Orion Ranch Observatory Blog

In a somewhat misguided attempt to improve the tracking on my Celestron CPC Deluxe 1100 HD 11″ EdgeHD telescope, I decided to perform the bearing upgrade described by Gary Bennett on the NexStar Resource Site.

I started by moving the EdgeHD to the tripod in the warm room in order to prepare for the azimuth axis rebuild.

I attempted to measure the force required to rotate the azimuth axis for a before/after test. I didn’t have a force gauge handy, so came up with a pretty simple scheme for using gravity to test for how much weight it took to overcome friction. By determining how much water weight was needed to get the axis to rotate, I could compare after the upgrade. Unfortunately, it turns out most of the friction was from the clutch assembly and not the bearings, so there’s really no way to use this information to determine if I improved anything.

After partially removing the set screw to clear the upper lip of the clutch base, the clutch knob unscrews completely revealing the Teflon pressure plate that lets the knob slip to loosen or tighten the clutch.

The spur gear servo motor drive turns the worm gear on the far side. You can see the black encoder on the back of the servo and the PEC reference sensor on the main worm gear shaft. The spur gears connecting the motor to the output shaft are typically covered with a shroud. Not sure why my unit doesn’t have it. Also not sure why they need a 1:1 gear vs. finding the space to direct drive the worm and eliminate that additional point of play.

The main board cover plate must be removed to get to the third screw on the front side cover panel. Turns out it’s not necessary to remove ALL the screws. The four screws on a rectangular grid hold the controller PCB to the panel, so removing the four screws along the edges allow removal of both the panel and board. See the re-assembly pictures for more info.

After removing the aluminum cover, I can access the third cover screw. I just left the board and cover hanging rather than having to label all the connections before disconnecting.

The main gear just slips off the bottom plate. There’s a bit of grease in the middle to let the brass gear slip when the clutch is disengaged. There’s a textured rubber pad on the plate to actually create the clutch grip.

Here’s a close-up of the clutch plate showing the rubber textured sheet, the grease on the hub, and one of the set-screw holes.

Here’s the brass main worm gear and clutch plate after wiping off most of the grease and contamination.

After removing the two set-screws and center screw, the clutch plate will slide off the center spindle of the AZ/RA axis. There are two flats for the setscrews and a key/keyway to keep the clutch plate solidly attached to the spindle, which is embedded in the non-moving aluminum base of the scope.

The nut came off the center spindle rather easily, although you can see the remnants of red lock-tite.

The tapered shaft bearing slipped out easily, freeing the upper assembly.

Here you can see the upper assembly after lifting off the base. The portion that rides on the outer bearing is just a flat surface with a taper to the middle. A lip around the edge minimizes dust infiltration.

It turns out that the CPC Deluxe HD mount uses a mix of metal and nylon bearings. The balls appeared to be greased in something the consistency of Vaseline. The nylon balls appear to be slightly larger than the metal, but that could be an optical illusion. This mix of metal and nylon appears to work much better than the old approach of using only plastic bearings and after removal of the clutch, the motion was quite smooth and easy. However, by the time I determined that, it made sense to investigate further. By this point, I’m already here so why not try the all-metal approach, saving the existing balls in case I need to put them back.

In the process of removing the bearing balls from the original installation, there were a number of machined metal chips in the bearing and grease that I removed when I cleaned everything up. It’s rather depressing just how dirty the mechanical components were left by Celestron’s manufacturing team.

After cleaning the base of both components to remove all old grease (and any metal bits), you can see the bearing channel and lip.

After removing all the grease with a vigorous dip in solvent (paint thinner) the center capture bearing is nice and clean.

I’m using AeroShell 64 Molybdenum grease, which is a high end aircraft grease with a broad range of operating temperatures and is suitable for high pressure applications. The 1/4″ bearings are stainless steel.

Here’s a picture with all of the 123 stainless steel balls installed with a coating of the moly grease.

