58 replies to this topic

[Claytoncramer]

I have long wanted a high quality small equatorial mount, sort of what if there was a Losmandy GM3. Something with a capacity of about 15 pounds and light enough that you could take off the OTA and the counterweights and lift the mount and tripod to move it.

I am not seeking GoTo, but I suspect if designed properly, some clever person could make it work with Gemini-2.

Why crowd source instead of buying one of the Chinese clones of the Vixen mounts? I would prefer to find a way to create something that could be built somewhere without slave or at least underpaid labor.

Such a project would involve different people working on design of different parts.

1. Declination axis and housing.

2. RA axis and housing with motor drive.

3. Tripod.

4. Setting circles. (Yes, very old school until someone gets Gemini-2 working.)

The ideal would be to use parts as close to standard raw materials and other maker's parts. Example: use 1" polar and declination axes so you can start with 1" steel shafts to turn to 1.000" size and use Losmandy counterweights.

Is this just a hopeless fantasy?

[jcj380]

Sounds like a great idea.

[photoracer18]

Likely. Crowd sourcing requires a market and at this time most people who would like those parameters are old fogeys with lots of history in astronomy (like me) and not the next generation of customers. Problem is lightness and solidity are problems that have opposing solutions.

Losmandy CWs are 1.25" by the way.

 

Think of it like cars you buy a new car and just don't bother to use some of the new features. Right now mount technology is driven by how easy you can make imaging happen. I did my first imaging in 1961. Now I don't do any at all after doing nearly everything I could do over decades. Underpaid labor has always been the key to any big industry, just look at history. Just because most astro companies are niche markets and labor is not the main costs does not mean someone can't figure out how to do it. I like precision parts so I happen to like mounts in general. But I seldom use go-to and I have to admit I recently bought one of the Chinese strain wave technology mounts. Not because of the technology but because they solved the weight equation and at 76 that is most important to me. I have a couple of older non-go-to Astro-Physics mounts because I like them. But now I have a mount that weighs less than one of their counterweights, one of their lightest counterweights, in fact lighter than any Losmandy makes yet it can hold a serious telescope. But astronomy is not an endless market so it will reach its saturation point within a few years.  If they keep launching more satellites maybe sooner than the we think.

[Michael Covington]

I believe there is already an open-source computer control for existing mounts -- can't remember what it is called.  An open design for the whole thing, with as much use of standard machine parts as possible, is a great idea.   Before the computer era, there were a good many homemade equatorial mounts and drives.

[chinacat]

After going to the trouble of designing and fabricating/machining the mount, why use an off the shelf part for the simplest part? 
 

…use Losmandy counterweights.

[chinacat]

https://onstep.group.../main/wiki/3860 ?

I believe there is already an open-source computer control for existing mounts -- can't remember what it is called.  An open design for the whole thing, with as much use of standard machine parts as possible, is a great idea.   Before the computer era, there were a good many homemade equatorial mounts and drives.

[Michael Covington]

OnStep.  That's the name I was trying to remember.  Thank you!

Edited by Michael Covington, 01 December 2023 - 08:43 PM.

[22SQM]

Clayton,

 

I've been working on a home brew mount for the same reasons. I have no idea how it will turn out, but I've already sunk $400 into it so I think I'm committed. At this stage, its just a bunch of notebook drawings and parts, but it may be prudent to do the whole thing in CAD before I continue. 

Here is a Google drive I've started to document some of it. You will need some imagination to put the concept together.

 

https://drive.google...?usp=drive_link

 

It is premised on using no machining tools, just drill press, chop saw or table saw with metal cutting blade, and hand tools.

 

I was going to use T-channel, but regular 6061 tubing is cheaper and I think lighter for the same strength.

The tubing in the pics hasn't been cut yet. I just bought a bunch of on-sale 1"x12" x1/8"wall tubes.

The concept is a more distributed, wide stance Aluminum instead of stronger, heavier steel, which can't be made without a machine shop.

As of now, the DEC section will use 1/4" wall 1.5"x3" and 2"x3" rectangular tubes. Who knows if it will work.

 

I've made a home brew guiding system with AC Synchronous motor and VFD before for guiding. 

This one will use stepper motor(s), a programmable indexer, and microstep driver.

 

I have a spreadsheet with all the gearing and stepping options to match the sideral and guiding rates.

It will have a standard ST4 RJ12 port for guiding.

 

I haven't decided on a worm or tangent arm for DEC yet. I don't normally guide in DEC since I polar align with a PoleMaster. But it will need at least a slow mo for DEC.

 

I will also need a new tripod.

Any tripod suggestions will be welcome. It needs to be portable and have a flat head so I can mount a 1/4" Al base plate to it (~6"x 9").

Edited by 22SQM, 02 December 2023 - 04:19 PM.

[Claytoncramer]

I have always preferred a round tube mount with legs sticking out. This is pretty easy. A 6" OD aluminum tube with 1/4" wall. Legs are the bottom made with a triangle with bracing inside the triangle. (alternatively a solid triangle 1/4" thick with lightening holes.) Drill and tap 1/2"-13 holes at the end of the legs for Shepherd casters. Mount the legs into the tube by drilling through holes through tube, tap and drill through interior of triangle so bolts from inside tube screw into legs

[weis14]

...

