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What are your favorite exposure settings for tracked Milky Way shots?

astrophotography dslr imaging
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#1 impresently

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Posted 15 May 2019 - 07:43 PM

I'm looking to do a pretty large stitched mosaic of the Milky Way under Bortle 1.5 skies.

 

I will be using a Sigma 35mm f/1.4 Art lens on an unmodified Canon 6D mounted on an Atlas EQ-G, and potentially guided. I know... sounds overkill.

I'm thinking about stopping down to F/2 to eliminate the coma in the corners. ISO will be somewhere between 400 and 1600. And I will be stacking.

Right now I am thinking F/2, 150 sec, and ISO 800 for each panel.

 

My question if you were doing a tracked, and potentially guided shot of the Milky Way under a Bortle 1.5, what would your ideal exposure settings be ?

 

Edit:

I should add this is for a mosaic shot of the sky only; no foreground. The idea is to get the exposure right so I can pull out as much detail of the Milky Way as possible in processing, but not overbloat the brightness of the stars. 


Edited by impresently, 15 May 2019 - 08:02 PM.


#2 bmhjr

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Posted 15 May 2019 - 07:50 PM

I used 30 sec with the same lens and camera at ISO1600, f1.4. So, you may be able to get close to 60 sec at ISO800, f2.

https://astrob.in/236389/B/

Bill
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#3 Jim Waters

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Posted 15 May 2019 - 07:52 PM

ISO 1600 and expose until the histogram gets between 20 and 25%.  Also try 800 .  Shoot RAW.

 

If you are taking a SINGLE IMAGE turn ON Long Exposure Noise Reduction LENR.  If you are taking multiple and stacking turn it OFF.

 

EDIT - Shoot at f/2.8 to 4.  Wide open the stars will bloat. 


Edited by Jim Waters, 15 May 2019 - 08:12 PM.

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#4 Jim Waters

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Posted 15 May 2019 - 07:54 PM

I used 30 sec with the same lens and camera at ISO1600, f1.4. So, you may be able to get close to 60 sec at ISO800, f2.

https://astrob.in/236389/B/

Bill

Real nice image...



#5 t_image

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Posted 15 May 2019 - 10:28 PM

I'm looking to do a pretty large stitched mosaic of the Milky Way under Bortle 1.5 skies.

 

I will be using a Sigma 35mm f/1.4 Art lens on an unmodified Canon 6D mounted on an Atlas EQ-G, and potentially guided. I know... sounds overkill.

I'm thinking about stopping down to F/2 to eliminate the coma in the corners. ISO will be somewhere between 400 and 1600. And I will be stacking.

Right now I am thinking F/2, 150 sec, and ISO 800 for each panel.

 

My question if you were doing a tracked, and potentially guided shot of the Milky Way under a Bortle 1.5, what would your ideal exposure settings be ?

 

Edit:

I should add this is for a mosaic shot of the sky only; no foreground. The idea is to get the exposure right so I can pull out as much detail of the Milky Way as possible in processing, but not overbloat the brightness of the stars. 

FWIW,

I do a lot of crazy high-ISO astro video at 1/30s exposure realtime.

One thing I can lend from my experience that will come into play,

whether in large or small ways,

is the variance that I experience with regard to sky conditions from the same location that I can see changes that long exposure equation....

And by sky conditions I mean the water droplet content and dust/debris content in the air that can vary from night to night..

Seems like a no-brainer but my gear gives me the luxury of noticing this visually realtime in my live display...

With dark skies you will benefit greatly as the airborne particles will less reflect any light pollution,

and you are less at a risk of the sky approaching the point of blow out,

but be aware this variance can cause differences that you may not notice that night but back in the processing room while zoomed in,

you may notice things..

So it doesn't seem like you expect a magic setting,

but with some of the advice above the better plan is to assess the conditions and adjust given what the sky offers....

 

So the other unorthodox thing I'll leave you with:

In getting proper exposure, I like using a waveform monitor:

 

Digital Photography Review discovers the waveform tool:

https://www.youtube....h?v=hAT-mjS2kyc

 

But instead, you could pre-plan particular bright stars that will be in the frame and can shoot a test shot,

upload it into your laptop,

and then crop to the particular stars and look at their isolated histogram in PS**.

Or you could use the eyedropper to reveal the individual pixel values associated with those bright stars to give you the best baseline for where your exposure will be

***[of course you need to have an idea of where your stacking and processing lead in adjusting a RAW,

since you have to debayer an image to see its histogram or pixel values in PS...

Otherwise you could do the same assessment with RAW with particular tools in your stacking software, esp. PI or Rawdigger, etc........

Just random thoughts for the over-kill mindedsmile.gif


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#6 tkottary

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Posted 16 May 2019 - 12:48 AM

You need to stop down the 35 art to atleast f 2.8 to get decent stars overall frame including corners. I have done multiple tracked sky mosaics with 35 art and d810 at f2.8 and 180s.  


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#7 impresently

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Posted 16 May 2019 - 01:25 PM

You need to stop down the 35 art to atleast f 2.8 to get decent stars overall frame including corners. I have done multiple tracked sky mosaics with 35 art and d810 at f2.8 and 180s.  

