Capturing the Astro Trifecta Shot - Foreground + Milky Way + Meteor Shower

rcolman · 08-10-2016, 07:38 PM

[Astrotracer can be set in any mode (software allows it), but it only effectively works in B (Bulb) mode (as stated above by Steve). In B mode, it is not possible to use the camera own intervalometer (I.e drive mode = INT), but, by pressing the green button we can set the duration of exposure with a dial wheel for up to 5 minutes. If more than one frame should be captured using an external intervalometer to trigger the shutter in B mode+astrotracer, I'm not sure if the stars would still be aligned when stacking multiple Astrotracer frames. However, regarding ISO and aperture settings, f4 ISO400 + 4 minutes exposure (<5 minutes) should work, or even f2.8 ISO200 (very clean) 4 minutes + low shutter speed noise reduction (dark frame subtraction), should deliver very clean images, so no frame stacking necessary to improve image quality. Without dark frame substration, at ISO200, the slow shutter speed noise only become visible beyond 10 minutes exposure, therefore, even with a slow lens (f4, f5.6), I believe it is possible to produce high quality Astrotacer images with the Pentax K1]

I am trying to produce a shot incorporating an interesting foreground, the Milky Way overhead, and the perseid meteor shower taking place.

Normally, with my precious Sony, I would take a series of short, maybe 15-20 sec milky way shots, and stack them. Then ai would focus of a very close foreground, usually with a 14mm or fisheye lens, and make that my foreground. then i would composite the two into a final image.

However, my new K-1 offers some new possibllities, considering Biz-engineer's comments above.

So, here is my current plan:

1) Capture my foreground shots.

2) I don't know how long I can run Astrotracer with a 14mm lens. I will experiment tonight to find out. I am thinking about 2 min exposures at f/2.8 at whatever ISO works to give me a skyglow about 1/3 of the histogram from the left. Since the camera is supposed to be ISO-invariant, it should not make that much difference.

3) Setup the intervelometer to run a bunch of these of several hours. If I am running dark frames for each shot, then I need to set the intervelomete for about 4.5 minutes becaus of:

2 min exposure + 2 min dark frame + processing + disk write

The intent is not to stack these various exposures, but to select the ones that have the most interesting meteor trails.

Does this setup make sense?

Tnk for any comments.

DeadJohn · 08-10-2016, 08:22 PM

Consider turning off in-camera dark frame subtraction. You don't need that for every photo - it will waste time that could be better spent getting photos of meteors. If you fear your exposures will be too noisy, take a set of four manual dark frames at the end of your sequence (or in the middle if outdoor temperatures change a lot), then when processing average the dark frames, create a master dark, and subtract the master dark from your keeper light frames.

CDW · 08-10-2016, 09:37 PM

I've heard of a white spot issue on some Sony sensors. It shows up on my K1 on long exposures with what appears to be hundreds, if not thousands, of hot pixels. Turning on long shutter noise reduction seem to eliminate it. Nevertheless, so many 'defective' pixels is disturbing.

rcolman · 08-10-2016, 10:02 PM

Originally posted by DeadJohn

Consider turning off in-camera dark frame subtraction. You don't need that for every photo - it will waste time that could be better spent getting photos of meteors. If you fear your exposures will be too noisy, take a set of four manual dark frames at the end of your sequence (or in the middle if outdoor temperatures change a lot), then when processing average the dark frames, create a master dark, and subtract the master dark from your keeper light frames.

yes, I was thinking about that as well. It is really a waste of precious imaging time. In addition, a stack of 4 or 8 dark frames will be lower noise than a single dark frame. It is easy tio subtract dark frames in DSS, but not sure how to do it in photoshop or lightroom.

Medex · 08-10-2016, 10:12 PM

Originally posted by CDW

I've heard of a white spot issue on some Sony sensors. It shows up on my K1 on long exposures with what appears to be hundreds, if not thousands, of hot pixels. Turning on long shutter noise reduction seem to eliminate it. Nevertheless, so many 'defective' pixels is disturbing.

