A mug astro-photography question

[BobT]

My first attempt at astro-photography. I was out camping and Venus looked particularly nice so I put the E-M1 + 50-200mm on the tripod. I found it incredibly difficult to focus. Even the slight slack in the focussing ring was enough to put it off. I can't understand why it's so sensitive. In daylight, focussing at infinity is no issue.

[RAH]

I think that with a modern by-the-wire lens, which generally has no stopping-point at infinity, the only really reliable way to set it at infinity is to pre-focus it ahead of time (before it gets dark) at some distant object (I'd use AF for this), then switch it to manual focus and don't touch it.

[Daniel Bradley]

Yeah, focus-by-wire.... I hate it! Did you try turning focus peaking on. It helps... MF at night seems really touchy because you notice the slightest differences that might not be noticed during the day. It is hard to do, even with my 600mm telescope with a 1.4 TC attached. Astro photographers often use a thing called a Bahtinov mask (google it) over the lens to make it possible to focus REALLY accurately.
That all said, Venus with only 200mm on an E-M1 isn't going to be more than 6-8 pixels across, so even if you do get the focus right on, you will not see much.

[BobT]

Thanks Daniel. I often see amazing amateur astro pics so I figured it wouldn't be so hard. I was just blown away with the difficultly. I don't understand why something millions of kms away should be so hard to focus. You are right, Venus wasn't much but then the full moon came up and I got a good pic of that. I was camped within sight of the Siding Spring Observatory on the far horizon, one of the darkest places on Earth so I had to take the opportunity. I was mainly there for the native blooms.

[Daniel Bradley]

Astro photography is one of the MOST difficult kinds there is! The problem with focusing is that the slightest turn of the screw will move the focus by light years! Add air into the equation and you are in for some real challenges. Air is the worst enemy of any long lens guy. I hate the stuff! It can act like a lens and throw the focus in and out constantly. Stacking is the only solution, unless you have a couple of extra billion dollars lying around and good connections with NASA.
When I got my telescope some years ago I thought I would be able to do some astro work, but soon came to realize that it is much too difficult for me to make it satisfying, and I was not willing to 1, spend a bunch of money on equipment, 2, spend hours and hours processing, and 3, freeze my butt off on the only clearish nights to be found around here, in the middle of winter and in the mountains. Things like this (stack of 31 shots)



or at best, this (stack of 6 shots)



are the limit of my abilities.

If you are in a good area... ok, so maybe you can't see the north star, but otherwise...... dry and clear air, overall shots of the Milky Way etc incorporating landscape elements into the shot, are certainly possible and can be very satisfying.
I remember as a kid, maaaaaany years ago, camping out in the mountains of Colorado. Never any worry about rain so we would just sleep out under the stars. They were so bright they would keep me awake! Here, on the outskirts of Vienna, we are lucky to even see the big dipper.

[BobT]

Your Moon shot is amazingly sharp. I like the shot of the space station too. Clearly they had switched on their clocking device . Coincidently, as a kid, I spent some months in winter in a village in Austria at about 900m. I recall being on my skis on a crystal clear day looking up. With the sun so low, the zenith was so dark blue I could see stars at mid-day. Mind you I'm talking more than half a century ago. The few times I've been back since, most parts of Europe now seem to be enveloped by an incessant fine haze. Air pollution I'm guessing. We don't see that so much down here except on still days in a large city. Thank God for the clarity slider in Lightroom. It seems to cut through the haze. But I digress. I guess 1've come to the realisation that where DOF tables might say that at f3.5 one has DOF from 680m to ∞, that's pretty academic (meaning useless) as far as astro-photography is concerned.

[Daniel Bradley]

"Thank God for the clarity slider in Lightroom."
.... AND the dehaze slider! The three together, contrast, clarity, and dehaze can work wonders. It seems that each modifies the contrast in different areas of the tonal spectrum; contrast over all, clarity in the mids, and dehaze more in the darks, at least it seems that way to me. As the files from the E-M1 Mark II are a little "thin" (can't outsmart physics... not many photons in those tiny pixels) those sliders as well as the color sliders have become very important.

[BobT]

Unfortunately for me, dehaze is one of the goodies they are deliberately keeping from stand alone LR users. Nevertheless, I'm enjoying the lower cost and in any case I don't have the bandwidth for CC (despite living only 20km outside Sydney).