Thanks so much for this.

 

Lenstip review showed little if any coma on the corner stars at F2:

https://www.lenstip...._and_bokeh.html

Is that not what you have experienced?

 

Also, Im wondering if you had any experience going one stop brighter in exposure time at those settings. Is there any more detail to be pulled going brighter?



#8 Alen K

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Posted 16 May 2019 - 08:18 PM

Lenstip review showed little if any coma on the corner stars at F2:
https://www.lenstip...._and_bokeh.html

The lenstip test uses a rectangular LED target. As a point source (well, a point source spread by diffraction) a star is a much tougher target.
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#9 whwang

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Posted 16 May 2019 - 09:58 PM

Check this out:

https://www.flickr.c...57667599730890/

 

Use the left arrow to see images taken under different apertures.  Note that there could be a sensor tilt.  So not everything you see is caused by the lens.

 

For 6D's pixel size, I would say F2.8 is a good choice for 35/1.4 Art.

 

Cheers,

Wei-Hao


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#10 impresently

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Posted 16 May 2019 - 10:20 PM

Check this out:

https://www.flickr.c...57667599730890/

 

Use the left arrow to see images taken under different apertures.  Note that there could be a sensor tilt.  So not everything you see is caused by the lens.

 

For 6D's pixel size, I would say F2.8 is a good choice for 35/1.4 Art.

 

Cheers,

Wei-Hao

Very helpful. Thanks.

That's more coma than I had thought or read about.

I know that it is typical of wider field lenses opened up quite a bit, but isnt this lens one of the least problematic of lenses in that category? Can you think of one that's better?

 

Edit:

By the way, this is my first exposure to your work. I'm sure I'm not the first to say your Milky Way mosaics are absolutely mind-blowing. They must have taken extraordinary planning.


Edited by impresently, 16 May 2019 - 10:41 PM.


#11 whwang

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Posted 17 May 2019 - 12:06 AM

Thank you.  The Milky Way mosaic took some planning, but not much.  The real pain in the butt is the processing.

 

As for 35mm, I think Canon's latest 35/1.4 can be somewhat better than the Sigma, based on the lens testing book I mentioned in another recent thread.  Sigma's own 40/1.4 is substantially better.  Other than these two, I can't think of any other 35mm lens that can come anywhere close and does not have Zeiss in its name.

 

I know the coma can be disappointing, but that's the current limit of optics.  Sigma's Art lenses are already the best (including corner performance) for the price I am willing to pay.

 

Cheers,

Wei-Hao


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#12 impresently

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Posted 17 May 2019 - 09:04 AM

Thank you.  The Milky Way mosaic took some planning, but not much.  The real pain in the butt is the processing.

 

As for 35mm, I think Canon's latest 35/1.4 can be somewhat better than the Sigma, based on the lens testing book I mentioned in another recent thread.  Sigma's own 40/1.4 is substantially better.  Other than these two, I can't think of any other 35mm lens that can come anywhere close and does not have Zeiss in its name.

 

I know the coma can be disappointing, but that's the current limit of optics.  Sigma's Art lenses are already the best (including corner performance) for the price I am willing to pay.

 

Cheers,

Wei-Hao

Thanks so much again. This is incredibly helpful.

 

There are literally at least a dozen questions I have about your process, but I'm going to limit it to a two here. By the way, agreed on the processing time... that's where my obsessiveness gets the best of me.

 

First...

For this project, I'm going to be renting lenses for two weeks, so money is less of an object. I thought I had settled on the Sigma 35mm as well as Tamron's 15-30mm 2.8 to give myself a range of imaging options. Both came highly recommended by those here at CN and by LensTip in part due to their corner performance on a full frame. You mentioned Zeiss, which hadn't come as recommended by LensTip in this category. If money weren't an object, what would your ideal lens be?

 

Second... 

I noticed you were doing 30 seconds at ISO1600 stopped down to F4 for each panel, stacking ~100 (wow) for each. Since I am tracking, and potentially guiding, I was planning on 2.5 to 5 minute exposures at ISO800 stopping down to 2.8, which I believe would ultimately make it a few stops lighter than what you had for yours. I planned on 24 panels, stacking 4 to 5 for each. My plan is to do 2 six-hour sessions (or 4 three-hour) to complete the imaging. Besides potentially turning 30 hours of integration into 60 or 120 hours, is there a reason you chose not to go a few stops lighter? Is there not more detail to be pulled in processing going longer on exposure time?

 

Thanks again.

 

Kind regards,

Christian



#13 whwang

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Posted 17 May 2019 - 10:43 AM

Hi Christian,

 

It's hard to say.  I probably will not pick a Zeiss, because data about their astrophotography performance are so sparse.  The Sigma 40mm is really awesome, but I would worry about sensor tilt caused by its weight (more precisely, lens tilt caused by a small play in the lens mount).

 

On my A7R, I did 30 sec to avoid its star-eater problem.  It's really too short, but I have no choice.  If I am using my D800, I would go for probably 3 minutes under ISO 800 and F4.  I use my 50mm Art at F3.5 to F4.5, to avoid coma.

 

Cheers,

Wei-Hao


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