To help you with star trails and stacking

[A.S.I.G.N. Observatory]

I was asked a good question by another member about how to do star trails with lots of timed and sequential images of the stars.

I thought i might share my answer with you all as I get asked this question a bit. Hopefully this may help more than just the one fellow.

Here's a cut and paste:

Hi there Mike,

Deep Sky Stacker is designed for just that- stacking multiple images of exactly the same thing, aligning all the stars in each frame with each other to produce one single image that has a much better signal to noise ratio. Best when the camera is on a tracking telescope mount or platform, so that all the images are identical and no stars move from the camera's perspective.

To get the long star trails in circular patterns, you need to set the camera on a stationary tripod, take a heap of 30 second exposures over a few hours then use a program called startrails.de (http://startrails.de/) This program will place the images over each other so that the foreground remains still, but the stars are built up in their advancing locations to make the circumpolar circles.

Alternatively you can use all these images in a movie program like adobe premiere or even windows movie maker to make a time-lapse sequence like a movie where the foreground stays still and the sky rolls overhead.

Got some instructions here that might help mate.

Image Stacking (http://www.asignobservatory.com/index.php?option=com_content&view=article&id=84&Itemid=125)

Time lapse (http://www.asignobservatory.com/index.php?option=com_content&view=article&id=79&Itemid=118)

Hope it helps mate.

Cheers,

Baz.

[VegasBoz]

Came across this post this morning after trying my first attempt last night and vowing to research and learn what I need to get a better picture.

Thanks for the info.

[A.S.I.G.N. Observatory]

Keep at it mate, the rewards are fun and satisfying!

[IVOlution]

good one Baz...helpfull info, got to try this one day or better said night.

[Drakeskakes]

Good info! I havn't gotten a chance to do much of this since I live in the city but when Im out in the coutry ill definately give it a shot!

[Craggles123]

Thanks for the info

I have a location in mind that I would like to try my first star trails.

I would like to get the circular type pattern in the sky.

Just wondering how I go about achieving something like this, I'm thinking around 250 exposures at 30 seconds each or there abouts, there is some light pollution where I am so I need to expose enough to get star details but not so much that the light pullution kills the bottom of the sky.

Do you think 250 exposures will be enough?

And am I best doing this kind of shot on the night of a new moon? Or can it be achieved other nights as long as the moon isnt in the frame.

Sorry if these are noob questions, but I'm a noob :P

[A.S.I.G.N. Observatory]

Thanks for the info

I have a location in mind that I would like to try my first star trails.

I would like to get the circular type pattern in the sky.

Just wondering how I go about achieving something like this, I'm thinking around 250 exposures at 30 seconds each or there abouts, there is some light pollution where I am so I need to expose enough to get star details but not so much that the light pullution kills the bottom of the sky.

Do you think 250 exposures will be enough?

And am I best doing this kind of shot on the night of a new moon? Or can it be achieved other nights as long as the moon isnt in the frame.

Sorry if these are noob questions, but I'm a noob :P
G'day mate. Yes, 250 exposures will be a great start to creating a summative star trail image.

The old way would be to take a long exposure of ten or fifteen minutes in a dark sky on a fixed tripod, so the motion of the stars burns a trail on your film or sensor. Unfortunately, this way if there is any light pollution, there will come a point where the image becomes over exposed, drowning out all your stars.

With startrails.de (http://startrails.de/) , when you take your 250 short exposures of 30 seconds or less, the program will ask you to select one frame for the foreground, then as long as your foreground hasn't moved, it will summate all the images together so each one advances as a freeze-frame on top of the last. Your sky and foreground will stay nice and dark, while the star trails build up to become concentric circles.

The moon can be used for different purposes. Sometimes a little bit of moonlight can make your foreground interesting, by illuminating it slightly and therefor you will get colour and detail, instead of just a dark silhouette (Just don't have the moon in the frame). A thin crescent is good for this. otherwise, the darker the sky, the better, so no moon (new moon) is best.

Baz.

[Craggles123]

Thanks for that mate

So with those exposures I should be able to get something similar to this?

http://www.flickr.com/photos/tristenmurray/4529703000/

The centre where the stars appear to be rotation, is that where the image was focused / the centre of the original frame or is that just how it works depending on the rotation of the earth?

[A.S.I.G.N. Observatory]

Thanks for that mate

So with those exposures I should be able to get something similar to this?

http://www.flickr.com/photos/tristenmurray/4529703000/

The centre where the stars appear to be rotation, is that where the image was focused / the centre of the original frame or is that just how it works depending on the rotation of the earth?
The reason the stars are circling like that, is because the camera is aimed at the celestial pole. If you are northern hemisphere, you will need to aim toward the star Polaris. If you are southern hemisphere, toward the constellation Octans.

[Craggles123]

Ok I'm in Perth, I'll have to do some research and find this octans constellation

thanks :)

[A.S.I.G.N. Observatory]

Just take the long axis of the Southern Cross, it looks like a kite-shape. Take the axis out four and a half times it's length from the tail of the kite and you will be in the right spot. The stars there are pretty faint and hard to see, so we don't have it as easy as the northern hemisphere with it's bright Polaris Star.

