Achromat Vs Semi-APO Vs APO - What's The Difference?

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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#41

Post by notFritzArgelander »


Bowlerhat wrote: Mon May 31, 2021 2:26 am Other than scientific "APO", in practicality there are other definitions. Like "Marketing APO" - which brands just abused the term "Apo" for selling scopes which isn't..and there's also "Practically APO" which an experience of CA-free in non-APO scopes. I mean I use my classic scopes a lot and tbh I don't see CA (because of long focal length). There's also "Lens APO" where people start to define "apo" based on lens numbers..that doublets can't be APO, or the opposite. This is muddled up further by types of glass. FPL 51,53, 55, BK71, FCD 100, etc..

As a person who has used mirrors, achromats, EDs, fluorites..and eventually long achros, I'd say the term is rather flexible in the field. Personally, I'd just stick to Roland Christen's definition: "bringing 3 wavelengths to a common focus and be corrected for spherical aberration at two wavelengths."
While it's true that Roland Christen's use of the definition is correct, he was not the first to use the principle in designing lenses. So the definition isn't "his". The history of who authored the definition first is murky because optics companies in the 19th century kept a lot of data proprietary. The first practical example of an apochromatic lens used for telescopes (AFAIK) is the Cooke triplet in 1893 invented by Harold Dennis Taylor. But Zeiss's Ernst Abbe probably invented the concept earlier and applied it to microscopes in 1886, the current definition is from Abbe. So Christen is using Abbe's ideas.

https://en.wikipedia.org/wiki/Harold_Dennis_Taylor

https://en.wikipedia.org/wiki/Ernst_Abbe
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#42

Post by Bowlerhat »


notFritzArgelander wrote: Mon May 31, 2021 2:44 am
Bowlerhat wrote: Mon May 31, 2021 2:26 am Other than scientific "APO", in practicality there are other definitions. Like "Marketing APO" - which brands just abused the term "Apo" for selling scopes which isn't..and there's also "Practically APO" which an experience of CA-free in non-APO scopes. I mean I use my classic scopes a lot and tbh I don't see CA (because of long focal length). There's also "Lens APO" where people start to define "apo" based on lens numbers..that doublets can't be APO, or the opposite. This is muddled up further by types of glass. FPL 51,53, 55, BK71, FCD 100, etc..

As a person who has used mirrors, achromats, EDs, fluorites..and eventually long achros, I'd say the term is rather flexible in the field. Personally, I'd just stick to Roland Christen's definition: "bringing 3 wavelengths to a common focus and be corrected for spherical aberration at two wavelengths."
While it's true that Roland Christen's use of the definition is correct, he was not the first to use the principle in designing lenses. So the definition isn't "his". The history of who authored the definition first is murky because optics companies in the 19th century kept a lot of data proprietary. The first practical example of an apochromatic lens used for telescopes (AFAIK) is the Cooke triplet in 1893 invented by Harold Dennis Taylor. But Zeiss's Ernst Abbe probably invented the concept earlier and applied it to microscopes in 1886, the current definition is from Abbe. So Christen is using Abbe's ideas.

https://en.wikipedia.org/wiki/Harold_Dennis_Taylor

https://en.wikipedia.org/wiki/Ernst_Abbe
Yeah, the debate starts to pick up again when modern commercial scopes are starting to be more available and affordable. Of course there are examples prior.
I just think technical debates about it won't end because there are so many factors about it. Funnily it also birthed to "Mirror APOs" which circlejerks from mirror users that "well just use reflectors because then it'd be "CA-free!"

I've gone behind debating about it since I use classic scopes, it doens't matter much to me anymore, hahaha :lol:
Cats: Lomo mini mak, Acuter Maksy 60, Celestron C5 XLT
Refractors: Tak FC60NZ, Vixen custom 60/910, Vixen FL102s, Vixen Ozuma, Zeiss Telementor II, , Goto Kogaku 65mm, Nippon Kogaku 65mm, etc
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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#43

Post by notFritzArgelander »


Bowlerhat wrote: Mon May 31, 2021 2:54 am
notFritzArgelander wrote: Mon May 31, 2021 2:44 am
Bowlerhat wrote: Mon May 31, 2021 2:26 am Other than scientific "APO", in practicality there are other definitions. Like "Marketing APO" - which brands just abused the term "Apo" for selling scopes which isn't..and there's also "Practically APO" which an experience of CA-free in non-APO scopes. I mean I use my classic scopes a lot and tbh I don't see CA (because of long focal length). There's also "Lens APO" where people start to define "apo" based on lens numbers..that doublets can't be APO, or the opposite. This is muddled up further by types of glass. FPL 51,53, 55, BK71, FCD 100, etc..

