max video length for the moon?

[iwols]

hi just wondered what the max video length for the moon is thanks

[ONIKKINEN]

I would say no limit, just keep the target centered as it will drift with imperfect polar alignment over time.

File sizes do get ridiculous after a while, more than 50gb files take forever and a half to stack so keep an eye on that maybe.

[iwols]

what do most use?

[CraigT82]

I usually shoot 5k frames at a time which at 100 fps is just under a minute. There not really a time limit but as mentioned by Onikinnen the file sizes get huge quickly especially if capturing full sensor size 

[iwols]

thanks guys

[vlaiv]

Actually there is a time limit, but it depends on several factors - and not all factors contribute the same and at the same time.

Moon close to horizon is slightly smaller than when it is at zenith. This is due to position of observer and rotation of the earth.

When it is close to horizon - then distance includes radius of the earth - but when it is directly above - distance does not include radius. That amounts to difference of about 1.66%

If your lunar disk is say 2000px in diameter - that will be 30 ish pixels of difference at those two positions.

Not sure if stacking software can account for this (and I think it can't). So first limit is set by how far away (or closer) we move during recording.

Second thing is - lunar phase. Full lunar cycle is about 28 days, so sun changes position with respect to lunar face at about 12.86 degrees per day. That is half a degree per hour.

Now, if sun is shining directly at lunar face that we are imaging (full moon) - this change is minimal, but if we image the terminator - some really interesting effect might happen due to this.

Shadows that are already long can grow quite rapidly due to this.

If light is already hitting a crater at shallow angle (like at terminator) - then very small change in angle can make it noticeably longer.

For this very reason there is only limited amount of time that Lunar X and V are visible - like just couple of hours.

In any case, I'd say that you are safe if you image for less than an hour - as above effects won't be visible.

[neil phillips]

I also wonder about the question of diminishing returns. 10.000 Frames is probably enough. So why take 20.000. ? let alone 100.000

The gains would be minimal going to very long time scales