I have recently started playing around with my Nikon D700 and some astrophotography work. I had used it a little in the past with a LX200 10" F/10 (pixel scale of ~0.65"/pixel) which gave what appeared to be reasonably sharp results although nothing fantastic with 6s exposures!
I have recently put it on my 130mm F/5 astrograph (~2.59"/pixel) and everything appeared soft, almost out of focus. I used as bahtinov mask to focus although the PA at the time still left some trailing at 30s so it could very well have been that that was the issue.
Monday night I did some wide field with my 24-120 Nikkor lens, zoomed to 120mm, digitally zoomed in as much as possible and then eyeballed the focus (smallest star possible) before going back to 24mm. This gives an image scale of ~72.58"/pixel, so, VERY under sampled.
This is what I got.
To me it looks like the stars are quite bloated, if I was using a mono sensor I would say that the focus is way off. My question to anyone has has used OSC (this is my only OSC that I have used), is it the fact that the D700 is a OSC with 8.445 micron pixels that gives this bloated look or is it my focus?
I am thinking I may need to get a bahtinov mask for this lens if focus is the issue.