Quote:
Originally Posted by Joshua Bunn
Thanks Greg,
I dont seem to be able to find a pentax 67 105mm F2.8 only the F2.4, do you have any links to the lenses you recomended? Actually, is this one of them here http://www.iceinspace.com.au/forum/d...9Af0J5EwgAOw== ?
Can this lense and the one bellow be stoped down and the FL made shorter/longer etc. and do these lenses, and other manufacturers, have filters built into them to block some wavelengths of light ?
Theres a SMC pentax 67 300mm F4 here http://www.iceinspace.com.au/forum/d...9Af0J5EwgAOw== , is this the 300mm you were ferering to, and from your experience, would this lense have the aberations you said the F4 55mm had?
Also, you said you use a FLI PDF electronic focuser between the cameras's filter wheel and lens, are there other options that you know of to conect it to the stl camera. Actualy PreciseParts.com may be able to supply something.
thanks
Josh |
It seems the longer the focal length of the lens the less you seem to hit aberrations.
Here is a list of Pentax 67 lenses and a rating for each:
http://www.antiquecameras.net/pentax6x7lenses.html
I have 55mm F4 which is very widefield but with the 16803 camera (twice the size of STL11) it showed significant star issues in the corners wide open. Closing down the iris to F5.6 or more reduced it but not fully handle it.
Binning 2x2 did give round stars though at slightly reduced resolution.
105mm perhaps it is F2.4 works wide open with no aberrations with my Proline 16803 which is quite a feat. 300mm F4 also does as well.
I get a small amount of chromatic aberration which shows up as magenta bright stars. It is fairly easy to handle in Photoshop with the selective colour tool and reduce magenta.
The 105mm I like the most:
http://www.pbase.com/gregbradley/image/137896676
I also have a Nikon ED 180 F2.8 which worked well on an STL. I'll link some images I took with this.
You don't need a PDF focuser or Atlas to focus it. You can do it manually if you are really careful. I doubt though with the fine shifts required for accurate focus you can do it manually to the same standard. You can also rig up a Robofocus with a belt drive around the lens to focus it.
Greg.