A. T.

Once again I come to my UHH family for advice. My wife and I will be traveling to Wyoming for three weeks starting September 7th to enjoy that wonderful place once again. I am an avid wildlife and landscape photographer but would like to photograph the night skies. I have been reading and watching videos on the subject and I came across a few who were talking about the use of a star tracker for better image quality of the stars and possibly the milky way. I know absolutely nothing about a star tracker and would like to get input from you guys and gals about the subject as well as the need, or not, for a star tracker. I have professional equipment and an assortment of fast lenses. What is your opinion and or advice on the subject? Thanks again for my very valuable family in this forum.

geonque Loc: Kitsap Co., WA

The problem with astrophotography is not just that the light is faint, but that the long exposures needed to record the full depth of the subject gives the stars (actually the Earth) time to move. That results in the "trails" that you see when a still camera is just pointed at some heavenly object. Star trackers are basically machines that compensate for the Earth's movement to hold the image steady relative to the camera. It is essentially the same thing as a motorized equatorial mount on a telescope, but the camera lens is used instead of a telescope to form the image. You might want to see if anyone in your neighborhood has such a telescope. Most people who spent a gazillion bucks on a telescope probably stopped using it after a few cold nights, and they come up for sale pretty often on Craig's list. The ones designed for a bare camera are usually less common. If you have a fast enough lens/sensor, and you do not need to image really faint stars or the Milky Way in detail, a good tripod is all you need.

A. T.

First, thanks for such a quick response. I do have fast lenses and a very sturdy tripod and I really don't know of anyone with a telescope. I guess my question is that while it is a possibility that I would print the image if the quality was good enough I don't have a problem with using my current equipment if the image was print quality. So, with that being said, do you think that would be possible without the tracker?

rcarol

There is also a formula that you can use to ensure That you get sharp stars rather than star trails. I believe the formula is as follows: Time (in seconds) = 500/FL (focal length of lens) If anyone can verify that the formula is correct, I would appreciate it.

KenY Loc: Glenside, Pa

That formula will give a good starting point. Your results may vary. Try different shutter speeds up and down from what the formula gives you. If you get star trails, you'll need to shorten the shutter time.

geonque Loc: Kitsap Co., WA

The benefit of long exposures is that you will be able to get images of fainter objects, like putting an image intensifier in the signal chain. So regardless of your equipment, you will be able to record fainter stars/galaxies if you can hold the exposure longer. Assuming you are not limited to a heavy light polluted vantage, you can spend some nighttime hours with your camera and tripod, and see for yourself if that is the result you are looking for. In pristine darkness you can see more stars with your naked eye than your camera could likely make without star trails. On the other hand, with an astronomically stabilized camera you can likely take pictures of dimmer objects than your eye can detect. Some of the satellite cameras remain focused on one point for hours to days in order to collect enough light/radiation/data to see many light year distant objects. There is also a software option, analogous in some ways to HDR processing to increase focus, that will stitch together sequential images to create stars without star trails. In really dark skies (of which there are few these days) your camera will not get any more light, although your eyes see things you cannot see in the city, so it cannot image less bright objects at the same exposure, but the object images will be drowned out by the noise of scattered light in the atmosphere. That is analogous to how atmospheric haze fogs out distant objects in a terrestrial landscape, and why your eyes cannot see the stars at noon.

Trackers are expensive, so unless you want to rent one and spend some time learning how to set it up you might better settle for getting a picture that is less impressive than your naked eye can see.

https://beltoforion.de/en/astrophotography/untracked_astrophotography.php

dlmorris Loc: Loma Linda, Ca

For Milky Way shots, a reasonable wide angle fast lens should work just fine. Try a higher ISO, and use exposures no longer (in general) than about 30 sec. You can use a star tracker for longer exposures, but then the horizon shows motion. Just use a good tripod and a remote shutter. Some of those really good pictures you see use a lot of post processing.
So here is what you do—- take your camera outside wherever you may be even now (unless you are in the middle of a city) and shoot away! Different exposures. Different lenses, and so fourth. “Film” is cheap! And it lets you get familiar with your camera under those conditions. You probably won’t get anything worth saving, but good for learning. Some people shine flashlights at whatever trees or hills or whatever in the foreground. Experiment! Because done wrong, you can ruin an otherwise good shot.

