Thanks, Jeff. My initial test was very positive. We are now in the rainy season here in South Florida, which makes it difficult to enjoy the night sky. But, I'm thinking of imaging lunar craters whenever it all comes together. Soon...

Ed

 

On May 9th I finally gave the platform its initial imaging run on the moon. I spent some time adjusting the motor tracking speed and finally found the sweet spot. My East/West alignment was off, enough to cause a slow drift - a good thing when imaging planets and the moon. Being the initial run, I didn't mess with trying for accurate polar alignment, plus it was good enough for what I wanted to do.


Lunar craters Arzachel, Alphonsus and Ptolemaeus (center)

One characteristic of the platform is that stiff gusts of wind do induce a little shake. The same thing happens when using my 6" Mak on the CG-4, so no surprise, and it's something I know how to deal with. It was not a good night for imaging with anything, but I really wanted to try out the platform. A small quirk I found was one spot during tracking that made the image jump a little, a bump. It turned out to be a small bit of wood finish buildup on the rear track, which was easy enough to rectify with a sharp knife in about 2 seconds.

A small mod I made to the bracket that holds the drive shaft and cut-off switch was to drill the mounting holes one drill size larger. This gave me a bit of adjustment to align the motor and shaft perfectly, although it ran fine as it was. I also radiused the inside edge of the drive shaft head. I very sparingly used light lithiun grease on the bearing surfaces of the drive shaft and bracket. This thing purrs like a kitten and is smooth as a baby's behind throughout the travel.

Ed

 

I have had the platform for about a month now and have made a couple of mods. One mod was to glue a 3/8" wide strip of thin leather to the drive surface of the top plate:


Thin leather strip glued to drive surface

A couple of nights ago I set up the platform, but the drive shaft didn't move the top plate - not enough traction. Tropical weather can be fickle and harsh, and can do weird things sometimes. I had the thin leather and glue in the garage. Within about two minutes I had the leather strip cut out and glued to the driving surface, which I let dry overnight.

The other mod I made was to install a T-Level on the base:


Red T-Level added to base

On a level interior floor the platform is spot on. However, the patio slab has to be angled to let the rain water run off. As soon as I placed the base on the patio slab I immediately saw the bubble was off, just as I had expected. A 1/8" piece of hobby plywood placed under the front feet leveled the base. I'm thinking about making adjustable front feet, but the small piece of plywood is so easy to use.

Ed D

 

I have been working on things and innovating since before I was ten.

Ed

 

Last night I set the scope and platform up, making sure the platform was level and polar aligned. The T-Level I added is a very useful addition. I tried it on a few stars in different parts of the sky and tracking was great. This morning I set it up in the family room and timed the platform travel. I'm getting 41 minutes of tracking time. This is plenty for my visual, and especially for lunar and planetary imaging, which takes only a scant few minutes.

So far so good, but I'm needing more 9V batteries, and that's a good thing!

Ed

 

UPDATE 10/16/2022: I kept having some issues with the platform drive, very annoying little glitches. I believe these platforms may be good for use with lighter 6" or 8" Dobs, but the weight of my 10" seems to be pushing it. The original drive system, although effective, was crude:


Original motor drive - I installed the electrical connector.

I thought about how to make a more refined drive system, one with a flexible coupler. The motor output shaft miked at 5mm, and the drive shaft 8mm. I found a 5mm/8mm coupler on eBay for a whopping $4.39 shipped to my mail box, the shipping costing more than the coupler. I used a nylon spacer I had in a junk drawer between the coupler and motor to prevent any possible binding:


Coupler and motor shown with nylon spacer.


Coupler installed on motor.

I had a long stainless steel bolt with an 8mm shaft that I made the drive shaft out of. I purposely made it extra length and knurled it in the mid-section for better grip of the drive surface. The entire shaft was polished with 400 grit, including the knurling. I didn't want sharp knurling that would eat away the drive surface, only enough to afford a good grip:


Polished shaft in my very old Harbor Freight Mini-Lathe.

I didn't like the little wood screw used to mount the motor to the platform. I drilled the hole all the way through and used a longer bolt and nut to mount the motor. The bolt doesn't have to be tight, snug works best. I put everything together, aligned it and snugged it down:


Motor assembly with new drive shaft and coupler.

As you can see in the above picture, I modded the motor for use with a six AA cell holder. The battery is held on the platform with velcro, which I stapled on with an upholstery stapler.

Weather has not been cooperating, so I tested the drive in my family room:


Testing the modded drive.

I'm glad I tested it because it revealed that the battery cable had to be routed to the right of the motor to avoid pinching as the platform moves. No big deal to screw in a small wood eyelet and Ty-Wrap the cable to it:


Picture of battery cable securing method.

In my limited testing indoors the platform appears to be tracking very smoothly now. The glitch spots seem to be gone. I'm anxious for a clear night so I can test my platform under the stars.

Just like mass produced Dobs, this platform has been a work in progress. Like I said previously, I think this platform is better suited for 6" and 8" Dobs. My 10" is really pushing it, and I would say it's a bit undermounted.

The Dob and the platform are works in progress. Stay tuned.

Ed D

 

Very nice. I'm guessing you're powering up a 9V motor drive for a GEM and/or heater strips? Years ago I installed a Celestron 9V drive on the RA of my CG4 mount to track planets. The 9v batteries used on these motors don't have much amperage, especially for the load, and internal battery heat builds up enough to affect performance. The high environmental temperatures down here don't help. A larger capacity 9V battery runs cooler and output is stable.

The reason I use AA cells is because I make sure I have an ample supply in my hurricane prep kit for the lanterns, radio, etc. They eventually expire and I'm too cheap and ecologically sound to toss them out unused. I also have a couple of Harbor Freight portable jump starters that I keep charged for reserve hurricane power, which do double duty to power my astro dew strips, fan, etc.

Ed

 

UPDATE 10/23/2022: Finally got the platform and 10" Dob out under the night sky. I observed Jupiter at medium-high power, tracking through three full cycles and a few partial cycles. I'm happy to report that the platform tracks smoothly without any issues. Although the 10" Dob is undermounted, the platform settles down in reasonable time after focusing or touching the scope. Also, the six AA cell battery works so much better and consistent than the 9V 'transistor' battery.

The only other mod I want to make to the platform is installing adjustable feet to make leveling easier. Currently I'm using a thin piece of hobby plywood under the North feet - Crude, but effective. I will report and post pictures whenever I get around to doing the mod.

Ed