Setting the upper body carefully on the base, everything rolls quite nicely, although the all-metal bearings are a bit noisier as the balls rattle against each other. The next step of re-inserting the thrust bearing to capture the unit ended up being the hardest part of the whole process. The tolerance to the center shaft was so tight that the bearing tended to bind with only a mm or so of engagement when not perfectly aligned. This resulted in having to remove the entire assembly multiple times to use the scope to pop of the bound bearing. In the process, the new bearings were upset at least once and had to be re-worked. ARGH! Eventually it went on correctly and I was able to complete assembly. Given the constantly greasy hands, and simple reverse process, it didn’t make a lot of sense to take a bunch of pictures going back.

Finishing up the re-assembly with a shot of the aluminum cover attached to the controller PCB, you can see the four screws that I shouldn’t have removed that attach the panel to the aluminum standoffs.

Here’s a shot of the re-greased main gear and worm assembly after running everything in.

And finally, all closed up, here’s the finished re-assembly of the AZ/RA axis base.

Next up, I still have to rebuild the DEC axis that’s given me more problems in the past. We’re currently in a full moon phase so there’s no point in remounting it anyway, so I haven’t tested it after the alteration (I hesitate to call it an upgrade at this point). More to follow when I get things tested.

As usual, there are more images in the gallery than I embedded here, so if you follow the link icon, you can browse any details you missed.

So I finally bit the bullet and upgraded to Windows 10 on my observatory machines.  After the tremendous headaches I had on my main machine when I migrated from the pre-release Windows Insider version to the final released version, I wasn’t anxious to update all my other machines, but needed to do so before the one year “free upgrade” period was over.  The Microsoft tech who finally addressed the licensing and activation problem I was having on my main machine actually recommended I wait for a few months to update anything that I didn’t have to.  I wholeheartedly agreed!

Given I was already running Windows 8 that I didn’t care for, and using Classic Shell as a desktop replacement to make in usable (and actually even better UI that Windows 7) there was no reason NOT to do the Windows 10 update, other than the fear of things going wrong.  The biggest concern there was in being able to use some of the unsigned drivers I’m using to control various older pieces of equipment.  I also wanted the option to easily go back if needed, which meant imaging the drives and either setting up for dual boot or just swapping drives, as in the case of my laptop.  That actually ended up being a bigger pain than expected to get dual bootable images, but I eventually got there and performed the update to Windows 10 on one of the images.  As expected, I ended up losing all my drivers as Windows tried to use the latest incompatible versions.  On most I was able to just tell it to downgrade to the older driver, but did have to go through the rigmarole to get one unsigned version of an FTDI driver in place to get my focus motor working again.

At any rate, after re-installing Classic Shell and a few other things, I’m up and running with no real difficulties (other than the one Blue Screen of Death that killed one of my PCs with the roof open, forcing a trip to go reset everything).  Only time will tell if there are any long term issues that I’ll see.

I’ve spent the last month or so capturing wide field images with my Sigma 70-300 mm on my Celestron Nightscape.  (Ok, so they’re really Fall Wide Fields.)  With the stack of adapters I’m using to get from the Nikon bayonet to the T-ring on the Nightscape, I can only get to focus between 200 and 300 mm.  At 200 mm that’s a wide enough field of view to capture the entire Andromeda galaxy and the full sword of Orion.  The results turned out pretty decent.

For a number of years now I’ve been peripherally involved in the effort to bring a planetarium to Central Texas.  The brain child of Torvald Hessel, the effort to create the Austin Planetarium eventually grew into the Texas Museum of Science and Technology, which recently opened its doors in Cedar Park, TX (northern suburb of Austin) about a mile or so from where I work.  A couple of weeks ago I had the privilege to spend some time there and help a little bit with the set up of the new semi-permanent planetarium at the museum.  Scheduling and Customs problems meant that I didn’t get to help out as much as I’d hoped, but I did get to help move the assembled geodesic dome frame into place.  Unfortunately I didn’t have my camera with me then so I missed getting pictures of the frame, but I did get pictures of the covered dome while the field service team from the supplier was working on installing the eight projectors that make up the resulting image.

