings with the 12.5mm APM.
In one overnight, the skies were clear, very dry, and dark, with no haze at all in the air. I noticed no EOFB.
[12.5" with Paracorr @f/5.75]
In the other overnight, the skies were clear, not dry, and with a little more haze in the air. I did notice EOFB.
But that night I also noticed it in about a half dozen other eyepieces not known to have any EOFB.
So is the EOFB environmental, or intrinsic to the eyepiece? The jury is still out.
My next time out, I will make a point to look specifically for it in every eyepiece I use.

Thanks Don I'm more eager than you for your next session 🙂😀

#32 quercuslobata

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Posted 01 August 2020 - 06:33 PM

https://luntsolarsystems.com

What about this site?

Eyepieces.etc does not have the 20mm in stock.

In my recent experience they don’t indicate on their website when things are out of stock - I was looking for something out of stock at eyepiecesetc, but it turns out that it was out of stock there too. So if you go that route you might want to call first.




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