Dob mount for a C8?

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pakarinen United States of America
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Dob mount for a C8?

#1

Post by pakarinen »


Reading the latest Sky&Tel this morning and an article on a classic Dob got me thinking (always a dangerous thing).

I have a deforked classic C8 that's been languishing in my basement for some time now. Nobody is interested in buying it apparently and I'd also be concerned about the corrector if I had to ship it.

So... anybody ever make / use a Dob mount for a SCT? I imagine it would be on the heavy side, but I'd probably use it mainly for lunar and it wouldn't have to go to a dark site. I was thinking height could be troublesome, but I sit down to observe, so it wouldn't have to be more than ~4 feet tall.

What are the flaws in this plan? I have a tablesaw, chopsaw, electric drills, and other tools for woodworking. I'd just need to buy materials.
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Re: Dob mount for a C8?

#2

Post by stewe »


Sounds a bit peculiar, but at first glance, an SCT with a Dob mount sounds way better than an SCT with no mount and no use.
Because the SCT has a short tube and you want it to be at least 4 feet tall, it sounds like its center of mass will be pretty high, as well as its vertical axis, which might cause instability. But you could counter that with a (removable) ballast weight at the very bottom of the mount and/or making the base much wider than the top. Or you could design it to be a "tabletop" Dob.
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pakarinen United States of America
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Re: Dob mount for a C8?

#3

Post by pakarinen »


Vielen dank. I hadn't considered a tabletop Dob, but that would probably make more sense (and be easier to build). I also like the ballast idea.
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I drink tea, I read books, I look at stars when I'm not cursing clouds. It's what I do.
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Re: Dob mount for a C8?

#4

Post by JayTee »


A novel idea, especially the tabletop variant. My only concern was with balancing such a short tube. You don't have a lot of moment arm to work with to get a good balance for the friction type bearings that are usually used with a Dob mount.

Cheers,
JT
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
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Re: Dob mount for a C8?

#5

Post by Bigzmey »


DOB mount works for newts because EP is positioned at the top of OTA. For SCT EP is at the bottom, which would make observing very hard with a DOB mount.
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: Dob mount for a C8?

#6

Post by bladekeeper »


Bigzmey wrote: Wed Feb 26, 2020 3:19 am DOB mount works for newts because EP is positioned at the top of OTA. For SCT EP is at the bottom, which would make observing very hard with a DOB mount.
Nah, just make it wide enough to stick your face in there and maybe hang a chin strap on it. :lol:
Bryan
Scopes: Apertura AD12 f/5; Celestron C6-R f/8; ES AR127 f/6.4; Stellarvue SV102T f/7; iOptron MC90 f/13.3; Orion ST80A f/5; ES ED80 f/6; Celestron Premium 80 f/11.4; Celestron C80 f/11.4; Unitron Model 142 f/16; Meade NG60 f/10
Mounts: Celestron AVX; Bresser EXOS-2; ES Twilight I; ES Twilight II; iOptron Cube-G; AZ3/wood tripod; Vixen Polaris
Binoculars: Pentax PCF WP II 10×50, Bresser Corvette 10×50, Bresser Hunter 16×50 and 8×40, Garrett Gemini 12×60 LW, Gordon 10×50, Apogee 20×100

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Re: Dob mount for a C8?

#7

Post by kt4hx »


You had an idea, and here is one solution for you. Sort of a table-top dob/SCT. :)

http://celestialwonders.com/dob4sct/
Alan

Scopes: Astro Sky 17.5 f/4.5 Dob || Apertura AD12 f/5 Dob || Zhumell Z10 f/4.9 Dob ||
ES AR127 f/6.5 || ES ED80 f/6 || Apertura 6" f/5 Newtonian
Mounts: ES Twilight-II and Twilight-I
EPs: AT 82° 28mm UWA || TV Ethos 100° 21mm and 13mm || Vixen LVW 65° 22mm ||
ES 82° 18mm || Pentax XW 70° 10mm, 7mm and 5mm || barlows
Filters (2 inch): DGM NPB || Orion Ultra Block, O-III and Sky Glow || Baader HaB
Primary Field Atlases: Uranometria All-Sky Edition and Interstellarum Deep Sky Atlas
---------------------------------------------------------------------------
"Astronomers, we look into the past to see our future." (me)
"Seeing is in some respect an art, which must be learnt." (William Herschel)
"What we know is a drop, what we don't know is an ocean." (Sir Isaac Newton)
"No good deed goes unpunished." (various)
Some people without brains do an awful lot of talking, don't you think?” (Scarecrow, The Wonderful Wizard of Oz)
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Re: Dob mount for a C8?