The dome consists of a metal geodesic framework to create a spherical structure, and then an internal screen and external cover are applied to the framework.  Negative air pressure is used to keep the screen spherical within the framework, while positive pressure keeps the outer cover taught.  Internally, the screen approaches the floor in the front, while going above the door in the back, giving a hemispherical view with a slight tilt.  The exterior is decorated with a combination of lunar landscape, constellations, and steam punk gears.

Here’s a shot with the air pressure system in the back. You can also see the vents for air conditioning.

Introduction

With the remote location of the observatory, I’m pretty limited on my choices for internet, especially since I’m more interested in uplink data rates rather than downlink, in order to facilitate remote control of the observatory.  Of course being able to stream videos while I’m out there is nice too!  At any rate, the uplink limitations and latency pretty much knock  out satellite service, and point-to-point wireless services are very limited in my area.  That really only leaves cellular service.

I originally bought a zBoost 3G cell booster which has performed quite well.  At the time I was resigned to living with the 500 kBps or so I could get from 1xEV-DO on the Sprint network.   I initially purchased a 3G phone from Virgin Mobile (an MVNO on Sprint’s network) but before I got around to activating it, Sprint activated their 4G LTE network along the highway about 5-6 miles from the observatory.  I was surprised and excited to discover that the zBoost booster worked for their 4G signal, but never really investigated what Sprint had done at the time.  So, back to Virgin Mobile for an LTE phone to take advantage of the additional bandwidth, although that came with a 2.5 GB LTE cap before it throttled down to 3G (and later 2G!) speeds.  I also added a Wilson Electronics wide band directional antenna (a small log periodic dipole array in a radome) and was able to regularly obtain 5 Mbps uplink and downlink speeds.

In February of this year I obtained a pair of signal boosters (Home 4G and Connect 4G) from weBoost (formerly the same Wilson Electronics who makes the antenna above) through the Amazon Vine program.  Both units have essentially the same amplifier module in them, and despite the claim that they worked for all US carriers, I wasn’t able to get them to work properly for the Sprint network.  After quite a bit of diagnostics on the land and in the lab, weBoost agreed that they really weren’t suitable for my application due to the fact that the channel Sprint is using for LTE is at the edge of the band over which they’re designed to work.  Rather than going into all the details here, you can see the review on Amazon for more information.

During the discussions with weBoost, they suggested that their more expensive (i.e. over twice the price) Connect 4G-X would likely work better for the Sprint network.  I told them I’d be glad to test it for them, and after a bit of pressure from some readers of my review, they took me up on it and sent me a unit to test.

Initial Impressions

First off, right out of the box (or even in the box) it’s apparent that this kit is a major step up from the Home and standard Connect models.  The packaging is about three times the size, owing to the larger cables and booster amplifier module.  The booster itself is in a heavy cast metal case (providing a better heat sink) compared to the small plastic case for the boosters in the Home/Connect 4G.  The 4G-X booster is about 7 x 9″ compared to a little over 4 x 6″ for the 4Gs.  The kit also comes with a pair of Wilson low loss cables (75′ and 60′ I believe) for the interconnections between the antennas and the booster, as well as a 700-2700 MHz LPDA directional antenna for the outdoor connection and patch panel antenna for internal distribution.  These are the equivalent antennas to those provided with the Connect 4G, but unlike the 4G, which uses cheaper 75 Ohm cable typically used for cable TV, these are all 50 Ohm cables and connectors.  The superior performance of the low loss N-type cables does come at the cost of some flexibility (both literally and figuratively), and will require a bit more professional level of installation than your typical cable TV installation.  Unlike the F connectors used on the 75 Ohm RG-6 cables, N connectors cannot be easily installed in the field and require special tools and expertise.  Thus, you’re generally relegated to using the supplied cables or order specific lengths as needed.  Also, the much larger connector size will require a sizable hole for penetration into the building.  Overall, this is much more of a professional grade solution and will need that additional care in the installation.

