Basics of Astrophotography

Astrophotography is the photography of astronomical objects, celestial events, and areas of the night sky. In simple terms, it’s taking photographs of an object in space, whether with a point-and-shoot camera, an amateur telescope or any other type of camera, and the object can include anything from the moon to the Milky Way.

If you feel astrophotography isn't your cup of tea then you are at the right place! Want to try your hand at astrophotography but really don't know where to start? I'll tell you where and how.

A typical astrophotography equipment setup includes an equatorial mount, telescope, lenses, camera, light-pollution filter, camera tripod and a few additional accessories required to run the camera throughout the night.

Do I need fancy equipments to do astrophotography? Surely, you don't.

Now, let’s understand some of the basic terms used in astrophotography; you can skip these for now ;)

A photograph of star trail (Image via earthsky.org)

1. Stacking - Taking multiple photos of the same subject, each with a different focused spot. This is followed by the use of post-processing software to align the focused portion of each image into one final-and-focused image. For example, Star trails. A star trail is a type of photograph that uses long exposure times to capture the apparent motion of stars in the night sky due to Earth's rotation. A star-trail photograph shows individual stars as streaks across the image, with longer exposures yielding longer arcs.

2. Dark frame - taking photos with the lens cap ON

3. Light Frame - taking photos without the lens cap ON

4. Shutter speeds - The nominal time for which a shutter is open at a given setting. It runs in fractions of a second, usually around 1/1,000th of a second at the shortest exposure to many seconds at the longest.

5. 500 Rule - Ideal Exposure time = 500/ (focal length x crop factor)

6. Crop factor - In digital photography, the crop factor is the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference

7. Magnification/Power - Ratio of focal length and lens diameter

8. RAW photos - Raw photos are like negatives

9. Photograph noise - It is a grainy veil in a photograph, obscuring details and making the picture appear significantly worse.

10. Photometry - Measuring the brightness of the sky

11. Erecting Eyepiece - Makes the view the right way up. Not generally used for astrophotography as it does not matter what way up these are.

12. Barlow lens - It is a concave lens that when placed between a telescopes objective lens or mirror and the eyepiece, will increase the magnification of the telescope.

My personal astrophotography equipment includes the following -

1. Bresser Telescope (Quasar 80/900 EQ Sky) - Focal length, focal ratio = 900mm, f/11.2; Aperture = 80mm; Available magnifications = 45X, 100X, 135X, 225X, 675X

2. EQ2 Equatorial Mount.

3. Lenses - Barlow Lens 3X, Erecting Eyepiece 1.5X, K 9mm, K 20mm.

4. Phone camera.

How and where to start?

My first shot at astrophotography

Before you begin, remember that astrophotography cannot be learned overnight. It requires lots of patience and tons of work behind post-processing. Personally, I feel there is so much to learn in astrophotography and I have just begun. It all started with observing the planets and moon through the telescope until I realized that I can take photographs of whatever I observe. After failing at several attempts, I was finally able to take a photograph of Saturn. This blurry image told me that all the time I spent on aligning the telescope, bringing Saturn to focus and then finally clicking this photograph mattered more than the "quality" of the photograph. Certainly, I realized that I can see things that not many people can.

Now, let me drive you through the basic steps to start with amateur astrophotography,

Step 1 - Before you begin, make sure you have the basic equipments ready. Here, I'll be guiding on doing astrophotography using a telescope. The other basic equipmets include telescope mount, lenses and a DSLR/mobile camera.

Step 2 - Find out the current position of the celestial body you plan to observe. Various mobile apps like Star Chart, Sky Map, Star Walk 2, etc. or websites like https://theskylive.com/ are available for this purpose. Note its altitude and magnitude. I prefer a time when the celestial body has maximum visibility and altitude.

Step 3 - Choose an open ground or a terrace and set up the telescope there. Make sure you have an unobstructed view of the selected body. Make sure you use an eyepiece with the lowest magnification while setting up the telescope. This ensures lesser time for aligning the telescope and bringing the body to focus.

Step 4 - Locate the actual position of the object in the sky through the naked eyes. Point the telescope roughly at the portion of the sky where the object is located. Once this is done, use the knobs 1 & 2 to make finer adjustments to the declination and ascension until the telescope points exactly at the object. For easier and quicker adjustments, use the finderscope. This step usually takes some time and is one of the most tricky steps in amateur astrophotography.

Refer for step 3 and 4

Step 5 - Once the telescope is aligned accurately, use the knob 3 for bringing the object to focus (from a blurry view to a sharp view). Rotating the knob changes the distance between the eye-piece and the aperture lens, thereby bringing it to focus. Make sure you turn the knob slowly to minimize the tiny movements in the telescope alignment. This will ensure that the object stays in focus.

Steps 4 and 5 usually require some skills and can be mastered with experience. Don't worry if you are unable to align it accurately initially. That's completely normal. Just make sure you keep trying.

Step 6 - Since the object is now in focus, you have the option to choose any of the available magnification lenses to improve the object's view. Magnifying helps in observing finer details of the body. Make sure you change the lens steadily without disturbing the telescope alignment.

Step 7 - Voila! You are almost there. Now sit back and observe, while making sure the object stays in focus. But wait, we forgot to click a photograph. Since neither do I have the special telescope accessory required to mount a DSLR nor do I have a DSLR ;) I prefer taking photographs through my phone camera. It gives me a satisfactory quality of photographs.

Step 8 - It's time for some post-processing, i.e, Image editing. I personally use the common image editing softwares available for post-processing. The main goal is to adjust the different parameters of the photo to improve its quality and clarity of object under observation.

My astrophotography gallery

bringing

Saturn's view through the eyepiece (Left - unfocused, right - focused)

Left - Using a point & shoot camera; Right - Using telescope

Don’t have a telescope?

No problem at all. Who said telescope is a pre-requisite for astrophotography. At some point in our lives, all of us must have taken a photograph of the moon using our mobile cameras or DSLR and must have wondered how it must be like to be on the moon. It's time you realize that you have already been doing astrophotography! Surprised?

Simply, follow these steps -

• Find clear skies (away from light pollution)

• Open manual setting on the phone camera. If this setting is not available, download a manual camera app.

• Set ISO setting to around 400-1600; focus = infinity; exposure time = 20-30 seconds (you can use the "500 rule" as mentioned in the basic terms)

• Click a photo in RAW format.

Some Post-processing Softwares

I personally don't use any of these softwares since I take photographs through my mobile camera. I used the common editing apps available on our phones. Things could have been different if I use a DSLR. List of the softwares -

• Deep Sky stacker + Photoshop

• Star Trails

• Star Max

• Auto Stekkert

• Registax

• Astromomy.net

• Pipp

Haven’t we all looked at the stars and wondered how we all came to existence. That’s it. You are good to go. You already have that one special ingredient required for astrophotography, the spirit of inquisitiveness. Go ahead, find clear skies, locate the object you wish to photograph and keep clicking photos. Remember, this inborn curiosity in us is what fuels astrophotography. Although the photo quality might not be good, your willingness to spare some time out to take "astrophotographs" is what matters more. So, cheers to the newly found astrophotographers in you!

#Astrophotography #StayCurious