Astro Tracker Field Tests
In the previous post I described how you can make an astro tracker in two evenings. It is time to check his work and draw the first conclusions.
Here is an example of a photo taken with it:
Yesterday was the first successful night with a clear sky. I packed up and went to the cottage 15 km from Dnepropetrovsk. The distance is not sufficient to exclude flare from the city, but for the first experiments it is quite suitable.
')
After preliminary balcony tests, I made two significant changes to the controller’s firmware. The first is that when the power is turned on, the engine immediately begins to rotate. This allows you to simply turn on / off the power to start the engine. And the second - changed the direction of rotation of the engine. I hid all the electronics in a black box and tried not to climb into it in the process of shooting so as not to shine my eyes once more.
At the site, I began with an attempt to orient the tracker’s rotation axis to the Polar Intake. This turned out to be the biggest problem for the whole evening.
First, I had no scope. I had to look along the canopy using the angle between it and MDF as a sight. But it is very, very inconvenient, because I can't keep him and the North Star in focus.
Secondly, my tripod head is not designed for very accurate aiming at the object. There are absolutely no elements on it to make very precise and small rotations. Those handles that are very short on it, they have a small lever. And when I hung the second tripod head and the camera with the lens on the astro tracker, it turned out that a very large load with a large lever began to act on the main head, which made any precise guidance impossible in principle.
It turns out that you need to come up with some kind of mechanism for accurately pointing the tracker to the pole without using a tripod head. You also need to provide a sight.
I performed the initial setup using a gyroscope in the phone. I set a tilt angle of 49.2 degrees and brought the tracker to my eye towards the pole.
Further, I used this method because nothing more accurate without changing the design will not work.
Also during the experiments it turned out that the rigidity of the structure raises a number of questions. After the shutter is triggered at a focal length of 200mm, micro-oscillations arise (even with a pre-raised mirror). I avoided this by closing the lens review with my hand for a couple of first and last seconds of exposure.
I made the first test shots with the engine turned off and then with the engine turned on. The difference was significant:
F / 4, ISO 320, 75mm, 79 sec.
There is a static frame on the left, on the right - with an astro tracker. This is a picture angle, 1: 1 scale. Tamron 28-75 / 2.8 draws in the corners somehow not very beautiful.
And this whole frame:
Just below the center of the frame is the Polar Star.
Then I decided to try a longer shutter speed at a wide angle and no longer around the pole where the rotation is minimal but aside. The result impressed me:
28mm, f / 4, ISO 320, 149 sec.
Gaining courage and doing even longer exposure. I make one by one 2 frames (212 and 260 seconds, f / 3.5, ISO 320, 28 mm). I played a little with them in the editor and stuck it together to reduce the noise and increase the brightness. The camera looked almost vertically up, so that, fortunately, no glare from the neighbors got into the lens.
Oh yeah! This is what it was all about. Huge placers of stars, the Milky Way is visible, a good study of details, there are no tracks. I am pleased.
Well, this is not enough for me. I turn to 70-200 / 2.8. You have to re-adjust the tip of the tracker to the pole. This time is quite difficult. The weight of the camera with a large lens. The accuracy of the sight is even less than in previous experience.
In the process of testing, it becomes clear that the shutter speeds longer than 60 seconds will have to be forgotten until now - the tracks are climbing. But at shutter speeds per minute, things don't look so bad. You also have to raise ISO up to 1600 to get a good exposure.
200mm, f / 3.3, ISO 1600, 64sec.
Here is a 1: 1 scale fragment.
Next, I started experimenting with tuning to the polar star. Also, he almost completely “closed” the halves of the tracker to reduce the dangling of the stud. In the process of experiments, it was possible to take several pictures of the famous Andromeda galaxy (M31). Finding it in the sky was not easy for a newcomer. But the program SkEye in the phone helped. I never saw the galaxy itself with my eyes. Caused purely by secondary signs. But once finding her in the sky, then it was already easy.
