July 24,2001
I decided to investigate the possibility of building my own telescope. I initially searched magazine ads, later visiting the respective web sites. I really liked the truss-type telescope designs as a practical way to own a large-aperture telescope. A 15" to 17.5" aperture would probably be the most I could both practically build and afford.July 26,2001
Weight has definitely become a concern, as well as a limiting factor on size.August 1, 2001
My telescope project has officially been dubbed the "Stargate-1", complete with a logo.August 28,2001
I just got a big help- The Dobsonian Telescope, by Richard Berry and David Kriege. This book was invaluable in guiding my design efforts, as well as detailing practical construction matters.September 22, 2001
I went to a star party at Island Lake State Park in Michigan. While I'd hope to get some technical advice, I did get to see what I was in store for. I got to see M13 through a 22" Dobsonian, which was very impressive. The view through a 16" Dobsonian was also very impressive.September 23, 2001
The red flashlight that I had brought to Island Lake was woefully inadequate. So I went to The Shack and picked up some super-bright LEDs and made a flashlight that did much better.October 7, 2001
I came up with an idea to use thermoelectric coolers to control dew formation on the secondary mirror.October 28, 2001
For months, I'd been scribbling down ideas for mounting the truss tubes. None of my ideas to date looked any good. And then the answer came, in an e-mail from atm.net: a company which has a ball-and-socket design to secure the truss tubes.December 16, 2002
I finished up the designs for the spider vane and secondary cage assembly.January 12, 2002
Previously, I had intended to design and build my own digital setting circles. But in considering the amount of time it would take, plus the fact that I just don't quite have the math down, I opted to buy a commericially-made computer. I still need to worry about mounting it. I thought about using small plastic gears to couple the axes to the encoders.January 14, 2002
I bought the 90mm Orion ShortTube refractor to use as my finder scope, as well as a quick getaway telescope.January 21, 2002
I began work on the dew controller. For now, I'm just working on the power control circuits for the TECs.January 23, 2002
The Stargate project has officially been funded. The main and secondary mirrors have been ordered from Discovery Telescopes, and are are expected to be ready for the 2002 Memorial Day weekend construction date.January 29, 2002
The design of the dew controller power circuit for the TEC has been very problematic. Mainly, power MOSFETs don't like being driven by TTL-level signals. For now, I opted to use a DPDT relay to switch between heat and cool on the TEC (in place of the classic H-bridge), and a single power Darlington transistor to turn the power on and off. It works, and even reduces the parts count some. While, I would prefer an all-transistor design, using a relay should work without a problem. After all, its sole purpose is to switch between heat and cool, heat being default. The relay, then would only be on at start-up. The mirror's temperature throughout a viewing session will only go down, so heat will only be needed then. Now I need to find a humidity sensor.February 6, 2002
February 20, 2002
I bought a pair of thermistors to use with my dew controller. I had previously intended to use a precision integrated circuit temperature sensor (like the LM34). But why? All I need to do is determine the temperature difference between air and mirror. And with a sensor like the LM34, comes analog-to-digital conversion. I plan on using the Basic Stamp 2 as my controller (as I already have one). The BS2 already has a means for me to measure the thermistor directly, using simple software to iron out its non-linearity. And I believe that I have located a suitable humidity sensor. Plus, I may use a DC motor module (the Motor Mind B from Solutions Cubed) to handle power switching of the TEC.Also, I have been working on heat load calculations to get an idea of how much heating/cooling will be needed. This will be needed in picking a large enough TEC and a starting point for software settings.Lastly, I have read discussions about using TECs to cool down the main mirror. I'd thought about this previously, but dismissed it. Now however, I will give the idea some more consideration.March 1, 2002
I ordered teflon for the bearings.March 2, 2002
I've just about given up on finding a humidity sensor. All the companies that I could find either had products way out of a practical price range, or were just not interested in selling small quantities. I made a simple chilled-mirror hygrometer (all I really need is dew point). But, because of complexity, parts count, and power consumption, it may not be practical. The whole idea is on life support, and I may just work with mirror and air temperature alone.March 3, 2002
I've ordered the focuser, truss tubes and tube clamps. Work continues on an idea to cool the main mirror faster than by using a fan alone.March 4, 2002
