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Planetary imaging with Q3.5 and Barlow --help please!

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#1 Tom3

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Posted 12 August 2019 - 12:26 PM

I am having trouble imaging through the Barlow on my Q 3.5.  Using a ZWO camera on the axial port I have no trouble imaging the moon and Jupiter etc.  But I would like to be able to Image through the eyepiece port and put in the Barlow.  If I put the camera in the I eyepiece port t I can again image Jupiter (for instance) but once I swing the Barlow into place the image goes away.  Not even light for an out-of-focus image can be seen.  My camera has a 23 mm diagonal so it should be plenty big to capture the light coming through the Barlow even if the image is a bit off-center.  Any help you can give me would be appreciated.

 

Thanks,

Tom



#2 sg6

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Posted 12 August 2019 - 12:36 PM

Reads that the barlow is simply moving the image plane and so the camera is in effect out of focus.

Usually people add a barlow to extend the position of the image outwards so I expect that you need to move the camera out when the barlow is put into the optical path.



#3 munirocks

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Posted 12 August 2019 - 01:32 PM

When I flip the Barlow in with an eyepiece in place I need to turn the focus knob approximately one whole turn anti-clockwise to refocus. You'll probably have to do the same with the camera in place. I'd be surprised if the scope didn't have enough focus range to deal with it.



#4 RobertPettengill

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Posted 13 August 2019 - 08:26 AM

Even a slightly out of focus image of a bright planet may not be visible with a camera. If you change focus too quickly you may pass through the focal point faster than your camera can respond. 

Using a distantan object during daylight you can count the number of turns between Barlow and eyepiece focus points. This will help you get close. 

 

Questar makes a Barlow for the axial port that works well for planetary imaging. An alternative is to get the Vernonscope Brandon to standard filter thread adapter.  This will let you use a standard Barlow at the eyepiece port. 


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#5 Tom3

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Posted 13 August 2019 - 04:22 PM

Even a slightly out of focus image of a bright planet may not be visible with a camera. If you change focus too quickly you may pass through the focal point faster than your camera can respond. 

Using a distantan object during daylight you can count the number of turns between Barlow and eyepiece focus points. This will help you get close. 

 

 

Good idea, I will give that a try.

Thanks,

Tom



#6 Tom3

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Posted 14 August 2019 - 12:10 AM

Rob,

Your suggestion worked; I made a mark on the focus knob so I could easily count revolutions (needed about 2).  I also realized (duh) that I would need to increase exposure or gain.  Raised exposure far enough to see Jupiter's moons for fine focus.  As the night went on I was able to reduce exposure time: probably my camera cooling down.

 

Thanks again,

Tom




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