It turned out such a frame:
63 sec, 200mm, f / 3.2, ISO 1600
Here is a 1: 1 scale fragment:
After trimming, adding three frames, color correction and street magic droplets, we got a picture from the beginning of the post:
Well, not bad for the first time.
So, summing up, we can say that the astro tracker really works. Its accuracy is enough to work even with a 200mm lens and 21MPx cameras. However, the design requires significant refinement to improve the quality of pointing to the pole without using the head of the photo pole.
With the help of an astro tracker, anyone can join astrophotography. It does not require significant investment (subject to the presence of the camera, shatativa and desires), it is fun and informative.
PS Although someone I am cheating. While I waited for each frame with a duration of several minutes, I was overcome by green melancholy. It was necessary to take with him and a telescope.
Here is an example of a photo taken with it:
Yesterday was the first successful night with a clear sky. I packed up and went to the cottage 15 km from Dnepropetrovsk. The distance is not sufficient to exclude flare from the city, but for the first experiments it is quite suitable.
')
After preliminary balcony tests, I made two significant changes to the controller’s firmware. The first is that when the power is turned on, the engine immediately begins to rotate. This allows you to simply turn on / off the power to start the engine. And the second - changed the direction of rotation of the engine. I hid all the electronics in a black box and tried not to climb into it in the process of shooting so as not to shine my eyes once more.
At the site, I began with an attempt to orient the tracker’s rotation axis to the Polar Intake. This turned out to be the biggest problem for the whole evening.
First, I had no scope. I had to look along the canopy using the angle between it and MDF as a sight. But it is very, very inconvenient, because I can't keep him and the North Star in focus.
Secondly, my tripod head is not designed for very accurate aiming at the object. There are absolutely no elements on it to make very precise and small rotations. Those handles that are very short on it, they have a small lever. And when I hung the second tripod head and the camera with the lens on the astro tracker, it turned out that a very large load with a large lever began to act on the main head, which made any precise guidance impossible in principle.
It turns out that you need to come up with some kind of mechanism for accurately pointing the tracker to the pole without using a tripod head. You also need to provide a sight.
I performed the initial setup using a gyroscope in the phone. I set a tilt angle of 49.2 degrees and brought the tracker to my eye towards the pole.
Further, I used this method because nothing more accurate without changing the design will not work.
Also during the experiments it turned out that the rigidity of the structure raises a number of questions. After the shutter is triggered at a focal length of 200mm, micro-oscillations arise (even with a pre-raised mirror). I avoided this by closing the lens review with my hand for a couple of first and last seconds of exposure.
I made the first test shots with the engine turned off and then with the engine turned on. The difference was significant:
F / 4, ISO 320, 75mm, 79 sec.
There is a static frame on the left, on the right - with an astro tracker. This is a picture angle, 1: 1 scale. Tamron 28-75 / 2.8 draws in the corners somehow not very beautiful.
And this whole frame:
Just below the center of the frame is the Polar Star.
Then I decided to try a longer shutter speed at a wide angle and no longer around the pole where the rotation is minimal but aside. The result impressed me:
28mm, f / 4, ISO 320, 149 sec.
Gaining courage and doing even longer exposure. I make one by one 2 frames (212 and 260 seconds, f / 3.5, ISO 320, 28 mm). I played a little with them in the editor and stuck it together to reduce the noise and increase the brightness. The camera looked almost vertically up, so that, fortunately, no glare from the neighbors got into the lens.
Oh yeah! This is what it was all about. Huge placers of stars, the Milky Way is visible, a good study of details, there are no tracks. I am pleased.
Well, this is not enough for me. I turn to 70-200 / 2.8. You have to re-adjust the tip of the tracker to the pole. This time is quite difficult. The weight of the camera with a large lens. The accuracy of the sight is even less than in previous experience.
