<p>You are using the webcam as an electronic eyepiece. People have been using various types of cameras as eyepiece for decades.</p>
<p>The reason for the small field of view is the small (1/4&quot;) sensor of the camera. Only a part of the actual field of view strikes the sensor. The field of view of your telescope will likely cover a 2&quot; eyepiece. You are putting a 1/4&quot; sensor into the middle of a 2&quot; circle. Tne sensor only sees the center portion of the total field of view.</p>
<p>Most use focal reducers in front of their cameras to increase the field of view of their electronic eyepieces.</p>
<p>I started electronic viewing twenty years ago with webcams and CCTV security cameras. I now use several Mallincam Astro cameras.</p>
<p>Google &quot;electronic eyepiece for telescope&quot; or &quot;electronic assisted astronomy&quot;. You will useful information once you get past all the advertising.</p>

CC BY-SA 4.0
2021-05-10T18:45:58.417Z
2021-05-10T18:45:58.417Z
L d Bonnie
<p>I am a beginner in astronomy.</p>
<p>I have a Maksutov telescope (90mm/1250mm). Generally I do observation with a 25mm wide angle eyepiece, but sometimes due to light pollution I can't see many stars.</p>
<p>So I modified my webcam and converted to a telescope camera.</p>
<p>I can take detailed pictures of moon craters, but the FOV is very small. Is there any way to increase FOV? Can I set the camera on the eyepiece?</p>
<p>note: I am not expecting high quality DSLR-like images, but expecting more stars due to a longer exposure time.</p>

CC BY-SA 4.0
2021-05-10T05:11:58.140Z
Interesting question, welcome to Astronomy SE! Can you explain a little more about the modification? Did you remove the lens of the webcam, and remove the telescope eyepiece, and just put the webcam's image sensor at the focal plane of your telescope? Any more details that you can add to your question will be helpful, and if it's easy, a photo of the setup too. That way people can better recommend what might work in this case. *Thanks!*
uhoh
CC BY-SA 4.0
2021-05-10T05:17:17.443Z
One way to do this would be to restore your webcam (put the lens back on) and place it at the exit pupil of your eyepiece. The webcam works roughly the same as your eye, so if you put your eyepiece back in the telescope and put the complete webcam in front of it just as you would put your eye there, you would get a much bigger field of view. Wherever the actual pupil of your eye normally is, you put the pupil of the webcam lens (somewhere in the middle of the lens). You have to experiment with moving it forward or backward, just like we do each time we start looking to find the right distance.
uhoh
CC BY-SA 4.0
2021-05-10T05:20:25.770Z
But if you then want to look at a planet like Jupiter or Saturn, something small, you would go back to your modified system and remove the eyepiece and put the image sensor directly at the telescope's focal plane.
uhoh
CC BY-SA 4.0
2021-05-10T09:43:07.680Z
@uhoh yes I removed the webcam lens and using direct sensor to capture light coming from primary lens of telescope.
I tried putting webcam with lens on eyepiece, but the image is not covering entire lens, and almost 20-30% image is covered with black border of eyepiece. Any way to overcome this?
Laxmikant Dange
CC BY-SA 4.0
2021-05-10T12:45:01.970Z
You need to start sharing more information about the problem before expecting a solution. Please *edit your question* and add all details there (not just in comments) and please upload an image showing your resulting images when you put the webcam up to the eyepiece. If possible add a photo of the webcam and eyepiece, and any information you have about them. Do you know the model of your eyepiece? Then we might be able to check the eyepiece "apparent FOV" and pupil distance.
uhoh
CC BY-SA 4.0
2021-05-10T12:46:57.867Z
As I mentioned before, you have to move the the webcam around to the right place so that its entrance pupil matches the eyepiece exit pupil. It will be A LOT easier to explain and answer after you share more details and hopefully some simple photos of the setup. *Thanks!*
uhoh
<telescope><amateur-observing><photography>
How to reduce magnification and increase FOV of a camera attached to a telescope?
Laxmikant Dange
# How to reduce magnification and increase FOV of a camera attached to a telescope?

(Asked by: username_0 on 2021-05-10)

I am a beginner in astronomy.

I have a Maksutov telescope (90mm/1250mm). Generally I do observation with a 25mm wide angle eyepiece, but sometimes due to light pollution I can't see many stars.

So I modified my webcam and converted to a telescope camera.

I can take detailed pictures of moon craters, but the FOV is very small. Is there any way to increase FOV? Can I set the camera on the eyepiece?

note: I am not expecting high quality DSLR-like images, but expecting more stars due to a longer exposure time.

**Tags:** telescope, amateur-observing, photography

> **Comments:**
> **username_1**: Interesting question, welcome to Astronomy SE! Can you explain a little more about the modification? Did you remove the lens of the webcam, and remove the telescope eyepiece, and just put the webcam's image sensor at the focal plane of your telescope? Any more details that you can add to your question will be helpful, and if it's easy, a photo of the setup too. That way people can better recommend what might work in this case. *Thanks!*  
> **username_1**: One way to do this would be to restore your webcam (put the lens back on) and place it at the exit pupil of your eyepiece. The webcam works roughly the same as your eye, so if you put your eyepiece back in the telescope and put the complete webcam in front of it just as you would put your eye there, you would get a much bigger field of view. Wherever the actual pupil of your eye normally is, you put the pupil of the webcam lens (somewhere in the middle of the lens). You have to experiment with moving it forward or backward, just like we do each time we start looking to find the right distance.  
> **username_1**: But if you then want to look at a planet like Jupiter or Saturn, something small, you would go back to your modified system and remove the eyepiece and put the image sensor directly at the telescope's focal plane.  
> **username_0**: @username_1 yes I removed the webcam lens and using direct sensor to capture light coming from primary lens of telescope. I tried putting webcam with lens on eyepiece, but the image is not covering entire lens, and almost 20-30% image is covered with black border of eyepiece. Any way to overcome this?  
> **username_1**: You need to start sharing more information about the problem before expecting a solution. Please *edit your question* and add all details there (not just in comments) and please upload an image showing your resulting images when you put the webcam up to the eyepiece. If possible add a photo of the webcam and eyepiece, and any information you have about them. Do you know the model of your eyepiece? Then we might be able to check the eyepiece "apparent FOV" and pupil distance.  
> **username_1**: As I mentioned before, you have to move the the webcam around to the right place so that its entrance pupil matches the eyepiece exit pupil. It will be A LOT easier to explain and answer after you share more details and hopefully some simple photos of the setup. *Thanks!*  

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## 1 answers

### Answer by username_2 on 2021-05-10. Score: 2 | Accepted answer

You are using the webcam as an electronic eyepiece. People have been using various types of cameras as eyepiece for decades.

The reason for the small field of view is the small (1/4") sensor of the camera. Only a part of the actual field of view strikes the sensor. The field of view of your telescope will likely cover a 2" eyepiece. You are putting a 1/4" sensor into the middle of a 2" circle. Tne sensor only sees the center portion of the total field of view.

Most use focal reducers in front of their cameras to increase the field of view of their electronic eyepieces.

I started electronic viewing twenty years ago with webcams and CCTV security cameras. I now use several Mallincam Astro cameras.

Google "electronic eyepiece for telescope" or "electronic assisted astronomy". You will useful information once you get past all the advertising.


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