Is this just a hopeless fantasy?

Probably.  I and many others have long pestered Roland Christian to re-introduce the Astro-Physics AP400GTO mount without success.  It would be a perfect match for the recent Stowaway and 110GTX refractors, but unfortunately I don't think it is going to happen.  If it does, it will probably have dual axis absolute encoders and have a high price point ($5k or more).  

 

The smaller equatorial mounts are going to be harmonic drive going forward to save weight and will cater to the needs of imagers first and foremost.  This is because imagers (1) seem to be willing to spend more money than visual users and (2) the migration of many visual users, like myself, to alt-az mounts in recent years.

[Claytoncramer]

1/2" OD x 12" long available at ACE for $10 each. To keep it compact and stuff keep the shafts short. Amazon has 1/2 x1-1/8 x5/16 needle bearings. Use 1 1-8" ID aluminum tube. This might require some boring on the lathe to give enough space to slide the bearing inside from each end and a couple of set screws to hold the bearings in place in the tube. Then a little heat on the bearings for a press fit on the shafts. This might be easier to do first on end then on the other end because you need to leave the bottom of the shaft exposed for the clock drive. Dry ice on the shaft also can be used to shrink the shaft for a press fit.

Drill bolt holes on the north bound polar axis to mount the declination axis housing. The attachment likely requires a part square or perhaps notched to fit without slip on the polar axis end and rounded to make an even fit on the declination axis. Perhaps even a bit of a flange so that bolts can lock the flange into tapped holes in the declination axis housing. The declination axis is similar to the polar axis with a longer axis to provide room for the counter weights.

The OTA end of the declaration axis needs a couple bolt holes on which to mount the saddle. Parts cost about $100.

Tripod for another night.

[Helyis]

As suggested, have a look at OnStep for the software part, it work really well, and relatively easily, including goto and other advanced features. For a cheap controller, i'm using this : https://mr-deep-addicted.com/?p=1873 as it cost less than 20€ to make.

However, I have two other comments to make :

 

- are you sure a lightweight anf hight quality mount without "slave-like" labor doesn't already exist commercialy ? Although pricey, it is what the Avalon M-zero look like to me (less than 5kg, made in Italy)

- if you really want to go to the DIY direction, i'm not really sure the traditionnal GEM style is the way to go, as they require rather specialized mechanical parts, that aren't really within reach of individuals. While I don't bite the AM5/3 hype (for multiple reasons), harmonic drives seem to be a really interesting perpective for DIY and cheap mount. The guy who made the OnStep controller is also working on multiples DIY mounts, including one that use chinese commercial harmonic drives, with results looking really promising (around 2-2.5kg in total, with published RMS at 0.7"). The BOM and plans are not available yet, but will be in the future. https://mr-deep-addicted.com/?p=2270 .

Edited by Helyis, 08 December 2023 - 06:44 AM.

[555aaa]

If I was going to do this on the cheap, with zero machining, I’d do a tangent arm drive with stepper motors for both axes, and have belt driven encoders on both axes. It would be push to with tracking for maybe 15 minutes or so. It would take a little chunk of code to linearize the tangent arm drive. The belt driven encoders lets you use cheap encoders but still get good on sky resolution. It would make a good arduino project but personally I hate arduino and would use a TI motion control microcontroller or whichever brand floats your boat.

Edited by 555aaa, 09 December 2023 - 03:01 PM.

[Claytoncramer]

Materials.  I was looking for sources of needle bearings, 1" OD steel rod, and 1.25" ID aluminum tube, and I wondered "Would aluminum rod be stiff enough?"  Then I thought a little longer.  Would .5" carbon fiber composite be stiff enough?  Yes and far lighter.  Instead of aluminum tubing, use carbon fiber composite tube.  Especially in these smaller diameters they are available and not hideously expensive.  Fasteners are an issue.  Steel has a electrochemical corrouion problem with carbon fiber composite.  So does aluminum.  Stainless steel is apparently pretty good except in seawater.  (Stay out of the ocean.)  Titanium is apparently perfectly fine.  The needle bearings are steel but there are barrier materials to handle this.  See this discussion about the corrosion problem.  Many parts are best bonded with epoxy; only items that might require replacement should be held by screws. 

 

I suspect you could make a very stiff mount with 3' tripod weighing about five pounds with extraordinary stiffness.

 

This would like require carbide taps; steel taps will likely be substantially dulled in carbon fiber.

Edited by Claytoncramer, 10 December 2023 - 03:38 PM.

[555aaa]

The stiffness of a shaft goes as the fourth power of the diameter. A half inch shat is 8x less stiff than a one inch shaft, for materials where Young’s modulus is the same.

[luxo II]

.... Something with a capacity of about 15 pounds and light enough that you could take off the OTA and the counterweights and lift the mount and tripod to move it.

I am not seeking GoTo...

This exists. They've only been around for the past 40 years, in one guise or another.

 

1. an EQ3 mount with handset for RA tracking. No GOTO.

