optics question for the egg spurts

[Kaptain Klevtsov]

Thinking about focal ratios and stuff today, I realised that the SLR lenses that I'm toying with (T mount - fit straight onto the SC3 - 62mm f/8 " 'scope" costs a few quid off e-bay) I realised that the amount of light I'm collecting is spread out over what was supposed to be a 35mm film frame in a roughly 40mm Dia. circle. Most of the light is wasted as the 1/3" chip size is a fraction of that. Is there a way that I can aim all (or at least more of) this light onto the chip and therefore collect 3 or 4 times as many photons?

I'm guessing that this is a function of the lens design and therefore not easily mended, but if there is an "optical funnel" available it would help greatly.

Captain Chaos

[Naz]

Only solution I can come up with would be 2 or 3X tele convertor, but you loose light through the glass.

naz

[Kaptain Klevtsov]

I thought that they spread the image more thinly than ever? Aren't they a sophisticated diverging lens that spreads out the image to double the original size?

I would like to keep the image scale the same, just use the available aperture to get all the light where it should go.

Thinking about this some more tells me that it can't work, the photons missing the chip are from things that are not part of my desired image so they're just noise anyway. I bet that's how focal reducers work.

Worth a thought anyway.

Captain Chaos

[Naz]

They increase the apparent focal length, as per a barlow.

There is not anything that can do the trick that you want, unless you use another lens, of short focal length, eg an ep?, that will refocus the image onto a smaller area. I can see how it might be possible, but the mechanics evade me at the moment, must have another beer. hmmmmmm :scratch:

naz