2" EPs with an 8" SCT?

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Ylem
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2" EPs with an 8" SCT?

#1

Post by Ylem »

I use a FR/C and have been doing so for decades.
I have never tried 2" EPs nor do I own any.
So I was curious if others here have.

My other question is does the FR/C have to be removed, or can it be successfully used with the 2" EPs?
Clear Skies,
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Re: 2" EPs with an 8" SCT?

#2

Post by Bigzmey »

I have a few 2" EPs and use them on occasion, but 90% of my observing is carried with 1.25" EPs. The main purpose for 2" EPs is to get wider FOV.

You can get away with using 2' EPs in shorter focal range with FR. For 2" in 25-50mm range vignetting with FR will be quite noticeable.
Scopes: Stellarvue: SV102 ED F7; Celestron: 9.25" EdgeHD F10, 8" SCT F10, 6" SCT F10, Omni XLT 150R Achro F5, Onyx 80ED F6.3; Meade: 80ST Achro F5.
Mounts: ES: Twilight I; Bresser: EXOS2; SW: SkyTee2, AzGTi; UA: MicroStar.
Binos: Orion: Little Giant II 15x70, WorldView 10x50, Nikon: Action EX 16x50 & 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68s; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV; Russell Optics: SuperPlossls.
Diagonals: Baader: BBHS silver mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: Positive lock prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S; Astronomik: UHC, Orion: UltraBlock, SkyGlow.
Observing: DSOs: 1936 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 1498, S110: 77). Doubles: 1382, Comets: 15, Asteroids: 88
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Re: 2" EPs with an 8" SCT?

#3

Post by notFritzArgelander »

Whether the FR/C can be used successfully depends on the details. I've done so with happy results and with unhappy results. If you use too long a fl EP you might see the central obstruction.

I regularly used 2" eyepieces with and without the Astro Physics reducer on my Edge 9.25 when I had it. It worked just fine either way. I really enjoyed my 2" Panoptic EPs, Tak LE 50mm and others (various Gary Russell offerings) without.

My Intes MK66 takes 2" eyepieces and has been a great instrument overall but reducers give it fits! I have 2 Intes reducers and they're fine for imaging but visually unacceptable.

The Orion 127 Mak has a 1.25" visual back, doesn't it? I'm not sure if 2" eyepieces will be workable at all in it. Not only do you have to fight the central obstruction but there is the baffle diameter to consider. You might well NOT have enough open optical path to support a 2" eyepiece. What reducer are you using?

One solution that I love for getting wider field views out of a Mak is the GSO 1.25" 0.5x focal reducer. It screws into eyepieces like a filter and is cheap enough that you can buy several and avoid switching in the dark. I've dispensed with a finder scope for my VMC110L at f10 since I can get about a 3 degree TFOV with 25mm eyepiece.

I've also used 2" eyepieces with the VMC200L but haven't tried reducers with them yet.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: 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 III, Vixen Porta II, Celestron CG5, Orion Sirius EQG
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Re: 2" EPs with an 8" SCT?

#4

Post by Ylem »

notFritzArgelander wrote:
Fri Jun 26, 2020 12:56 am
Whether the FR/C can be used successfully depends on the details. I've done so with happy results and with unhappy results. If you use too long a fl EP you might see the central obstruction.

I regularly used 2" eyepieces with and without the Astro Physics reducer on my Edge 9.25 when I had it. It worked just fine either way. I really enjoyed my 2" Panoptic EPs, Tak LE 50mm and others (various Gary Russell offerings) without.

My Intes MK66 takes 2" eyepieces and has been a great instrument overall but reducers give it fits! I have 2 Intes reducers and they're fine for imaging but visually unacceptable.

The Orion 127 Mak has a 1.25" visual back, doesn't it? I'm not sure if 2" eyepieces will be workable at all in it. Not only do you have to fight the central obstruction but there is the baffle diameter to consider. You might well NOT have enough open optical path to support a 2" eyepiece. What reducer are you using?

One solution that I love for getting wider field views out of a Mak is the GSO 1.25" 0.5x focal reducer. It screws into eyepieces like a filter and is cheap enough that you can buy several and avoid switching in the dark. I've dispensed with a finder scope for my VMC110L at f10 since I can get about a 3 degree TFOV with 25mm eyepiece.

I've also used 2" eyepieces with the VMC200L but haven't tried reducers with them yet.
With regards to my Orion 127 Mak I also have been using the 6.3 FR with good results.

But you bring up a good point, The Orion is set up for 1.25 EPs, but the Skywatcher comes set up for 2" EPs. Same scope, 27mm port.

That's a head scratcher LOL
Clear Skies,
-Jeff :telescopewink:

Orion 127 Mak, ST80
Celestron Celestar
8SE, C90 Mak
A big box of Plossls :D
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Re: 2" EPs with an 8" SCT?

#5

Post by JayTee »

I use the Celestron .63 FR routinely on my C11. I also use explore scientific 30mm 82° and 20mm 100° eyepieces (both are 2 inchers). Using the 20mm 100° is like looking through a porthole into outer space. Your eye has no border reference so you feel like you're floating in space with this eyepiece. It is a very cool effect.

