No one uses recommended exposure length?

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GaryFarmer
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No one uses recommended exposure length?

Post by GaryFarmer »

I have viewed Robin’s lecture regarding recommended exposure length more than once. The very people who have pointed to the lecture, and commend it, do not even come close to using the recommended exposure lengths. I understand that these are the recommended “minimum” exposures but every YouTube channel I watch use exposures of 20-50 times these recommendations. What am I missing?
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admin
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Re: No one uses recommended exposure length?

Post by admin »

Hi,

perhaps the most important thing is that there is no harm in going past these exposure lengths as long as you don't run into either of these two problems

1) tracking/guiding problems
2) oversaturation of stars or the background

On the flipside, there's very little to be gained by going past the recommended length except that you have less data to process at the end of the day. Certainly not a big improvement in image quality of your final stacked image.

Hopefully I've saved at least a few people from going through the (rather expensive) cycle of

take a few images with relatively short exposures => post on forums to ask how they can be made better => get told to take much longer subs => struggle with tracking/guiding => buy new equipment (guider/fancy mount) => get images that are not much better (or at least are not better due to longer subs)

Cheers, Robin
umasscrew39
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Re: No one uses recommended exposure length?

Post by umasscrew39 »

Hi Gary

I agree that most, including myself, have fallen victim to using longer exposure times than are required. That, like Robin stated, does lead to saturated stars at times, all looking white and sometimes bloated. The star shapes are also affected by oversampling or undersampling, depending on your scope and night seeing. However, another newer (not better) reason many, like myself, are using longer exposure times than are necessary is that some of the new larger frame cameras (APS-C and full frame) produce very large file sizes. If you have a lot of them your computer will basically come to a crawl unless you have a powerful, upgraded system. I recently purchased a powerful Threadripper desktop and it still takes significant time to process large file sizes, especially if you have dozens or hundreds of frames. Overall, I think the larger frame cameras and better mounts that are coming available have unfortunately lead folks to think that longer is always better- which, of course, is false.

Bruce
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