I improved my idea for the chilled-mirror hygrometer. Also, I ordered TECs for both the secondary mirror and for a prototype cooler for the main mirror. A power module (the Motor Mind B) was ordered to control the secondary mirror TECs.March 7,2002
The focuser, truss tubes, tube clamps and Motor Mind power module have arrived.March 18, 2002
With a heat exchanger milled using a program that I wrote, I tested a prototype cooler for the main mirror. It was enough of a success that I will begin designing a new one incorporating the lessons learned from the first. I will also need to buy that deep-cycle battery I had intended for later now, as my power supply is inadequate to fully power the TECs, pump and fan motor (I dimmed the lights during my test when I switched it all on!).April 16, 2002
Today I have finalized the design of the heat exchanger for the main mirror cooler. After weeks of tests and battling problems, such as pump motor overheating and deciding power limits for the coolers, the design is ready to go to metal. I will also order the altitude bearings tomorrow from Obsession Telescopes. Materials for the secondary cage are being gathered. Also, I finally found a humidity sensor for the secondary mirror controls. Knowing humidity and dewpoint could also be important for operating the mirror cooler.April 23, 2002
I received the humidity sensors from Fascinating Electronics today. I built a test circuit on solderless breadboard to see how well the sensor would work. The circuit is based around the low-power version of the 555 timer chip used as an oscillator. RH varies the capacitance, and subsequently the frequency of the oscillator. I was concerned that because capacitive-type humidity sensors have such small values (in the picofarads) that stray capacitance would be a problem. My concerns were unfounded. I measured the initial frequency, then took the board into the bathroom and steamed it up. A variation of nearly 10 KHz, which will be easy to measure. More accurate calibration is now needed. And since I'm waiting on everything else, as it seems, I can focus on the controller, now.April 29, 2002
I received the side bearing rings.May 18, 2002
Earlier this week, I received the completed parts of the heat exchanger modules. I had to wait several days for screws and such to put it all together for a test. I think it works well, and is ready for a field trial.Also, I will have to contact the mirror builder as I've heard no news on it, and Memorial Day is fast approaching.May 19, 2002
I went shopping for miscellaneous hardware (screws, bolts, wheels, etc.) and realized that the mirror cooler may interfere with the collimation bolts; at the very most, require long enough ones to clear the cooler.May 24,2002
Just hours before I leave for Georgia, I learn that my mirrors won't be ready in time.May 31, 2002
In the past two days, I mounted the heat exchanger on board cut to fit the mirror cell. In my tests, I was astounded to get up to 12 degrees cooling. I see now how important fan placement is with my mirror cooler.June 5, 2002
It was a lot of work gathering materials, cutting, drilling, tapping, grinding and welding. But the mirror cell is pretty much done. I couldn't have done it without my father's help.June 7, 2002
The whole day was spent working on a bracket for the finder scope, and it's rock-solid.June 8, 2002
I've got the secondary cage now; all I have to do is drill a lot of holes for the spider and truss tube clamps. Also, the wood was cut for the mirror box, rocker and ground board.June 25, 2002
The mirrors have finally arrived, and a project that has slumped along had just shifted into high gear.June 29, 2002
The rocker box has been glued.July 13, 2002
After getting so much done on the mirror box, rocker and ground board, I was most dismayed to find an error in the construction of the mirror cell!July 15, 2002
For whatever it's worth, the ground board is done.July 17, 2002
I glued the Formica to the cast aluminum bearings that I bought from Obsession. However, as I found out, contact cement doesn't work that well on aluminum. But at least it held enough for me to use epoxy.July 28, 2002
After so much work, all that is left for the mirror box, rocker and ground board is touch-up paint. I still do have to drill holes for the electrical controls and truss tube clamps. But now I can focus my attention on the secondary cage and electrical controls.August 5, 2002
I did a check to guage how heavy the telescope will be, and got one royal wake-up! The mirror box alone, with mirror, will weigh about 106 pounds! And the ground board/rocker/mirror box/secondary cage together will be too high to be stacked together in my Jeep. The cage will have to be set aside, and that won't be space efficient.August 9, 2002
After looking over the practicality of things, if I don't address the weight and size issues, this telescope will likely get used only once or twice a year. With that in mind, I have begun designing the Stargate-2. The rocker and mirror box will be replaced with ones of welded aluminum, and will be much shallower. The secondary cage, truss tubes and electrical parts will be reused and unchanged. I will, however, finish the Stargate-1 to learn as much as I can to make the next design more practical and ergonometric.August 15,2002
