OleMe Loc: Montgomery Co., MD

Firstly, note that I'm primarily after images of the Milky Way. I've read about the 500 rule / rule-of-thumb for avoiding star trails. My understanding is that applies to 35 mm camera lenses.

How about micro 4/3rds? Say a 28 mm lens, which in my case is probably ~ 1.6 x 28 or ~49 mm equivalent for a 35 mm camera.

Gear: I've sold a lot of more bulky equipment and am making the BIG MOVE to Micro 4/3rds, most likely an Olumpus OMD E M-10 Mark III. While I want a Olymput Pen-F but will likely settle for more bang for the buck.

I've got a choice of a 28 or 45 mm lens, both F/2.8. Which would be best for Milky Way? Might an 14-42 f/3.5-5.6 "kit" lens be enough - I'd like to save a few bucks? I won't be going "pro" / "prime."

FWIW: I've read several on-line guides, including Night Photography: How to Photograph The Night Sky, by Dave Morrow.

Thanks for your guidance.

/Roger

juan_uy Loc: Uruguay

Hi, AFAIK the "500 rule" is for 35mm equivalent as you said.
In my case, for example, as I have a Nikon DX (APS-C) camera I would use 500/(1.5*FL) instead of 500/FL.

I think, not sure, that for micro 4/3rds the factor would be 2, so the formula would be 500/(2*FL).

In any case, as you can see the wider the length the longer the time you will be able to have the shutter open (all other conditions equal).

Before spending more money, give it a try with the lenses you already have. Depending the low light capability of your camera you may get "good enough" results.

You can use this calculator to play around: https://www.photopills.com/calculators/spotstars

OleMe Loc: Montgomery Co., MD

Thanks, Juan.

I won't be able to "play around" in advance. Too much sky shine here in metro Washington, DC.

juan_uy Loc: Uruguay

A good option, not sure if they have one for your camera, are Rokinon/Samyang lenses, they make wide manual lenses that are affordable and give good results.
For astro, being manual is not a problem (you'll use the lens manually in any case).

As I said, the widest the better, so for your camera with a crop factor of 2 (confirm if that is the case) you would have to aim to 8 or 10mm lens. For this type of photography crop factors are detrimental.

I have used a lens equivalent to 16.5 at f2.8 that allows me exposures of up to 30 seconds without trails.
I recommend you get a combination that gets you at least at 20 seconds, what it would be around 25mm equivalent or around 12mm in micro 4/3rds (wider than that would be even better).

Then it will depend on how good your camera behaves at high ISO. You can try different levels and see afterwards which one gives the best result.

Another tip, although you can change it in PP (if shooting RAW, what you should for astro), is to change the WB to something around 3500-4000, so you will have a better feedback from your in-camera preview.

Obviously you will need a sturdy tripod and head, turn off any stabilization, use live view or mirror lockup or shutter delay, I would also use a remote shutter release in addition.
I strongly suggest turning off long exposure noise reduction (if you want to use it, turn it on for the final shot but not for the previous test ones).

I am no expert, just have tried some times, I think I summarize (without much order) the tips I can give :)

mikeroetex Loc: Lafayette, LA

Love Big Bend, you will be amazed at how dark it can really be. Like being outdoors in a photo lab darkroom. I could barely see, it was hand-in-front-of-my-face dark.
You may find this article helpful. The rule of 500 is changing, but MFT camera would be Rule of 200 according to them. Me? I just use Photo Pills app. Best $10 you will ever spend.
Have a great trip!
https://www.nationalparksatnight.com/blog/2019/4/13/new-rule-for-shooting-the-sharpest-stars-in-the-sky?utm_term=0_5fe0716fe0-70329fcdfa-110832761&mc_cid=70329fcdfa&mc_eid=c6acf03266

juan_uy Loc: Uruguay

I second PhotoPills recommendation, full of features!
It sounds expensive for an app, because we are used to 1 or 2 dollars, but it is very reasonable at 10 with the amount of tools it has, how it works, and the assistance you will get from it.

It is a "must have" to plan your night shoots in advance, starting now :)

jwm1944 Loc: Maryland

for dark skies where you are go to the Atlantic coast. Assateague Island N.P.

CraigFair Loc: Santa Maria, CA.

"The 500 rule for a full-frame camera requires you to set your camera to ISO 3200 or 6400.
500 / focal length / 1.6. For example, with a 50mm lens it is 500 / 50 / 1.6 = 6 seconds (approximately).

JimH123 Loc: Morgan Hill, CA

Regarding the question on 28mm f/2.8 or 45mm f/2.8, there is a 2nd factor to consider besides FOV. If you take the 28mm f/2.8 at wide open, the objective is 10mm. Or if you take the 45mm f/2.8, the objective is 16.1mm. If you compare the area of the 16.1mm objective vs the area of the 10mm objective, the 45mm lens will gather about 2.5X more light. But the FOV will be narrower. This can be remedied by doing a panoramic and stitching.

Or you can crank up the ISO and use the 28mm lens.

Also, when you do a panoramic of a number of images, the sizes of the stars will appear smaller after stitching. You may find stars do not stand out when this is done.

Another important thing to consider is the amount of lens distortion you are going to encounter with each of the two lenses. Some lenses are really good. And others, not so good. You can decide what you have with some experimenting. And speaking of experimenting, you really don't need to consider the 500 rule with digital cameras. Just take some test shots and look at your results. Then pick the settings that look good to you. Back in the film days, we didn't have that luxury, and had no idea how good or how bad our results were until the film was developed. That's a limitation we no longer have. With a binary search where you take one that is too long, then one that is too short. Then you try a shutter time half way in between. After that shot, you know whether to half the time above it or below it. This method gets you down to the optimum time in just a few test shots. You can keep going and half the distance again and again for finer resolution. But most likely, that precision isn't necessary.

When taking astro shots, stacking multiple images really reduces noise and improves the look of stars. A good piece of SW to use for this is the free Sequator. It allows you to have a stable terrestrial shot and to stack a large number of sky images into one.