As a person who has used mirrors, achromats, EDs, fluorites..and eventually long achros, I'd say the term is rather flexible in the field. Personally, I'd just stick to Roland Christen's definition: "bringing 3 wavelengths to a common focus and be corrected for spherical aberration at two wavelengths."
While it's true that Roland Christen's use of the definition is correct, he was not the first to use the principle in designing lenses. So the definition isn't "his". The history of who authored the definition first is murky because optics companies in the 19th century kept a lot of data proprietary. The first practical example of an apochromatic lens used for telescopes (AFAIK) is the Cooke triplet in 1893 invented by Harold Dennis Taylor. But Zeiss's Ernst Abbe probably invented the concept earlier and applied it to microscopes in 1886, the current definition is from Abbe. So Christen is using Abbe's ideas.

https://en.wikipedia.org/wiki/Harold_Dennis_Taylor

https://en.wikipedia.org/wiki/Ernst_Abbe
Yeah, the debate starts to pick up again when modern commercial scopes are starting to be more available and affordable. Of course there are examples prior.
I just think technical debates about it won't end because there are so many factors about it. Funnily it also birthed to "Mirror APOs" which circlejerks from mirror users that "well just use reflectors because then it'd be "CA-free!"

I've gone behind debating about it since I use classic scopes, it doens't matter much to me anymore, hahaha :lol:
I'm not much interested in the debate either. I divide the usages into the "technically correct" three wavelengths in the same focus plane and the "marketing hype". In the past I had the use of a 19th century Zeiss 5" apo and an 18.5 inch Alvan Clark achro. Student days were sweet.... ;)
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#44

Post by Bigzmey »


The topic could be as simple or as confusing as people make it. It often comes down to "my scope is more APO than yours because it has FPL 53 glass", there is no hope there. :lol:

However, the way I see it is that if you can't detect CA visually or by AP then the scope is APO for your purpose. It could be slow achro, or well made ED doublet or (obviously) reflector or SCT.

Easy to decide/test for scopes you already have, but purchasing the next one could be complicated. I have been thinking about 6" APO/ED scope for awhile. ED doublets are more affordable, lighter and easier to balance, but my guts tell that I will see CA in them no matter what people say. 6" APO triplets... they are just too rich for my wallet. At the end I went with 9.25" Edge SCT for about half of the price of new 6" ED doublet. :D
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#45

Post by Refractordude »


Bigzmey wrote: Wed Jun 02, 2021 10:21 pm The topic could be as simple or as confusing as people make it. It often comes down to "my scope is more APO than yours because it has FPL 53 glass", there is no hope there. :lol:

However, the way I see it is that if you can't detect CA visually or by AP then the scope is APO for your purpose. It could be slow achro, or well made ED doublet or (obviously) reflector or SCT.

Easy to decide/test for scopes you already have, but purchasing the next one could be complicated. I have been thinking about 6" APO/ED scope for awhile. ED doublets are more affordable, lighter and easier to balance, but my guts tell that I will see CA in them no matter what people say. 6" APO triplets... they are just too rich for my wallet. At the end I went with 9.25" Edge SCT for about half of the price of new 6" ED doublet. :D
It only cost five cents to turn my 150mm f/8 achro into a 150mm f/12 APO with a 4 inch cardboard mask. Nice
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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#46

Post by Bigzmey »


Refractordude wrote: Wed Jun 02, 2021 10:32 pm
Bigzmey wrote: Wed Jun 02, 2021 10:21 pm The topic could be as simple or as confusing as people make it. It often comes down to "my scope is more APO than yours because it has FPL 53 glass", there is no hope there. :lol:

However, the way I see it is that if you can't detect CA visually or by AP then the scope is APO for your purpose. It could be slow achro, or well made ED doublet or (obviously) reflector or SCT.

Easy to decide/test for scopes you already have, but purchasing the next one could be complicated. I have been thinking about 6" APO/ED scope for awhile. ED doublets are more affordable, lighter and easier to balance, but my guts tell that I will see CA in them no matter what people say. 6" APO triplets... they are just too rich for my wallet. At the end I went with 9.25" Edge SCT for about half of the price of new 6" ED doublet. :D
It only cost five cents to turn my 150mm f/8 achro into a 150mm f/12 APO with a 4 inch cardboard mask. Nice
Strictly speaking to 100mm F12, but yes that's the way to go.
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#47

Post by Lady Fraktor »


Refractordude wrote: Wed Jun 02, 2021 10:32 pm It only cost five cents to turn my 150mm f/8 achro into a 150mm f/12 APO with a 4 inch cardboard mask. Nice
It will not be a apochromatic, the colour blur will be lessened slightly though.
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#48

Post by Refractordude »


