Achromatic and apochromatic doublets

Discuss your refractor type scopes here.
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Achromatic and apochromatic doublets

#1

Post by James »


are all apochromatic doublets made out of ED glass and do they have the same design as achromatic ones?
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Re: Achromatic and apochromatic doublets

#2

Post by Bigzmey »


Mechanical and optical design is very similar. The only difference is that in APO doublet one of the two glass elements in the objective is replaced with ED glass.
Scopes: Stellarvue: SV102ED; Celestron: 9.25" EdgeHD, 8" SCT, 150ST, Onyx 80ED; iOptron: Hankmeister 6" Mak; SW: 7" Mak; Meade: 80ST.
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.

Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2382, Comets: 34, Asteroids: 255
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Re: Achromatic and apochromatic doublets

#3

Post by Lady Fraktor »


The general layout of the elements will be the same if comparing a Fraunhofer achro to a Fraunhofer apo or Steiheil apo to a Steinheil achro but you could not take the extra low dispersion element from one and put it in the other.

Each element has two specific curves needed for its focal length to make it mate to the other element(s)
You could likely replace a element from a mass produced achromat to another similar achromat or apo to apo but not achro to apo, the different curves would not match up.
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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Re: Achromatic and apochromatic doublets

#4

Post by Lady Fraktor »


To your first question, any ED doublet will have one element made of extra low dispersion glass, Lanthanum is a common mating lens.
Each glass type (FPL-53, OK-4, FPL-55, etc) will have a designed curve to mate with the extra element.
Focal length design, style of design (Fraunhofer, Baker, etc) and precision of figuring/ polishing will also dictate needed curves.

Is there something specific you are looking for?
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
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Re: Achromatic and apochromatic doublets

#5

Post by Refractordude »


Why do the Skywatcher ED doublets cost more than some Explore Scientific triplets? The least expensive triplet should cost more than an ED doublet of the same aperture, but that is not always the case. I love my 150mm f/8 achromatic. For very distant objects like galaxies I use full aperture. For closer brighter objects I use a 100mm or 90mm aperture mask. However, a 150mm Ed doublet would be nice to own. What would you say is the best 150mm ED doublet under $3000? The first question is more important to me. Left click the images. Thanks all
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Re: Achromatic and apochromatic doublets

#6

Post by notFritzArgelander »


It's not a simple matter of counting optical surfaces. Figuring, polishing and testing cost time and money. Not all companies make the same effort for each optical surface.
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: Achromatic and apochromatic doublets

#7

Post by messier 111 »


Refractordude wrote: Mon Feb 08, 2021 11:38 pm Why do the Skywatcher ED doublets cost more than some Explore Scientific triplets? The least expensive triplet should cost more than an ED doublet of the same aperture, but that is not always the case. I love my 150mm f/8 achromatic. For very distant objects like galaxies I use full aperture. For closer brighter objects I use a 100mm or 90mm aperture mask. However, a 150mm Ed doublet would be nice to own. What would you say is the best 150mm ED doublet under $3000? The first question is more important to me. Left click the images. Thanks all
Image
Image
From what I was told, here it would be a case of pure marketing, the 120 ed that sells very very well.
I spoke to two dealers, one told me that the glass used by sw was also of better quality and that explored just want to have a market share.
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Re: Achromatic and apochromatic doublets

#8

Post by Bigzmey »


Refractordude wrote: Mon Feb 08, 2021 11:38 pm Why do the Skywatcher ED doublets cost more than some Explore Scientific triplets? The least expensive triplet should cost more than an ED doublet of the same aperture, but that is not always the case. I love my 150mm f/8 achromatic. For very distant objects like galaxies I use full aperture. For closer brighter objects I use a 100mm or 90mm aperture mask. However, a 150mm Ed doublet would be nice to own. What would you say is the best 150mm ED doublet under $3000? The first question is more important to me. Left click the images. Thanks all
Image
Image
When I was looking for my first APO/ED scope I have asked the same question as you and went with my guts and better price. I bought ES 100mm APO triplet over SW doublet, and it was a great scope. Later I trade it up for ES 127mm APO which was well made scope to. So, no regrets here going with ES. ES also comes with better focuser and machined rings.

Now, from what I hear SW doublets are good performers to. But, based on my experience I don't believe they are optically better than ES triplets. Although there are advantages of doublets for visual (faster acclimation time, easier to collimate, easier to balance).

For the second part of the question, I have considered 6" APO/ED frac so many times, but I feel that the much better (and cheaper) option is Celestron Edge HD SCT. From what I read 150mm ED doublet under $3000 are not that well corrected for CA, some also have collimation issues. I have traded my ES 127 APO triplet for Edge HD 9.25" and very happy with the result.
Scopes: Stellarvue: SV102ED; Celestron: 9.25" EdgeHD, 8" SCT, 150ST, Onyx 80ED; iOptron: Hankmeister 6" Mak; SW: 7" Mak; Meade: 80ST.
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.

Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2382, Comets: 34, Asteroids: 255
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Re: Achromatic and apochromatic doublets

#9

Post by AstroBee »


I can't speak to the SkyWatcher models but I have the E.S. ED127mm model you posted above and I've been extremely happy with it. Both visually and imaging with the E.S. 3" 0.7x reducer/flattener.
All of the images I've posted here were taken with that setup.
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Re: Achromatic and apochromatic doublets

#10

Post by Refractordude »


AstroBee wrote: Tue Feb 09, 2021 4:08 am I can't speak to the SkyWatcher models but I have the E.S. ED127mm model you posted above and I've been extremely happy with it. Both visually and imaging with the E.S. 3" 0.7x reducer/flattener.
All of the images I've posted here were taken with that setup.
Any violet color at high mag?
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Re: Achromatic and apochromatic doublets

#11

Post by AstroBee »


Refractordude wrote: Tue Feb 09, 2021 4:56 am
AstroBee wrote: Tue Feb 09, 2021 4:08 am I can't speak to the SkyWatcher models but I have the E.S. ED127mm model you posted above and I've been extremely happy with it. Both visually and imaging with the E.S. 3" 0.7x reducer/flattener.
All of the images I've posted here were taken with that setup.
Any violet color at high mag?
None that I've ever noticed. And I also have their 152mm doublet. The purple fringing is very apparent through it.
Greg M.~ "Ad Astra per Aspera"
Scopes: Celestron EdgeHD14", Explore Scientific ED152CF & ED127 APO's, StellarVue SV70T, Classic Orange-Tube C-8, Lunt 80mm Ha double-stack solar scope.
Mounts: Astro-Physics Mach One, iOptron CEM70EC Mount, iOptron ZEQ25 Mount.
Cameras: ZWO ASI2600mm Pro, ZWO 2600MC Pro, ZWO ASI1600mm
Filters: 36mm Chroma LRGB & 3nm Ha, OIII, SII, L-Pro, L-eXtreme
Eyepieces: 27mm TeleVue Panoptic, 4mm TeleVue Radian, Explore Scientific 82° 30mm, 6.7mm , Baader 13mm Hyperion, Explore Scientific 70° 10mm, 15mm, 20mm, Meade 8.8mm UWA
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Re: Achromatic and apochromatic doublets

#12

Post by pakarinen »


Is lanthanum really worth the extra cost or is it just marketing? I'd Google, but I'm lazy. ;)
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Re: Achromatic and apochromatic doublets

#13

Post by notFritzArgelander »


pakarinen wrote: Fri Jun 04, 2021 1:38 pm Is lanthanum really worth the extra cost or is it just marketing? I'd Google, but I'm lazy. ;)
:text-thankyoublue:
Totally worth it.
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: Achromatic and apochromatic doublets

#14

Post by notFritzArgelander »


pakarinen wrote: Fri Jun 04, 2021 1:38 pm Is lanthanum really worth the extra cost or is it just marketing? I'd Google, but I'm lazy. ;)
:text-thankyoublue:
Let me back off my "totally worth it" to the extent of adding a "within reason". What are you thinking of getting?
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: Achromatic and apochromatic doublets

#15

Post by Greenman »


As far as I can see it is a mixed bag, Explore triplets have a good reputation, but they don’t use FPL53 (rather going for Hoya FCD001 ED). As said elsewhere, the matching and machine work, air spacing etc. all affect the performance. Waving FPL53, triplet etc. are marketing ways of selling by specification. At the end of the day, we are being sold to.

Forums tend to be full of people saying, you must have a; XYZ; ABC; or DEF for this or that. Read reviews, in a wide variety, watch videos, and at the end of the day make your choice for your work.

As a salesman I can honestly tell you that specifications are a marketing ploy, often the more glorified the specification the more hyped the product. I work for a top end spectrometer company, our competitors carefully tune their specifications to beat ours on paper. How do we combat this? Happily invite them to do a side-by-side comparison- that is reality.

Want to compare telescopes - find a way to look through them... :Astronomer1: 8-)
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Re: Achromatic and apochromatic doublets

#16

Post by pakarinen »


notFritzArgelander wrote: Fri Jun 04, 2021 4:48 pm
pakarinen wrote: Fri Jun 04, 2021 1:38 pm Is lanthanum really worth the extra cost or is it just marketing? I'd Google, but I'm lazy. ;)
:text-thankyoublue:
Let me back off my "totally worth it" to the extent of adding a "within reason". What are you thinking of getting?
80mm F7 EDL. I'd sell my ST80 and ST120 to help finance it. Or not. :whistle:
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Re: Achromatic and apochromatic doublets

#17

Post by Lady Fraktor »


pakarinen wrote: Fri Jun 04, 2021 6:59 pm 80mm F7 EDL. I'd sell my ST80 and ST120 to help finance it. Or not. :whistle:
Do you have a link to share?
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
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Re: Achromatic and apochromatic doublets

#18

Post by notFritzArgelander »


If you mean this one?

https://www.teleskop-express.de/shop/pr ... ektiv.html

Then totally worth it. I paid $600 for the SV ED80 Access which is ED + lanthanum and I am very, very happy with it. I think the OEM is the same. The SV had a higher price because of additional QC.
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: Achromatic and apochromatic doublets

#19

Post by BFaucett »


Lady Fraktor wrote: Fri Jun 04, 2021 7:03 pm
pakarinen wrote: Fri Jun 04, 2021 6:59 pm 80mm F7 EDL. I'd sell my ST80 and ST120 to help finance it. Or not. :whistle:
Do you have a link to share?

from Astronomics
ASTRO-TECH AT80EDL REFRACTOR OTA FCD-100 AND LANTHANUM F/7 DOUBLET
https://www.astronomics.com/astro-tech- ... -3515.html

Cheers! Bob F.
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Re: Achromatic and apochromatic doublets

#20

Post by notFritzArgelander »


BFaucett wrote: Fri Jun 04, 2021 7:55 pm
Lady Fraktor wrote: Fri Jun 04, 2021 7:03 pm
pakarinen wrote: Fri Jun 04, 2021 6:59 pm 80mm F7 EDL. I'd sell my ST80 and ST120 to help finance it. Or not. :whistle:
Do you have a link to share?

from Astronomics
ASTRO-TECH AT80EDL REFRACTOR OTA FCD-100 AND LANTHANUM F/7 DOUBLET
https://www.astronomics.com/astro-tech- ... -3515.html

Cheers! Bob F.
Yes, that would work too.
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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