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Atik OAG Off Axis Guider


FLO
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The new Atik OAG off axis guider has finally arrived, and very nice it is too! This picture taken today shows the quality of machining and attention to detail.

atik_oag_off_axis_guider.jpg

To recap:

It fitst directly to the Atik EFW2 Motorized filter wheel and features a moving prism that enables selection of the most suitable stars within the corrected field of view.

Based on the Takahashi M54 x 0.75mm thread so caters for large-format sensors up to and including 35mm format.

A silky-smooth helical fine-focus mechanism with three extension rings enables a range of cameras and autoguiders to reach focus.

For further details and an up-to-date price please visit our website.

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Excellent. I definitely see one of these in my future, especially for that price, but...

If I wanted to use my Atik Titan as the guide camera, would it fit, or would it collide with the imaging camera (314) at the back?

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Woo :) Although this will need to wait until next month.

Next thing is to work out what is going to be needed to attach the pentax. Removing the russian doll focusing extensions at the back, the following is possible:

Pentax

->M84 4-in-1 adator to 2"

->ATIK OAG

->[OAG-guider] ATIK 16ic without adaptor?

->M54 adapter I'm assuming a T-ring to M54 would be required?

->ATIK 383L+

The extension tube would be loaded with a 2" Baader UV/IR cut (I have the 1.25" version atm) for mono imaging initially. Then, before winter I'll add a EFW2 and LRGB (and I hope with more steerage over the 36mm vs 2" debate) whilst removing the extension tube for backfocus..

Edited by NickK
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  • 3 weeks later...

I'm recovering from the anger this has caused after receiving it today.

Just be warned that the M54 nose has such a small tolerance that it will very easily get jammed. Mine has jammed to the point it's impossible to extract and I will now have to get a new extension and M54 nose from somewhere..

The kit contains:

1x 2" to M54 nose adaptor

1x OAG assembly

3x varied thickness t-thread rings for the guide cam

3x bolts to attach the OAG directly to the EFW2.

The OAG is really targetted at EFW2 owners as it's not sold with the required connector to attach a CCD. The OAG body itself is a M54 thread right through. This means in order to use a T-threaded CCD camera instead of a EFW2 on the other side you will need to source a male-to-male M54 to T-thread adaptor.

Edited by NickK
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Sorry to hear you are having difficulty Nick. We will happily send you a replacemant extension and nosepiece. Alternatively feel free to return the OAG for a refund.

Perhaps our product description is in need of editing to prevent confusion?

The Atik OAG is a new product so we have sent one together with an EFW2 filter wheel to Steve Richards for testing. We should soon have a better idea of it's strengths and weaknesses.

HTH,

Steve

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After heating it, freezing it.. I'm not sure you'd take the pieces after the final resort rubber mallet was used to try to resolve it.. both the nose and extender have warped rather than separate.

Edited by NickK
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No, this was the smooth nose piece (ie 2") into the smooth bore 2" extension tube.. No threads involved!

edit: All the attempts to remove the nose from the extension were done without the main OAG present.. so it's fine.

Edited by NickK
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I have looked through your orders Nick so know you are using the Revelation focus extender. I have tried some Atik OAG 2-inch nosepieces in Revelation focus extenders and found the same, the fit is too tight. Interestingly the Atik nosepiece fits into our other focus extenders and the Revelation extender works well with other products with 2-inch nosepieces. I guess the problem you are experiencing is due to the Atik nosepiece being on the large side of what is acceptable and the Revelation extender being on the narrow side. Individually they are fine but together they jam.

We have dispatched another Atik nosepiece together with a William Optics focus extender so you should be up and running soon :)

We shall also let Atik know so they can decide whether it is worth reducing the diameter of the nosepiece by a smidgen. Meanwhile we will be careful not sell Revelation focus extenders with the Atik OAG.

Thank-you for the feedback and apologies for the inconvenience.

Steve

(Don't worry about returning the original nosepiece and extender, I doubt they will be usable after your rubber mallet excercise ;) )

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Just to add to the 'knowledge base', I have a Revelation 50mm 2" Extension Tube (brass compression ring, single locking screw) and have test fitted the 54mm to 2" nosepieces from both the OAG and the EFW2 Filter Wheel (the shoulders are a slightly different design from one another) and both are a very snug fit but release absolutely perfectly.