Lady Fraktor wrote: Thu Jun 03, 2021 4:34 am
Refractordude wrote: Wed Jun 02, 2021 10:32 pm It only cost five cents to turn my 150mm f/8 achro into a 150mm f/12 APO with a 4 inch cardboard mask. Nice
It will not be a apochromatic, the colour blur will be lessened slightly though.
With my scope a four inch mask eliminates the blur a whole lot. With a three inch mask it is completely eliminated, but I lose resolution. This Celestron 150mm f/8 is great. There really is no need for the mask, but there is a slightly/barely noticeable yellow hue I see on the surface of the Moon. There is also a thin blue line on the edge of the Moon. With my Meade LX70 120mm f/8.3 the false color is very obvious with Moon craters fulled with blue.
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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#49

Post by Lady Fraktor »


Have you checked focuser alignment and lens collimation?
Granted these are large achromats with simple magnesium coatings but they do a good job.
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#50

Post by Refractordude »


Lady Fraktor wrote: Thu Jun 03, 2021 8:59 pm Have you checked focuser alignment and lens collimation?
Granted these are large achromats with simple magnesium coatings but they do a good job.
The Meade can not be collimated.
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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#51

Post by Lady Fraktor »


Refractordude wrote: Thu Jun 03, 2021 9:09 pm
Lady Fraktor wrote: Thu Jun 03, 2021 8:59 pm Have you checked focuser alignment and lens collimation?
Granted these are large achromats with simple magnesium coatings but they do a good job.
The Meade can not be collimated.
I will send a PM
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#52

Post by notFritzArgelander »


Refractordude wrote: Thu Jun 03, 2021 9:09 pm
Lady Fraktor wrote: Thu Jun 03, 2021 8:59 pm Have you checked focuser alignment and lens collimation?
Granted these are large achromats with simple magnesium coatings but they do a good job.
The Meade can not be collimated.
That is a surprise. I had the Orion version of the same scope and successfully collimated the objective lens which led to an outstanding improvement in performance.
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#53

Post by Lady Fraktor »


I looked at some images online and it appears the Meade does not have a push/ pull system
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#54

Post by notFritzArgelander »


Lady Fraktor wrote: Thu Jun 03, 2021 10:01 pm I looked at some images online and it appears the Meade does not have a push/ pull system
Well that’s disappointing. If you could collimate the optics would be fine. I sometimes think about reacquiring the scope. Since the Celestron version seems to have a push-pull cell, it can still be considered.
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#55

Post by Bigzmey »


notFritzArgelander wrote: Thu Jun 03, 2021 10:09 pm
Lady Fraktor wrote: Thu Jun 03, 2021 10:01 pm I looked at some images online and it appears the Meade does not have a push/ pull system
Well that’s disappointing. If you could collimate the optics would be fine. I sometimes think about reacquiring the scope. Since the Celestron version seems to have a push-pull cell, it can still be considered.
Orion/Celestron/SW achros are all made by Synta. I believe Meade outsources to a different company.
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: Achromat Vs Semi-APO Vs APO - What's The Difference?

#56

Post by Lady Fraktor »


Bigzmey wrote: Thu Jun 03, 2021 10:51 pm
notFritzArgelander wrote: Thu Jun 03, 2021 10:09 pm
Lady Fraktor wrote: Thu Jun 03, 2021 10:01 pm I looked at some images online and it appears the Meade does not have a push/ pull system
Well that’s disappointing. If you could collimate the optics would be fine. I sometimes think about reacquiring the scope. Since the Celestron version seems to have a push-pull cell, it can still be considered.
Orion/Celestron/SW achros are all made by Synta. I believe Meade outsources to a different company.
Synta actually only makes certain sizes of SCT (the rest are made in USA), all of the refractors are outsourced.
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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dagadget United States of America
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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#57

Post by dagadget »


Bigzmey wrote: Wed Jun 02, 2021 10:21 pm The topic could be as simple or as confusing as people make it. It often comes down to "my scope is more APO than yours because it has FPL 53 glass", there is no hope there. :lol:

However, the way I see it is that if you can't detect CA visually or by AP then the scope is APO for your purpose. It could be slow achro, or well made ED doublet or (obviously) reflector or SCT.

Easy to decide/test for scopes you already have, but purchasing the next one could be complicated. I have been thinking about 6" APO/ED scope for awhile. ED doublets are more affordable, lighter and easier to balance, but my guts tell that I will see CA in them no matter what people say. 6" APO triplets... they are just too rich for my wallet. At the end I went with 9.25" Edge SCT for about half of the price of new 6" ED doublet. :D
Going to have to let you try my AT 152EDT sometime. Can you spell road trip? Or not but my AT 152 does not have FPL 53 but I have not seen color in it either. FK-61 Glass with Lanthanum and at F/8 I have pushed it very hard indeed. Very nose heavy but that I can deal with.
Astro-Tech AT 152EDT Ioptron GEM 45 Mount AKA FracZilla
Celestron C11 Carbon Fiber CGEM II Mount AKA Cloudzilla
Sky Watcher Mak Cas 180 Ioptron IEQ 30 AKA MoonZilla
AT 92 on IEQ 30 Pro AKA ClusterZilla
Home Made 8 inch Newtonian Reflector on Rocker Box AKA Scopezilla
Celestron 4 1/2 114 mm Newtonian Telescope 910 F/L GT Mount AKA Frankenscope.


