SharpCap Forums

Hi,
I have a D=114mm, F=900 reflecting telescope and a Svony SV105 USB telescope camera. I set up the telescope to view the moon using a 20mm lens and could see the full disc of the full moon through the lens. When I used the camera, I could only see part of the moon disc (it appeared to be zoomed in). I may be missing something very simple being a new user, but what setting do I need to use to lower the magnification of the camera / zoom out. I tried the zoom setting in Sharpcap, but it just seemed to make the screen area smaller rather than making the image smaller. My aim was to take a
photo of the full moon disc.I thought that I might get a full screen image of the whole of the moon Any ideas please? Thanks.

Hi,

I'm afraid that your combination of telescope and camera are not able to produce a full lunar disk image between them. The telescope will produce an image of the moon at its focal plane dash you can see this image if you put a piece of white card at the focal plane of the telescope in place of the camera or eyepiece. This image at the focal plane will be considerably larger than the sensor of your camera, so there is no way to fit the whole moon image onto the centre at once using that telescope and camera combination.

To be able to take a full lunar image you would either need to have a camera with a significantly bigger sensor or a telescope with a substantially shorter focal length. You can find various websites that allow you to calculate the field of view of particular telescope and camera combinations to help you understand this issue further.

Cheers, Robin

Hi, Thank you for the kind advice. I will try again using a 76mm x 350mm Dobson reflector.
Cheers Graham

Graham

As Robin says there are sites which can show what can be seen by a particular scope/camera combination.

The one I use is https://astronomy.tools/calculators/field_of_view/. This is a good tool to use when making decisions about the best combinations of scope/camera for imaging particular objects.

For your particular camera, the specs are (from Amazon):

Selecting The Moon and adding these specs to the FOV calculator:

the results would be:



For your second telescope:

the results would be:

So telescope 2 is a better option with your camera, providing you can get focus.

Planetary objects can be selected as can Messier objects by using the drop down lists at the start of the page.

Dave