I have come up with both a partial fix for the Stargate-1 and design validation test for the Stargate-2. I will cut the top six inches off the mirror box, making it the same height as the proposed mirror box for the Stargate-2. I need to see if the longer truss tubes will be stable and having if the mirror so close to the side bearing's rotational axis will cause balance problems.August 24, 2002
I cut six inches off of the mirror box and trimmed about 17 pounds. Encouraged by the results, I started drilling out 1 inch holes in the rocker. I generated more wood chips than results.September 15, 2002
I finished drilling out holes in the secondary cage to lighten it, and successfully eliminated 1.2 pounds. In fact, it even looks better like this. Balance has been a big concern since I moved the center of gravity (and rotation) so low to the ground. I've been using an advanced CAD program, MS Paint (Well, hey, it works!), to help in the design of the new mirror box and rocker. And with an Excel spreadsheet, I've been trying to predict balance. I think that I can get away with 10 pounds of counterweights, at the most. But the finder scope has been difficult to model and predict, and my calculations have more uncertainty.September 19, 2002
I was working on the problem of how to mount the 90mm refractor telescope I had intended to use as a finder scope. It is way too big to mount on the secondary cage. So, I planned on mounting it on the mirror box. But when I shortened the mirror box, I also lowered the finder scope. Now, for the eyepiece to be comfortably high enough above the ground, the main telescope will become top-heavy when tipped far enough forward. And then I remembered an idea that I had seen months earlier, but had discounted- using a reflector telescope as finder. By its very design, I can have the eyepiece at a practical height without upsetting balance. I looked at both building one and buying one, but I think buying one will be far more practical. Just the cost of a fast 4.5 inch mirror, secondary mirror and focuser approach the cost of a commercially-made reflector!September 28, 2002
I just finished a series of experiments to see how much coolant and ice is needed for the primary mirror cooler to be effective. Also, I tested the coolant detector and finished drawing up the plans for the control circuitry.September 29, 2002
I may have come up with an idea to make my primary mirror cooler iceless.November 10, 2002
I have finished my experiments for the iceless cooler. I tried everything from varying the number of TECs (which worked, but comes with a costly power budget) to cascading TECs. While an iceless cooler will not work as effectively as one using ice, it eliminates the need for it, and does so using power already available. Plus, I still leave open the option to use ice. I also collected a lot of emperical data, which will be useful when writing the software for the controller.January 5, 2003
I have nearly finished wiring the controller. I wish that I could have done this on a printed circuit board. But with as many changes that I have made since I began construction, that would not have been practical. Also, I have all but finished the design for stoppers intended to protect the mirror. They will be a part of the mirror box, rather than the mirror cell. Also, I scrapped the plan to integrate the mirror cell with the mirror box. It complicates the design too much. So, I will go back to a modified mirror cell, and the cooler will be part of it. Lastly, I have finished a rough design for the Stargate-2 mirror box. I need to see how much more weight I can trim, but the hard reality is that the assembled mirror box with mirror will weigh in near 95 pounds! Just the mirror, side rings and mirror cell weigh together nearly 70 pounds!January 19, 2003
I have put a priority on finishing the Stargate-2 design. I really wasn't pushing it until I tested out the Stargate-1. But since the mirror cell and, subsequently the mirror cooler, are no longer tied to the design, I can go forward. Also, while I did not meet my weight objectives, the new design is approximately 10 pounds lighter. And the combined ground board, rocker, mirror box and secondary cage height will meet the rigid 33 inch requirement.January 23, 2003
How ironic, on the anniversary of the Stargate project, that it has all but been decided not to finish the Stargate-1! But when you consider the design problems and changes, is there anything more to gain? It won't easily stow in my Jeep. It is designed around a mount to accomodate a refractor, which I abandoned as a finder months ago. It is heavier. When aimed at a 90 degree altitude, the eyepiece will be just too high to safely view through (with my short ladder). The mirror cell, which has been plagued by construction and design problems, has been improved upon. In fact, the mirror cell had been the biggest obstacle toward completing the design of the Stargate-2. The mirror cell was integrated into the design of the mirror box, and subsequently, the still untested mirror cooler. With the change, if the cooler fails to meet its design goals, I can leave it off. Not that leaving it off will change much. The main mirror is fixed in height because of the mirror stoppers. In fact, even if I could drop the mirror two inches (the mirror cooler omitted), balance won't change much (according to my best calculations). And if I am just weeks away from finishing the new design, why would I want to put in the main mirror, then take it back out? The new design fixes all of the problems plaguing the first.January 27, 2003