I started my analysis by simply swapping the new 4G-X amp for my zBoost amp in my existing system.  My first impression from that test was extremely positive.  The apparent performance is significantly improved over the Home and Connect models, with 7-10 Mbps data rates (10+ burst, ~7 sustained) on uplink and downlink.  That also exceeds the ~5 Mbps from the zBoost unit I’ve been using.  The only problem I found was a side effect of just how much gain this amp has, in that it was difficult to get  enough isolation between the network antenna and the interior one, even though the physical separation is on the order of what is recommended (probably 40 feet horizontally and 20 in elevation, with the antennas facing in opposite directions).  Even after completing the permanent installation and taking steps to mitigate the feedback loop (see discussion at the end of the testing segment below) I still couldn’t completely eliminate a partial overload from other signals from other carriers/towers in the same band I’m interested in.  This is simply another indicator of just how powerful this amplifier unit is.  If you’re just trying to bridge the connection between a strong external signal into a shielded interior (e.g. metal building) this amplifier may actually be overkill.

Frankly my only negative comment would be that I actually had to go online to find the  real  manual that described the status lights, etc.  The kit just came with a single page quick install sheet and directed you online for the manual.  That seemed a rather insignificant savings not to include a printed manual with that information, and more importantly, if a user were out trying to install this where they didn’t have internet access (which is essentially what I was doing), then expecting them to go online to figure out why it s not working is probably NOT the best idea!

Here are a few pictures of the antenna installation and setup. First is the new weBoost antenna mounted horizontally and lower in elevation and pointed towards a different tower. You’ll see in the antenna analysis later why that’s still not quite enough isolation.

Here’s the large penetration through the wall after sealing it back up.

Here’s the booster sitting on top of the warm room ceiling. The flat panel patch antenna (not shown) points down through the ceiling to the room below.

Laboratory Testing

The remainder of this review is going to get rather technical and provide results obtained in my wireless lab using equipment most people would never have access to.  My first step was to perform a gain comparison between the 4G-X and the (in this case) Home 4G amplifier, which is identical to the Connect 4G amp down to part number, but has a different connector for the indoor antenna.  The results below show that the 4G-X is superior in gain, bandwidth, and flatness.  With up to 70 dB of gain (granted only at a couple of frequencies) the performance is pretty impressive! Given that for a free-space line-of-sight condition, every 6 dB corresponds to roughly 2X in range (probably more like 1.5x in typical environments), the improvement in downlink range is obvious. Add to that, every 3 dB corresponds to twice the power output, so the difference in cost for the better amplifier is not surprising either.  Note to be fair that the difference between the 50 Ohm system used to measure both amps and the 75 Ohm system of the 4G amps may have some impact on the performance, but that is generally expected to be small given the way these were tested.

Zooming in on the peaks in each band shows a 6-10 dB improvement of the 4G-X over the 4G.

The difference in the roll-off and smoothness of the filter in Band 25 at 1995 MHz where the Sprint LTE channel resides is apparent.  Note however, that some of the ripple in the 4G results may be due to the 50/75 Ohm mismatch.

The uplink results aren’t as markedly different between amps in the high bands, although differences in the filters are still visible, and the low band gain is better on the 4G-X.

Next I developed a test to specifically evaluate Band 25 LTE performance of a cell phone.  Here I tested receiver sensitivity of the phone on the low, middle, and high (Sprint LTE) channel of Band 25 with and without the amplifier in place at different data rates.  This gives a true measure of realized gain, taking into account the degradation introduced by the amplifier itself.  The results showed that the 4G-X is still maintaining 50-55 dB of gain across modulations over the no-amp case.  I tried repeating this test with the Home 4G but unfortunately couldn’t even get a stable connection.