I have tried both 5 times and if they were mine, I'd be happy with them as I'd rather snug than loose. If the manufacturing tolerance was out from batch to batch of either the extension tube or the nosepiece, a point would be reached where they would be too tight but that's not the case with the off the shelf samples I have in my possession.

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We shall also let Atik know so they can decide whether it is worth reducing the diameter of the nosepiece by a smidgen.

The response from Atik :)

The adapter is exactly 50.8mm in diameter, so it should work with any 2" focusers/extensions. It's the first time we ever had such a report. We'll reduce the diameter a little on future parts, just to make sure this won't happen again.

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I have no 50.8mm 'control' tube to work from but my digital callipers show a diameter of between 50.85mm and 50.91mm during repeated tests. Rotating the tube resulted in no shift in the measurement.

Not especially highly scientific but I have never had cause to doubt the general accuracy of my callipers and have double checked against an analogue pair and all bar the second decimal point, they agree so my own conclusion is that my own sample of the tube is most likely just over 50.8mm in diameter. How much? A smidgen!

However, to repeat, it fits my Revelation extension tube very nicely.

Edited by steppenwolf
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very snug fit but release absolutely perfectly.

Yup the Baader 4-in-1 M86/84 to 2" adaptor (two screws - one compression and the other a lock) works with the 2" nose supplied with the ATIL 383L+. It's a snug fit but feels stable and secure - what I would expect. As FLO Steve has observed - it's one of those things that requires the convergence of the planets..

I'll get mysef a M54 to T-thread male-to-male and post my experiences. The only thing I can see being a problem is if the threading causes a collision between camera body and guider focuser once it's tightened up.. but a couple of adaptor rings could sort that out and as I'm using 2" right through there shouldn't be any vingetting from the noise mounted filters.

Edited by NickK
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  • 2 weeks later...

I can answer that! There's a hidden couple of grub screws in the EFW2 that hold the main camera adaptor (separate from the guide camera).

Screw in the camera then untighten the screws and the camera can be rotated. Tighten up again and it's all done.

location.png

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I'm not sure I understand, Nick. Does that not mean that in order to rotate the guide camera you have to rotate everything except the main camera, including the whole filter wheel assembly? Surely that could cause changes in the balance of a scope.

I received my OAG today, and I am very happy with it. I tried it out this evening and it seems to work well. I need to fiddle with the focus some more, and possibly tinker with the amount of protrusion of the OAG's prism, but other than that all is well.

The only snag I have found is that I would like the guide camera (Atik Titan) to be lined up with everything, but it seems that isn't possible; once it's screwed in securely, it lies at 45 degrees or so compared to the rest of the system. Am I right in thinking this is just the way it is, or is there some clever way to bring the camera into alignment?

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Usually you don't rotate the guide camera on it's own around the optical axis. If you have a large sensor CCD you could start clipping the light cone in the corners of the CCD.

You can rotate the while lot but the CCD camera itself can be rotated using the grub screw.

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Thanks, Nick, that explains my first question. However, I'm still wondering about the second one: If you imagine the axis around which the guide camera turns as you screw it into OAG, is there a way to adjust the orientation in that axis, so that when the camera is screwed on fully, it sits "square". It would make it easier to make RA and Dec movements on the hand controller correspond to left-right-up-down in PHD, etc. It would also allow movements on the main camera and guide camera to correspond in a less confusing way for my addled early-morning brain.

Wow, that explanation is no better. :) Would a picture help?

Edited by fatwoul
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I understand what you mean.

The thread of the 16ic tightens to the point the sensor is square to the optical plane for the light coming in*.. i.e. when the screw threads tighten, the camera sensor is aligned to the prism (although there's a circular hole the light comes through - the prism is rectangular).

This means if a star moves along the X axis of the imaging camera sensor (assuming it's aligned by rotation), then the star moves along the X axis of the guide camera.

* I have two of the extending back focus rings in place for the 16ic that come with the OAG.

I understand why you wish to rotate the guide camera - to align the RA along the X axis and DEC against the Y axis, resulting a better accuracy.

Edited by NickK
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