What Causes Edge Of Field Brightness In Eyepieces?

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What Causes Edge Of Field Brightness In Eyepieces?

#1

Post by Refractordude »


Thanks to you all.
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Re: What Causes Edge Of Field Brightness In Eyepieces?

#2

Post by Lady Fraktor »


That is a debate that has been ongoing for years.
The only thing everyone seems to have concluded is the smaller the AFOV the less chance of it being seen.
Not all widefield eyepieces will show it either.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
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Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
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Re: What Causes Edge Of Field Brightness In Eyepieces?

#3

Post by Ruud »


It would have to be scattered light. After all, an eyepiece doesn't generates light by itself.

It could also be that what's really going on is centre of field darkening. After all, central rays travel through the central parts of the lenses, which are thicker.

It could further be an illusion, like a contrast effect between the region inside the edge of the field and the darker region outside.

It could be analogous to the canals on Mars: often reported, but not really there.

As long as we haven't resolved whether it is and what it is precisely we can't get much further.

I tend to think that if it is real it is scattered light and if it is not real a contrast effect.

If it is real it should be easy to record. How often has the effect been imaged? Photos would really help solve the question whether it is a thing at all and would provide a first step to reproducible data.
7x50 Helios Apollo 8x42 Bresser Everest 73mm f/5.9 WO APO 4" f/5 TeleVue Genesis 6" f/10 Celestron 6SE 0.63x reducer 1.8, 2, 2.5 and 3x Barlows eyepieces from 4.5 to 34mm
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Re: What Causes Edge Of Field Brightness In Eyepieces?

#4

Post by Lady Fraktor »


This is a image taken by William Pialoni using I believe a ES 82°
I think I bookmarked the thread so if I can find it later I will post it.
edge of field brightening.jpg
Apparently there are technical issues, please wait patiently :lol:
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
Eyepieces: Antares to Zeiss
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Re: What Causes Edge Of Field Brightness In Eyepieces?

#5

Post by notFritzArgelander »


Do you mean Bill Paolini?
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: What Causes Edge Of Field Brightness In Eyepieces?

#6

Post by Ruud »


I do know of one EOFB picture, probably the same Gabrielle is referring to, but that was taken in an almost completely dark room, using a telescope pointing straight at a wall. I too think it was BillP who posted it.

The problem with the setup used for this picture is that the telescope itself would block some of the weak ambient light reflected by the opposite wall, preventing it from reaching the spot where the telescope was pointing to. This would create a penumbra on the photographed wall with its darkest part in the centre of the telescope’s view.

So with the brightness values of the image stretched, one might expect that the centre of the field looks darker from the setup alone. This indeed is shown in the image. No EOFB needed.

The sort of pictures I would like to see would have to be taken from a dark site on a number of Moonless nights using an array of different eyepieces. If from these pictures, an eyepiece was found to consistently cause brighter edges we’d have something to study. Right now we only have anecdotes.

For now, in the absence of evidence of EOFB, I am inclined to believe it is not a thing in itself. I expect it is a combination of scattered or stray light or something like a contrast illusion, possibly even motivated imagination.
7x50 Helios Apollo 8x42 Bresser Everest 73mm f/5.9 WO APO 4" f/5 TeleVue Genesis 6" f/10 Celestron 6SE 0.63x reducer 1.8, 2, 2.5 and 3x Barlows eyepieces from 4.5 to 34mm
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Re: What Causes Edge Of Field Brightness In Eyepieces?

#7

Post by Lady Fraktor »


Yes the image you have seen is the one Bill took
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
Eyepieces: Antares to Zeiss
The only culture I have is from yogurt
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