Digital astrophotography: beginning

Although my hobby is the amateur astronomy and I’ve been watching the sky for a few years, I began to take photos about the sky only a few months ago.
After I’ve got some experiences in this topic, I decided to write a blog, because it was not easy to get the necessary information how to do it or what type of pictures I can take with different cameras and devices. To tell the truth, I didn’t want to spend a lot of money while I didn’t know it will worth.
Just to clarify, I wont introduce the professional digital astrophotography or all parts of this theme but try to introduce what kind of problems a beginner can run into and how nice photos he can take with different cameras.
So, it is an astrophotography description from a beginner to beginners. Because I am also a beginner, please forgive me if I make some mistake.
Before starting the post, let me draw your attention that you shouldn’t expect such a perfect photos as Hubble Space Telescope does, but don’t forget: creating own photos can be so magical and I think it’s a very good thing in the life.
However, if you don’t want to take photos, you can watch the sky looking into the telescope with your naked eyes, and it also can be very amazing. Unable to write the experiences of the first look when someone discovers the moons of the Jupiter or the rings of the Saturn, and usually everyone shouts: “wow, it’s moving…”
In the furthermore, I assume that you already have some astronomy knowledge and tried to use a telescope, if not, you should learn the basics before dealing with astrophotography.

And now, here is a list that you need for astrophotography:

The telescope

To choose the best telescope is always a hard decision because there are a lot of different telescope types, some of them are suited to watch the Moon and the planets, and with other ones you can observe the deep-sky objects. In my case, I am using a Skywatcher 150/750 Newton reflector telescope, the numbers means that the diameter of the telescope is 15 cm, and the focus length is 75 cm.
Generally, this is an entry-level class for astrophotography, the telescopes under this class are not capable to make good photos.
However, choosing the telescope is always based on compromises because for bigger telescopes need bigger place and it’s difficult to move them but you can use them to take better photos. Usually the ones having shorter focus are offered for looking deep-sky objects, and the ones having longer focus are offered for looking planets but as you will see, this is just a recommendation.
Here are a few photos about my telescope:

The mount

First of all, what you have to know on it: the mount is at least so important as the telescope, in the astrophotography. When you use your telescope at high magnification (200-300x), a little wind can cause bigger excursion in the telescope, and it makes impossible to take photos. In my case, I have an EQ-3 mount, with all equipments its weigh is around 20 kg. This is an basic mount for astrophotography, but the bigger ones can be very heavy and if the observation point is far from your location or you need to move the telescope more than 10-20 meters, it can be very exhausting.
However, it’s recommended to use better mount, but this is also a hard decision, because you need to choose between the easiest moving and the massive, stable mount. Anyway, using more stable mount, you can take better photos.

The driving

Now, you have a telescope and a mount, but to take photos you need a motor to control the telescope. Due to the Earth rotation, the objects are also moving on the sky and the telescope needs to follow them. For example, the Jupiter will go out from the field of view during 20 sec at 200x magnification. The easiest way is to use a RA driving motor, but if you want to take photos about the deep-sky objects, you should use a better system, like computerized auto-guiding (GOTO) systems. For now, I am using only RA driving.

The following video will illustrate how quickly Jupiter is moving without driving:
The Jupiter without driving

The camera

Basically, you need to know two things:
The CCD cameras are used to make films about the planets or the Moon, and a special computer software will create the photos from this film (which contains hundreds of frames).
For taking photos about deep-sky objects, DSLR cameras are used with long exposition time because these objects are very pale, and the camera needs to collect as many light as possible. Due to the long exposition time, a precision driving is also needed and a massive mount. However, the DSLR cameras are very expensive thus I recommend to use it if you already have one, or you already know the basics of astrophotography. Because I don’t have DSLR camera, I wont introduce it in this blog.
I will only take photos with compact camera and with CCD camera.

Compact camera

Most of the people would like to take photos with its compact camera, no doubt, it’s the simplest solution, but the compacts are not really suitable for this purpose. However, you can take very nice photos about the Moon.
In the furthermore, I will compare the photos taken by a compact camera to a CCD camera.

First photos

I am using the following equipments: Skywatcher 150/750 Newton telescope, oculars, barlows, EQ-3 mount, RA driving, Scopium planet camera, a compact camera (Samsung s760) and a notebook for storing the films and photos.

Firstly, let’s see what kind of photos you can expect, if you take same photos with a compact (the target is the Moon, in order at 80x, 160x, 240x magnification):

The above photos succeed very good, taking into consideration that the Moon is an ideal target for compacts, because it has good brightness and no apparent rotation. Based on my experiences, using lower shutter speed (1/30, 1/45) I could take better photos.

But what will happen if I try to take photos about the Jupiter?

 

The photos would be blurry, and not too detailed. That’s the disadvantage of the compacts. You cannot remove the lens of the photo camera thus you need to use also an ocular in the telescope and thats the reason why you cannot make very good photos. It does not matter in case of Moon, but it is in case of planets or the deep-sky. Tuned the compact settings my best picture was the next:

In the next step, let’s see what kind of photos can we take using the Scopium planet camera. Actually, this is a special CCD camera with built-in IR filter and it can join into the telescop easily. Ocular is not required, and there is no lens for the camera thus you can minimize the lens errors. The maximum resolution is 640×480 and the maximum frame rate is 30 fps. This camera can record the video in raw uncompressed format, that means that 1 frame will be ~1 MB thus a 10 seconds length video will use 150-300 MB space on the disk and you have to make a dozen video in a night.

To take a photo in proper resolution, I need a barlow lens, it will increase the focus of the telescope, after using it, the the focus will be 225 cm. Because the size of the CCD chip is usually very small, you also need to use a barlow lens. As I mentioned it earlier, it’s very important to drive the telescope because the sky objects are moving very quickly. In the following, I will show a few photos about the Jupiter without driving:

I think these photos are better then the previously ones created by compact, but they are not really detailed.

And now, here are the bests. I created the following photos with Scopium camera, using 3x barlow lens and with RA driving:

 

I think the above photos tell everything. The difference is amazing compared to the compact. Just a notice:
You can see the similar picture in this telescope even if you look it into with naked eyes, so the Jupiter will be as detailed as you can see it on the above photos (it’s good to know, because a lot of deep-sky objects are so beautiful only on the photos due to the long exposition time).

Making deep-sky photos with compact

As mentioned earlier, DSLR cameras are the best for this purpose, but I tried to use my compact to take photos about deep-sky object. However, the pictures would be noisy and not too detailed, but I expected worse pictures after reading a tons of forum about it. Based on my experiences you should use as long shutter speed (if it can be set on the camera) as the motor can follow the object without diversion and increase the value of ISO to a highest value (e.g.: 800).
The following pictures will be created by Samsung s760 at 50x magnification and using 8 seconds shutter speed with RA driving.
The first photo shows the Pleiades (M 45), the second one the Andromeda Galaxy. I think these are the best for this compact, if you want to take better photos, you need to get a DSLR camera.

 

Now, here are a few photos about the Moon created by Scopium camera. As you can see, the resolution was less thus the photos contain only a little part of the Moon but they are sharper and more detailed even at higher magnification. If you would like to see the full Moon, you need to use focus reductor.
The third photo was created at higher magnification, the diameter of crater on the middle of the picture is “only” 100 km (Theophilus crater), and the minor crater on the right side of this is 24 km (Madler crater):

 

Update: I’ve uploaded my sky photos to flickr: pzolee’s sky photos

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