Cheers,
JT
∞ Scopes: Celestron CPC1100 #2 Scope: 8" f/7.5 Dob AP Scopes: TPO 6" f/9 RC, ES 80mm f/6 APO G&G Scopes: Meade 102mm f/7.8, Bresser 102mm f/4.5 Guide Scopes: 70 & 80mm fracs
∞ Mounts: iOptron CEM60, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
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Re: 2" EPs with an 8" SCT?

#6

Post by notFritzArgelander »

Ylem wrote:
Fri Jun 26, 2020 1:21 am
notFritzArgelander wrote:
Fri Jun 26, 2020 12:56 am
Whether the FR/C can be used successfully depends on the details. I've done so with happy results and with unhappy results. If you use too long a fl EP you might see the central obstruction.

I regularly used 2" eyepieces with and without the Astro Physics reducer on my Edge 9.25 when I had it. It worked just fine either way. I really enjoyed my 2" Panoptic EPs, Tak LE 50mm and others (various Gary Russell offerings) without.

My Intes MK66 takes 2" eyepieces and has been a great instrument overall but reducers give it fits! I have 2 Intes reducers and they're fine for imaging but visually unacceptable.

The Orion 127 Mak has a 1.25" visual back, doesn't it? I'm not sure if 2" eyepieces will be workable at all in it. Not only do you have to fight the central obstruction but there is the baffle diameter to consider. You might well NOT have enough open optical path to support a 2" eyepiece. What reducer are you using?

One solution that I love for getting wider field views out of a Mak is the GSO 1.25" 0.5x focal reducer. It screws into eyepieces like a filter and is cheap enough that you can buy several and avoid switching in the dark. I've dispensed with a finder scope for my VMC110L at f10 since I can get about a 3 degree TFOV with 25mm eyepiece.

I've also used 2" eyepieces with the VMC200L but haven't tried reducers with them yet.
With regards to my Orion 127 Mak I also have been using the 6.3 FR with good results.

But you bring up a good point, The Orion is set up for 1.25 EPs, but the Skywatcher comes set up for 2" EPs. Same scope, 27mm port.

That's a head scratcher LOL
But although the optical elements (primary, secondary, and meniscus) MIGHT be identical the different size visual backs implies differences in the baffling scheme. So... not the same scopes, I fear, is quite likely. If you have in mind modifying the visual back of your Orion to accept 2" EPs you need to check the baffling first.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: 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 III, Vixen Porta II, Celestron CG5, Orion Sirius EQG
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Re: 2" EPs with an 8" SCT?

#7

Post by Ylem »

From what I heard and read they are the identical scopes.

I have no desire to use 2 inchers with it, but the question why Skywatcher did that is certainly "baffling".
Marketing ploy I guess.

I'm on the fence if I want to even go that route with the C8.
Clear Skies,
-Jeff :telescopewink:

Orion 127 Mak, ST80
Celestron Celestar
8SE, C90 Mak
A big box of Plossls :D
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Re: 2" EPs with an 8" SCT?

#8

Post by notFritzArgelander »

Ylem wrote:
Fri Jun 26, 2020 12:39 pm
From what I heard and read they are the identical scopes.

I have no desire to use 2 inchers with it, but the question why Skywatcher did that is certainly "baffling".
Marketing ploy I guess.

I'm on the fence if I want to even go that route with the C8.
Well, since the baffling likely has to be different what you’ve heard and read about “identical scopes” is likely false. Only true in marketing tense.

Marketing tense is a verb form in which the sentence is true only until the customer buys one and looks at it carefully. Even if the optical elements are identical, the visual backs are different. If the baffling ISN’T different to accommodate that, then one of them will have inferior stray light control.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: 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 III, Vixen Porta II, Celestron CG5, Orion Sirius EQG
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Re: 2" EPs with an 8" SCT?

#9

Post by helicon »

I use 2" eyepieces about 80% of the time in both the 10" Dob and the 152mm Achro.
-Michael
Various scopes, 10" Zhumell Dob, ES AR152, AWB 5.1" Onesky newt, Oberwerk 25x100 binos, two eyeballs
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Re: 2" EPs with an 8" SCT?

#10

Post by notFritzArgelander »

notFritzArgelander wrote:
Fri Jun 26, 2020 4:41 pm
Ylem wrote:
Fri Jun 26, 2020 12:39 pm
From what I heard and read they are the identical scopes.

I have no desire to use 2 inchers with it, but the question why Skywatcher did that is certainly "baffling".
Marketing ploy I guess.

I'm on the fence if I want to even go that route with the C8.
Well, since the baffling likely has to be different what you’ve heard and read about “identical scopes” is likely false. Only true in marketing tense.

Marketing tense is a verb form in which the sentence is true only until the customer buys one and looks at it carefully. Even if the optical elements are identical, the visual backs are different. If the baffling ISN’T different to accommodate that, then one of them will have inferior stray light control.
I'm not satisfied with how I structured the logic of this post so I am coming back to it for another go around.

