Osprey

On 26/02/2020 at 00:11, fwm891 said:

At approx. 2 steps per second that will appear jerky in an eyepiece so you may want to either increase the micro stepping rate

Should I try for 1/8 or 1/16 steps?  I think the 4988 boards I have will do 1/8...not sure of the 1/16, will have to research that one.

And so I understand right, you're advocating adding gearing to reduce this even further?

@Cosmic Geoff What isn't shown is the new track system (multi piece c channel for lack of better description) I am printing to keep the belt from slipping off the aluminum band around the larger wheel.  Right now, I am trying to understand how to calculate and then code my own testing software before downloading the real deal stuff (either someones custom software or onstep).  I would like full operational capabilities of both my observatory and scope(s) from a web based browser.  This is my very first scope build so I am cutting my teeth in every way...I expect a lot of mistakes and generous feedback   Thanks for the ideas too!!  Worm gearing would be nice but I haven't figured out how I would make that happen at this point in the game...and would it be cost effective for a first build?

On 26/02/2020 at 00:11, fwm891 said:

I think you've got timing and distance measurements crossed. 

LOL...by the time I got done typing all of that...I think my eyes were crossed too!!!  Will rework the numbers on paper so I understand...if not,  I'll yell again

@fwm891 Getting back to the calculations....

I bought a NEMA 17 high torque motor with 11.9 mm diameter 20T pulleys.

According to the math you've shared with me, here is what I come up with:

86,164.0905 seconds per sidereal day

86,164.0905 / 360 deg = 239.344696 seconds per 1 deg.

239.344696 sec/deg divided by 60 sec = 3.989078 min/deg

The stepper motor is 400 steps per revolution @ .9 deg / rev.  I want to micro-step it down to 1/4 which should produce 1,600 steps per .9 deg thus it would take 1,777.777778 steps to make 1 degree (1600/.9)

The ratio of the horseshoe diameter to the stepper pulley is 102.45:1 (1219.2 mm diameter to 11.9 mm diameter).

This produces circumferences of 3,830.117 mm and 37.384953 mm respectively

I figured out that the amount of travel the horseshoe can move is 346.8 degrees (total of 13.2 degrees taken out for telescope cut) so in theory, I can achieve 3,689.7 mm of travel (3,830.117 mm * 96.3333%)

Pulley diameter is 11.9 mm

11.9 * pi = 37.384953 mm circumference

37.384953 mm * 3.989078 min/deg = 149.231493 mm of travel per deg

149.231493 mm * 360 degrees = 53,687.33762 mm total travel required?

At this point, I get lost in where I am going.  53.6k mm of travel is far greater than 3.8k mm.  Help from here would be appreciated

Bill

@Andy_ZH Good morning from a balmy Michigan!!  Any chance I can get your code to load on my Pi Zero W?  I have a high torque NEMA 17 motor and spare drivers, working on the motor housing currently...revising the screw locations and such but am closing in on getting ready to test the RA side of the system.  Thanks and hope all is well on your end

Bill

11 hours ago, Andy_ZH said:

This will not be a horseshoe mount. This will be a Dinosaur-Shoe mount!

@Andy_ZH LOL.  It weighs quite a bit already.  I tried to turn a roller on the lathe the other day and while I did get it flattened, it still doesn't work so I just grabbed a prototype idler pulley off my printer (41 hour job) and will clean it up and fit the bearings in once I get the magic elixir of life in my system (coffee for the lay person).

11 hours ago, Andy_ZH said:

Did you already try your scope in combination with a camera or visually at a star?

Yes, but ehhhhh...... Yes, I did test it on a star buuuuuuuuuttttttttt...the star was 93 million miles away. I have not taken the solar filter adapter out to test it on anything else.

Here's a photo op with the scope resting on top of the cradle.  Still don't have the rollers right and need to purchase the 1" bearings so I can mount the scope proper.  getting close, can taste it 😛

11 hours ago, Mick J said:

loving the block supports

@Mick J LOL...don't forget the barrels...they need love too!!! #Barrels lives matter #LMAO

Not as horrendous as it sounds.  The bit only cut fatty tissue...but close enough that I could see the muscles...didn't bleed much.  Think I was in shock because the only thing that really hurt was when the P.A. was giving me lidocaine shots...those hurt the most.  Over all...great story to sit around the table and drink coffee to lol

*Lake Huron is all freshwater.  This even happened Feb 2019 - plenty of ice still on the big lakes... no sharks were harmed in the telling of this story*

Here are some update photos of my build.  Main wheel is 48" in diameter and the smaller is 15".  Please pay no attention to the mess...it IS a garage after all 😛 I'm thinking that I will finally get to use that 1" flat aluminum stock I bought last year for my observatory...use it to line the bigger wheel edge.  This will help out with minor imperfections in my router work.  I had to overcome a router phobia as almost a year ago, my Craftsman router flipped out of my hands and landed on my right thigh - still spinning.  24 stitches later and many people scratching their heads about how a shark would end up in Lake Huron...I was home, shoveling snow (the router ripped my jeans, slowing the bit, but by the time it was over, I had what appeared to be a perfectly shaped shark bite - upper and lower jaws - on my thigh.).

@skybadger Not to nitpik but you have a lot of broken links within your site...possible removed pictures or incomplete hyperlinks.  Tried to look at your mount but the hyperlink was broken...all I could view was the thumbnail. Just so you know

Bill

4 hours ago, skybadger said:

Use of a 'pressed'' gear like you describe has been successful but I wouldn't do it into the end grain of a sheet of ply... is that where the strip of oak is envisaged ? There will be much more variation than routed disk on bearing.

