Science (knowledge) starts by performing observations by observers and by asking questions. However that does not mean that the observers are the most important. The most important is what they are observing
A typical case is an exploding star or supernova, considering all observers which observe the same exploding star. All observers at the same distance from the star, in a sphere around the star, will observe something different. It is that knowledge you should try to capture.
The pictures of a supernova, showing a visible impression, are impressive. But that is not the most important. The most important is the distribution of all matter: visible and invisible. All this matter influences each other.
But if you consider any binary star system, its all visible and invisible matter that influences both stars (objects), even if both stars (objects) are invisible.
The conclusion is that observers are no part of the physical explanation of the behavior of stars. That does not mean that comets can not loose mass when they circulate around the Sun or energy when they emit photons as visible light.
However there is an other reason why observers should not be 'trusted'. A typical case is when length contraction is observed.
Consider two obervers A and B situated at position A and B along a straight railroad track. The length of the train is l. The front of the train is at position A
At t0 the train starts to move from A to B. When the front of the train is a distance l away from observer A there is at t1 a light flash. This flash will reach observer A at t2 (which comes from the front of the train) later as t1. That means if at t1 observer A can see the front of the train this image comes from a position (earlier and) closer than l. That means observer A will observe length contraction.
For point B and observer B a rather similar situation exists.
Consider at t4 the front of the train is at the same position as observer B. At that same moment t4 can observer B observe the back of the train?
If at that same moment t4 a light signal is issued from the back of the train the observer B will observe that light signal later at t5.
If at t4 the observer receives a light signal from the back of the train that signal always has been transmitted earlier at t3. That means the observer at B observes length expansion.
The next question becomes: are length contraction and length expansion some thing physical? The answer is no. It is a visible illusion.
1. Consider you stay right up, with both hands against a shoulder.
2. You stretch your left hand slowly. Your left hand represents the front of the train. Your arm represents the train. (left hand back to shoulder).
3. You stretch you right hand, vast. Now you move your right hand slowly to your shoulder. That represents an approaching train, moving towards you.
4. You turn 180 degrees and you continue to move your right hand, which now becomes your left hand, untill your left hand is completely stretched.
5. What the items 3 and 4 represents is a train which approaches you, passes you and moves away from you, at a constant speed.
6. Is there any length contraction, or expansion involved in this train. I would say: No
7. But what about the observer? The observer observes both first length expansion and then length contraction which is in physical contradiction that the physical mass of the train has not changed.
8. This is different than the observation that the time indication on a moving clock runs slower than the time indication of a clock at rest.
Lesson is that the total universe, the state of the earth, and any instant represents one physical reality.
That can also be demonstrated by an universe filled with clocks, all at rest, as part of a 3D grid, which all run synchronuous.