In the process of testing, it becomes clear that the shutter speeds longer than 60 seconds will have to be forgotten until now - the tracks are climbing. But at shutter speeds per minute, things don't look so bad. You also have to raise ISO up to 1600 to get a good exposure.
200mm, f / 3.3, ISO 1600, 64sec.
Here is a 1: 1 scale fragment.
Next, I started experimenting with tuning to the polar star. Also, he almost completely “closed” the halves of the tracker to reduce the dangling of the stud. In the process of experiments, it was possible to take several pictures of the famous Andromeda galaxy (M31). Finding it in the sky was not easy for a newcomer. But the program SkEye in the phone helped. I never saw the galaxy itself with my eyes. Caused purely by secondary signs. But once finding her in the sky, then it was already easy.
It turned out such a frame:
63 sec, 200mm, f / 3.2, ISO 1600
Here is a 1: 1 scale fragment:
After trimming, adding three frames, color correction and street magic droplets, we got a picture from the beginning of the post:
Well, not bad for the first time.
10 tips for newcomers like me
1. Dress much warmer than during the day. Even now it is summer, but at night the temperature drops to +12 (or even lower). Sitting long and still very cold. I wore a winter down jacket, hat and gloves and still froze at the end. I went to bed at 3 am at most precisely because I was cold.
2. Thermos with tea and cookies. Must have.
3. Bring along a folding table and a white tablecloth. It was very convenient for me to put everything on it. In the darkness on the white tablecloth the outlines of objects are visible so it is more convenient to find what you need on it.
4. Comfortable chair. Sit will have a long time. Better to be comfortable. I used the beach folding lounge chair.
5. Spare batteries, flash drives, camera.
6. Night dew falls. Cover your equipment and appliances with rags until you use. Check optics periodically. Take a microfiber to wipe moisture.
7. At night, one is a bit scary. React to any rustle. I think it would be better if someone is around.
8. Turn on the mirror pre-lift in the camera. Use the trigger cable.
9. Try not to move around the tripod while it is shutting down. No jumps, beats, vibrations, loud music.
10. Watch your feet. Do not hook on a tripod. Easily knock off alignment on the Polaris.
11. Bonus free advice only for those who opened the spoiler.
You can use the angular viewfinder. Here is this:
It has a double zoom mode from the viewfinder, which greatly increases the visibility of stars with an eye when sighting.
2. Thermos with tea and cookies. Must have.
3. Bring along a folding table and a white tablecloth. It was very convenient for me to put everything on it. In the darkness on the white tablecloth the outlines of objects are visible so it is more convenient to find what you need on it.
4. Comfortable chair. Sit will have a long time. Better to be comfortable. I used the beach folding lounge chair.
5. Spare batteries, flash drives, camera.
6. Night dew falls. Cover your equipment and appliances with rags until you use. Check optics periodically. Take a microfiber to wipe moisture.
7. At night, one is a bit scary. React to any rustle. I think it would be better if someone is around.
8. Turn on the mirror pre-lift in the camera. Use the trigger cable.
9. Try not to move around the tripod while it is shutting down. No jumps, beats, vibrations, loud music.
10. Watch your feet. Do not hook on a tripod. Easily knock off alignment on the Polaris.
11. Bonus free advice only for those who opened the spoiler.
You can use the angular viewfinder. Here is this:
It has a double zoom mode from the viewfinder, which greatly increases the visibility of stars with an eye when sighting.
So, summing up, we can say that the astro tracker really works. Its accuracy is enough to work even with a 200mm lens and 21MPx cameras. However, the design requires significant refinement to improve the quality of pointing to the pole without using the head of the photo pole.
With the help of an astro tracker, anyone can join astrophotography. It does not require significant investment (subject to the presence of the camera, shatativa and desires), it is fun and informative.
PS Although someone I am cheating. While I waited for each frame with a duration of several minutes, I was overcome by green melancholy. It was necessary to take with him and a telescope.
Source: https://habr.com/ru/post/228035/
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