[Bertrand3000]

Hello everyone,

Coma is an optical defect which can be really annoying when you are shooting stars. My Sigma 10-20 F3.5 is my best lens when it comes to stars photography, but it is affected by strong coma, which means, stars become elongated on the edges. Still, coma is almost never tested in lenses reviews, especially lenses for Pentax.


I am not looking for the ultimate coma-less lens, but I would like by experience of fellow photographers the lenses which are rather well corrected for coma.

I am aware of the Samyang 14mm F2.8, which is the prime example of a lens which is very well corrected for coma, but what about the others?

I especially wonder about :
- DA 14 F2.8
- DA 15 F4 Limited
- DA 21 F3.2 Limited
- Sigma 17-50 F2.8
- Tamron 17-50 F2.8
- Samyang 16mm F2.0

What are your thoughts?

[luftfluss]

Hello everyone,

Coma is an optical defect which can be really annoying when you are shooting stars. My Sigma 10-20 F3.5 is my best lens when it comes to stars photography, but it is affected by strong coma, which means, stars become elongated on the edges. Still, coma is almost never tested in lenses reviews, especially lenses for Pentax.


I am not looking for the ultimate coma-less lens, but I would like by experience of fellow photographers the lenses which are rather well corrected for coma.

I am aware of the Samyang 14mm F2.8, which is the prime example of a lens which is very well corrected for coma, but what about the others?

I especially wonder about :
- DA 14 F2.8
- DA 15 F4 Limited
- DA 21 F3.2 Limited
- Sigma 17-50 F2.8
- Tamron 17-50 F2.8
- Samyang 16mm F2.0

What are your thoughts?

Lenstip has tested most of those lenses, and they test for coma.

[BigMackCam]

I can't speak from personal experience. but the Samyang 16mm f/2 - whilst not perfectly corrected - tests quite well with respect to coma...

[jatrax]

This might be of interest: Lonely Speck’s Ultimate List of Best Astrophotography Lenses – Lonely Speck

[MossyRocks]

I really like the Laowa 12mm f/2.8 Zero D. while not perfect wide open you really have to pixel peep to see coma and it is completely gone at f/4. While not on your list is one I would consider if looking. I haven't used any of the others but the extremely low distortion is a benefit when stacking and stitching.

[stevebrot]

Still, coma is almost never tested in lenses reviews, especially lenses for Pentax.

There is coma and then there is coma as it applies to astrophotography. Most modern lenses pass muster for pictorial subjects such that the usual testing does not flag that aberration; hence, no reports on reviews. After all, why flag a weakness that will only present for pinpoint light sources on a black background and then mostly in the corners? That is why the dozen or so yearly inquiries regarding coma on this site are mostly from people wanting a good lens for astro work and why the same three or four lenses are always suggested on those threads with another three or four strongly cautioned against.

Question: Why the specific lenses on your list and why not the Samyang 14mm/2.8?


Steve

[disasterfilm]

Pretty much all of the modern rectilinear Samyang/Rokinon lenses are fantastic for this.

14 / 20 / 24 / 35 on FF
16 on APS-C.

The 10mm isn't a great performer on the extreme edges.

The Irix 15 on FF does pretty well stopped down to f/2.8

Haven't shot my Laowa 12 in an astrophotography setting. It's unnecessarily wide for FF star photos, but I'm likely to give it a shot next spring on a crop camera.

[MossyRocks]

Haven't shot my Laowa 12 in an astrophotography setting. It's unnecessarily wide for FF star photos, but I'm likely to give it a shot next spring on a crop camera.

You will like it on crop, I managed this on my first time shooting it at night wide open. You really have to pixel peep to find coma wide open and it does almost as well as the SMC A* 400mm f/2.8 ED [IF] in that regard. I don't know how it compares to the Samyang/Rokinon 135mm f/2 UMC as I haven't had a chance to take mine out for a spin (maybe tonight) that lens is supposedly a stellar performer.

[DWS1]

I've never noticed any problem with the Pentax A-28mm 2.8. But, I use it on a crop sensor.

[normhead]

I bought the Rokinon 14 2.8 or this purpose. However I've never actually used it for astro-photography. It's never the less a great Lens.

[Bertrand3000]

Thank you all for the replies. I did mention the Samyang 14mm F2.8 but I did not ask about it since it's coma resilience is well known.

Still, on APS C, wouldn't the Samyang 16mm better for astro since it is a whole stop brighter than the 14mm?

[Qman]

The DA 14 2.8 has noticeable coma. I suspect the best Pentax lens will be the DA 11-18 since it is set up to use a defogging heater for astrophotography. If they did that then they must have tried to optimize the coma.

[stevebrot]

Still, on APS C, wouldn't the Samyang 16mm better for astro since it is a whole stop brighter than the 14mm?

It might be, but the 14/2.8 is $100 cheaper...


Steve

(...mine will be here on Friday...)

[ZombieArmy]

With the Samyang 14mm I'd do some testing to make sure your copy isn't decentered. Mine sadly was and I haven't had another copy since.

[Lowell Goudge]

There is coma and then there is coma as it applies to astrophotography. Most modern lenses pass muster for pictorial subjects such that the usual testing does not flag that aberration; hence, no reports on reviews. After all, why flag a weakness that will only present for pinpoint light sources on a black background and then mostly in the corners? That is why the dozen or so yearly inquiries regarding coma on this site are mostly from people wanting a good lens for astro work and why the same three or four lenses are always suggested on those threads with another three or four strongly cautioned against.

Question: Why the specific lenses on your list and why not the Samyang 14mm/2.8?


Steve

Never tried the Samyang 14/2.8 for Astro work but I will highlight that this lens has significant barrel distortion.

Of course since ther are no straight lines in the heavens, you would likely not notice