Ideal 300mm Lens for DSO work

[Calypsob]

Hello I am looking around for a good 300mm lens to image with.  I want to shoot at F4 and I need to keep the cost below $700 if possible.  I posted another thread on cn requesting .cr2 image samples with the canon 300mm ef, but after looking around I am open to explore other options as well.  I notice alot of the 300mm lens images on astrobin come from European countries so I figured I might get some good opinions on here.  Ideally I want a lens that can shoot wide open at F4 without any coma or chromatic abberations.  A 300mm F2.8 stopped down to F4 would be fine as well.  I looked at the older nikkor 300mm f2.8 ed series and it seems that the images are on par with the Canon  ef 300mm F4 L.  There is a pentax 645 edif green star which unfortuantely seems to fall a bit short in regard to color correction, while the newer but very expensive version with a gold ring, color corrects even the 5DSR out to the edges without coma or chromatic abberation.  Those are really the only lenses I have looked at.  Can anyone recommend anything else that performs well at 300mm F4 ? 

[Earl]

have you looked at medium format lenses?

[zicklurky]

The Pentax M* 67 ED IF has a good reputation. Marco Lorenzi used one quite a bit: http://www.glitteringlights.com/Images/Nebulae/i-zrf9nWL/A

[Calypsob]

12 minutes ago, Earl said:

have you looked at medium format lenses?

Yes, pentax 645 is medium format.  

[Calypsob]

8 minutes ago, zicklurky said:

The Pentax M* 67 ED IF has a good reputation. Marco Lorenzi used one quite a bit: http://www.glitteringlights.com/Images/Nebulae/i-zrf9nWL/A

Thanks, I am trying to figure out why there would be such a big difference between the 67 edif and the 645 edif.  I know that 67 is an even wider format.  Maybe that is why it corrects color better, because the central sweet spot is bigger.  

[alexbb]

I have a 300 F4 L from Canon and 2 Tair 3s. While the first one handles much better the chromatic aberrations, the Tair are ok too in narrowband.

I didn't shoot much with the Canon in colour, mostly narrowband. It has some tilted element inside I suppose as the stars in 2 corners are more elongated/bloated.

You can check some of my processed images. Unfortunately, I'm unable to provide you any raw files as I'm in a business trip.

Canon narrowband: https://stargazerslounge.com/topic/290494-elephants-trunk-widefield/

Canon + Tair, Canon only, Tair only: https://stargazerslounge.com/topic/287913-ic434-new-rgb-old-ha/

Several others images: https://stargazerslounge.com/gallery/image/31929-m31-f300-2016-summer-p12jpg

 

HTH,

Alex