[David Ransley]

If you see the two pointers "alpha and beta centauri", then draw a pependicular line that halves the line between the two stars. Extend the imaginary line line until it crosses the extended long axis of the southern cross. Now you have a point normally slighty above the celestial pole.

look at the cross' extended line and try and memorize that length in multiples of the axis fro the days you don't have the pointers at hand.

http://www.juriepieterse.com/personal/CanoeTripOrangeRiver/Southern_cross_stars_for_direction.htm

This page has a good picture of the point where you end up in relation to the celestion pole.

http://www.southernskies.com.au/astronomy/cross.htm

[Coppatop85]

What sort of settings do you guys use for your stacked vs unstacked images?

Would it be something like this:

1 Long Image -- Lower ISO (100-400?) Long shutter speed (45min+), what sort of aperture?

For 30s stacked images
Higher iso? 800 or so? 30s sequential exposures. Again, what aperture?

[A.S.I.G.N. Observatory]

For all star, nebula or Milky Way Galaxy or other galaxy images, aperture as wide as your lens will permit! In telescopes aperture is KING. The distant and faint light needs every opportunity it can get to reach the sensor so open it right up!!

Let's take one type of shooting at a time.

1. My subs for stacking will depend entirely on how bright the object is, (if through a telescope) and how much light pollution there is. In my suburb, depending on the amount of smoke or moisture in the air, I can get around five minute subs (Tracking with a telescope mount). Out in the bush away from the city a bit, I can get about 8 minute subs before the light pollution from the city starts to show itself badly. With the Canon on the telescope I shoot ISO 800.

2. My subs off the telescope (fixed tripod and 18-55mm lens) for time-lapse will always be around 25 to 35 seconds depending on the FL. I shoot at 18mm because that is the shortest FL and widest angle I can get with my gear. If I had a 14mm lens, I would go for longer if I could before the star-trails start to show. The longer the FL, the less time you have before the stars start to trail.

In short, for this you need to get as MUCH exposure as you can WITHOUT star motion showing.

Generally I will shoot on around ISO 800 for this, but I have shot in ISO 1600 and still had good results.

Baz.

[Blazin]

Thanks Baz,

I've been trying to ensure I understand the theory behind the shots rather than just flipping settings around. A true understanding will always yield better results. Your input is making me more and more confident!

I hope to have some seriously amazing images/time-lapse footage after my trip up north in a few weeks!

[mtbdudex]

btw, Baz your various threads and David Ransley have helped my Star Trails and Milky Way stacking. I posted in the Photo section. Neat stuff, my eyes are tired from late nights though....

[A.S.I.G.N. Observatory]

LOL, Mike, you will get used to it. going to bed at midnight is a very early night for me!

Wonderful to hear of your successes mate. Keep at it!

Baz.

[rpcruab]

Thanks for the info! I have been attempting, and failing to produce a good star trails shot for some time now.

[Coppatop85]

What sort of settings do you guys use for your stacked vs unstacked images?

Would it be something like this:

1 Long Image -- Lower ISO (100-400?) Long shutter speed (45min+), what sort of aperture?

For 30s multiple stacked images
Higher iso? 800 or so? 30s sequential exposures. Again, what aperture?

Still clueless here, anyone have any insights?

[A.S.I.G.N. Observatory]

Originally Posted by Coppatop85
What sort of settings do you guys use for your stacked vs unstacked images?

Would it be something like this:

1 Long Image -- Lower ISO (100-400?) Long shutter speed (45min+), what sort of aperture?

For 30s multiple stacked images
Higher iso? 800 or so? 30s sequential exposures. Again, what aperture?
Still clueless here, anyone have any insights?

I already answered here mate. However, if you want to do the star trail shots, then take the same as you would for a time lapse, say-3 or four hours worth of 30 second exposures, then load them all into startrails.de (http://startrails.de/) software.

For all star, nebula or Milky Way Galaxy or other galaxy images, aperture as wide as your lens will permit! In telescopes aperture is KING. The distant and faint light needs every opportunity it can get to reach the sensor so open it right up!!

Let's take one type of shooting at a time.

1. My subs for stacking will depend entirely on how bright the object is, (if through a telescope) and how much light pollution there is. In my suburb, depending on the amount of smoke or moisture in the air, I can get around five minute subs (Tracking with a telescope mount). Out in the bush away from the city a bit, I can get about 8 minute subs before the light pollution from the city starts to show itself badly. With the Canon on the telescope I shoot ISO 800.

2. My subs off the telescope (fixed tripod and 18-55mm lens) for time-lapse will always be around 25 to 35 seconds depending on the FL. I shoot at 18mm because that is the shortest FL and widest angle I can get with my gear. If I had a 14mm lens, I would go for longer if I could before the star-trails start to show. The longer the FL, the less time you have before the stars start to trail.

In short, for this you need to get as MUCH exposure as you can WITHOUT star motion showing.

Generally I will shoot on around ISO 800 for this, but I have shot in ISO 1600 and still had good results.

Baz.

[Coppatop85]

Would a 10mm Fisheye lens @ 3.5 be better for star trails as opposed to a 17mm lens? @ 2.8? I might stop both of them down a bit to get a little sharper.

[A.S.I.G.N. Observatory]

Would a 10mm Fisheye lens @ 3.5 be better for star trails as opposed to a 17mm lens? @ 2.8? I might stop both of them down a bit to get a little sharper.

You need to let in as much light as possible. Stopping down reduces the light that gets to the sensor, meaning you have to expose longer to get the light in and therefore elongated stars.

Fisheye is all personal taste but I personally think they are yuck.

Baz.