In use
After correction of some “youthful errors”, especially on smoothness of bearings, it’s time to use the thing in “real” conditions. We are in April, with a very variable weather and clouds rolling fast into the sky. But looking into the holes between the clouds will be enough to see what the telescope is worth.
Mounting takes arount 12 minutes, and the T400 is ready for observation. Collimation is made easy with added collimation rods, that make the process a lot easier. Pointing with the quickfinder device and 28 mm eyepiece is a breeze. M51, M81 are found immediately, and even M1 can be found quickly and appears in the eyepiece without requiring “night vision”. So lightwise this is more than expected, and I can feel the différence with the C11 SCT (around twice the light collection power).
But the real Mc Coy came during the first “true” observing night, from the gazing of M13. Quickly pointed at 28 mm, then viewed with a Nagler 20 (90x magnification). Stars are resolved, numerous, fabulous. A real treat. We are eager to have a real night to confirm this. Observation of M57, which has just risen up, is another wonder. I had never seen this nebula this way : the small pale ring has become a well defined donut with its slightly elongated shape and the darker area in the center. It looks like it is on photos (less for color).
Then during one following night, I eventually could have a true observation of M51, where spiral arms start being distinguished in the halo sorrounding the two galactic centers. Eventually on planetary field, observing Saturn brought satisfaction. at 140x magnification, colors are obvious, Cassini division as well as cloudy areas can be guessed easily. Unfortunately weather conditions were too unstable so far to allow a greater magnification, but we stayed on a very good impression.
All in all this is a success, and the T400 perfectly lives up to the expectations. I’m awating better weather to finally be able to play with the beast.
Transportation
Initial design allows to “fold” the scope parts into 2 boxes for transport. The secondary cage and base fit into the rocker, with the handle available. There is even enough room for storing the focuser as well as some accessories (eyepieces, barlow, etc…). The primary case is handled alone and acts as a “mirror box”. Still are the altitude bearings and tubes to carry.
Secondary mirror & holder are protected in a very simple fashion : a piece of water tube 100 mm wide fits just around the secondary mirror. With 2 caps we have a nice protective box for the mirror and the spider center (yet another “stolen” idea 🙂 ).
Upgrades
Once the first light was achieved, validating that the optics were functional, I was able to draw up a list of upgrades made to the telescope to make it more efficient and user-friendly. I am listing them here to give the reader a few ideas…
- Eyepiece board reinforcement: Done to limit flexing when using heavy, wide-field “grenade” eyepieces.
- Gluing straps onto the bearing surfaces: The strap/Delrin combination provides the perfect friction coefficient (neither too much nor too little! ;-)).
- Installing Delrin pads on the rocker box: This ensures a much smoother motion. The strap-on-wood friction was not smooth enough.
- Buying a camping mat from Decathlon: Used to make a dew shield for the primary mirror cage. It also protects the mirror, which is otherwise exposed to the elements (especially during public outreach events, which can be risky).
- Eventually, this baffling was replaced by a Lycra light shroud covering the entire truss tube. It is much more effective and secure (against dew, frost, and the public!).
- Buying a tarp: To cover the telescope in case of drizzle or rain.
- Adding a strut between the altitude bearings (half-bearings): This greatly stiffens the whole assembly.
- Building a new square ring base: Done to improve the telescope’s stability (no more tipping over when pulling the truss tube!).
- Reworking the primary mirror collimation bolts: They were bottoming out, so I added shims/washers. It is crucial to carefully calculate the height of the three collimation points right from the start.
- Placing shims under the focuser: To realign it with the optical axis. Even with great care, it is hard to get a wooden structure perfectly square (or at least, I do not know how to do it ;-)).
- Crafting collimation rods: To allow primary mirror collimation “from the top” (eyepiece side). This saves you from bending down and allows you to collimate directly on a star.
- Adding carrying handles: For transporting and handling the primary mirror box. Despite all good intentions, the box + primary mirror easily weighs 20 kg, which is heavy to handle…
- Adding a cooling fan under the primary mirror: To speed up thermal equilibrium (cool-down time).
- Adding a secondary mirror dew heater system: To prevent dew formation (in progress).
- Replacing the JMI focuser with a “Feather Touch” focuser: Much sturdier.
Now, on to the observations!!!