1) Put on my best Spock imitation voice. Logic dictates that a 1.25" visual back scope and a 2" visual back scope cannot be the identical same scope. That's just going by the specifications though.

2) Assume, charitably, that somehow the rest of the scopes in question are identical. Then the baffling has to be suboptimal and stray light control is not as good as it could be. The design of the baffling for a catadioptric cassegrain starts with the primary, secondary, and corrector, if any, specifications. I grant that those could be identical. The critical parameter for designing a baffling system is the size of the visual back. A 1.25" and a 2" visual back have different baffling requirements. Therefore....

1) If the baffling design of two "otherwise identical" scopes is optimized for a 1.25" visual back then it is suboptimal for a 2".
2) If the baffling design of two "otherwise identical" scopes is optimized for a 2" visual back then it is suboptimal for a 1.25".
3) If the baffling design is a compromise, then it is not optimal for either.

The baffling design depends critically on the visual back size.

So if the optics and baffles are truly identical then the scope will not be as good as it could be according the the trilemma above. If the baffling is a compromise and truly identical it will be suboptimal for both visual backs. If optimized for one visual back the other will be suboptimal.

I hope that makes my thinking clearer at any rate.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: 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 III, Vixen Porta II, Celestron CG5, Orion Sirius EQG
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Re: 2" EPs with an 8" SCT?

#11

Post by Ylem »

Bones!!
Get Spock off the bridge! LOL

I see what you are trying to say though.

These Maks have been sold with the 1.25 visual backs for years.
Then just recently SW decided to put a 2" VB on it. Reports say there is a lot of vignetting.
And if you have fat fingers, it's hard to focus because the "hand grenade" is in the way.

The whole thing is odd to me.
Clear Skies,
-Jeff :telescopewink:

Orion 127 Mak, ST80
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Re: 2" EPs with an 8" SCT?

#12

Post by notFritzArgelander »

Ylem wrote:
Mon Jun 29, 2020 12:28 am
Bones!!
Get Spock off the bridge! LOL

I see what you are trying to say though.

These Maks have been sold with the 1.25 visual backs for years.
Then just recently SW decided to put a 2" VB on it. Reports say there is a lot of vignetting.
And if you have fat fingers, it's hard to focus because the "hand grenade" is in the way.

The whole thing is odd to me.
Well.... that is enough information to solve the trilemma! ;)

If there is vignetting on the 2" visual back version then the baffling was optimized for the 1.25" version and the decision to market the optics with a 2" visual back is technically poor!

BTW Spock is in command on this ship..... :lol:
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: 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 III, Vixen Porta II, Celestron CG5, Orion Sirius EQG
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Re: 2" EPs with an 8" SCT?

#13

Post by Ylem »

Sounds logical.

So back to my C8, I think I may go shopping for a 2"er :)
It has a 37mm baffle tube, I should be able to find something to work nicely :)
Clear Skies,
-Jeff :telescopewink:

Orion 127 Mak, ST80
Celestron Celestar
8SE, C90 Mak
A big box of Plossls :D
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Re: 2" EPs with an 8" SCT?

#14

Post by notFritzArgelander »

Ylem wrote:
Mon Jun 29, 2020 12:49 am
Sounds logical.

So back to my C8, I think I may go shopping for a 2"er :)
It has a 37mm baffle tube, I should be able to find something to work nicely :)
Without doing a ray tracing.... my gut tells me that it might vignette slightly. It won't be nearly as bad as for the 127 optimized for a 1.25" (31.75 mm). My MK66 and VMC200L are both designed for a 2" back.

Hey, if the vignetting is too much for you.... there's always the 9.25 solution! ;)
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: 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 III, Vixen Porta II, Celestron CG5, Orion Sirius EQG
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Re: 2" EPs with an 8" SCT?

#15

Post by Bigzmey »

Ylem wrote:
Mon Jun 29, 2020 12:49 am
Sounds logical.

So back to my C8, I think I may go shopping for a 2"er :)
It has a 37mm baffle tube, I should be able to find something to work nicely :)
Without reducer I can use 2" EPs with max field stop in my 8" SCT. There might be some mild vignetting, but not readily detectable.
Scopes: Stellarvue: SV102 ED F7; Celestron: 9.25" EdgeHD F10, 8" SCT F10, 6" SCT F10, Omni XLT 150R Achro F5, Onyx 80ED F6.3; Meade: 80ST Achro F5.
Mounts: ES: Twilight I; Bresser: EXOS2; SW: SkyTee2, AzGTi; UA: MicroStar.
Binos: Orion: Little Giant II 15x70, WorldView 10x50, Nikon: Action EX 16x50 & 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68s; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV; Russell Optics: SuperPlossls.
Diagonals: Baader: BBHS silver mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: Positive lock prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S; Astronomik: UHC, Orion: UltraBlock, SkyGlow.
Observing: DSOs: 1936 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 1498, S110: 77). Doubles: 1382, Comets: 15, Asteroids: 88
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