Could you post picture with that hot spot? How long should be the exposure? Thank You

08-10-2016, 07:38 PM	#1
rcolman Senior Member Join Date: Jul 2016 Photos: Albums Posts: 118	Capturing the Astro Trifecta Shot - Foreground + Milky Way + Meteor Shower [Astrotracer can be set in any mode (software allows it), but it only effectively works in B (Bulb) mode (as stated above by Steve). In B mode, it is not possible to use the camera own intervalometer (I.e drive mode = INT), but, by pressing the green button we can set the duration of exposure with a dial wheel for up to 5 minutes. If more than one frame should be captured using an external intervalometer to trigger the shutter in B mode+astrotracer, I'm not sure if the stars would still be aligned when stacking multiple Astrotracer frames. However, regarding ISO and aperture settings, f4 ISO400 + 4 minutes exposure (<5 minutes) should work, or even f2.8 ISO200 (very clean) 4 minutes + low shutter speed noise reduction (dark frame subtraction), should deliver very clean images, so no frame stacking necessary to improve image quality. Without dark frame substration, at ISO200, the slow shutter speed noise only become visible beyond 10 minutes exposure, therefore, even with a slow lens (f4, f5.6), I believe it is possible to produce high quality Astrotacer images with the Pentax K1] I am trying to produce a shot incorporating an interesting foreground, the Milky Way overhead, and the perseid meteor shower taking place. Normally, with my precious Sony, I would take a series of short, maybe 15-20 sec milky way shots, and stack them. Then ai would focus of a very close foreground, usually with a 14mm or fisheye lens, and make that my foreground. then i would composite the two into a final image. However, my new K-1 offers some new possibllities, considering Biz-engineer's comments above. So, here is my current plan: 1) Capture my foreground shots. 2) I don't know how long I can run Astrotracer with a 14mm lens. I will experiment tonight to find out. I am thinking about 2 min exposures at f/2.8 at whatever ISO works to give me a skyglow about 1/3 of the histogram from the left. Since the camera is supposed to be ISO-invariant, it should not make that much difference. 3) Setup the intervelometer to run a bunch of these of several hours. If I am running dark frames for each shot, then I need to set the intervelomete for about 4.5 minutes becaus of: 2 min exposure + 2 min dark frame + processing + disk write The intent is not to stack these various exposures, but to select the ones that have the most interesting meteor trails. Does this setup make sense? Tnk for any comments.

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08-10-2016, 08:22 PM	#2
DeadJohn Pentaxian Join Date: Jan 2011 Location: New York Posts: 4,833	Consider turning off in-camera dark frame subtraction. You don't need that for every photo - it will waste time that could be better spent getting photos of meteors. If you fear your exposures will be too noisy, take a set of four manual dark frames at the end of your sequence (or in the middle if outdoor temperatures change a lot), then when processing average the dark frames, create a master dark, and subtract the master dark from your keeper light frames.

08-10-2016, 09:37 PM	#3
CDW Site Supporter Join Date: May 2011 Location: Big Island, Hawaii & Utah Posts: 457	I've heard of a white spot issue on some Sony sensors. It shows up on my K1 on long exposures with what appears to be hundreds, if not thousands, of hot pixels. Turning on long shutter noise reduction seem to eliminate it. Nevertheless, so many 'defective' pixels is disturbing.

08-10-2016, 10:02 PM	#4
rcolman Senior Member Join Date: Jul 2016 Photos: Albums Posts: 118 Original Poster	Originally posted by DeadJohn Consider turning off in-camera dark frame subtraction. You don't need that for every photo - it will waste time that could be better spent getting photos of meteors. If you fear your exposures will be too noisy, take a set of four manual dark frames at the end of your sequence (or in the middle if outdoor temperatures change a lot), then when processing average the dark frames, create a master dark, and subtract the master dark from your keeper light frames. yes, I was thinking about that as well. It is really a waste of precious imaging time. In addition, a stack of 4 or 8 dark frames will be lower noise than a single dark frame. It is easy tio subtract dark frames in DSS, but not sure how to do it in photoshop or lightroom.

08-10-2016, 10:12 PM	#5
Medex Pentaxian Join Date: May 2013 Location: Vilnius Posts: 1,020	Originally posted by CDW I've heard of a white spot issue on some Sony sensors. It shows up on my K1 on long exposures with what appears to be hundreds, if not thousands, of hot pixels. Turning on long shutter noise reduction seem to eliminate it. Nevertheless, so many 'defective' pixels is disturbing. Could you post picture with that hot spot? How long should be the exposure? Thank You