Just two days earlier, I realized that my mirror stoppers could replace the sling for supporting the main mirror. I finally came up up with a design for the stoppers that should be robust enough to do the job.January 30, 2003
I was just hit with a great idea. While I was thinking of where to place the coolant tank for my mirror cooler, I wondered if I could eliminate the tank completely. My iceless cooler was intended to eliminate the need for ice in the coolant. But I could never chill the coolant down to anywhere near the temperature of ice water using air-cooled TECs- the heat load is beyond what they could handle. Eliminating the tank and such a large heat load could make it workable. The result will be a welded aluminum tank replaced by a milled aluminum module- basically a supersized version of the ones used to cool the mirror. I will have to construct a test fixture to determine viability.February 10, 2003
The iceless cooler design is done. Now to turn the design into a program for a CNC mill.February 22, 2003
I finished redesigning the diagonal holder support. This one is more fixture-friendly, and I intend to make it also on a CNC mill.February 23, 2003
I finished the reservoir for the iceless cooler, and tested the pump.March 10, 2002
I finished the design of the mirror box and rocker. I will have to send this to a shop, as I neither have the equipment nor the experience to weld aluminum.March 23, 2002
I finished assembling the iceless cooler (the module itself was milled last week). However, after all the work, the results were less than encouraging. The cooler works- barely. A more complete analysis is needed before further action is taken.March 24, 2002
After more experiments, I came to the conclusion that the module itself presents too large a heat load for the TECs. A better heatsink may also improve performance. Version 2 is now under design. The initial design is two inches shorter and one half pound lighter. But until I have done a better analysis, I won't machine Version 2.April 6, 2003
Over the past two weeks, I have been analyzing the iceless cooler design. Software from a TEC chip manufacturer was very helpful. I finally came to the conclusion that to make this work better, I will need to lower module mass, increase TEC chip count (and power useage!), and heatsink area. With that, a design for Version 3 has been finalized and approved. It will take me about two weeks to write and test the CNC programming.April 26, 2003
I have re-redesigned the amplifier electronics for the temperature sensors (Will a PCB ever be possible?). My main goal is to expand the dynamic range, as it was too limited, particularly on the high end.June 29, 2003
Since welding the frame has been delayed, I have went over the mirror box design in a effort to make it lighter. My goal is to knock ten pounds off. And I think I can come close to this. Just like with the secondary cage, I tend to overdesign things.August 24, 2003
After several failed attempts to come up with a lighter mirror box, I finally came up with a design that knocks off about twelve pounds.December 6, 2003
After endless delays, a four day marathon of marking, cutting, grinding and buffing makes parts for the mirror box and rocker ready for the welder. Also, the frame of a redesigned mirror cell, made for the new mirror box, is done.March 26, 2005
After three solid days of welding and grinding, the mirror box and rocker are finally each an assembly. And the weight of the mirror box was close to my estimated 23 pounds, weighing in at 24.4 pounds.May 4,2005
I have been working for over a month now, drilling, tapping, cutting and grinding. My goal is to have the basic telescope ready by June for the Wisconsin Observer's Weekend at Hartman State Creek Park (and first light!). The cooling system and controller will not likely be ready by then.May 11, 2005
I haven't even finished the Stargate-2, and now I have already have design goals for the Stargate-3. It's so typical of me to overdesign things, and the mirror box is far stronger- and heavier- than it needs to be. Also, I discovered problems with the rocker.May 19, 2005
I finally let go of the idea of being able to both heat and cool the secondary mirror; heat is what is most likely to be needed. It was just too complex to cool the secondary mirror to be practical, and I'm aiming for a more simple design. But from this finale came the idea of a no-pump cooler for the primary mirror,June 4, 2005
While it was overcast when I arrived at Hartman Creek SP yesterday, I continued working on the telescope with all of the tools that I had brought. And today, I finally finished the mirror cell- I am ready for the mirror. But while I was cleaning up, it started to rain! Worse yet, there are forecasts of severe weather, with even tornadoes possible. The only practical choice was to pack up and go back home. It looks like first light is again fated to be at the light-polluted shore of Lake Michigan. But all was not a total loss. Besides finally getting the telescope ready for the mirror, I saw how things look as an assembly. And I came up with ideas to improve the mirror stoppers and a more space efficient way to stow the small reflector being used as a finderscope.June 5, 2005