David
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Bigzmey United States of America
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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#58

Post by Bigzmey »


dagadget wrote: Fri Jun 25, 2021 5:32 pm
Bigzmey wrote: Wed Jun 02, 2021 10:21 pm The topic could be as simple or as confusing as people make it. It often comes down to "my scope is more APO than yours because it has FPL 53 glass", there is no hope there. :lol:

However, the way I see it is that if you can't detect CA visually or by AP then the scope is APO for your purpose. It could be slow achro, or well made ED doublet or (obviously) reflector or SCT.

Easy to decide/test for scopes you already have, but purchasing the next one could be complicated. I have been thinking about 6" APO/ED scope for awhile. ED doublets are more affordable, lighter and easier to balance, but my guts tell that I will see CA in them no matter what people say. 6" APO triplets... they are just too rich for my wallet. At the end I went with 9.25" Edge SCT for about half of the price of new 6" ED doublet. :D
Going to have to let you try my AT 152EDT sometime. Can you spell road trip? Or not but my AT 152 does not have FPL 53 but I have not seen color in it either. FK-61 Glass with Lanthanum and at F/8 I have pushed it very hard indeed. Very nose heavy but that I can deal with.
Good to hear David! For now 9.25" Edge fills my requirements nicely, but I love to hear about other people experiences with 6" fracs.
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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John Baars Netherlands
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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#59

Post by John Baars »


Bigzmey wrote: Fri Jun 25, 2021 5:54 pm but I love to hear about other people experiences with 6" fracs.
Some economic priced Skywatcher refractors have no push-pull screws. I had a discussion with a another Dutch owner of a 150mm F5 Startravel refractor like me. He wanted a better red-focus and did this by decreasing the spacing between the two lenses.

More important was the fact that he noticed the collimation changed every time he screwed the lens-cell on the tube. Even if the lens cell ended in the same position as before. A strong indication of the coarse ( maybe even slightly skewed? ) thread on the tube. He thought of placing a spacer in the lens cel underneath the lens, but that was not the right solution. The final configuration kept on being unpredictable.

He solved the problem by winding some gas fitter tape around the threaded end of the tube and than screwing the lens cell on. Very near to the final quarter turn he started looking at his collimating device and stopped when collimation seemed ok. Result is a well collimated instrument, even though the lens cell has no push-pull screws.

I thought you might want to know.
Refractors in frequency of use : *SW Evostar 120ED F/7.5 (all round ), * Vixen 102ED F/9 (vintage), both on Vixen GPDX.
GrabnGo on Alt/AZ : *SW Startravel 102 F/5 refractor( widefield, Sun, push-to), *OMC140 Maksutov F/14.3 ( planets).
Most used Eyepieces: *Panoptic 24, *Morpheus 14, *Leica ASPH zoom, *Zeiss barlow, *Pentax XO5.
Commonly used bino's : *Jena 10X50 , * Canon 10X30 IS, *Swarovski Habicht 7X42, * Celestron 15X70, *Kasai 2.3X40
Rijswijk Public Observatory: * Astro-Physics Starfire 130 f/8, * 6 inch Newton, * C9.25, * Meade 14 inch LX600 ACF, *Lunt.
Amateur astronomer since 1970.
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Re: Achromat Vs Semi-APO Vs APO - What's The Difference?

#60

Post by Bigzmey »


John Baars wrote: Sat Jun 26, 2021 11:10 pm
Bigzmey wrote: Fri Jun 25, 2021 5:54 pm but I love to hear about other people experiences with 6" fracs.
Some economic priced Skywatcher refractors have no push-pull screws. I had a discussion with a another Dutch owner of a 150mm F5 Startravel refractor like me. He wanted a better red-focus and did this by decreasing the spacing between the two lenses.

More important was the fact that he noticed the collimation changed every time he screwed the lens-cell on the tube. Even if the lens cell ended in the same position as before. A strong indication of the coarse ( maybe even slightly skewed? ) thread on the tube. He thought of placing a spacer in the lens cel underneath the lens, but that was not the right solution. The final configuration kept on being unpredictable.

He solved the problem by winding some gas fitter tape around the threaded end of the tube and than screwing the lens cell on. Very near to the final quarter turn he started looking at his collimating device and stopped when collimation seemed ok. Result is a well collimated instrument, even though the lens cell has no push-pull screws.

I thought you might want to know.
Good tip John! This seems to be reoccurring trend with 6" refractors, even some ED models. I saw a few reports that some don't hold collimation well and need frequent readjustments.
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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