Wanted Achromatic lens to make a focal reducer

5ash (Philip) · #1 14-05-2006, 12:29 PM

I need an achromatic lens 30mm- 38mm diameter with a focal length between 15 and 20 centimetres . Perhaps the objective of an old binocular would be a source. At present i'm using a 25mm 19cm focal length lens sourced from the telescope of an old spectroscope but its too small in diameter and vignetting is a problem , though quite reasonable images are obtained.
I can't afford a focal reducer at this time so any help with this project would be appreciated. regards philip

RAJAH235 · #2 14-05-2006, 11:44 PM

This is usually a good place to find stuff.....

http://www.surplusshed.com/
HTH.

L.

avandonk · #3 15-05-2006, 03:07 PM

Do you want to use it for photography? What sort of T-mount do you have for your 350D. What size focuser on the scope.
I may be able to help as I have a large range of AC doublets and know where to get more. This will cost you heaps of nothing!
Bert

5ash (Philip) · #4 15-05-2006, 10:59 PM

Hi bert
my T-mount is from scopestuff , its a short collar ring type about 50mm long with an inside diameter of 38mm . [U](its[B]#tassintheircataloguehttp://www.scopestuff.com/ss_tadpt.htm ) I am using an lx90 for deep sky pics . The t-mount fits on the visual back followed by t-mount and 350d. I thought my best bet was to place the ac lens inside of the t-mount so that the camera still clears the base of the mount.my present setup is with a small 25mm diameter ,19cm focal length lens placed just inside the visual back I'd be much obliged if you can help me out as i'd like to be able to take much better pics.
regards philip