90mm Doublets?

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pakarinen United States of America
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90mm Doublets?

#1

Post by pakarinen »


I see 90mm triplets for sale all over the place and several 90mm achros, but no 90EDs. Any reason why there aren't any doublets? Too much overlap with 80mm and 102mm? Just curious. :think:
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Re: 90mm Doublets?

#2

Post by Lady Fraktor »


There used to be a lot of 90 mm triplets and doublets but the market seems to prefer 80 mm and 102 mm at the moment. Wait 5 years ;)

The brain needs about 20 mm aperture difference to see any significant difference in the view if all parameters between the refractors are equal.
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: 90mm Doublets?

#3

Post by Bigzmey »


pakarinen wrote: Mon Mar 20, 2023 6:06 pm I see 90mm triplets for sale all over the place and several 90mm achros, but no 90EDs. Any reason why there aren't any doublets? Too much overlap with 80mm and 102mm? Just curious. :think:
Would you buy 90ED though if you have 102ED?
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: 90mm Doublets?

#4

Post by Nakedgun »


~

The only doublet apochromat I'm aware of is this one:

https://www.sciencecenter.net/hutech/pr ... age/10.htm



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Re: 90mm Doublets?

#5

Post by Lady Fraktor »


Bigzmey wrote: Mon Mar 20, 2023 7:38 pm
pakarinen wrote: Mon Mar 20, 2023 6:06 pm I see 90mm triplets for sale all over the place and several 90mm achros, but no 90EDs. Any reason why there aren't any doublets? Too much overlap with 80mm and 102mm? Just curious. :think:
Would you buy 90ED though if you have 102ED?
If it was something unique I may, if just a regular refractor off the shelf most likely not.
A bit like my current 100 mm f/10 and 105 mm f/9.5?

Remember a supposed ED is just a slightly better corrected achromat
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: 90mm Doublets?

#6

Post by Lady Fraktor »


Nakedgun wrote: Tue Mar 21, 2023 3:46 am The only doublet apochromat I'm aware of is this one:
https://www.sciencecenter.net/hutech/pr ... age/10.htm
They should just call that a camera lens :lol:
Though with a Panoptic 41 mm it would give just under a 5° FOV if your into widefield viewing.

If you keep a eye on the Stellarvue site a pre-owned 90 mm Raptor will occasionally appear for sale. Wonderful telescopes
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: 90mm Doublets?

#7

Post by pakarinen »


I would consider a 90mm, depending on needs /circumstances - smaller, lighter, cheaper than a 102 ED - like if I were downsizing. Or maybe not. :think:
=============================================================================
I drink tea, I read books, I look at stars when I'm not cursing clouds. It's what I do.
=============================================================================
AT50, AT72EDII, ST80, ST102; Scopetech Zero, AZ-GTi, AZ Pronto; Innorel RT90C, Oberwerk 5000; Orion Giantview 15x70s, Vortex 8x42s, Navy surplus 7x50s, Nikon 10x50s
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Re: 90mm Doublets?

#8

Post by Lady Fraktor »


Instead of unique I should have said purpose fit instead. Downsizing is a good example.
The SV 90 mm Raptor triplets are a carbon fibre tube.
From memory most 90 mm refractors tend to be longer focal lengths as well, Synta and Meade both produced some very nice achromats in the past.
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: 90mm Doublets?

#9

Post by Bigzmey »


Purpose fit, I like that. If one already has 80mm and 102mm, getting 90mm of similar design would cut it really thin. There will be not enough performance gain stepping up from 80mm or weight loss stepping down from 102mm. However, getting one of different design (ED vs achro, slow vs fast) would be worthy consideration.

For me getting 80mm was purpose fit. My Onyx ED just barely fits carry-on pelican case. An inch longer and it would not be air travel friendly.
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: 90mm Doublets?

#10

Post by Nakedgun »


Lady Fraktor wrote: Tue Mar 21, 2023 4:38 am
Nakedgun wrote: Tue Mar 21, 2023 3:46 am The only doublet apochromat I'm aware of is this one:
https://www.sciencecenter.net/hutech/pr ... age/10.htm
They should just call that a camera lens :lol:

~

Visual only, for me.


:

IMGP5103 - Copy (4).JPG
:



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Re: 90mm Doublets?

#11

Post by Lady Fraktor »


Nakedgun wrote: Wed Mar 22, 2023 12:47 am Visual only, for me.
The best way, insert eyepiece and view. None of that voodoo the AP people participate in!

I have never seen a Borg refractor here before, how are they for views/ build quality?
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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Re: 90mm Doublets?

#12

Post by pakarinen »


Borg 90. <Sigh> And there is/was one for sale on AM. Unfortunately, I don't have that much dinero in the astro budget right now.
=============================================================================
I drink tea, I read books, I look at stars when I'm not cursing clouds. It's what I do.
=============================================================================
AT50, AT72EDII, ST80, ST102; Scopetech Zero, AZ-GTi, AZ Pronto; Innorel RT90C, Oberwerk 5000; Orion Giantview 15x70s, Vortex 8x42s, Navy surplus 7x50s, Nikon 10x50s
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