2. Takahashi EM-11 Temma 2Z

3. Vixen "Great Polaris" (GP) mount, various versions.

 

Since you're obviously not intending to use this for imaging, for visual there is something better: The Skywatcher All-View mount, which is altaz, tracks perfectly well, has a full SYNSCAN handset with GOTO and all the bells and whistles.

 

I had one briefly and stupidly sold it - these are perfect for a small portable visual scope provided you make one improvement - put it on a decent tripod, as the one supplied is hopelessly flimsy. Yes its one plug ugly mount (probably why it was a failure as a product) but it works well.

Edited by luxo II, 10 December 2023 - 10:51 PM.

[balcon3]

The Vixen AP mount seems to meet most of your criteria. It is rated at 13.2 pounds (and people have confirmed that this is accurate). It is modular with optional RA and Dec axis motors. Very light. Made in Japan. It's push-to, so can use without motors also if you wish. Gets excellent reviews. Just doesn't have setting circles, but maybe they could be added somehow.

Edited by balcon3, 11 December 2023 - 01:09 AM.

[Claytoncramer]

The Vixen AP mount seems to meet most of your criteria. It is rated at 13.2 pounds (and people have confirmed that this is accurate). It is modular with optional RA and Dec axis motors. Very light. Made in Japan. It's push-to, so can use without motors also if you wish. Gets excellent reviews. Just doesn't have setting circles, but maybe they could be added somehow.

Is the Vixen AP sold in the U.S.?  It seems like Chinse clone competition caused Vixen to largely withdraw.

[balcon3]

Is the Vixen AP sold in the U.S.?  It seems like Chinse clone competition caused Vixen to largely withdraw.

I don't know. I don't live in the US. Telescope Express in Europe sells them and I know that people on this Forum order from them regularly. Just make sure you choose DHL as the delivery carrier. I sometimes buy from Kyoei-Osaka in Japan. They have very good prices on Japanese-made items and even with the shipping it can come out significantly cheaper than buying from a dealer outside of Japan. They are reliable.

[Claytoncramer]

Kyoei-Osaka does not list the Vixen AP.  Telescope Express does but mount only.  I do not see a tripod offered there.

[Claytoncramer]

The stiffness of a shaft goes as the fourth power of the diameter. A half inch shat is 8x less stiff than a one inch shaft, for materials where Young’s modulus is the same.

Thank you for the reminder.  Carbon fiver composites depending construction type have Young's Modulus "between 150-760 gigapascals (GPa)." https://element6comp...iber-so-strong/  The high end varieties are roughly 4x that of steel.  1/2" carbon fiber (at least the high-end versions) would exceed or match steel.

[balcon3]

Kyoei-Osaka does not list the Vixen AP.  Telescope Express does but mount only.  I do not see a tripod offered there.

I just checked and Kyoei-Osaka most definitely does list the Vixen Ap. The Vixen mount page is:

 

https://www.kyoei-os...99144/list.html

 

You can use the translation option at the top right to translate the page from Japanese.

The fourth and fifth rows have the AP mount options. The "Vixen AP equatorial mount" is the version without motors. The "Vixen AP equatorial mount with STARBOOK ONE controller" is the version with RA motor. The "Vixen AP-WM" is the version with 2 motors.

[Claytoncramer]

I confess that some of my interest in this is not the ability to buy off the shelf. I like making things. I made a fixed latitude undriven equatorial mount thirty years ago from Red oak, 1/2" steel shafts, and pillow block bearings. It was only supporting a 3" f/4.5 Newtonian.

I am intrigued at making a mount almost entirely of carbon fiber to get the ultimate grab and go mount, one so light that I perhaps even carry it out with my Televue-85 attached.

Rather than starting completely from scratch, maybe take the barely adequate EQ1 mount apart and slowly remake every part possible from carbon fiber. Some parts might need to be done using cast carbon fiber. A complex part could be to make a mold, fill it with carbon fiber then fill with epoxy and suck it to a vacuum. The advantages include no need to design from scratch and ability to reuse the existing motor and drive electronics as primitive as it is.

[Scott99]

Interesting ideas Clayton.  I recently posted about the need for very simple EQ mounts that are no longer on the market, speculating that pretty soon we'll see someone take on this task for their retirement job or something.   This Vixen one is nice, but I was thinking of something bigger. 

 

Just a very simple EQ mount with nice bearings.  Personally I would like one with no electronics whatsoever except RA drive and manual dec slow motion, or a simple dec motor for slow motion adjustments. 

 

I think this could be done for the price of something like a Discmount DM6.  These are extremely popular mounts.   I suspect a simple EQ mount with equally smooth bearings and movements would be a big seller.   How many of us would love something like a DM6 with RA tracking?  Most of the people I know from the internet with 5-6" refractors have a DM6.

 

It's a wonderful mount with one massive, glaring deficiency: no RA tracking.

Edited by Scott99, 15 December 2023 - 12:52 PM.

[Claytoncramer]

I had to sell my business SciopeRoller because it was consuming about 20 hours a week and since my 2014 stroke that is a bit much. Now I am doing the same number of hours working as an expert witness in gun ban laws. Any time that I spend has to be when I am not busy