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Off-Axis Guiding....Help!

stefski

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stefski

stefski

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Hi All,

Just got one of the babies. I've got my main camera (Atik 16ic) in focus, but can't get any stars (even out of focus ones) in the guide camera-spent an age last night trying:(. Any tips or tricks would be really helpful. The OAG I've got is the 'Brightstar' one - basically exactly the same as the Orion Deluxe.

Cheers in advanvce,

Stef

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Helen

Helen

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I've got one of those too Stef. Daylight is the answer - and maybe some T extensions! When I get mine out to pack for Kelling later I'll try and get a picture of the set up that works for me with my SXH9 and the autoguider. IIRC I used a variable T extender from astroboot.

Helen

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stefski

stefski

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Cheers, Peter:).....I'm at work at the mo:(....Piccies would be at home.

However, I found that if I put the extender on the main path of the OAG, the focuser didn't have enough in travel to focus the main camera BUT if I took off the extension tube from the main path I didn't have enough out focus (I hope I've used the right terminology:confused:). I added in my filterwheel (instead of the tube) and I got focus easily enough. The watec camera (my guider at the mo) has a similar focus distance to the Atik (usually only 2-3mm). Are there any rough measuremrents I can do? I tried (very roughly) to measure an approximate path length into the guide cam..no joy:(?

Any ideas, or do you need to see the piccies?

Once again, many thanks in advance for any hints and tips.

Stef

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Psychobilly

Psychobilly

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Helen,

Once you haev found the spacing that works I would replace the variable T with solid extensions as the Variable T is likely to be a source of flexure... I have a couple of them and just use them for "testing" spacings. You can shim them but fixed rings would be a much better option...

Peter...

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stefski

stefski

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Cheers Helen:). Was just replying to Peter when I saw your response. Daylight....Hmmm.....Helen, I don't suppose you know how far away a daylight target needs to be from my scope for the watec to focus it (TMB 80 LOMO, F6), or a way of calculating it?

....I'm being very naughty.....I really should be working:p!

Stef:D

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stefski

stefski

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Stef,

Ken (Merlin66) has gone over this a few times so a quick serach might pop up the answers your after.. or at least what measurements you need to look at...

Peter...

Cheers again Peter.....I think we keep leap-frogging replies:). I'll have a look at Ken's advice.

Many thanks to you both:D....I really must do some work now, before I get told off!:blob10:

Stef

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stefski

stefski

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Steff..

Basically you wil have to add extensions to whichever is the shortest path...

Peter...

Hi Peter,

Forgive me if this sounds stupid, but how do I know by looking at the set up which if the shortest path:icon_scratch:? Is there a way of measuring, or do I just guess-timate:).

Cheers,

Stef

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stefski

stefski

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:DMany thanks to Peter, Helen and Ken!

Last night, I got the guide cam focused in the daylight, then fiddled when it got dark. I needed a few extra extensions to get it to focus! At first the stars looked like out of focus flying saucers. I soon realised that was because the guide cam was not sitting snuggly in the holder - once straightened the stars became circles:). A bit more fiddling produced focus:hello2:!

I suppose my only concern now is that it is difficult to tighten the holder enough to keep the guidecam looking straight. This took a while to do last night and I'm not convinced that at certain angles, the weight of the guidecam (particularly the cable at the back of it, which are heavy) will shift it out of alignment:icon_scratch:.....Still I'm glad I got it working.....Now for the wonders of PHD:icon_eek:!!!

Stef

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SteveP

SteveP

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Stef

I know from my nown experience that setting up an OAG can be very frustrating to begin with.

As Helen says, it's easier done during daylight hours. The critical point though is to ensure that the image plane of the imaging CCD is at the the same distance as the plane of the guide camera's CCD. This doesn't have to be exact to begin with if your OAG has some means of adjusting the focus of the guide camera. You may need to experiment with different extenders.

HTH

Steve

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