JimH123 Loc: Morgan Hill, CA

Some examples are useful to see how star trails are formed if the shutter time is too long.

First image is Comet Neowise in July 2020. The FL was 360mm and was done on an APS-C camera. Shutter time was 2 sec and the ISO was 25600 @ f6. 38 images were stacked to help reduce the noise. And with stacking, there was the need to do some cropping too, and it was cropped fairly heavy. You can see the stars are a bit elongated towards the upper right.

Second image is a FL of 100mm @ f4. Shutter time was 6 sec at ISO 3200 using a m4/3 camera for an effective FL of 200mm. Thirty images were stacked. It was cropped, but not as heavy as the first image. Again, you can see star trails.

Should point out that the comet was to the north and the closer one gets to Polaris, the shorter the trails will be. As you move farther away from Polaris, the longer the trails will be.

The best advice is to do test shots and zoom in and look at your results.

Also be aware that some lenses are much better at doing stars than are other lenses. And the wider you open the aperture, the worse the lens faults become. The price of the lens and the manufacture of the lens are not necessarily a good indicator of how good or how bad a lens it. You can do tests on your lenses before you go.

See: https://www.lonelyspeck.com/lenses-for-milky-way-photography/

Stars are point sources of light and can really create distortions which cause stars to absolutely look terrible. Some lenses are far better than others at this. Types of distortions include CA, Astigmatism and Coma distortion plus others. And stopping down a bit can certainly minimize the problem. You want wide open, but if the stars look bad, you have to stop down a bit. And stacking can certainly help.

For more info on distortions you may encounter, see:
https://www.handprint.com/ASTRO/ae4.html

One more piece of advice is focusing. Stars only look good at perfect focus. If you try to split the distance to have something close in focus as well as the stars, it won't work. The stars have to be the ones in focus. As a star goes out of focus, it turns into a disc that gets wider and dimmer. The light that you have from a star is then spread across that wider disc and the result is that it gets dimmer real fast.

And I don't like marking on the lens to show where best focus is. Just not good enough. I find on a mirrorless that I need to use focus magnifier for focus. Not peaking. And I start with a brighter star and get the best focus I can. Then I turn my attention to dimmer stars. And with these stars, I focus for brightness. At best focus, the star is as small a point of light as the lens will allow and all that light in one tiny spot makes it appear brighter. As you rock the focus back and forth an almost imperceptible amount, the star can dim to completely out of sight back to as bright as possible. And as your dim star becomes as bright as possible, look for an even dimmer star and repeat. This process produces the best possible focus.

Comet Neowise in July 2020

(Download)

Also Comet Neowise, different camera and lens

(Download)

A. T.

Thanks, sounds good to me. Although I would love to get some really good shots of the night sky and can afford an expensive star tracker, that's really not my passion. So, I think I will do exactly as you suggested....go out in the night sky and experiment with my equipment. I want this trip to be pleasant and without stress so trying to become proficient with something that I have never used or even seen is really not a wise thing to do, in my opinion. Thanks again for the advice....well taken.

A. T.

Thanks for the advice and suggestions but I think I will just stick with my equipment, experiment with different exposures before hand and go with what I have rather than spend money on something that I might use a couple of times and will take a considerable amount of time trying to become proficient with something that I am totally not familiar with.

A. T.

Thanks for the advice. I will go out at night here at home and experiment with the formula to see what I get and make adjustments from there. Again, thanks for the response and information.

A. T.

Okay, thanks for the suggestions. I'll go out here at home and experiment with the formula and make adjustments as needed.

A. T.

Okay, I got. Thanks for the response and suggestions. I'll go out and practice this technique in the skies beforehand.

awesome14 Loc: UK

No one really knows what a star is supposed to look like. But for heavenly bodies you can use fast ISO, short exposure in a video. Then, you feed the video into a program that extracts all the really good frames. It blends those together, and you get an image that appears to be 10x the resolution of the video frame.

JBRIII

Also, to avoid trailing, the tracker needs to be aligned to Polaris, another thing to be learned and not for the first time. The moon, sun (*****with a special filter*****), and the aurora can be done fairly easily without a tractor.