Strong Mounts
My single most expensive piece of kit is the pier I built in my back yard. It’s a 12″ concrete cylinder, reinforced with rebar, and poured nearly 5′ below the ground so that it connects with bedrock.
Why make such a big deal out of what is, effectively, a glorified tripod?
To explain, let’s do some math (sorry). My long-focal-length telescope with my astro camera has a field of view of 0.53° x 0.36°. That’s pretty small.
My astro camera divides that horizontal field of view into 4,144 pixels, which means that each is sampling 0.46 arcseconds of the sky. That translates to 0.0013° per pixel. That’s tiny!
To maximize the sharpness of my images, I never want the the mount to gain or lose more than 0.46 arcsec during a given exposure; otherwise the information in one pixel will bleed into its neighbors and fine detail will blur. In conventional photography, exposure times are usually fractions of a second. In EAA and astrophotography, exposures are measured in 10’s of seconds or minutes. So keeping the “flex” in the system under 0.46″ is both important and challenging.
When I first started astro-imaging. I placed my telescope, mounted on its tripod, on my deck. It’s a well built deck and a figured it would be just fine. Nope.
I found it almost impossible to polar align my scope accurately. Typically, I’m trying to get the alignment within 2 arcminutes. The problem is that when I stepped up to adjust the alignment, my body weight would deflect the floor-boards more than 2 arcminutes.
Whenever even a modest breath of wind would hit the deck, the image would blur right up. I ended up setting 4 second exposures, and could only image on calmer than average nights.
Today on my pier, I’m routinely able to polar align to an error of less than a single arcminute, and standing next to the telescope has no effect. With the EdgeHD at 2,032mm, I’m able to image 30 seconds routinely, 60 seconds on calm nights, and 15 seconds on breezy nights. Using my Askar V at 270mm, I’ve imaged in winds up to 20mph.
Bottom line, the stability of your telescope mount is critical. Not everyone can build a pier, but locating your telescope on solid ground, and investing in a good quality tripod is essential.