Hi Dennis,
Well I can not be positive that this was taken at f/15 it could be f/25 as I was also using two barlows in conjunction on the same night. I didn't record any specificates of the equipment I used for the shot, just the date, I will have to learn to record my information of my shots for future reference.
So I am uncertain as to the focal length used but I have split this visually twice now in this instrument on extremely clear nights so I do believe this is the pup, the photo has been enhanced quite a bit in Maxim DL 5. When the photo was in its raw state the pup was not visible in the shot and only appeared after tweeking it quite a bit.
If it is not the pup then what is it???? any ideas. I know of no stars this bright next to Sirius?
My 150mm has a focal length of f/5 and the Meade LPI has a approx focal length of 6mm, combine this with a 3xbarlows and a 2xbarlows.
I have not calculated the field of view of the LPI, but when this dust storm (cough cough cough)moves on I will check it out and let you know.
Rod