Random imaging question..

[ddefoe]

Hi, 

Forgive me if this is a really stupid question but I can't find an answer anywhere! 

Does the magnification /fov change when attaching a zwo camera to the ota? 

I'm looking at starting to do some lunar imaging and I am trying to figure out which zwo to get? 

As there will be no eyepiece what magnification would it be at. 

I have a c8 and my 25mm gives a full view but have no idea what a zwo would look like? 

Thanks

[knobby]

This site 

https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://www.12dstring.me.uk/fovcalc.php&ved=0ahUKEwjK_5uCw6jXAhWLqaQKHaivC_cQFggmMAA&usg=AOvVaw3MVsD8owRcYIV5Y0tlvfxw

Shows what objects look like by inputting your scope etc.

[Olsin]

I've used an asi120mm on my C8 and i wasn't overly impressed although that could very well have been because of bad to middle of the road seeing.The incredily small FOV makes good seeing conditions critical if you want to get a good focus. It's always seems to be jumping all over the place everytime i look at it.
You can use this FOV Calculator to check out any combination of scope/ep/camera FOV. Click on "visual" if you want scope/ep FOV and "image" if you want scope/camera FOV.

https://astronomy.tools/calculators/field_of_view/

 

[ddefoe]

Ok.... I had a look and it shows me that I would only be able to image a tiny square of the moon.....! 

Is this right?? I even put in an 80ed and that didn't even capture the whole moon. 

How do people capture the moon in totality? I was recommended the best way was to take a video and registax etc... But this seems a bit pointless if I'm only going to see a tiny portion of it. 

Help please... 

[geordie85]

There's 3 main options, buy a scope with a wide fov, buy a camera with a large sensor or make a mosaic 

[ddefoe]

ok...so would there be a camera solution for my scope to view the moon in totality or would the cost of a sensor that large not be worth it?

[ddefoe]

maybe another silly question, if i am then looking at planets and trying to get a larger sensor to fit more of the moon in, would the planets then not be too far away? is there a way of zooming in from the camera or adding a barlow?

[geordie85]

Have a play on here https://astronomy.tools/calculators/field_of_view/

It'll help you decide what camera best fits your scope for full lunar imaging. If you don't want to spend lots of money on a larger sensor ccd/ cmos camera you could always buy a cheap dslr for the moon.

With the planets a barlow is always a good idea since the distances between us and them are vast and will be quite small without one. 

[ddefoe]

with a dslr would it work with taking video and using registak on this video as well? or would just taking pictures work?

 

[ollypenrice]

Let's take a step back and establish some principles.

1) There is no such thing as magnification in imaging. This comes up often but, basically, we can say that binoculars magnify 8x or telescopes magnify 200x because we have something to magnify. The something is the apparent size of the object seen naked eye, it's naturally perceived or unaided size. A camera doesn't have a 'natural size' for an object so it cannot be multiplied by 8 or by 200.

2) The size of the sensor has no effect on the level of detail captured. Cropping the image, or capturing it on a smaller chip with the same sized pixels, simply reduces the field of view. (Looking at a distant object through an empty cardboard tube reduces the field of view in just the same way, but it does not magnify like a telescope.) In other words a small chip is not in any way equivalent to a zoom lens and the term 'crop factor' should be expunged from the language!

3) The size of the pixels, though, does have an impact on the level of detail (potentially) captured and on the size of the object when presented on your screen. If you take the same planet in the same scope with half-sized pixels the outgoing image will be 4x larger by area than it was from the larger pixels. (Seen at 'full size' one camera pixel is given one screen pixel.) I say potentially captured because there comes a point at which the seeing, the atmospheric turbulence, blurs incoming details so that they will be lost before they arrive.

So the key question is, How many pixels does your camera put under the object?  If the seeing allows it, it is this which tells you how large and detailed an image you'll obtain from a given set of optics.

Olly

[ddefoe]

Ok, so larger sensor = more pixels which = greater field 

My question would be that a camera with a large sensor is going to be more expensive than a smaller sensor camera. However using the fov tool it makes saturn for instance really small. Is this an issue or as it is greater quality would it crop better and retain quality or would the cheaper smaller sensor camera be better for planetary observing??

Thanks

[ollypenrice]

50 minutes ago, ddefoe said:

Ok, so larger sensor = more pixels which = greater field 

Thanks

That's true for pixels of a given size. However, I have two CCD cameras, one with a tiny chip and one with a huge chip. However, the one with the tiny chip has tiny pixels, so the pixel count is not as different as is the chip size.

Olly