I have just finished the first test of a prototype no-pump cooler for under the primary mirror. It will still use thermoelectric coolers as with the pump-based mirror cooler. This design also obsoletes the iceless cooler.June 11,2005
I have completed a tentative design for the Stargate-3. Still waiting for a clear night.September 1, 2005
...Chevron seven encoded and locked...Wormhole established! Oops, sorry, wrong Stargate. I had hoped for first light to happen out West, on my summer trip to Wyoming, Utah and Arizona. The only thing really left to do to make my telescope work was trim the truss tubes to the correct length. I had calculated what the length should be, and added a two inch fudge factor. What I didn't expect was how time-consuming marking, cutting, deburring and drilling eight poles could be. Especially since it was done mostly in the dark. I ran out of trip, and the telescope just sat in my Jeep. Until tonight. Poorly aligned, but clearly in focus. So, first light did not occur under the mountain skies of Wyoming. Nor did it occur in the blackness of the desert nights at Arches National Park in Utah. Instead, it occured by the light-polluted shore of Lake Michigan, near Chicago.November 21, 2005
I received an e-mail from an astronomer in Australia. He had also built a Peltier-based mirror cooler. The main difference is that his system contacts the mirror directly, while mine creates cooled air. I decided to investigate how such an approach could be made to work in my design.March 22, 2006
After a top-down redesign, after months of waiting, construction of the Stargate-3 begins. Yesterday, the aluminum arrived. Today, I started cutting big pieces into smaller ones to get ready for welding next month.April 10, 2006
Construction is about to start on the Stargate-3, and I realize now that the secondary cage needs to be redesigned. As it is, the cage will be reduced from 14 inches to 9. I will also replace the flimsy aluminum mirror supports with stiffer stainless steel ones. The mirror holder will be shifted closer to the top, allowing more accessible adjustments.April 17, 2006
The welds have barely cooled, and I may need to redesign the rocker. The new design is less than a pound lighter than its predecessor! However, the mirror box is nearly perfect- and ten pounds lighter. The ground board looks good, too.August 21, 2006
I got the metal for the new rocker, spider vanes and light shield, and started cutting the parts.September 24, 2006
Work has been going along slowly on the Stargate-3, especially on the new rocker and secondary cage. But this weekend's star party (IDSSP) at Panther Creek State Park in central Illinois has re-energized the project- both in terms of action and ideas. I saw the value of adding a green laser pointer for aiming on the secondary cage. And I may also put a small right-angle finder scope on the secondary cage. It was also clear that digital setting circles are all but a necessity.September 30, 2006
I have largely finished a redesign of the controller. Most of the LEDs have been eliminated, replaced by an LED display. The humidity sensor has been replaced with a pre-calibrated module. The analog electronics for mirror temperature and battery voltage monitoring have been simplified. Also, a small battery (2-4 amp-hour) is being added, capable of powering the controller, mirror fan and dew eliminator on the secondary mirror, reducing the need for the main battery (when the primary mirror cooler is not needed).November 25, 2006
Earlier on, I had considered designing and building my own digital setting circles. But I dismissed it as too complex. But the idea has been resurrected, and with new twists. I will incorporate both a real-time clock and a GPS receiver. From a list of internally stored celestial objects or manually entered celestial coordinates, alt-az coordinates will be generated and displayed. A separate display for the telescope's altitude and azimuth can be added later.April 23, 2007
Work on the telescope had slowed down, expectedly, in the winter doldrums. But just before April, work on the secondary cage resumed. Then a marathon effort during the week of Good Friday resulted in the new rocker and secondary mirror support being welded, and the stainless steel spider vanes were cut. Also, a heatsink for the mirror cooler was welded, drilled and tapped. Momentum on the project continued with machining of the side bearing supports and mirror stoppers with a tabletop CNC mill.May 14, 2007
Judgment Day. For the secondary cage, that is. I just finished construction, and it's ready for preparation to be painted. But how heavy is it? With the added weight of the focuser standoff block, a 7X50 finder and stainless steel spider vanes, will it be top heavy? I was hoping for no more than 15 pounds, and bracing for near 20 pounds. It weighed in (minus focuser and accessories) at 13.9 pounds.September 15, 2007
