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Author Topic: OAG Spacer  (Read 178 times)

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Offline peterr

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OAG Spacer
« on: 20:22:56, 10 September, 2017 »
Hi Folks,

I gave up with OAG last year and went back to an ST-80 riding piggyback however attempting round 2 with OAG and think I have discovered the issue.  The filter wheel and off-axis guider are both startlight xpress connected to my MN-190 however to achieve focus with the Lodestar X2 I cannot get the stem low enough in order to get the focus adjuster lower enough, it's about 2mm out and you can see from the photo the stem is hitting on top of the filter wheel.  The stars in the Lodestar are almost there, I have white blobs but not in focus.
Problem is the 460EX is connected to a Moonlite focuser and focusing out only requires minimal steps (1,500) and is only about 1.5mm of travel. If add a spacer such as 5mm like this (https://www.altairastro.com/5mm-M48-Spacer-Extension-Ring.html) to move the camera out and make the OAG/Loadstar able to achieve focus then the 460EX would be out as I would not have enough inward travel, same problem if I add it on the OAG side.
This is the slimline OAG (I think it's the only one they do) so the faceplates are 17mm, the original faceplate with the filter wheel is around 25mm but has no slot for the OAG stem and would probably push out the focusing on the 460 anyway.
Not sure how to fix this one, naturally a dremel is the last resort.......In the photo the OAG focuser adjuster has been raised up for easy of viewing the stem hitting the filter wheel.
Could it a different brand OAG?.

Thanks

Peter
Sky-Watcher Explorer 190nm, AZ-EQ6, Lodestar X2, Atik 460EX, SX FW, SX OAG, Baader 1.25" LRGB + HaSIIOIII, Canon EOS 500D Unmodified, Orion ST80

Online Nimbus

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Re: OAG Spacer
« Reply #1 on: 20:51:52, 10 September, 2017 »
Any chance of a photo showing the whole back end of the scope please? Jim
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Offline peterr

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Re: OAG Spacer
« Reply #2 on: 20:54:51, 10 September, 2017 »
Yep, I can do this tomorrow and upload.

Thanks Jim.

Peter
Sky-Watcher Explorer 190nm, AZ-EQ6, Lodestar X2, Atik 460EX, SX FW, SX OAG, Baader 1.25" LRGB + HaSIIOIII, Canon EOS 500D Unmodified, Orion ST80

Offline chris.bailey

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Re: OAG Spacer
« Reply #3 on: 22:09:36, 10 September, 2017 »
Peter

Can you not move the pick off prism further towards the edge of the light cone, the light falling on the prism is at the same focal point but the stem then clears allowing the Lodestar to be moved closer in. Hope that makes sense.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
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Offline peterr

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Re: OAG Spacer
« Reply #4 on: 07:43:34, 11 September, 2017 »
Chris,

That's what I need to do but the top of the pick-off prism tube is what's hitting and sitting on top of the filter wheel.  Getting the tube and prism down another 2mm will give the me necessary adjustment range with the focal adjust on the oag/lodestar.

Unless i've missed a trick somewhere?

Thanks

Peter
Sky-Watcher Explorer 190nm, AZ-EQ6, Lodestar X2, Atik 460EX, SX FW, SX OAG, Baader 1.25" LRGB + HaSIIOIII, Canon EOS 500D Unmodified, Orion ST80

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Re: OAG Spacer
« Reply #5 on: 07:53:48, 11 September, 2017 »
Peter unless there is a component you can remove (and you have exhausted all your adjustments) , which would then require you to move the focuser out then the only other options I can think of would be a lower profile focuser or to move the primary mirror up the tube producing the same effect. HTH Jim
EQ8 Pro
TAK FSQ 106 EDX4
ATIK 16200 Mono & Lodestar OAG, EFW2 2" Filters
Focusmax4, Robofocus
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Offline chris.bailey

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Re: OAG Spacer
« Reply #6 on: 08:32:10, 11 September, 2017 »
That's what I need to do but the top of the pick-off prism tube is what's hitting and sitting on top of the filter wheel. 

Exactly. Unless yours is different to mine, there are two adjustments, the pick off prism can move in and out and then the Lodestar adapter moves on the pick off prism stalk. Moving the pick off prism out a couple of mm allows you then to slide the Lodestar adapter in a bit further. I know I messed around with mine for ages before getting it all right.

Chris

LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo

Offline peterr

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Re: OAG Spacer
« Reply #7 on: 12:33:30, 11 September, 2017 »
Yep I have both adjustments same as yours.  However I cannot move the focuser adjustment down anymore because the top of prism stalk is bumped up against the Lodestar glass so the only thing that can move down is the stalk itself but the base holding Loadstar is bumped on the filter wheel.
I could take a few mm of the top of the stalk but risk destroying the thread the loadstar connects as well as having cut metal (well sanded) up against the loadstar glass?.

Peter
Sky-Watcher Explorer 190nm, AZ-EQ6, Lodestar X2, Atik 460EX, SX FW, SX OAG, Baader 1.25" LRGB + HaSIIOIII, Canon EOS 500D Unmodified, Orion ST80

Offline chris.bailey

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Re: OAG Spacer
« Reply #8 on: 12:39:19, 11 September, 2017 »
understood. If you have the Lodestar glass tight down on the stalk, there is not a whole lot more you can do.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo

Offline peterr

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Re: OAG Spacer
« Reply #9 on: 11:45:44, 12 September, 2017 »
understood. If you have the Lodestar glass tight down on the stalk, there is not a whole lot more you can do.

I was afraid of that.  Oh well, i'm not ready to attack it yet will go through another round of double checks and measurements first.

Thanks

Peter
Sky-Watcher Explorer 190nm, AZ-EQ6, Lodestar X2, Atik 460EX, SX FW, SX OAG, Baader 1.25" LRGB + HaSIIOIII, Canon EOS 500D Unmodified, Orion ST80

Offline petevasey

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Re: OAG Spacer
« Reply #10 on: 19:13:21, 13 September, 2017 »
I believe a similar problem with the QSI built in OAG has been solved by inserting a thick glass disc below the Lodestar - it moves the focal plane out by a couple of mm.  Maybe someone who has a QSI with this arrangement could confirm this.  But I don't know if it is possible with the SX OAG.

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

Offline Darkstarshado

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Re: OAG Spacer
« Reply #11 on: 20:54:29, 13 September, 2017 »
I was going to suggest a weak Barlow (say 1.4X) - you'll lose some FOV (not good as OAGs have such a small one anyway) but it would take the focal point out quite a bit.  Peter's idea sounds bettr if it will work for you though.

Rob
Paramount ME, Orion Optics(UK) VX14, Skywatcher150p, Skywatcher ED100. Canon 450D,350D, Atik One 6.0, Lodestar X2, QHY5LII, DMK21, Roll-off obs.

Offline peterr

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Re: OAG Spacer
« Reply #12 on: 12:59:50, 14 September, 2017 »
Thanks chaps.  I'll do some investigations on both these routes...........

Peter
Sky-Watcher Explorer 190nm, AZ-EQ6, Lodestar X2, Atik 460EX, SX FW, SX OAG, Baader 1.25" LRGB + HaSIIOIII, Canon EOS 500D Unmodified, Orion ST80

 

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