Having trouble doing long exposures -- Star Trails

[NedM]

The other night I went out into the mountains to do some long exposures of the stars.
I didn't have any previous experience in star photography but I shadowed a lot of photographers who did.

I went out, setup my tripod, and had my shutter release remote on standby.
I shot in Manual, and set my shutter speed to bulb.

This was the result.
Terrible I know, but not bad for my first try.
I'm wondering why the stars aren't so bright, and there's TONS of noise!
Also, why are there what seems to be thousands of red dots when you zoom in?

Here is my camera settings:
20 min exposure
f/18
ISO-200

I figured I would use a high fstop to get better sharpness.


What did I do wrong?
And what should I do next time?

 

[shefjr]

I have a couple of thoughts. First the general idea for most lenses is that they operate best between f8 and f11. Using f18 IMO isn't necessary. Second, I think(and am not positive) that when shooting long exposures your sensor could heat up and you get what are called hot pixels. Hence the stationary red pixels in your photo.
As to the noise looks, I'm not sure why it would look like that. There are two great tutorials here on the forum which I will link you to. I highly recommend reading them. There are some redundancies but, there are also some differences that are worth noting.

Sw1tchFX
http://www.thephotoforum.com/forum/articles-interest/276016-shooting-night-pictures-stars-stuff.html

Manaheim
http://www.thephotoforum.com/forum/...aheim-s-ultimate-guide-night-photography.html

I hope this helps you.

 

[D-B-J]

Simply don't use a long exposure. For my star trail photos, the best way is to shoot wide open, focus properly(a little in front of infinity), and take a half hours worth of 30 second exposures. Then use software like star-stax to stack the images into a trail photo. These shorter exposures ensure limited noise, and more control. My last trail setup was a d7000, sigma 17-50 2.8, shot at 2.8, ISO 1600, 30 second exposure. I shot 64 images, it took a few minutes to stack the images, and it turned out well. I've never had great success just shooting a 30 minute exposure-the sensor heats up and I end up with a shoddy image.

Best,
Jake


Sent from my iPhone using Tapatalk

 

[Propsguy]

Your exposure is too long (causing sensor noise), your aperture is totally wrong (shoot wide open if your lens is sharp at that aperture, or stop down a little if it helps) and your ISO is needlessly low (shoot at 400 to 640 and there won't be any appreciable increase in noise). As mentioned by DBJ, stacking is far more effective method and keeps astrophotography images close to noise free.

 

[KmH]

Since the stars or anything else more than 1 mile away from a DSLR are effectively at infinity, a small lens aperture is not needed to produce a deep depth of field (DoF).

You don't say what lens or focal length you used, but at 55 mm, using f/4 and a point of focus distance 1 mile (5280 feet) from the camera the near limit of the DoF would be 127.4 feet in front of the camera while the far limit would be infinity. Plug the numbers into a DoF calculator - Online Depth of Field Calculator

If you change only the point of focus distance to 10 miles (52,800 feet) the near DoF limit only increases by 2.9 feet to 130.4 feet from the camera. The far limit stays at infinity.

Also not mentioned is what it is that cause image noise with a 20 minute long exposure.
The cause is heat, which results in thermal image noise.
The image sensor has to have power applied to it. Electrical circuits have resistance and that resistance to the flow of electrical current causes heat.

Understanding Depth of Field in Photography
Understanding Sharpness
Digital Camera Image Noise: Concept and Types

 

[jsecordphoto]

Like others have said take lots of shorter exposures and stack them. I do 30 minutes-an hour of 30 second exposures at f2.8 usually at iso1600 or 3200

 

[Photocreater]

Just out of interest is it possible to stack them using photoshop or Lightroom?

 

[jsecordphoto]

it is possible in photoshop but much more time consuming. StarStax is free and takes 2 seconds

 

[NedM]

Thank you all so much!
Each of you explained exactly what I needed to do!
Your comments and suggestions will definitely help me the next time around.
I'll be sure to read-up on plenty of tutorials, and apply what I've learned.

Cheers!

 

[Smokeyr67]

Hi Guys,

Just looking at the StarStaX FAQ, and it looks like it's best to shoot in jpeg, am I right?

Shane

 

[18.percent.gary]

Hi Guys,

Just looking at the StarStaX FAQ, and it looks like it's best to shoot in jpeg, am I right?

Shane

You definitely still want to shoot in raw.

Once you import your series of raws into Lightroom or whatever just choose ONE of them and make your crucial edits like WB, exposure, contrast, noise reduction and sharpening etc. Then sync those settings to the rest of the raw files in the series. Finally, export the series of edited raws as full size max quality jpegs and THEN process them in your stacking program.

The biggest reason to do it this way is to have full control over white balance and being able to dial in the correct amount of noise reduction, instead of just taking what the camera would give you as default when shooting jpg.