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58 minutes on Orion and Monoceros with an 85mm Budget Lens

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#1 CodeBlind

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Posted 21 October 2018 - 10:24 PM

In the middle of the summer, I picked up a used Rokinon 85mm F/1.4 lens on Craigslist for $180. I know used Rokinons are iffy, but I didn't have an 85mm prime for my portrait photography and I was willing to take the risk at that price point. I've been trying to do a decent astro test ever since.

 

This is 58 minutes between Orion and Monoceros, captured over a 2-hour period between rain squalls. It's the only 58 minutes I've been able to capture since mid-August due to scheduling conflicts and bad weather (this monsoon season, while providing much needed moisture, won't seem to end). I had to throw out the other 62 minutes because of high-altitude clouds.

 

 

    20181012-orion-and-monoceros-800.jpg

 

 

Captured on a stock Canon 6D and Rokinon 85mm F/1.4 @ F/2.8

29x120s lights @ ISO1600

18 darks

20 flats

10 bias frames

Calibrated/stacked with some home-brew code

Aligned using Hugin

Stretched/Curved in Lightroom 6

 

Thoughts on the lens

 

So ... this lens is great for portrait photography, but not so much for astro. Light falloff at F/2.8 isn't terrible, and coma is pretty good to the edges of APS-C, but it gets pretty bad in the FF corners. Chromatic Aberration is downright terrible. I may try this again with a UV cut filter to see if it helps, but I'm not getting my hopes up. I hope to do a more thorough test when the weather improves.

 

C&C welcome and appreciated!


  • Starman27, eros312, calypsob and 1 other like this

#2 Jerry Lodriguss

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Posted 22 October 2018 - 12:03 AM

Looks like you got a pretty good deal for $180. smile.gif

 

Jerry



#3 CodeBlind

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Posted 22 October 2018 - 01:19 AM

Looks like you got a pretty good deal for $180. smile.gif

 

Jerry

Yeah, not too shabby. I think I can do better given a little more time with it :)



#4 calypsob

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Posted 22 October 2018 - 09:37 AM

You handled the CA pretty well, its easy to shift the CA spectrum in camera raw. Just zoom in and figure out how many pixels the ca accounts for and then bump the purple slider.  Then you use the slider beneath the purple slider and push the split slider to the right so you can shift the purple/reds back into the yellow spectrum which typically seems to be where fringing begins on this lens. 

 

I must admit that this will not work well if it is more severe than about 4 pixels. 

I would suggest stopping this lens down to F4, the coma and ca at that aperture will be much better controlled and the details will be surprisingly sharp.

 

Despite technicalities you got a nice image, keep em comin.




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