DIY Guide Scope

I noticed that even with a careful polar alignment, I was getting star trails at 336mm focal length and 30-second exposures. A better polar alignment would fix this, but my Vixen Great Polaris sags a bit due to differential load and the tripod hub flexing, so I can never be too sure of my polar alignment from night to night.

The answer obviously is to auto-guide. I used the ZS 70ED as the guiding tube a few nights ago, and got about 20 arc-seconds of peak-to-peak RA error, which is pretty OK except for a large spike once every worm cycle. The Great Polaris has a large drift in declination though:



Today I took apart the declination axis, cleaned it up and loosened it a bit, and lubricated it (with canola oil, since I didn't have any engine grease or white lithium).

I made this short (80mm focal length), fast (f/2.8) guide scope out of an old Mamiya medium-format lens to which I'd epoxied a 1.25" eyepiece holder. Here it is bolted to my William-Optics ZS 70ED, with a Meade DSI Pro camera.

Since I now have the dedicated guide-scope, I can put the DSLR on the ZS 70ED tube now.

William-Optics 0.8X Reducer/Flattener II

I got this flattener sometime in September last year due to the amazing egg stars (field curvature) of my William-Optics Zenithstar 70ED small refractor. I haven't gotten around to making a before-and-after comparison until now.

Center (this is Rigel) without and with the flattener. The stars aren't perfectly round due to my imprecise polar alignment.

without flattener	with flattener

And the edge (not extreme edge)

without flattener	with flattener