Unveiling the universe's mysteries with a deep sky telescope is a thrilling adventure. As Edwin Hubble once said, “Equipped with his five senses, man explores the universe around him and calls the adventure Science.”

This summer, I attended an observational astronomy program at Copenhagen University. As a soon-to-be master's graduate in astrophysics, it was my first hands-on experience with a telescope, making it both exciting and educational.

Our observations utilized the Nordic Optical Telescope (NOT) located on La Palma, Canary Islands. Due to the ongoing pandemic, we had to conduct our observations remotely, which meant that while we missed out on the physical presence beneath the telescope, we still controlled it through the same systems as if we were there.

What should we observe? This was the first critical question. Our goal was primarily to gain experience rather than answer specific scientific queries. Thus, we began brainstorming potential targets based on visibility and interest.

The universe is vast, with countless hidden gems to explore. Therefore, we compiled a list of potential observational objects, including:

• Stars
• Star clusters
• Galaxies and galaxy clusters
• Nebulae
• Binary star systems
• Novae and supernovae
• Quasars
• Solar system objects like comets or asteroids

Naturally, I hoped to discover something particularly captivating, like a new cosmic phenomenon.

As we researched interesting objects, we examined the visibility plot to determine what could actually be observed.

Visibility is key when selecting an object of interest. We needed to ensure it would be observable during our allotted time. Here are some critical factors to consider:

• The object must be visible in the night sky during our observation period.
• Ideally, it should be high in the sky to minimize the atmospheric interference.
• If the object peaks high in the sky, it's often better to observe it just before or after it peaks.
• The object should be away from the moon, especially for faint targets that could be overshadowed by moonlight.

To determine visibility, we referenced the celestial coordinates of our desired objects, using right ascension (RA) and declination (Dec).

Right ascension functions similarly to longitude on Earth, with 0h RA designated where the sun would be at the spring equinox from the equator. As the year progresses, the sun moves around the celestial sphere, which influences when we can observe specific objects.

In August, we aimed to find objects around 22h RA, based on the sun's position relative to the Earth. We also needed to consider declination, analogous to latitude, to optimize our observations.

The visibility plot helped us track the location of our chosen objects throughout the night on specific dates. For example, Cygnus X-1, a binary star system with a black hole, was highly visible for much of the night.

Now, with a list of observable objects, we needed to decide what kind of observations to make. We could capture stunning images of colorful nebulae or galaxies, or even the NEOWISE comet during its visit.

An alternative approach involved obtaining the spectrum of an object, which reveals which wavelengths of light are absorbed or emitted. This data helps classify the object, identify its molecular composition, or even detect exoplanets through light curve analysis.

Depending on our observational goals, we could choose between the ALFOSC or FIES instruments on the telescope. ALFOSC is excellent for capturing images and includes a spectrograph, while FIES specializes in high-resolution spectroscopy for bright objects.

When selecting filters for our observations, it’s essential to remember that images captured with a CCD detector are monochrome by default. To create a true-color image, we must take multiple black and white images through filters for red, green, and blue, then combine them.

Filters allow specific wavelengths of light to pass through. Narrowband filters target specific emission lines, while broadband filters let a wider range of wavelengths through. For the best results, we often use H-alpha for red, OIII for green, and either a B or V filter for blue.

As we finalized our observational blocks for each target, we prepared scripts to automate the process during our observation night. The telescope would then locate our objects and capture the necessary images or spectra.

The finding chart serves as a guide to ensure the telescope is pointed at the right object based on the coordinates. This precision is especially crucial for spectral observations, where accuracy is paramount.

After confirming our target, we proceeded with our observations, capturing stunning images with the NOT and ALFOSC instrument using B, V, and R filters.

These images can be processed further to achieve the desired color accuracy, resulting in breathtaking visuals.

The galaxies captured in these images are 300 million light-years away, offering a glimpse into the cosmos as it was when the light first began its journey toward us.

Another example from our observations was the Cygnus X-1 binary star system. We successfully captured its spectrum over several nights.

The motion of the binary system is evident when focusing on a narrow wavelength range, revealing shifts in absorption lines due to the Doppler effect as the stars orbit their black hole.

As astronomers, we are reminded of the vastness of the universe and the intricate dance of celestial bodies.

“Do not look at stars as bright spots only. Try to take in the vastness of the universe.” - Maria Mitchell, Astronomer