First Light for the Stargate-3 at 1941 CDT during the IDSSP 2007 star party. It is functional now, but with so many of the extra features yet to get working.September 27, 2007
I found out at IDSSP 2007 that the illuminator for a scale on the atltitude bearing worked too well. The glow was noticeable in the eyepiece. My first inclination was to design a circuit to turn on the illuminator only when alt-az motion was sensed. Instead, I simply put a push button on the secondary cage. I also dimmed the illuminator down. The full range of zero to 90 degrees is no longer visible from on top of the ladder. It is now 20 to 90 degrees, but that isn't much of a loss.October 14, 2007
I did a balance test to see if adding the weight of a 4.5" reflector to the secondary cage is tolerable. My results were inconclusive, as I did not include the eyepiece or finder scope in the test. Still, it would be doable, but with more counterweight than I would like. For now, I will try to improve useablity of the reflector mounted to the mirror box.October 28, 2007
I couldn't help but think back to IDSSP 2007, and the night of First Light. We all watched with concern, lightning off in the distance. And I, in particular, worried at how my all-metal telescope out in an open field resembled a lightning rod. I need to devise something to warn me when dangerous weather is approaching- especially when I am sleeping. Either a circuit to detect static charge in the air or still-distant lightning discharges. Perhaps I can hack a Strikealert and interface it to the controller.June 6, 2008
I brought the "Waterheater" to WOW 2008 to compare its performance against the Stargate-3. In March, while in Arizona, I was in a rural area. Orion was high in the sky, and all I had were binoculars. I wanted a telescope, but seeing how full-up the Jeep was, I didn't see how I could bring the Stargate-3. Plus, it's too cumbersome to safely set up in the dark. So, I decided that if the Waterheater performed well, I would scrap it for the mirrors. I would build a truss-type telescope, identical in construction to the Stargate-3, but smaller. Well, I was quite happy with the results, and the mini-Stargate project has begun.July 2, 2008
With simplifying the computer in mind (Translation- finishing it within my lifetime), I stripped it of most of the extras (GPS, display, clock). Its focus is to monitor temperature and humidity to prevent dew formation on the secondary mirror.July 14, 2008
I received the side rings for the mini-Stargate from Obsession Telescopes.July 24, 2008
My idea of strapping a small 4.5 inch reflector on the back of the mini-Stargate (as a finderscope) was deemed impractical and abandoned.September 25, 2008
I tested my cloud detector prototype, and it works very well. I had seen a review for one in an astronomy magazine, but the price was unacceptable. Well, am I not an engineer? I intended to reverse-engineer the idea. So, when I finally got around to doing it, I intended to refresh my memory on the device operation. Initially expecting to need an exotic, expensive, we-won't-sell-it-to-you-in-quantities-of-one type part, I found, courtesy of a Kitt Peak Observatory astronomer (see link above), a solution using a component that I already have..February 18, 2009
The mini-Stargate project is now in high gear- I just received the focuser and ball-and-socket joints.July 23, 2009
After months of hard work, First Light for the mini-Stargate at WOW 2009! There were numerous things that I learned, and after a review, I will make some fixes to the design. But the core design works. This telescope is both easy and fast to set up. Which was good, since we got rained on at WOW 2009.September 9, 2009
At long last, something finished. I fixed the problems with the mirror box (battery box, mirror cell, spacers for the ring bearings, edge protector), plus routed wiring for the convenience lights inside the box. I'm still waiting for new parts to be fabricated for the ground board and secondary cage. And then there's left to finish the computer, which is still suffering from Creeping Feature Syndrome.February 26, 2010
I just spent nearly two weeks, in time between welding training, working on both the Stargate-3 and the mini-Stargate. Aside from electronics and painting, I can finally declare both DONE. On the Stargate-3, I cut off 1-1/2 inches off of the secondary cage, and welded 1-1/2 inch spacers onto the mirror box. This was done so that I could fit it more easily into my Jeep Liberty (I verified that this modification works on March 6, 2010). I also added a teflon support bearing around the pivot bolt to balance the weight better, which may have been the cause of the laminate on the mirror box separating. I will have to reglue it, and may use silicone rubber instead of brittle epoxy. Work on the mini-Stargate was more extensive:Modifying the spider support (to allow easier access for an Allen wrench to adjust the secondary mirror).
Welding shims onto the rocker to correct contact angle with the side bearings.
Replacing the existing pivot bolt with a 1/2" bolt.
Modify the collimating bolts.
Made counterweights.
Made all-aluminum focuser box to replace wood focuser board.
Made LED pointer plate (pending testing) for altitude scale.