Finally I hauled a spectrum analyzer out to the observatory to see what was happening on my land.  The bottom curve is the measured signal directly out of the cable attached to the LPDA directional antenna with no amplification, and the upper curves are for the three different amplifiers.  For the most part, all three show about 60 dB of gain over the un-amplified signal.  However, this data clearly shows the problem with the (in this case) Connect 4G in Sprint’s G-block spectrum (right side of the curve), where the signal is rolling off over 10 dB across the channel.  In this case, the 4G-X outperforms even my zBoost amp by about 6 dB or so.  Again, not bad!  However, to be fair, one should note that cell signals are not constant in level, so these curves are representative samples of signals that varied up and down quite a bit over time.

Note too that at this point, the 4G-X was flashing orange on a couple of bands, indicating it was throttling the gain.  Thus, there’s potentially more gain to be had there, but really no way to get away from all the other clutter in the band.  I ended up installing the antennas/cables that came with the 4G-X and changing the orientation to maximize the Sprint channel while minimizing everything else.  I had to switch cell towers to a more obstructed line of sight, lowered the height of the antenna, and changed to horizontal polarization to get the best G-block signal.  However, that still never got me to a point that the Band 2/25 light quit flashing orange (although it did clear the warning on Band 5).  As you’ll see in the next section, the antenna directivity isn’t doing enough to isolate me from picking up signals from other towers, even when they’re 90 degrees away.  Thus, I’d expect this to be a significant problem for users even closer to the cell tower.  weBoost’s suggestion for this is to either try to point away from the interferers (and thereby reduce your direct signal too) or add metal baffles to try to increase the isolation from the side lobes.  Neither are ideal solutions, but there are limits to what you can do in this sort of situation.

Antenna Patterns

Finally, I managed to get some time in the wireless chamber to measure the radiation patterns of the two antennas provided with the Connect 4G/4G-X.  The internal panel antenna is also used as the external antenna for the Home 4G.  I tested the 75 Ohm versions, but would expect the 50 Ohm 4G-X units to be the same.  I didn’t try to determine gain, since that wouldn’t have been valid due to the 50/75 Ohm mismatch, but the directivity numbers will give you an idea of the antenna performance, excluding mismatch and losses.

First up is the directional LPDA used for the external link.  The pattern is well behaved across the specified band and about what I’d expect from this antenna design.  It’s not as narrow as could be obtained by the use of a narrow band Yagi antenna, but the 8-9 dB of directivity across the entire band makes for a decent performing antenna.  However, with over 100 degrees of beamwidth in the H-plane at the low band frequencies, and still 70+ degrees in the high bands, it’s easy to see why when vertically polarized as shown in the first picture, you’ll still get a decent amount of signal from the sides, with only a 5-10 dB reduction at 90 degrees from boresight.  On the other hand, it also means you don’t have to be pointing perfectly towards the cell tower to get the full benefit of the antenna.  Things are considerably better once you place the antenna horizontal, as evidenced by the E-plane results, which are down 15 dB or more at 90 degrees.  So as long as the horizontal component from the desired tower doesn’t drop by more than a few dB, the improvement can be substantial in terms of isolation.

The flat panel antenna is not quite as well behaved, which again isn’t all that surprising.  The design is obviously a dual patch antenna with two major resonant frequencies in the PCS and Cell bands.  It’s pretty well behaved in the low bands, but has some oddities in the high band patterns, and breaks up completely in between.  So, unlike the LPDA, this antenna really won’t be useful for anything outside the cellular bands that it’s designed for.  The directivitiy is generally lower and the beamwidths wider than the LPDA (although as the pattern breaks up at higher frequencies that changes), which is what you want from something designed to cover a large area in a house or building.

So in all, the antennas are well designed for their target applications.  It would be nice if weBoost published the antenna pattern specs as an aid for users who are trying to mitigate interference problems and adjust their systems.  While the average consumer might not know how to use this information, the installers of this professional grade system should.

Conclusions

I still have plans to try to tweak my setup and see if I can get out of the overload condition and get a little more performance from the 4G-X booster, but I’d say the 4G-X kit as a whole is a superior product for its intended application.  I’m quite pleased with the performance improvement I’ve seen so far.

