After 11 months in the making, July 2nd 2009 will be the historical date to remember when our 240 mm Newtonian saw First Light! July is not dark at all in Finland, but that didn’t prevent us from setting up in the back-yard to have a look at the moon. Predictably the clouds soon rolled in, and the first light picture shows trees. Apologies for the poor quality, a snapshot with my N95 phone-camera through the eyepiece:
Nevertheless, spirits were high as we earlier during the day with doubts in our minds had bravely drilled holes in the pristine wood-tube for the focuser and the 2ndary-spider. We were not 100% sure that the image would be nice or the focus-plane at the correct position - but everything seems to have turned out OK!
This picture shows the 300 mm telescope-rings. They are now quite close together and we plan on making a wider support for them. We needed to add two layers of felt-cloth under them to get a nice fit. This scope is much heavier than the 80ED, and it’s immediately clear that an EQ6-class mount is not overkill at all.
The 2-speed Crayford focuser with a 2″ to 1.25″ converter and an 8-24 mm click-stop zoom eyepiece. The grey ring around the scope is a 40 mm glassfiber band which was added to both ends of the tube as reinforcement. Two bolts that hold the spider in place are visible, one under the focuser and one just above the black fine-focus wheel.
The front end of the tube with the spider holding the secondary mirror. The inside of the tube was spray-painted black once, but we may still improve on that later.
A look inside the tube. At the bottom we see the parabolic 240 mm primary mirror, still uncoated, so it only reflects about 4 % of incoming light. Through the right edge of the mirror the mirror-mount and the collimation bolts are visible. An image of the secondary mirror is visible to the left.
The back-end of the tube holds the primary mirror mount. This consists of two wooden boards, one bolted to the tube with three L-shaped fittings, and the other ‘floating’ on top supported by three spring-loaded collimation bolts. The three wing-nuts are used for collimation.
Another view of the back end of the scope which shows the glassfiber reinforcement, and big washers used to spread the load of the primary mirror mount.
This is now my third 2.4 GHz radio after first having used a special module on the Futaba 3VCS, and then a Spektrum DX6 with the Noux (now sold). It’s the cheapest model, a DX5E, which will be used with my newest boat (soon to be featured on this site…).
It seems the Spektrum engineers are not reading this blog too keenly, I suggested an internal antenna back in 2007. Even if the antenna is short I don’t like it sticking out of the transmitter, so the first thing to do with the brand-new radio is to open it!
Here’s how the transmitter looks opened. Note the small battery compartment which only takes 4 AA-cells (down from 8 in the early days and 6 on the older DX6). There’s plenty of room for the antenna at the top of the transmitter, but just outside the top edge there’s a metal carrying handle which I thought wasn’t the best thing to have close to the antenna. So off it goes:
The handle detaches by opening two nuts on the inside of the case, after cutting a way some hot-glue which was used to secure the nuts.
Then the antenna needs to be made a bit smaller. What sticks out of the transmitter is actually first an empty plastic tube which just extends the antenna itself a little further from the case. By cutting away the small plastic bits that prevents the antenna from rotating 360-degrees it all disassambles nicely, and I’m left with the narrow coax-cable and the antenna:
The antenna can now be hot-glued to the top of the back casing:
I’ve also applied some hot-glue to the holes where the handle was attached. Now all that remains is to close the case again, making sure that no wires are caught between the casing or screws:
And we have ourselves a Tx with an internal antenna! The way it should have been designed in the first place - if you ask me. What remains is to tape or plug the old antenna opening. Previously I’ve had no range or other problems whatsoever with this kind of arrangement, but naturally I take no responsibility if you try this and void your warranty and damage your transmitter.
About 9 hours compressed into 38 seconds. 566 frames shot at 1 minute intervals from around 10:00 in the morning to 19:36 in the evening. Played back at 15 frames per second, which makes for a ~900x speedup.
I first re-sized the jpegs to 1024 pixels wide and then used this matlab script to assemble the AVI-file. The original 20 Mb AVI may have better resolution than the youtube version.
Canon 20D with 17-40/4L lens on Manfrotto 486RC2 ballhead and Velbon Sherpa pro CF 635 tripod. Timing with a ‘Yongnuo’ TC-80N3a remote from dealextreme.com.
When epoxy cures it releases heat in an exothermic reaction. I was adding some glass-fibre reinforcement to the telescope tube and mixed 140 g of L285 epoxy into an ordinary plastic cup. I got about half-way through the job when I noticed the cup heating up. I tried putting it in a cold water-bath, but it was too late by then… It quickly got very hot and all of it cured instantly! At room temperature this resin should have a 60 min pot-life, but now it cured in about 5 minutes. Not much harm done, but I understand these things can cause fires and all kinds of trouble when people deal with kg or tens of kg amounts.
Note to self: 100 g or more of L285 needs to be mixed in a shallow container with lots of surface-area which provides cooling. RTFM.
Does anyone else have pictures or stories about exothermic melt-downs?
The mirror has been figured and ready for some time now, but we’ve been so busy with other things that the telescope hasn’t been finished. Now the plan is to assemble the mirror-cell, mount the 2ndary, and install the focuser so we can do some initial star-testing before aluminizing the mirror. Nice images of the moon and planets (Saturn, Jupiter) should be doable even though it’s summer.
