Looking for a recommendation for a ultra-wide angle lens

[ChrisPBacon]

I’m looking for and would sincerely appreciate your recommendations for the best prime EF-mount ultra wide-angle lens for use on Canon EOS crop-sensor (7D) and full-frame cameras (specifically 6D, and 6D Mk. II) for astrophotography.

(While there are excellent zoom lenses available, the possible risk of chromatic aberration makes them impractical.  That said, I’m a relative novice to astrophotography and still have a great deal to learn — so if you use a zoom lense for astrophotography, please let me know of your experience.)

I’m imaging asterisms and the Milky Way which require relatively longer exposures but I wish to avoid having stars appear oblong in shape from too-long an exposure; to that end, I need the fastest glass possible to obtain as much detail a lens is capable of capturing — as well as the quality of the detail that is captured. Canon’s 14mm f/2.8L is a good lens, but is it the best quality glass (assuming that cost is not a factor) on the market?  It must be heresy to ask if other manufacturers produce a better lens, but I’m willing to consider all contenders as long as the lens is compatible with my Canon cameras: price is not a consideration.

As I disable autofocus and image stabilization in taking these types of photos, a manual focus (only) lens such as those made by Zeiss is perfectly acceptable.

I’m well aware that below f/2.8, price increases dramatically: while having an equatorial mount would allow for longer exposure times without star distortion, it would create problems for foreground terrain blurring and additional post-production labor, which I’d like to avoid if possible. My 6D is heavily modified for heat reduction and has had its IR filter removed so that light in wavelengths of 656.28 nm appear in photos, but the scale of these structures make use of a telescope impractical.  Light pollution poses another difficulty with increased exposure times, so high-quality fast glass is a better option for my purposes.

Any lens f/2.0 or below, in the range of 8-18mm, might be ideal.  I would appreciate anyone with experience with this lens type sharing their recommendation.

[ChrisPBacon]

Thanks, Tim.

I have a Losmandy G-11 equatorial mount for 5-hour exposures, and a small Sky Watcher mount/tripod for shorter durations.

The 500 rule is a good start, but using it when utilizing the Canon EF 24mm f/1.4L II USM for 20 seconds causes the stars to appear oblong: I use 17 seconds and tweak the ISO.

[TCampbell]

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@ChrisPBacon wrote:
Thanks, Tim.

I have a Losmandy G-11 equatorial mount for 5-hour exposures, and a small Sky Watcher mount/tripod for shorter durations.

The 500 rule is a good start, but using it when utilizing the Canon EF 24mm f/1.4L II USM for 20 seconds causes the stars to appear oblong: I use 17 seconds and tweak the ISO.

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Hi Chris.  The G11 is a fantastic mount (just make sure it's accurately polar aligned).  If your G11 has the Gemini 2, there is a Polar Allign Correction (PAC) mode (Scott Losmandy has a YouTube explaining how to use it.  Just go to YouTube -- there's a Losmandy YouTube channel).    I use a G11 ... and a GM8 ... and a StarLapse (I really like their mounts).

The "500 Rule" is meant for full-frame camera sensors (roughly 36mm x 24mm).  The 500 rule should be valid for your full-frame bodies.  For crop-frame bodies (APS-C at 1.6x crop-factor or APS-H at 1.3x crop factor) you would want to divide 500 by the crop factor.  E.g. if using a 7D body then you'd use 500 ÷ 1.6 = 312.5 ... and then divide the lens focal length into that for the number of seconds (e.g. with a 24mm lens it's about 13 seconds).   

The more liberal rule was the "600 Rule" ... but on close inspection some people find a slight amount of elongation (hence the "500 rule" to be a bit more conservative and most people are happy with that).  I'm wondering what camera you were using when you said you needed to cut the exposure time to 17 seconds.

I use a QHY "PoleMaster" to achieve highly accurate polar alignments (within a few arc-seconds of the true pole).  Equatorial mounts can use "modeling" to work out factors such as "cone error" or even moderate inaccurate polar alignment issues and creating a "model" (really only recommended for permanent observatories.  If you setup/take-down the mount each time you use it then a model is a waste of time) will only help you achieve more accurate "go-to's" but will not do anything for tracking accuracy.  With plate-solving software (astrometry.net and similar), the solving will give you ultra-precise go-to's and the rest is all about mount quality, balance (a slight imbalance where the "east" side of your mount is just a tiny bit heavier will help reduce "float" in the worm/spur gear backlash) and above all ... an accurate polar-alignment.   The PoleMaster camera aligns the "mount" -- not the "scope".   SharpCap also has a polar alignment feature ... but the field of view of a camera through a telescope is usually narrower than 5° -- so it needs a better initial estimated alignment to use it.