July 11, 2010
I just began conceptializing a new telescope design, now dubbed the Stargate-Next Generation (SG-NG). It will include the mirror temperature features of the Stargate-3, the advanced sensors of the mini-Stargate, and new go-to capability. It is very possible that the SG-NG will be made (partly) by recycling the mini-Stargate.July 18, 2010
Just a week into the design process, and much of the design work of the mirror box and secondary is pretty much done. A 12.5" conical mirror has been settled on, and I am still waiting for specifications on a suitable mirror cell. I dropped the idea of motorizing the SG-NG, in favor of digital setting circles. That fact also guarantees that I can use the rocker and ground board of the mini-Stargate.September 12, 2010
At the 2010 IDSSP, the modification to the Stargate-3 was tested, and balance was improved. However, I cannot escape the fact that this telescope is just not portable. And, unless I can brainstorm some kind of jig to keep the poles stable during setup, this is a two-man telescope. With portability being my number one design parameter for the foreseeable future, I plan to sell the Stargate-3. With this, I may even be able to consider a 14.5" mirror. Mirrors larger than 12.5" were dropped from consideration largely because of cost, but also because that they wouldn't fit into a 14" SQ box. However, I later determined that trying to put a 12.5" mirror into a 14" SQ box was also unfeasible. Also, in addition to the secondary mirror, dew control for the finderscope and eyepiece has been deemed an issue. Plus, digital setting circles have been made a priority.July 1, 2011
In a chance conversation at WOW 2011 about my planned electronics to measure sky quality conditions, a thought came up to turn that information into something more useful- such as maximum magnitude limits.August 18, 2011
The SG-NG project is back on the move. It was stalled out for awhile, partly over funding and partly over mirror size. It's settled (didn't I say that a year ago?), a 12.5" primary mirror. I am currently working on the "science package" (the sky quality sensors), readying them for testing at IDSSP 2011 in September. I plan to start buying components for the SG-NG in a month or so. It is my hope to finish the SG-NG in time to trot it out at WOW 2012. Ignoring funding issues, after I had done all of the heavy construction and welding for the mini-Stargate, I was still left with weeks of finishing work. And, then being out of work, I had the time. Now? Not so. I hope to do the welding in early July 2012, a few weeks before WOW 2012. Good morning Mr. Phelps. This is your mission, should you choose to accept it...August 27, 2011
I came up with an idea (related to calculating magnitude limits) for an atmospheric haze detector. One approach employs a laser aimed at a linear sensor to measure the amount of scattering by the air. I tried both a green laser (536 nm) and blue laser (405 nm) to maximize Rayleigh scattering. But I just could not get either to appreciably scatter in such a short distance (5 feet max). Plan 'B' is to try using an absorptive spectroscopy approach. But I'm doubtful that I could make that work in the same small distance (I will try, however). Looks like water vapor will be the only atmospheric component (besides pressure) that I can measure.September 30, 2011
Well, the science package (v1.0) was a flop. The sky sensor was difficult to use as it was dependent on a shifting reference. The ambient light detector generated pulses impractically long for a controller with many tasks to perform to measure reliably. But the experiment wasn't a waste, and v2.0 is in the works.November 10, 2011
I switched to a 14.5" mirror for the SG-NG, largely to Michael Bakich's article, "Wander Winter's Deep Sky" in the December 2011 issue of Astronomy magazine (especially because of NGC 2359). I finally realized that I had to bite the bullet and go with the larger mirror. The 12.5" mirror would not be enough of an improvement over the 10" in the mini-Stargate to justify the cost and effort. A 14.5" mirror will be the best compromise between the unmanageable weight of the Stargate-3 and the back-friendly mini-Stargate.January 5, 2012
It's officially funded now, the Stargate-Next Generation (SG-NG). I just put down a deposit on a 14.5" mirror from R.F. Royce. Chevron one, encoded...January 27, 2012
I now have the focuser, ball-and-socket components, truss tubes, side bearings, and the secondary mirror and holder. I am still working on the designs for the mirror box (especially to deal with a cooling system) and the secondary cage. The mirror should be ready in April or May.July 7, 2012
I have just finished a week-long marathon in the shop, fabricating the mirror box, mirror cell, secondary cage ring, focuser bracket and more. I still need the spider vane hub and side ring bearings to be made. Unfortunately, I have no rush to finish, as the mirror won't be ready for WOW 2012.October 14, 2012
While IDDSP 2012 was met with more disappointment (the mirror won't be ready until mid-November. "Hopefully"), strong wind and rain, it was not without gain. First, it nudged the SG-NG out of its three-month-long stall. Second, it hammered home the point that my power supply for the mini-Stargate is flawed. The DC-DC converters were supposed to help conserve battery power. To my dismay, they are battery killers when at idle. That's useful for design on the SG-NG. Since I intend to work off a lower supply voltage, linear regulators won't be a liability. A laser heater will probably also be needed for the mini-Stargate.November 1, 2012
I got the first batch of electronic parts for both work on Samantha for the SG-NG, and rebuilding the power supply on the mini-Stargate.November 25, 2012
