Luke 21:25-26 corresponds to Revelation 6 the sixth seal. Which is right before Jesus returns down to earth.
You are mistaken (as usual). Note carefully Jesus own words in Matthew 24:
29 Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
Notice Joel 3:
15 The sun and the moon shall be darkened, and the stars shall withdraw their shining.
16 The Lord also shall roar out of Zion, and utter his voice from Jerusalem;
In Revelation, these cosmic signs are not shown because John did not see them - God chose for John not to see them. If John had seen them and written of them, they would be found after the 7th vial ends the week or just before Jesus return to earth in chapter 19. Jesus said "immediately after" the "tribulation..."
"Tribulation" is still going on in chapter 16.
Unless or until you come to the place you realize and understand that these cosmic signs will be shown TWICE, once before the week begins as a sign of the Day of the Lord, and then again after the days of tribulation have ended, 7 plus years later, as the sign of His coming, you will always be in error.
The book of Joel shows BOTH signs.
Unless or until you understand these two different signs are DIFFERENT - you will be in error. If the moon turned red but was invisible, how could it possibly be a sign of a blood red moon? Common sense tells us this moon is meant to be seen. On the other hand, if people are looking for the sun and moon, and neither can be seen, that too is a sign: total darkness! These are two different signs for two different purposes.
unless or until you come to understand that YOU CAN'T MOVE SEALS - as in thinking the 6th seal can be just before the Rev. 19 coming, you will always be in error.
Get this straight once and for all time: the seals' purpose is to seal the book so no one unauthorized can open it. Once a seal is opened, its purpose is finished and it is forgotten. (However, the event that a seal instigates may be ongoing, such as the church with the gospel.)
John marches us right through the seals one by one TO GET THE BOOK OPENED. That happens in 8:1. John does not have to tells us: "now the book is opened." We know the book is opened as soon as all 7 seals are opened.
The 70th week is what is INSIDE the book. In other words, if God can't find someone worthy to open the seals, He can bring NO 70th week.
Therefore, it is absolutely impossible (in fact silly) to make a suggestion or comment that the 6th seal is just before His coming to Armageddon.