Astrophotography Lens?

[LTCSZ]

Hello: I am just getting into astrophotography and am looking for a good, entry level wide angle  lens for my SL2...It needs to be f1.4 or f2.0...I am willing to consider used if in good shape...Any advice will beappreciated! Thanks...

[jrhoffman75]

Rokinon 24mm f/1.4 is one to consider.

Plenty of information available on YouTube for this topic.

[ebiggs1]

"Rokinon 24mm f/1.4 is one to consider."

The above Rok is a good lens. A bunch of my astro buds use one. But keep in mind it will behave like a 39mm lens on your camera. Not really all that wide for a deep sky lens. Although a stop slower the Rokinon 14mm F/2.8 lens (22mm equivalent) might be a better choice. I am sure either will work.

There is also the Rokinon 10mm f/2.8 which I know nothing about nor anyone that has one. One of the guys that shoots the sky said he was looking at it.

Rokinon is a unique lens maker.  People either love them or they hate them. I personally don't own one. But several of my friends do. I used to do a lot of astrophotography but I don't do much any more. I have a Tokina AT-X 16-28mm f/2.8 Pro FX Lens that does what little work I do.

[ebiggs1]

"It needs to be f1.4 or f2.0 ..."

BTW, you were inquiring about wide angle sky lenses? 

[shadowsports]

@LTCSZ,

The advice that Ernie and John has provided is excellent.

The only thing I can add is an endorsement for Rokinon glass.  I just purchased a 12mm f2.8.  I haven't used it for astrophotography, but can say from a performance and clarity standpoint, the optical quality is definitely there.  Even at the edges.

A fast lens is important, but I believe anything f2 or lower will be suitable if its primary use will be astrophotogrphy.  I went with f2.8 because I wanted something mostly for creative daylight situations.  Last consideration will be focal length.  (As Ernie pointed out).  If you use a FF lens on an APS-C body, your FOV will be slightly more narrow.  Only other thing I would suggest is a wireless remote control for shutter release. 

[ebiggs1]

"... but can say from a performance and clarity standpoint, the optical quality is definitely there."

This seems to be a characteristic of Rokinon lenses. They don't seem to have any problem with IQ. Although I have never owned one, I have been around them.  The build on some models isn't quite where I would want it or like it to be but for occasional use, I think they do OK.

[jrhoffman75]

The 14mm f/2.8 Rokinon is a very popular lens for star trail and Milky Way photography. It has very strong moustache distortion, which is not a problem for astro. It also has poor factory QC. Not uncommon to have to go through several copies to get a good one. But once you get a good one it performs well. 

Very fast lenses generally don't work out well for astro. Wide open they have edge problems - coma and sharpness issues. Need to stop down to address, which defeats the benefit of wide aperture. The fast and expensive Canon 14mm f/1.4 is an example of this. 

[ebiggs1]

"...fast lenses generally don't work out well for astro. Wide open they have edge problems ..."

What you are trying to convey is slower lenses don't have wide open aperture issues.  I doubt that is true across the board. MOF, it is my experience all lenses perform better stopped down at least one stop.

"It also has poor factory QC."

This is a point for all thinking about a Rokinon lens to consider.  I know guys that have purchased three, or one guy four,  Rokinon lenses of the same model .  They tried, tested, them and keep the best one of the bunch. OK it is a cheap lens so I guess this isn't a big surprise. Rokinon has to cut costs where they can but what happens to all these returned lenses?  Do they get put back in inventory?  These lenses I am talking about will look unused and have all their packaging exactly as it came. However, they aren't good lenses.

This is one reason I don't have one. I don't want to go through the hoops getting a good one, returning how many, although I love doing lens tests. 

[jrhoffman75]

"...fast lenses generally don't work out well for astro. Wide open they have edge problems ..."

What you are trying to convey is slower lenses don't have wide open aperture issues.  I doubt that is true across the board. MOF, it is my experience all lenses perform better stopped down at least one stop."

What I was intending to say is that very wide aperture lenses, because of the design compromises that need to be made, generally have edge problems that are detrimental for astro. The Canon lens, in particular, has bad coma wide open. Point stars look like batwing objects. Stop it down to f/2.8 and its OK.

The Rokinon f/2.8 at f/2.8 has no coma issues.

In addition, for astro, since stars tend to be a little diffuse anyway, razor sharp pinpoints aren't required (since the stars aren't). They just need to look like stars; stopping down doesn't generally benefit with lenses that the astro followers are generally identifying as "good" lenses (Rokinon and Irix).

What benefit might be gained from stopping down starts getting lost as noise increases. This is particularly true for Milky Way photography. Short shutter speeds are required to get point stars. SS could be 13 seconds or shorter. 

[LTCSZ]

Thanks to all that replied...Gives me lots to research!