When the plastic plug is removed, the coverage of my 10 -inch Celeston Dobsonian reflector works as a 2 -inch opening mask. This makes excellent to observe the moon when it is almost full. Credit: Michael E. Bakich
I hope this series of thoughts (can I call them blogs?) Help you become better observers. I will include advice and observation techniques, made on constellations, reviews of books or websites and curiosities. Since there is no right way to order this series, I will only do what I am thinking about on that day. Some will be short, others longer. Some will be for beginners and others will be a little more advanced.
I want to thank all the observers I have known that they helped me to be able to make such a list. Whether it’s a book, video, internet or person, he accepts my deepest gratitude. You know who you are.
Today’s topic: Masks openings
An opening mask is a device (it can be simple as a piece of cardboard with a hole cut in it) which increases the actual focal ratio of a telescope. For example, if you insert a 4 -inch opening mask on an 8 -inch F/6 telescope, it becomes, in fact, a 4 -inch F/12 telescope. He said in another way, is a way to drastically cut the throughput of the light of any telescope. So, someone with a 11-inch Schmidt-Cassegrain telescope could use a 3-inch opening mask to observe the moon during one of its brightest phases. The use of an opening mask can also tell you the minimum opening that someone would need to divide a double star.
Years ago, David Knisely, from Lincoln, Nebraska, shared a great idea with me: “I occasionally use a variable opening mask out of the axis that I built for my Newtonian reflector F/5.6 of 10 inches to judge the double star. The division between a couple becomes invisible.”
Fairly well -weighted technique, David. Thank you.
