Trevor it will fit and will occupy around 1/5th of the frame (vert) if you place it centre.
You will need a lot of exposure though with the 17-85mm EFS.
Just wanting to ease into DSLR astro work and I was looking for piggyback targets to get the hang of taking flats, bias and darks for longer exposures.
Its all new for me and I was interested if I could expect to get this object with such a basic lens.