The Planetary Society with Bill Nye (the Science Guy) had a Kickstarter campaign to develop a light sail CubeSat using public funds.  I just received my notice that they’ve completed the campaign and are ready to send me my goodie bag for supporting the project.  I came across the backer graphics and thought I’d post one here.  I might try to find a spot for it on the main page and direct that here.  For more information click on the image below or go to www.planetary.org.

I’ll see about posting pictures of all the swag once it arrives, but the level I bought includes a centimeter of sail (I don’t get that, it has to go to space!  I just get a certificate.), the ability to send my name (and my family’s names) to space (digitally), and some mission patches, pins, and T-shirt.

I’ve added a Links of Interest page with a lot of detail providing a handful of links to places I regularly visit or would like to regularly visit.  I also included information on some of my favorite telescope equipment vendors.  I hope you find it useful.  I’ll be adding a menu link to it from the main page when I get a chance.

So I got my Geoptik lens adapter and Losmandy camera mount in a couple of weeks ago.  We’ve been under cloudy skies pretty much constantly, so I haven’t had much opportunity to put this to use, but I’ve post some pictures of the setup.  It looks pretty nice, and the orange anodizing should go well with my Celestron gear, although the Edge HD doesn’t have much orange, other than the Losmandy rail itself.  It’s amusing that there aren’t really any instructions with the adapter, just labeled pictures and a bunch of material safety stuff in Italian!  Initially I was worried that the Canon flange didn’t lock tightly like it does on the camera, but that’s the purpose of the orange flange.  It’s a big lock nut that you screw down to hold the lens in place.  The silver ring on the front is the Nikon to Canon adapter I’d bought to use my Nikon lenses on my modded 450D.  I never got around to doing that, and now that I managed to brick the camera working on a cold finger mod, this is Plan B.  The Geoptik also comes with a threaded insert in the throat of the T adapter (that I’ll remove) to hold a 1.25″ filter, and the Canon version is also internally threaded for a 2″ filter.  I didn’t see that information before ordering, but turns out to be a bit of a bonus since all OPT had was the Canon and I’ll likely only be using my Nikon lenses!

The Losmandy adapter looks pretty nice too.  I normally go with ADM for these types of mounts, but the Losmandy was the same price with the dual V/L clamp, and looked a bit nicer with the rounded edges, etc.

As usual, follow the links to the gallery for more pictures.

Note the 1.25″ filter insert.  The flat is for an optional guide/finder scope mount.

Here’s a shot down the throat with the adapters removed.  If you look in the throat of the T-ring, you’ll see a threaded section for the 1.25″ adapter, as well as what appears to be a thread or two at a transition right before the screw holes for mounting the base.  I’m assuming that’s the 2″ filter thread that the documentation referred to.

Since this doesn’t appear to exist elsewhere online, I’ve scanned and uploaded the pertinent pages of the Geoptik adapter manual.

While I don’t want to clutter up my website with a bunch of ads everywhere, in some respects these days it seems like they make a site feel more complete!  At a minimum they’re more dynamic than just static pages.  I haven’t decided what I’m going to do, but figured I could try out a Google ad block here and see what happens.

Well, judging by the preview, nothing!  Not sure if there’s a way to allow the necessary scripts to run in a post or not.  I’ll have to play with it.

Hmm.  Added a plug-in to handle this, which is essentially embedding the same code.  Maybe Google just hasn’t updated my account yet to let this start working!  Let’s see what happens.

I’ve finally been getting a few good nights of imaging, and have been making some progress with my post processing.  I’m  still taking wide field shots with my AT-80LE, and now have the field flattener installed and working correctly, so things are looking pretty good.  I’ve just posted an image of the nebular regions around Messier 78 (NGC 2068) reflection nebula which includes NGC 2064, NGC 2067, and NGC 2071 as well. This region also contains McNeil’s variable nebula.  With the dark dust nebula running through the middle of the region, this is a really beautiful region near the Horsehead nebula in Orion.  The image was stacked from nine hours of 10 minute subs taken over three nights with my AT-80LE and Celestron Nightscape camera.