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TS-OAG Setup help needed.


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Need some help from any TS-OAG users out there to advise on how to get this OAG setup as i'm having no luck.

Are you supposed to have any spacers between the guide camera and the OAG itself ?

I'm using the QHY5 as my guide cam and I've spent approx 8 hours over 2 nights trying to setup the OAG and have been unable to focus anything that even loosely resembles a guide star.

I focus my main camera, and then take constant images in Maxim with the guidecam and it's feels like i've tried every possible position known to man but still nothing usable even making absolute minute adjustments.

The closest i've got so far include a huge square blob, but cannot seem to make it smaller, a large arc of light which look very similar to the diamond ring effect of a solar eclipse and the last variation is the looks like the topdown profile of a ship which exactly matches the shape of the hole that the prism holder slides into.

I just dont understand what i'm supposed to do to get it working...:)

Rich.

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Hope you found our little chat helpful Richard?

I've found that users either get it straight away or get their knickers in a twist :)

I intend to write a short guide to getting started with an OAG - based on my customers experiences, will forward.

bern

PS. The key element with the TS OAG is that the light path difference between straight through and up is approx 26mm IIRC.

Implement that, then do a daylight focus test on a distant object.

Edited by bern
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Well i've read quite a few reviews where people have had amazing results so i know it's just a matter of time, just beginning to wonder where i'm going wrong.

I'll try putting in my web cam and and taking video during the day and see how i get on.

Just desperate to get set up as i'm dying to do some imaging with my QHY9......:)

Rich.

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Get it close in daylight before trying to get the fine focus... make a note of the "close" position so that if you lose it on a star you can get back to that point...

I found replacing the thumscrews with solder tipped grubscews made a big difference - its better if you do this from the start before you run any risk of knarling up the channel that they tighten into...

With the OAG removed from the scope can you see the guide cam chip if you look into the front of the prism...

I am sure Bern (Modern Astronomy) will sort it out for you...

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I use a dslr and a DSI so didnt have any issues...

I did "daylight" setup an testing in the factory unit where i have 50' + of dark corridor as well and used an artificial star... i used the Equinoxe 66 on a photo tripod...

PM me your postal addy and i'll get some in the mail to you by 1st class post tonight...

They hold the guide cam tube a lot more securely...

Peter...

Edited by Psychobilly
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Rich,

You should be able to get images from both the DSLR and the QHY5 in daylight.

Look for a distant object with distinctive features. The the DSLR into focus and look at the opposite edge of the FOV where the pick-off prism is sitting, now move the scope to bring that area closer to the centre. What was previous close to centre should now be seen in the guider. Without touching the DSLR focus the guide scope.

Blue astra had some good images of a pylon showing the relative DSLR/Guide FOV's and the offset.

http://stargazerslounge.com/equipment-discussion/90916-orion-oag-first-light.html

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Rich,

The ts oag is really designed for a DSLR. If you use a conventional CCD then you need to position the chip in it about 55mm behind the oag to bring the guide beam far enough out to focus on.

Yes meant guide camera in the guider port of the oag.

Ken

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One point which might help. Don't worry about nailing the focus. Some people deliberately leave the guide star a tad off focus to spread the star's brightness profile which can improve the accuracy of the centroid.

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Ken,

Where does this 55mm come from ?

I'm not sure this can be correct as lots of people use the TS-OAG with DSLR and coma correctors.

Now we all know that coma correctors are required to be placed at 55mm so this means that the TS-OAG must be placed at around 46mm from the ccd surface which is very close to what i have.

Rich.

Edited by ribuck
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The ts oag is really designed for a DSLR. If you use a conventional CCD then you need to position the chip in it about 55mm behind the oag to bring the guide beam far enough out to focus on.

Hate to disagree Ken :) but I think it was just designed to be as thin as possible, though this certainly helps with a DSLR as it reduces the back focus requirement.

There's no specific need to position the CCD 55mm behind the OAG.

bern

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Rich - Pass?

With a DSLR the distance from the FP to the front face of a standard T Mount would be 55mm

The T adaptors for different cameras are a different thickness depending on the distance from the FP to the "Native" Mounting Flange...

I had the TS OAG setup perfectly and then took it apart to measure soem things for Steve L and it took me a while to get it setup again so I really dont want to have to take the setup apart again to measure it... Sorry :)

For got to say I have the EOS version....

Peter...

Edited by Psychobilly
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M25C and Lodestar required me to add a 10mm spacer to push the M25C (i.e imaging CCD) out further, then moved the guider extention (and lodestar) up and down to find focus. If you do this during the "plug" the gaps around the base of the mounting plate at the top with blutack or something (to prevent light creeping in).

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3+ hours in the baking sun at SGL5, fiddling the cameras and spacers and trying to focus on distant trees (including scaring the hell out of me when a huge bird landed on a branch right in the FoV of the guider!)... but yes, it was worth it! :)

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Rich, Peter, et al,

The 55mm is the standard distance from the front flange to the CCD in DSLR's. I've only see the TS OAG working with a DSLR so hence my assumption.

The closer the imaging chip to the rear of the OAG, the closer the guide camera needs to be to the top of the OAG housing.

As the housing is about 50mm diameter (?) and the back focus requirement of the QHY5 is 12.5mm this would give at least 50/2 +12.5 = 37.5mm if the guide camera was tight down on the edge of the housing. I assume this is unrealistic, so, the actual distance will be somewhere around 50mm??? which brings me back close to the DSLR 55mm. ( So much for logic!!)

Ken

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