dyximan

I presently own a Nikon D500 and will eventually upgrade to a FF Nikon. My questions are as follows
I am looking to purchase a !.2/1.4 or 1.8 lens as I would like to do more night/ long exposure and street photography with some indoor venues aswell. I have read a lot and looked a various lenses makes and models aswell as various coatings, blades, and focal lengths. Manual focus/auto focus. I would imagine with astrophograpy you would set you focal length at Infinity most if not all of the time? I am curious as to what specs most of you astro photographers use and or prefer.
I want to thank you in advance for your time and effort in this matter.

alberio Loc: Casa Grande AZ

I assume you mean set your focus at infinity. Sometimes a lens doesn't focus perfectly at the infinity setting, so you might have to try different techniques to get correct focus. Also some lenses don't perform as well at their lowest f stop. If you are doing just Milky Way nightscape shots you might not notice slight imperfections. Remember the longer the exposure the stars will have trails.

Europa Loc: West Hills, CA

^^^ +1

dyximan

That I understand about the trails that's why I was wondering if a 1.2 is that much faster than say a 1.8 to reduce the time the shutter is open. Is the difference between a 1.8 and a 1.2, 1 stop, 2 stops, half a stop, 3rd stop. This I don't know as well.

alberio Loc: Casa Grande AZ

I think between 1- 1.2 stops.

JimH123 Loc: Morgan Hill, CA

Many lenses, when used wide open, have considerable distortion that is exasperated with point source objects like stars. This distortion tends to get better as the lens is stopped down.

And some lenses are really good wide open.

Knowing which camp a particular lens is in is the problem we all face.

As for focusing at infinity, stars need perfect focus. I find that lenses that try to make it easy by stopping exactly at infinity often miss infinity. And that may mean not being able to reach infinity.

I prefer mechanical focusing lenses that provide a lot of rotational travel. Some mechanical focusing lenses only offer a short rotational travel, and are difficult to use.

Focus by wire is usually a real pain for focusing on stars.

The way I focus on stars is to use live view with focus magnifier on and peaking off and to start with a bright star and focus the best I can. Once I am close to perfect focus, dimmer stars start to become visible. Change your attention to the dimmest star you can discern and then slowly rock the focus back and forth until that dim star is at its very brightest. This rocking back and forth is where focus by wire doesn't work very well.

alberio Loc: Casa Grande AZ

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