Back-Focus 101: How Filters Affect Back-Focus

In this episode of Back-Focus 101, I describe how filters change the back-focus requirement of your optical system, both visually and mathematically. Filters don't change the back-focus distance by much (in most cases), but it is critical to compensate for the change as your focal ratio decreases (or, as the "speed" of the optical system increases). In other words, it is not absolutely necessary to add the extra back-focus when using a filter at f/10, but it becomes very critical at faster focal ratios. My Agena Astro Affiliate Link: https://bit.ly/3MiW5LL My High Point Scientific Affiliate Link: https://bit.ly/44XcvTv AFFILIATE LINKS: This description contains AgenaAstro and High Point Scientific affiliate links. If you choose to purchase after clicking a link, I may receive a commission at no extra cost to you. This helps me significantly in funding the channel and astronomy purchases, allowing me to produce tutorials and unbiased reviews that you can trust. If you enjoyed the information presented and/or found it helpful, please support my channel by making your astronomy purchases through my AgenaAstro or High Point Scientific link above. Thank you!