Rainy days and cloudy nights make me so restless. Tonight was another one of those nights. All day, I had been thinking about custom cutting a foam sleeping mat as a shroud for my Sky-Watcher 12″ Dobsonian Flextube. But on the way home, I came up with something a little more complicated and time-consuming. A custom-made cloth shroud.
Step 1: I measured the inside diameter of the top and bottom tubes and the distance between them. I came up with 42.5″ diameter x 23″ height. I went to the local Fabricland and bought a thick black cloth from the clearance section ($7).
Step 2: I measured again and noticed that I had to reduce the inside diameter by half an inch to account for the thickness of the cloth. The maximum thickness allowance is 0.5″, otherwise, the material will reduce the aperture. I folded and ironed the new measurements. My wife sewed the edges for me.
Step 3: I taped 2 and a half lengths of velcro ($3 from Dollarama) to the top and bottom edges of the cloth and ironed them on. But by that time, my wife had gone to bed. So I had to sew the width side by hand to form the tube (the sewing machine was too complex for me).
Step 4: I then taped the hook side of the velcro to the inside of the top and bottom tubes and attached the shroud starting from the bottom.
Step 5: With a little tug, I attached the top making sure it was taught all the way around. I looked through the focuser to ensure the shroud was not in the way of the primary.
Voila! A custom-made shroud just the way I like it. Tomorrow, I will be sewing the velcro onto the shroud because it is peeling off.
Today, I learned a lesson in troubleshooting a collimation problem with my new dobsonian telescope. When I took the secondary mirror off to install a washer, I could not properly get it collimated with my laser collimator on reassembly. One problem with laser collimators is that it assumes that the secondary mirror is already centred under the focuser. But that is easier said than done. Until now.
Symptom: When I looked through the collimating cap after a laser collimation, it looked like the above photo. The primary mirror’s clips were off-centre. It was actually worse than what the photo shows. However, the photo provides a clue of what the problem may be: the secondary is not centred.
So below were the steps I took to collimate after disassembling the secondary:
Step 1: Above, I rough aligned the secondary under the focuser and took a photo. To the untrained eye (like mine), my secondary mirror looked centred through the 1 mm hole of my collimating cap.
Step 2: That was until I took a ruler and measured it on my screen as shown above. So I kept adjusting the secondary until both sides were equal. I pinched to zoom for more accuracy.
Step 3: I used a right-angle diagonal focuser above from my refractor so that I can adjust the primary adjustment screws and receive instant feedback without walking back and fourth. I centred the donut to the reflection of the secondary.
Step 4: I replaced the collimating cap to verify alignment and it looked good as shown above. I then followed it up with a laser collimation and it still looked good afterwards.
Out in the field, I will be star testing it for fine tuning. My laser collimator was 99% true so if you plan on doing the same procedure above, check to make sure your laser collimator is properly collimated in the first place. Credits go out to the following AstronomyForum.net members for helping me troubleshoot the problem: mlk1950, CamelHat, andrejl2, Jason_D
My Discovery 8 EQ‘s equatorial mount is over 10 years old and it has been very ‘sticky’. It is a ‘Lin-Optics’ brand-name mount that I cannot find of any documentation on the web. Last week, I attempted to disassemble it to replace the lubrication but could not figure out how to remove the inner shafts.
This weekend, I finally had more time to look into the issue further. I needed a little bit more time to carefully figure out which set screws were meant to be removed, and which were meant to be tightened down in order to remove the shafts. It was like a rubik’s cube puzzle.
After an hour, I finally figured it out. The ascension shaft took me half as much time to figure out. I cleaned the parts with degreaser spray and wiped them clean with paper towels. If I could have collected the metal filings, I would say there was about a teaspoon of it. I then applied a generous amount of white lithium grease and put it back together.
Now, my mount is buttery smooth with the Newtonian telescope on it. It feels like I just bought myself a new mount. A fun project with long-lasting benefits.
It’s not like this hasn’t been done before, but I needed a red flashlight in a hurry so I put one together using a flashlight from the Dollar Store and red plastic folder kicking around. It takes at least 20 minutes for our eyes to dark adapt, and only a few seconds to lose it by shining a bright light into the pupil. Red light has the least effect on our dark adaptation so that we can observe faint objects and sketch them.
1. Flashlight. I bought one from the Dollar Store.
2. Red semi translucent acrylic folder or tote.
1. Use the head of the flashlight to trace a circle on the acrylic folder. The circle will be larger than the interior of the tube so make sure you trace the line as close as possible.
2. Cut out the circle making sure it is slightly bigger than the flashlight opening. The slight difference will make it push against the interior of the flashlight as well as provide maximum coverage of the white LED’s.
3. Insert plastic cutout into flashlight head. Because the cutout is slightly bigger, the edges will push against the opening to keep itself in place. If the piece is too big, cut away small pieces of it until it is just snug.
4. Turn on flashlight to test for light leaks. Redo if necessary.
If the light appears too dim, try it out in a dark room first, like a closet or bathroom. It might just be the perfect brightness. You don’t want it too bright.
Try this out. If you have ways to improve this Do It Yourself project, please share your comments below.