I started exploring the idea of expanding Samantha's capability. I came across an idea for a fluxgate magnetometer used to predict the occurence of auroras. Fine. Further searches showed a design that detects auroras directly by the telltale 557.7 nM oxygen spectrum emissions. Well, I'm hooked! It is clear, though, that Samantha will need a processor to handle all of the science instruments.December 2, 2012
Working on SAM (Steve's Aurora Monitor) design, I worried that even an APD / lense combo may not have enough gain to detect an aurora. I realized that the telescope itself could be used as a collector. After all, the idea is to warn me when I'm NOT observing.February 19, 2013
I finally got the 14.5" f/5 conical mirror from Royce. Now to get back to work building; WOW 2013 is only three months away!March 10, 2013
While it isn't a huge victory, but finishing the ground board for the SG-NG is, at least, a symbolic one. It just needs to be cleaned and painted. I'll do that when it warms up outside. For that matter, T'ealc (the laser pointer), the rocker and mirror box aren't that far from completion, either.April 28, 2013
I just finished redesigning the focuser mount. I just saw it as too heavy having that much weight so far from where the trusses converge. So, I moved the finderscope and mounted it on a nearby spider vane post, putting it right on top of the truss. I shaved off four tenths of a pound in the process.June 4, 2013
I just finished wiring a new laser power supply and beacon for the mini-Stargate. A linear regulator replaces that power hog DC-DC converter (it drained the battery when in no-load condition); the new beacon is simpler to build, has a shorter duty cycle (about 1 100 mS flash every 5 seconds) and a "sharper" flash.August 20, 2013
I put the Stargate-3 for sale on Cloudy Nights (please see the ad!). One inquirer asked about the weight, and sparked an unfortunate and dangerous (for me) chain of thoughts. If I can't sell it, can I redesign it so that it is more useable by me? There's nothing I can do about the mirror or side rings, but I've already decided that I can keep the rocker and ground board with no modification; there is no practical gain in shrinking the mirror box width or depth. I have already come up with possible fixes for the rear-adjust sling that never worked. I can apply the ultralight design concepts from the SG-NG to the secondary cage, easily cutting off several pounds off there and possibly fixing the balance problem (it needs more counterweight than I have now to stay stable at near-horizon altitudes). A lighter mirror cell has been conceptualized. And I can cut off height from the mirror box. Stargate-4, anyone? Somebody, buy it and save me from myself!November 6, 2013
I have sent out key parts for the SG-NG's secondary ring to be welded. I glued the laminate to the side rings and rocker (a messy job). And I think that I have found a suitable worm gear for driving the rocker. If I can come up with a workable clutch to disengage the drive when desired, then I will add this now.
January 24, 2015
The SG-NG mirror box is ready for testing. A new focuser bracket has been designed and modelled in AutoCAD, and if I can get access to a CNC mill, I will make it.June 5, 2015
I have redesigned the focuser bracket to match my skill level with Mastercam. Also, since I have access to a CNC and design tools, why not make other parts? I redesigned the spider vane posts to make them lighter, shaving off perhaps five cubic inches of aluminum. I redesigned the hydrogen line cavity filter, and designed an enclosure for the MAR 6 amplifiers.June 12, 2015
First Light for the SG-NG! Despite it being mostly rainy at WOW 2015, I was able to get one night to test the SG-NG. I don't know what star I was looking at, nor do I care. At last, I know the mirror works and the approximate focal length. I can now dispose of the wobbly adjustable truss poles and make permanent ones.October 15, 2016
After IDSSP 2016, I decided that the SG-NG needs improvement. The mirror box is too shallow (the primary mirror nearly touches the box cover), there is excess reinforcement (excess weight), and the rocker is not stable enough (the base is rectangular, limiting the size of the base- larger is more stable). I can reuse the mirror cell and secondary ring without modification for the SGNG-2.December 31, 2016
I have just finished redesigning the ground board, rocker and mirror box for the SGNG-2. This time, it was done with AutoCAD, to avoid design mistakes. I also have ideas on improving the fabrication process, as well. In any case, the rocker and ground board are larger for a more stable base. The mirror box is deeper and is expected to be approximately 2 pounds lighter. As for the secondary ring, it is fully painted. All I need to do is make an alignment template for the mirror, then I can fully reassemble the secondary.July 8, 2017
I spent the past week fabricating a new rocker, ground board and mirror box. The first two are done, but I could not finish the new mirror box.
June 2, 2018
The new mirror box is complete. To speed up fabrication, I simplified the design. But that added extra weight.
July 12, 2018
After weeks of work, the new mirror box, ground board and rocker were tested successfully at WOW 2018.
October 9, 2018
It has become apparent that I need to reduce the weight of the SG-NG mirror box. I just came up with a new mirror cell design that, with other reductions, could trim off five pounds or more.
April 26, 2019
I finished the version 3 mirror box and T-shaped mirror cell.
September 28, 2019
During a presentation at IDSSP 2019, I wondered if there was a way that I could mount the 4.5" telescope on the SG-NG.
October 5, 2019
I began making a bracket connecting the secondary ring and mirror box to support the 4.5" telescope.
October 27, 2019
I finished the bracket.
November 3, 2019
I came up with the idea of a sight tube to aim the telescope.
November 27, 2019
Both the 4.5" telescope and sight tube were tested. Alignment is another story, but at least both are viable.