#8

Post by Bigzmey »


kt4hx wrote: Wed Feb 26, 2020 11:50 pm You had an idea, and here is one solution for you. Sort of a table-top dob. :)

http://celestialwonders.com/dob4sct/
No kidding! :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: Dob mount for a C8?

#9

Post by kt4hx »


Bigzmey wrote: Wed Feb 26, 2020 11:55 pm
kt4hx wrote: Wed Feb 26, 2020 11:50 pm You had an idea, and here is one solution for you. Sort of a table-top dob. :)

http://celestialwonders.com/dob4sct/
No kidding! :D
As they say, necessity is the mother of invention! :lol:
Alan

Scopes: Astro Sky 17.5 f/4.5 Dob || Apertura AD12 f/5 Dob || Zhumell Z10 f/4.9 Dob ||
ES AR127 f/6.5 || ES ED80 f/6 || Apertura 6" f/5 Newtonian
Mounts: ES Twilight-II and Twilight-I
EPs: AT 82° 28mm UWA || TV Ethos 100° 21mm and 13mm || Vixen LVW 65° 22mm ||
ES 82° 18mm || Pentax XW 70° 10mm, 7mm and 5mm || barlows
Filters (2 inch): DGM NPB || Orion Ultra Block, O-III and Sky Glow || Baader HaB
Primary Field Atlases: Uranometria All-Sky Edition and Interstellarum Deep Sky Atlas
---------------------------------------------------------------------------
"Astronomers, we look into the past to see our future." (me)
"Seeing is in some respect an art, which must be learnt." (William Herschel)
"What we know is a drop, what we don't know is an ocean." (Sir Isaac Newton)
"No good deed goes unpunished." (various)
Some people without brains do an awful lot of talking, don't you think?” (Scarecrow, The Wonderful Wizard of Oz)
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Re: Dob mount for a C8?

#10

Post by notFritzArgelander »


YUP! Go for 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: Dob mount for a C8?

#11

Post by Bigzmey »


kt4hx wrote: Thu Feb 27, 2020 12:01 am
Bigzmey wrote: Wed Feb 26, 2020 11:55 pm
kt4hx wrote: Wed Feb 26, 2020 11:50 pm You had an idea, and here is one solution for you. Sort of a table-top dob. :)

http://celestialwonders.com/dob4sct/
No kidding! :D
As they say, necessity is the mother of invention! :lol:
I thought Bryan was kidding but with this design you do want to make sure that your face fits. :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: Dob mount for a C8?

#12

Post by JayTee »


Wait, the article doesn't say that his cranium will fit inside that container when the OTA is pointed at the zenith. Wouldn't that just beat all if you can't use this setup at the zenith because "yo' hed dont fit!"

Amusingly,
JT
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5
∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros.
∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3
∞ Binos: 10X50,11X70,15X70, 25X100
∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°

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Re: Dob mount for a C8?

#13

Post by AntennaGuy »


I like this idea, but I think one of the challenges with it in practice is the relatively narrow TFOV due to the long focal length of SCTs, which makes it harder to point them manually. Otherwise, I think it would be a lot of fun to Dob-mount a large 14" SCT OTA (f/11) like this one:
https://www.highpointscientific.com/cel ... -91038-xlt
Just good luck keeping it on your target...
:)
* Meade 323 refractor on a manual equatorial mount.
* Celestron C6 SCT on a Twilight 1 Alt-Az mount
Prof. Barnhardt to Klaatu in The Day the Earth Stood Still: "There are several thousand questions I'd like to ask you.”
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Re: Dob mount for a C8?

#14

Post by pakarinen »


My intention would be to use this for lunar so I’d think aiming would be ok. Of course, if it worked I probably wouldn’t be able to resist taking just a peek at some DSOs. :shifty:

I probably shouldn’t have sold the fork, but I had planned on selling the OTA so the pod and fork were just more clutter.
=============================================================================
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: Dob mount for a C8?

#15

Post by AntennaGuy »


* Meade 323 refractor on a manual equatorial mount.
* Celestron C6 SCT on a Twilight 1 Alt-Az mount
Prof. Barnhardt to Klaatu in The Day the Earth Stood Still: "There are several thousand questions I'd like to ask you.”
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Re: Dob mount for a C8?

#16

Post by helicon »


That's really cool. Turns it into a table top instrument.
-Michael
Refractors: ES AR152 f/6.5 Achromat on Twilight II, Celestron 102mm XLT f/9.8 on Celestron Heavy Duty Alt Az mount, KOWA 90mm spotting scope
Binoculars: Celestron SkyMaster 15x70, Bushnell 10x50
Eyepieces: Various, GSO Superview, 9mm Plossl, Celestron 25mm Plossl
Camera: ZWO ASI 120
Naked Eye: Two Eyeballs
Latitude: 48.7229° N
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