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Directly looking at mirror with webcam.

Imaging Equipment Celestron Accessories 3d printing
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#1 PortablePc

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Posted 08 May 2021 - 02:08 PM

Hello, I recently 3dprinted a design to fit my webcam in my telescope, it works perfectly but as expected I'm looking directly at the mirror, not the picture itself. Can someone help me in parts I need to fix this? Maybe a barlow will work. Thanks in advance smile.gif



#2 ButterFly

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Posted 08 May 2021 - 02:18 PM

You need to focus the light on the sensor.  A webcam has a lens on it.  The webcam lens takes diverging light and focuses it on the sensor.  A telescope produces converging light at its focal plane, which the webcam is not meant to be able to focus.  So your webcam isn't "looking at" the mirror, it's focused on the mirror and not the image comming off of it.

 

Either rip the lens off the webcam, use an eyepiece to deliver afocal light to the webcam, or go past the focal plane so that the mirror's light is diverging again.


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#3 spereira

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Posted 08 May 2021 - 03:40 PM

Moving to Beginning Deep Sky Imaging.

 

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#4 Mike in Rancho

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Posted 08 May 2021 - 04:43 PM

You need to focus the light on the sensor.  A webcam has a lens on it.  The webcam lens takes diverging light and focuses it on the sensor.  A telescope produces converging light at its focal plane, which the webcam is not meant to be able to focus.  So your webcam isn't "looking at" the mirror, it's focused on the mirror and not the image comming off of it.

 

Either rip the lens off the webcam, use an eyepiece to deliver afocal light to the webcam, or go past the focal plane so that the mirror's light is diverging again.

Yep, the webcam I use for guiding was the same.  Those lenses are really meant to create a rather wide-field view and not what we generally want for AP.

 

That said, "ripping the lens off" should maybe be done somewhat daintily, with a soldering iron, solder vacuum thingy, and sharp tweezers.  At least that's what it took on my MS Lifecam Cinema.


Edited by Mike in Rancho, 08 May 2021 - 04:43 PM.

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#5 ButterFly

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Posted 08 May 2021 - 05:19 PM

That was my polite suggestion to not start there.  Afocal is always the easiest place to start.  Duct tape and a sheet over it so it looks "pretty" is all one needs.  The software has a learning curve, so just feed it some data. 

 

Afocal's (digiscoping's) benefit in the long run is that it can reduce the effective f/ratio of the system, at the expense of whatever aberrations the eyepiece introduces.

 

Here, there already is a mount, but I really don't know how much its support relies on the webcam's lens' support.


Edited by ButterFly, 08 May 2021 - 05:20 PM.

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#6 PortablePc

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Posted 09 May 2021 - 08:23 AM

You need to focus the light on the sensor.  A webcam has a lens on it.  The webcam lens takes diverging light and focuses it on the sensor.  A telescope produces converging light at its focal plane, which the webcam is not meant to be able to focus.  So your webcam isn't "looking at" the mirror, it's focused on the mirror and not the image comming off of it.

 

Either rip the lens off the webcam, use an eyepiece to deliver afocal light to the webcam, or go past the focal plane so that the mirror's light is diverging again.

How can I do that exactly? Moving the webcam to the focal plane? My focal lenght is 650mm and my focal ratio is F/5



#7 ButterFly

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Posted 09 May 2021 - 11:48 AM

With the focuser, like everything else.  Take a look at the actual focal plane of your telescope.  Place a sheet of paper over the focuser and fix it there with rubber bands.  Move the focuser in and out until it forms an image on the sheet.  The Moon is the best target for this because it is big and hard to miss, and shows details on the sheet once focused.

 

Then look over Televue's imaging page.  In all cases, the light is ultimately focused onto the sensor, regardless of how many elements it went through.  Every imaging method is a variation or combination of these five methods.  Look over the benefits of each type, then decide how it it you wish to proceed.




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