Photographing Neowise with 600mm lens

Started 3 months ago | Questions thread
W5JCK
W5JCK Veteran Member • Posts: 3,600
Re: Photographing Neowise with 600mm lens

PHXAZCRAIG wrote:

I've been shooting 500mm and 700mm the last three nights.

Total newbie at this astro stuff. I have a new 500F5.6 prime, and an old 1.4TC, so I've been trying that from my porch.

With the 1.4 mounted, I have an actual 700mm, of FX format (D850).

What I've found is that if I go above about ISO 8000 I don't like the look of the noise I get, and particularly above 10,000. But I've got a slow lens to deal with - F8 wide open. The viewfinder is dark enough to make it extremely hard to find the comet in the viewfinder.

With ISO 8000 or so, I'm using 2, 3, and 4 second exposures, but I'm certainly getting star trails. Really, at 700mm I need to be shooting at 1 second or less, and at F8 I'm into very high ISO I don't like. Not sure I have much I can do here, besides stacking techniques I'm not prepared to do.

As for the focal length, it's been fine. I get all the tail I can make out of the background glow of the Phoenix city lights.

If you are shooting with f/8 and using a 1.4x teleconverter, Then that adds another stop meaning you are actually shooting at f/11. Way to small of an aperture.

You should probably be using a 200 to 400 rule, which means 0.3 sec to 0.6 sec shutter. To get a view of the tail you are having to use 4 sec, which causes long tails and high noise.
Bottom line is this: To get decent photos you need to use a much shorter FL lens which is much faster. Or you need to track. Right now you are at GIGO (Garbage In, Garbage Out). Sorry, but there is no better way to say it politely. Your setup will never produce good results under these conditions. Switch lenses and toss the teleconverter and you will see a huge difference. Trying to compensate by increasing shutter length and ISO isn’t a good solution.

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