Toucam and ED80 magnification

[Ant]

I did some imaging with the SPC900 (toucamIII) night before last.

I'm still processing the AVI's (and I found some old AVI's I forgot about)...

A question, the toucam at prime focus is equivilant to a 6mm EP (if memory serves me correctly?) Is that right?

So my ED80 has a focal length of 560mm, if the 6mm is right then at prime focus the toucam gives c93x magnification. So with a 2x barlow that becomes 186x and with a 5x barlow 465x...

Is that right?

Cheers

Ant

[daz]

That's as I remember it chum

[trevboyd]

Quick follow up to this if I may. Are all webcams equal when it comes to comparing their field of view to an eyepiece? Reason for asking is that I've just taken my Creative Live cam apart and attached to 120mm f/8.3 refractor and it feels like it has quite high mag.

Trev

[Ant]

I managed to get some images (reasonible ones as well) with the toucam and 5 x barlow.

This would mean that the magnification was 465x - this seems very high and 3 times higher than the theoretical maximum of 155 (3.1 x 50).

I am missing something here?

There was a stack of false colour (due to the barlow not being APO) which was remove in REGISTAX.

Ant

[SteveL]

Can I highly recommend CCD Calc for working out mag levels, arsecs/pixel, field of view for objects, different OTAs, etc. I use it all the time, and if the camera you have isnt in the list, you can create a new one and plug the correct values in. An invaluable tool

[themos]

Here's my calculation:

(4.5 mm, the diagonal size of the chip) * (3438, a constant to get the right units) / (560 mm, focal length) = 27.6 arcminutes FOV across the diagonal.

That's 10% less than the moon diameter, so you can work out which eyepiece gives you that view. Of course, 6mm eyepieces differ in their field of view so I find that short-hand a bit troublesome.

[Milamber]

What I think is causing confusion here is that nasty word "magnification". The ccd does not magnify an image in the way an EP does, all it can do is show you a bit of the image that is already there straight from the objective/primary/whatever. If it's a little ccd then you will only get a little bit of this image, but it will still fill the FOV of the camera nonetheless. A bigger chip shows more of the image and so you get a wider FOV, but not less magnification (better resolution maybe though but you don't want to go there )

Arthur

[Ant]

Cheers Arthur and all.

I'll add some pic's tonight and see if I can get my head around it.

Ant