Moon shot - prime focus w/ reversed lens to reach higher magnification

[pnugroho (Purwanto)]

Hi all,

This is my first attempt on shooting the moon, using prime focus with AstroMaster 130EQ.
But i'm using a bit different approach, by using a reversed lens to reach higher magnification, instead of directly attach the camera body to the focuser via an adapter (which i believe won't work since the focus point is far inside the focuser)

Here's the configuration:
Telescope's focuser -- 10cm extension tube -- reversed lens 28mm f/2.8 -- body.

I think it's around 32x-40x magnification (i'm not sure). Can anobody explain how to calculate the magnification using this kind of method?

need your comment/critics/suggestions...

thanks!

[Bloodbean (Troy)]

Wow very effective! I never thought of using that method before.

[dannat (Daniel)]

great result from the reverse lens - what is the thoery of using the lens backward? hanks daniel

[iceman (Mike)]

That's an excellent result! Very sharp and good tonal range. Looks like it worked very well.

[pnugroho (Purwanto)]

Thanks for the comments!

Daniel, the theory behind this method is that in photography you can use a reversed lens, becoming a macro lens which has very short focus distance, and can give you 1:1 or more ratio.
This is the situation that i'm using to reach higher magnification.
As for direct prime focus, i will only get around 13x magnification (650mm / 50mm).
By putting a reversed lens between telescope and body, it will act like barlow (without any loss in light intensity, i guess).
I'm wondering if i could also put a real 2x barlow after the focuser to reach even more magnification, but i don't have one.
It also depends on the focal length of the lens. 28mm is the perfect combination. i've tried to put 50mm reversed lens but i have to provide longer extension tube to get in focus.
Please CMIIW, since i'm not technically capable in optics theory.

Here's another shot. using 28mm reversed.