Messier 87 shot at a dark site in Arizona last month changed how I check collimation.

Found out my secondary mirror was off by 3mm after comparing star spikes in my 12 inch dob to the pro images from Kitt Peak, anyone else notice their gear alignment only after seeing what clean optics really look like?

2 comments

2 Comments

viola_cooper621mo ago

I had that exact moment two years ago after a trip to the observatory near Flagstaff... my 10 inch dob's secondary was off by nearly 5mm and I never knew until I saw what a perfect diffraction pattern looked like on their 20 inch scope. It's humbling to realize how much signal you're leaving on the table with sloppy alignment.

olivia5731mo ago

Whoa hold on, you're saying your secondary was off by 5mm and you never noticed? That's a huge shift. But honestly, that 20 inch scope's diffraction pattern is probably showing you more about your own scope's perfect collimation than you think. A 20 inch has way more forgiving tolerances for alignment compared to a 10 inch. A 5mm error on a 10 inch dob would make the image look like garbage on anything but the worst seeing conditions. Don't beat yourself up too bad - your scope was probably working better than you think, that 20 inch just lets you see the fine details easier.