Attempted astro with eos m + 22mm lens but frame flashed red and won't take shot

Started 10 months ago | Questions thread
bobkoure Senior Member • Posts: 1,575
Re: 3 + 3 + 3

bobkoure wrote:

PhotoTeach2 wrote:

bobkoure wrote:

PhotoTeach2 wrote:

bobkoure wrote:

PhotoTeach2 wrote:

Astro must be done in manual mode, (both exposure and focus).

Typical exposures are ISO-3200 @ f/2.8(3) @ 30-seconds. (I remember it as 3+3+3)

But since longer than 15-seconds can show "trails", I suggest using f/2 lens or ISO-6400 @ 15-seconds.

If you don't have a dual-mode sensor, like the D850, and are shooting in RAW, why bother raising ISO? Read noise?

I said "or" .... another choice is f/1.2 - 1.4 and then can even "lower" ISO, (below 3200).

The 3+3+3 is just any easy way to remember a "basic" exposure, (like Sunny-16 or Loony-11).

I realize that I'd have had better luck focusing if I boosted ISO for that. My point with ISO is that for a lot of cameras these days, it's just a gamma adjustment. I normally leave ISO Auto on, but I'd had it off for that test shot. Time to experiment

"Auto" ISO, (or any "auto" exposure mode), is not good for night sky because it will "lighten" it to an (18%) gray.

The question becomes, will it boost ISO high enough to blow out highlights? With a low read noise camera, higher ISO is pretty much a simple multiplication, which I can divide back in post - so long as my highlights aren't blown. I plan to experiment with this, eventually.

I tried boosting ISO to get a liveview that showed me the stars I was framing, but only see the very brightest ones. Not super useful, especially if I zoom the view in. Any idea how to deal with this? My D750 lets me set monitor brightness and monitor color balance - but not contrast. Without changing either of these, I get a grey field with maybe one star visible. There is, of course, an OVF, but I'm having trouble bending my neck to look through it with the camera on tripod and pointing overhead. Right angle attachment? Or maybe there's an open sight that I can attach, a la Nikonos, and use like a guide scope? I went googling and found a way to mount a reflex sight on a hotshoe. Is that the way to go?

BTW, I found a $6 hot-shoe to weaver rail adapterthat won't poke me in the eye if I try to use the OVF. Weaver sights are pretty cheap. I don't need an actual 'red dot', and, as my DSLR has no recoil   I could even use an airsoft sight.

 bobkoure's gear list:bobkoure's gear list
Nikon D600 Nikon D750 Nikon AF Nikkor 14mm f/2.8D ED Nikon AF Nikkor 20mm f/2.8D Nikon AF Nikkor 24mm f/2.8D +14 more
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