[ChrisPBacon]

I do an accurate pole alignment using the QHCCD Polemaster and have been using it over a year. I had a pad poured at my house for my telescope and despite its permanent mount, still do a polar alignment

Again, in case you missed it, I’ve used the 500 rule which, for a 24mm lens, gives the answer of 20.833 seconds.using 20 seconds, stars appeared slightly oblong so I’ve reduced the exposure to 17 seconds and adjusted the ISO upward to compensate,

[Waddizzle]

I use the EF 16-35mm f/2.8L II USM, and love it.  If it is not as sharp near the edges and corners, then I have not noticed it.  I have ot really looked for it, either.  I have noticed that it does seem to have a focus plane that is curved, with the camera at the center of a sphere or cylinder. 

I like the lens.   I cannot help but wonder if the soft edges and corners that people are observing are a side effect of lens correction.

[goalerjones]

I purchased the Samyang 14mm 2.8 for MWP. 1st time was bad, due to user error and not understanding infinity on a lens doesn't necessarily mean in focus, 2nd time was much better. I've recently added the Tamron 15-30mm 2.8 but have yet to take it back out to the desert for a go.

[ebiggs1]

I would certainly like to hear you thoughts about the Tamron SP 15-30mm f/2.8 Di VC USD G2 Lens.  It should be a real nice lens. I have not used the G2 but the SP is very good. At 15mm and f2.8 I think you will not like the softness for astro work. But f4 on should be fine

"I use the EF 16-35mm f/2.8L II USM, and love it"

I don't, as a matter of fact I stopped using mine for anything. It certainly is not anywhere close to being capable of astrophotography.

[Waddizzle]

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@ebiggs1 wrote:

"I use the EF 16-35mm f/2.8L II USM, and love it"

I don't, as a matter of fact I stopped using mine for anything. It certainly is not anywhere close to being capable of astrophotography.

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I have not used it for astrophotography.  I have found the manual focusing Rokinon 14mm T3.1 to be more useful for shots of the night sky because of its' focus scale and manual aperture ring.  It is impossible to adjust aperture when an electronic aperture lens is set to MF, and I do not want to switch it to AF.

The only drawback with the Rokinon is that it may be too wide, and creates barrel distortion on the edges.  This is not much of a problem with a single long exposure.  It becomes an issue when you start tacking photos, and auto aligning them.

[ebiggs1]

"... the Rokinon is that it may be too wide, and creates barrel distortion on the edges."

I would like to see a sample photo.  I no longer do sky photography. I only hear the results from my friends that do. I was into it heavily for a few years. I was a charter member of the Powel Observatory. When it moved to Missouri I pretty much quit.

Several of the Rokinon lenses are favorites.  Sometimes you have to get several to many before you get a good one. However when you get a good one it is good.

"...it may be too wide..."

When it comes to capturing the night sky, a camera lens that is fast and wide like the 14mm Rock works well.. You can capture much more sky and that is the purpose of such a lens. Now if you don't want a wide angel sky it may be too wide.  Usually not the case.

"...creates barrel distortion on the edges."

If all you do is shoot landscapes it doesn't matter.

[Waddizzle]

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@ebiggs1 wrote:

"... the Rokinon is that it may be too wide, and creates barrel distortion on the edges."

I would like to see a sample photo.  I no longer do sky photography. I only hear the results from my friends that do. I was into it heavily for a few years. I was a charter member of the Powel Observatory. When it moved to Missouri I pretty much quit.

Several of the Rokinon lenses are favorites.  Sometimes you have to get several to many before you get a good one. However when you get a good one it is good.

"...it may be too wide..."

When it comes to capturing the night sky, a camera lens that is fast and wide like the 14mm Rock works well.. You can capture much more sky and that is the purpose of such a lens. Now if you don't want a wide angel sky it may be too wide.  Usually not the case.

"...creates barrel distortion on the edges."

If all you do is shoot landscapes it doesn't matter.

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"The only drawback with the Rokinon is that it may be too wide, and creates barrel distortion on the edges.  This is not much of a problem with a single long exposure.  It becomes an issue when you start [stacking] photos, and auto aligning them."

You just love to take a few words out of context and apply your own meaning to them.  Have you ever tried to auto align and stack photos.before?  It sounds like you may have forgotten what is involved.

[ebiggs1]

Actually, my thoughts was, I truly doubt you have done any astrophotography. And, no, the Moon doesn't count.

"I would like to see a sample photo."

I'll wait !