Doesn’t work for me.
Is Z7ii different?

Shang....I would have used a lower iso but, in addition to the clouds you see, there was also a thin veil of cloud/haze OVER the comet as well.I
If you have a clear, DARK sky, you could shoot at iso 800 (maybe lower).

I have been "clouded out" every morning (and evening) that Neowise has
been visible! Finally, last night, a few breaks in the clouds and I got a quick shot thru a cloud-gap. I didn't have time to work with settings before it would be completely clouded out again, so I just guessed and shot!
Nikon 70-200E @200mm f/2.8 iso 1250 3sec....no tracking, so there's a tiny bit of "trailing" in the stars, visible as a slight elongation at full resolution.
Didn't have time for follow-up, corrective exposures before the comet was clouded out - again!

You've gotten plenty of excellent advice! Let me stress the ones regarding temperature: TAKE SOME WARM CLOTHES! The end of tourist season is my favorite time to go (although I don't know how crowded it's been THIS year). High Summer is generally a nightmare!
My wife and I visit Yellowstone every two years (alternating with Alaska).
While it IS true that you won't see ALL the wonders in 2 weeks (that would be like spending ONE DAY AT WALT DISNEY WORLD!), you CAN see quite a lot driving around. For a lot of wildlife, we drive around and, seeing wildlife at a distance (or, in the case of Bison...blocking the road and peering into your car!), park and take a relatively short hike towards them.
Over 10 years of these visits, we have NEVER seen bears EXCEPT along the roadway. Watched a mother black bear and her cubs devour berries from 10 feet away and got great photos through an open car window. Have seen several grizzlies, two with cubs, the same way.
I, too, am an astronomer/astrophotographer and have spent several nights, away from "civilization" observing and imaging. It's so dark you literally can't see ANYTHING (except stars) without a flashlight. One night I was on the shore of Lake Yellowstone, imaging the heart of the summer Milky Way AND its' REFLECTION on the water. I felt, more than heard, something behind me. I switched my red flashlight on, turned slowly around an there, not 5 feet away, was a huge bull Bison! I switched OFF the light, turned slowly back around and just stood there motionless. After about 5 minutes, the Bison got bored and shuffled away. Talk about an adrenaline rush!
I envy you your trip. With all the travel disruptions, I'm staying home this year.

I'm not dismissing Covid-19. But how can we know WHAT to believe when there are so many lies from both medical and political sources. This virus has been turned into a political crisis for the purpose of affecting the upcoming elections AND a medical scam.
I had a heart to heart talk with my personal physician of over 25 years..a man who is highly respected for his medical expertise and plain-speaking honesty.
He just lost an 82 year olds woman with terminal lung cancer and found that the hospital had changed the cause of death to Covid-19. Three days later, a 73 year old man with a lifelong history of heart disease, died of a massive coronary thrombosis. Agsin, the hospital changed the official cause of death to Covid-19.
This promoted him to meet with hospital administrators where he discovered that ALL of the deaths of his patients for the past 3 months (except one who died in a messy car wreck) had been categorized by the hospital to Covid deaths!
The hospital can receive about $3,000 for a "natural" death...But $13,000 for a Covid-19 death!
Given this, repeated at hospitals across the country, we DON'T KNOW the true mortality rate of the virus!

I have one of those and, for the price, that IS A good deal!

I had the opportunity to use BOTH the G1, the G2 AND the SIGMA Contemporary side-by-side-by-side with my D850 about a year ago.
I'll keep this short and sweet. I bought the G2 and have never regretted it!

Here is an image of last week's full moon shot at f/8.
ISO 100, 1/1000 sec. with a Nikon P1000 @2500mm, manual focus.
Tripod mounted (although with a little practice and the improved IS system, hand-holding can be accomplished...but why bother?). Keep in mind this was a so-called "SuperMoon" and was, in fact, about 30% brighter than a normal full moon.

Aperture is not the issue with the "mirror-lens" in question. A few years ago I tried ALL of the available makes of the 500mm mirror lenses at f/5 and f/8 for an astro-imaging test.They were all returned. Imprecise focusing and loss of contrast were the biggest complaints.
If you DO try focusing on a star or planet...bring the object to it's tightest, brightest, tiniest appearance and you'll be pretty close.

When not using one of my telescopes, I would usually shoot the moon with a Nikon D850 and Nikon 70-200E or Tamron 150-600 II. THEN, the P1000 was released and has taken over "lunar duties!

For most camera or lens combination you use, I'd recommend 1/500" as the absolute maximum exposure for a full or near-full moon. Even at that, you'll probably get blown highlights.
Depending upon the phase - somewhere between 1/250" and 1/1000" or so delivers good contrast and f/8. delivers enough depth of field to keep things in focus from center disc to limb. Once you get all the way up to f/16+ you'll usually start to see diffraction effects. YMMV.

Hope at least some of this helps.

Mike

Right back at'cha...Garry Owen...out!

To others on this thread. Please excuse this off-topic exchange.
It was just a "moment".

11Bravo here. Our basic color was DIRT! 😁 2/7 CAV

Hey CIB.... Thanks for your service. There are those of us who know what it takes to earn that badge.

Pile another YES on for the SB-400! I've had mine since the model first came out with no problems and it's been the "Most Used" flash unit on my D850.
Often, I just put it on the camera whether I plan to use it or not. The low profile has the advantage of keeping things compact and unobtrusive. As for redeye; bounce-flash indoors and it's never been a problem. Outdoors I've rarely had a problem with redeye, and tilting the flash head up a notch or two
fixes that. The Big Monster (compared to the 400), the SB700, only gets limited use. The 400 is the closest replacement for onboard flip-flash
that I've found.

PS....i dont think THIS image could compete with the quality of what we get with our D850s and Tamrons...but for small prints or online posting, its better than missing the shot! 😇

May I digress?

Just like many of you, I chose the Tamron 150-600 G2 for my D850 after side-by-side comparisons with the Sigma and Nikon 200-500.
They're excellent...but they ARE a bit heavy and awkward!
Just for fun I tried the NIKON P1000 as an "always have with me" substitute. I've posted other images with this camera... But, since this discussion was ongoing, I ran out in the backyard and took a shot I COULDN'T HAVE with the "bigger glass". The shot is of an Osprey, in the top of a fir tree from about 200 yards away. It's really dark (you can see the last rays of the sun lighting the tips of its feathers on the far side. This image is at 3500mm.
Yes...3500mm. You might just consider one of these cameras as an addition to your arsenal. I don't know if even the D850 could have enlarged a 600mm image as well as this. SOOC

Used Nikon 200-500, Sigma 150-600 Sport, Tamron 150-600 G2 with my D850. BOTH Sigma and Tamron (to my great surprise) equalled or exceeded the Nikkor!
The Sigma was ever so slightly sharper of the 3 but was simply too heavy for hauling around for long periods.
Tha Tamron came in 2nd and I have never regretted it.
With the exception of a Sigma ART 50mm f/1.4, the Tamron is the only other NON-Nikon lens I've ever bought!