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Lens focus control problem in frame and focus mode


mmastro

Question

I've recently started using BYEOS.  The frame and focus mode is great and I like the ability to change the focus on a Canon Autofocus lens.  However, I'm a little frustrated that I don't seem to be able to use the focus control unless I turn on the liveview.  I want to be able to fine tune the focus using whilst the camera is in 'snap image' loop.  This works in a fashion if I leave liveview on, but the signal to move the focus seems to work very intermittently whilst the snap image is in a loop.  Am I missing something here?

 

For me, to have the ability to alter the focus between looping snapimage shots would make focussing with a lens SO much easier.

 

Thanks

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8 answers to this question

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Just to be clear; This is only a limitation with Canon AF lenses, not in the case of using a Telescope with an ASCOM compliant focuser.

 

Also, to solve your current issue (with the canon lens) you may want to consider using a bahtinov mask and a bright star. You can achieve "perfect" focus with the mask on a bright star, then remove the mask and be assured that you will be in focus when you slew to your target (I'm assuming DSO targets, not planetary).

 

see: https://en.wikipedia.org/wiki/Bahtinov_mask

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If your concern is that you find that you need Longer Exposures in your Frame&Focus because of a Dim Target, you can Focus on a Nearby Bright Star - with a Bahtinov Mask or without - and then Slew the short Distance to your DSO Target.  (Focusing on DSOs or other Dim Objects is rarely successful because there is insufficient Detail to lift it above the Background Noise.)  (You can improve the Brightness of the F&F Image by 1) enabling "Exposure Simulation" in the Camera; and 2) raising the Exposure Duration in F&F to 2sec.)

In fact, you can Sync to that Bright Star in order to perform a Precision Slew to your DSO Target.

Then, once you are Focused and Slewed On-Target, then it is time to use a few "Snap Loops" in order to finalize your Framing.

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Could there be a solution to this problem by getting the software to automatically carry out the following sequence?

User = (U), software = (S)

open frame and focus screen (U)

select a special (snapshot lens focussing loop mode) (U)

turn off live view (S)

take snap shot (S)

display image  (S)

turn live view on (but don't display it on screen) (S)

Alter focus in a predefined time slot (U)

turn off live view (S)

take snap shot (S)

display image (S)

turn live view on (but don't display it on screen) (S)

 .. repeat until aborted by user

 

Would this work?

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Could there be a solution to this problem by getting the software to automatically carry out the following sequence?

User = (U), software = (S)

open frame and focus screen (U)

select a special (snapshot lens focussing loop mode) (U)

turn off live view (S)

take snap shot (S)

display image  (S)

turn live view on (but don't display it on screen) (S)

Alter focus in a predefined time slot (U)

turn off live view (S)

take snap shot (S)

display image (S)

turn live view on (but don't display it on screen) (S)

 .. repeat until aborted by user

 

Would this work?

 

That would work, but I think the best solution is when a lens is connected pausing the frame&focus could leave the mirror up, this way the lens drive would work and looping images would allow your to drive the lens between frames. This would put less wear on the mirror flipping up/down.

 

Regards,

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I find that I can use a Bahtinov mask with my 200 mm lens, but the 50mm lens just doesn't give me enough light or a bahtinov mask spikes large enough to accurately focus the lens.

 

 

You need a different mask for 50mm. There are online Bahtinov mask generators, then you can print it on a transparency and cut it out (just the outside) and use that.

 

http://astrojargon.net/MaskGenerator.aspx

 

You may have to play with the parameters to get enough light through.

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I find that I can use a Bahtinov mask with my 200 mm lens, but the 50mm lens just doesn't give me enough light or a bahtinov mask spikes large enough to accurately focus the lens.

I've had some success with a Baht Mask on my 50mm f/1.8.  It is a rather fine-vaned 58mm Baht Mask, and it only works on Bright Stars in the Center of the FOV.  But it works...

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