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ASI120MC focus with a 50mm guide scope


alcol620
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Hi folks

Just purchased a 50mm Mini guide scope to us with my ASI120MC camera. Unfortunately, unless I have missed something, adjustment of the guidescope will not bring the  camera into focus. Any ideas?

Thanks

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Hi dave

Thanks for that, I was hopeful, but just got the guider out of the box again and did what you suggested, but focus still failed. Distant rooftop still a vague outline!

Thanks for interest.

Alec

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Hi Dave

No, I have run the focuser, from one end to the other (until it virtually falls off). It would seem that I am getting near focus, how near I am not sure, when the focuser is wound down to the locking ring. Does this mean I need less distance from the lens to the chip or more distance? I have added more distance with the Barlow, so presumably there is a requirement to shorten the distance. I also added an f/6.3 reducer to the Camera and this did not solve the issue. I wish I understood focal lengths etc.

Help still required

Alec

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Hi folks

Problem solved.

I have been in touch with the vendor, Alan at 'Sky's the Limit', a great chap and very helpful, and he picked up on not being able to focus by moving the camera away from the lens suggested removing the spacer that is part of the guide scope to move the camera nearer the lens. (I didn't realise the tube of the scope came apart!) Tried out this morning and hey presto, I can get the scope into focus.

So rather than requiring lengthening, for this camera and scope set up the focal length needs shortening.

Thanks again folks for all your inputs, much appreciated

Alec

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Not sure if its more or less length, still working this stuff out too. I'm setting up a Skywatcher finderscope with QHY5 (and some youtube help) and haven't got as far as testing it tracking, but can get focus without any extension.

Might be worth asking Skys the Limit. I've had some stuff from him in the past, very nice guy and he's likely to have an idea of how to make it focus.

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  • 2 weeks later...

Hi Alec,

I have been reading your thread with interest as I have recently purchased a 50mm Orion Deluxe Guidescope to use with my existing ASI120MC.

http://www.scsastro.co.uk/catalogue/orion-deluxe-mini-50mm-guide-scope-with-helical-focuser-13022.htm?gclid=CjwKEAiArqKmBRCOj_qfmuqinnYSJAAkAYwGoQ1igruJWCABIKCz0MbxJRANQ4oxk6EcpqLcSC2yAxoCFHjw_wcB

Your guide scope looks similar to the Orion other than the Orion Deluxe has a helical focuser, in fact your Star guider looks almost identical to the regular Orion 50mm Guide scope.

Anyway I have not hooked up the ASI120MC to the Guide scope yet but your thread caught my attention. I will first try the helical focuser option as this has 12mm of travel according to the manual. Though it seems yours required being placed 'nearer' to reduce the Focal length which allowed you to focus. If I do have to remove a spacer on the Guide scope how easy is it? Also how if any effect does this have on the Focal Length of the Guide scope. This would be useful information for inputting into PHD etc.

Thanks

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In case anyone is interested I managed to answer my own question.

As the sky was surprisingly clear last night I added my ASI120MC to my Orion 50mm guide scope. After reading your post I decide to rotate the focuser clockwise so that it moved towards the front of the guide scope. After a few turns a screen full of stars appeared, fine tuned it and all good. At least I feel better about spending the extra money on the focuser!

Anyway this post helped me overcome any concerns I had.

Thanks.

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  • 2 weeks later...
  • 1 month later...

Further clarification required, shows my lack of knowledge.

Now I have removed the black spacer ring to get the ASI120 into focus. Does this mean that the guidescope now has a shorter focal length, or is focal length unchanged. I need to know this to make sure the correct focal length into PHD for guiding and drift alignment.

Thanks

Alec

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The focal length is a fixed property of the lens.  Removing bits or adding them will not change it (unless they also contain optical components).

What you have done by removing the spacer is allowed the camera to move forward to the point where the sensor can reach the focal plane of the lens.

James

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Thanks James.

I have continued to use the advertised focal length of the guider, but a thought crossed my mind that this should be adjusted. Thanks for the clarification.

Regards

Alec

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  • 2 weeks later...

In case anyone is interested I managed to answer my own question.

As the sky was surprisingly clear last night I added my ASI120MC to my Orion 50mm guide scope. After reading your post I decide to rotate the focuser clockwise so that it moved towards the front of the guide scope. After a few turns a screen full of stars appeared, fine tuned it and all good. At least I feel better about spending the extra money on the focuser!

Anyway this post helped me overcome any concerns I had.

Thanks.

Glad I found this thread as I am in the process of buying the Orion 50mm Guide Scope (with Helical Focuser) and looking into the ASI120MM :) Nice to see that they are working fine together ! Wasn't sure if paying extra £ for the focuser was worth it :)

It is always a worry when buying from the internet and not being able to test it first !

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Hi Vox45

Bought the focuser from Alan at http://www.ebay.co.uk/itm/380988676194?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Alan is a great chap and will answer any questions you might have on the products he sells. Offers a great Customer Service, top man.

More expensive versions about, but Alan's guides well using PHD and the ASI120MC.

Alec

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  • 1 month later...

Hi folks

Problem solved.

I have been in touch with the vendor, Alan at 'Sky's the Limit', a great chap and very helpful, and he picked up on not being able to focus by moving the camera away from the lens suggested removing the spacer that is part of the guide scope to move the camera nearer the lens. (I didn't realise the tube of the scope came apart!) Tried out this morning and hey presto, I can get the scope into focus.

So rather than requiring lengthening, for this camera and scope set up the focal length needs shortening.

Thanks again folks for all your inputs, much appreciated

Alec

Hi Alec,

Thanks for the tip. I have an Orion Mini 500mm Guide Scope ... looks identical to yours.

I took my ED80 with orion 50mm guide scope and ZWO ASI120MC guide camera out this weekend for the first time and I couldn't focus the guide scope (PHD didn't work, I just got a fix pattern on the screen).

Do you have pics of the spacer .... I don't recall one there. I hope this is a solution for me.

Richard

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Before buying a separate guide scope, I hope you know that you can attach virtually any 9 x 50 or 8 x 50 finder scope to a camera like ASI120 (that is what I have done) and make yourself a so called finder guider. You only need a 30 pound adapter

There is a great video about it:

and here is where you buy your little adapter:

http://www.modernastronomy.com/accessories.html#accAdapters

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Thanks for the posts, I think I'm getting closer to getting it to work. A friend in the field told me to set PHD to 1 sec exposure (I think other cameras use this), I read that for ZWO ASI120MC it should be .05 exposure time. This could explain over exposure. I did a test last night and fould a focus point most of the way along the 1.25 adaptor so I think I should have it soon. BTW the Orion guide scope only cost be $100 AUD, the one made from finder scope could have a problem with back focus?

Ric

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