Zoom with scope or camera? (1 Viewer)

Hi, I just started digiscoping, and this is a question I came across almost immediately. I'm sure it must have been discussed before, but after a couple of searches I couldn't find any mention of it.

Assuming vignetting is not a problem, if you want to increase magnification, is it better optically to zoom in using the scope (assuming you have a zoom ocular) or using the zoom on the camera? Thanks.

Except for optical sharpness, I guess one need also to consider the light throughput. Zooming in with the camera implies slower shutter speeds due to higher f-stops. Is it the same for the scope ocular?

I have a Swarovski ATM-80HD with the new 25-50 zoom.

Best to zoom your eyepiece before zooming the camera lens as long as your camera aperture diameter stays SMALLER than the exit pupil of your eyepiece.

Thanks RJM. I really appreciate you taking time to help out.

Now, your statement is with regards to light throughput I suppose?

While your statement is rather technical, I think I understand the reasoning. But, while exit pupil values for my ocular are available, how do I know my cameras aperture diameter? Sorry, this is a newbie question.

And what about sharpness? I'm not sure, but I assume that the scope is at its sharpest at the widest zoom, i.e. 25x in my case, while I suspect most point and shoot cameras are not at their sharpest at the widest end. So I thought perhaps from a purely optical sharpness perspective it would be advisable to zoom in on the camera a little bit to avoid the widest focal length (while also staying away form the long end, where camera lens sharpness generally deteriorate)?

Aperture diameter is the lens focal length divided by the F ratio. You get the range of diameters from the lens specs. To get the exact values at every zoom step you can snap a pic at each step and check its exif data.

Because of their tiny lenses, all digicams are very sharp even wide open. They tend to get less sharp as the lens gets slower, ie, F5.6 to F8 due to diffraction. In fact, most digicams seldom have apertures slower than F8.

Frankly, the Swaro 24x-50x mag is optimized for digiscoping so I would not worry too much about this. There are more hurdles in digiscoping that will have more impact on your images.

Rick

advice on camera needed

Hi, I have the same 25x50 zoom with AST65 with DCB adapter. I consider buiyng the new Samsung TL500/EX1 (for its bright lens), but I am not sure if the camera zoom (24x72) will do to eliminate the vignetting. If not - what camera would you recommend cinsidering the fact that anyway I will have to buy new camera for digiscoping. (Now I have Sony DSC WX 1, which has no manual focus and has 5x zoom, and hence is not recommended by Swarovski - they allow 4x zoom at maximum).
Regards, Piotr