@skybadger Yes, I would mold and trim the leading edge of the plywood in either maple or oak...if this was the method I chose to use.  Today, my goal is to fabricate the circle jig for the mount and bonus would be to cut out the first few pieces of the mount. Being a full time caregiver...my days are very fluid...goals turn to dreams at times.

54 minutes ago, Andy_ZH said:

Hi Osprey,

 

thanks for the pics. I have some more questions. Sorry if I seem to be pedantic, but I just cannot imagine some things:

You are aiming for solar observing. The sun runs on the ecliptic. But the (e.g. at equinox), when you scope points to the ecliptic, the scope will be within the plane of your horseshoe. Do you have enough space there? Without mirror, you will not be able to access the eyepiece point. Even worse, in summer when the sun is above the sky equator, your observation point will be between the horseshoe and the floor. Or did I get something wrong? I would have guessed that for a refractor, a fork mount would be more appropriate.

> Writing software to enable a mount to star-align & goto is orders of magnitude more complex than just tracking.

Well, yes, there is some more coding involved, but this is also no rocket science, but some more advanced geometry calculations. The difficulty comes when you try to do too much within a microcontroller (Arduino) where C is the only option of programming language.

I described my planned Raspberry Pi project here:

if you like, I can share my code with you. It is not yet ready for open-sourcing, but I can drive two stepper motors quite precisely. There is no need for an Arduino, my software runs just directly from the pi and it simply needs two 2209 drivers.

Your refractor seems to be quite fast. Will you use some H-alpha filter with it? If not, I wonder if it will have an enormous chromatic aberration.

Friction drive (without teeth): This would be ok in case you just do visual observations. But since there are no teeth on a friction drive, your tracking / goto could drift (=slide) away over time. Therefore, you would also need some encoders in order to get feedback of your actual position. I believe with a pure friction drive, stepper motors don't make sense anymore since you are loosing the advantage of the stepper with its discrete steps.

How about the following suggestion: Use a threaded bar to drive the horseshoe. With your wooden horseshoe, after applying some pressure and driving the horseshoe with the threaded bar for a while, it will grind its own thread into the wood. For instance, a M12 threaded bar has 1.75 mm per turn, which would give you your necessary gearing ratio. E.g. with a horseshoe circumference of 1.75 meters, you would have 1000 motor turns per day, which should be perfect.

Best

Andy

Andy, 

I plan on having a digital camera involved.  Currently I have a G3 camera from Orion that does quite well with the little 80mm I retrofitted.  I have a mylar type filter on the 80 mm. 

With my web degree, I know the basics of C and C++.  How they pertain to real life programming may be a little sketchy.  Nothing Google or Youtube hasn't been asked yet....lol.  I would be greatly interested in seeing your code.  Maybe I can learn more and contribute something towards the cause some day?

Yes, the refractor is very fast...objective FL is only like 200 mm if I remember right and the secondary lens is around 180 mm.  All told, the length of the notch in my horseshoe will be around 975 mm (38 3/8 approx).  As for the aberration...most likely because these were only school lab quality lenses.  Nothing you would find from a custom lens retailer.  There will be limitations not only by quality but also by this being my first full build.  This is why I chose solar vs deep sky.

Your idea of letting the threaded rod cut its own grooves is quite interesting...the mount is to be made from plywood but who is to say that I cannot find some maple or oak laying around and steam it to fit the curve? My party and I can cry if I want to lol!!! (ok, that remark shows my age lol)

Bill

Will keep everyone up to date, including photos as I go.  @skybadger friction drive...would that be like a rubber-ish type wheel directly in contact with the edge of the shoe?  I've seen images like that while figuring out my own design but the question remains in my head: Friction more / less reliable than a toothed belt?  I understand that if built properly, both should be close to equal, each having their own pros / cons.

@Andy_ZH I really wasn't sure how to drive this mount yet...the biggest variable is to be product availability vs cost.  Are geared cogs and tracks readily available at a reasonable cost vs. a toothed belt drive system?  As stated, I'm still in the designing phase, catching up on documentation.  Was looking at some grooved pulleys, like 3d printer ones, earlier today to get an idea on how to design / construct my mount.  I also bit the bullet and went an purchased the sheets of plywood necessary once the drawings are to my liking.

All said...here's what's in my mind:

I would like to utilize high torque stepper motors to either drive a belt system (preferred) or a worm / track system. How is still unknown at this time...

I would like to utilize as much 3d printing into this setup as I can.  I can hold my own with SketchUp Make and 3D Builder.

I would like a raspberry pi to handle the computerized portions but will give way to an arduino / combo if necessary. (Will learn code if necessary - am aware of Indi and KStars)

As for anything above and beyond...I am putty armed with computers and a 3d printer lol.

Attached are the images you requested...the mount is still in the design phase, I need to add in the bars to support the side bearings of the scope...coming soon

H.E.Li.O.S is a 6.5" refractor.  The dew shield, whole focusing assembly, and side bearings have been 3d printed by my Anet A6.  I had to modify several pieces of the focusing assembly from their original versions I found on thingiverse (https://www.thingiverse.com/thing:3586112).  

So there's where I sit...I know I still have a bit of road to haul but "living is all in the journey"

@JamesF I will give him a lookup, thanks for the tip!!

5 hours ago, fwm891 said:

@Osprey Oops see below...

Typo in above... Total = 86,164.0905 seconds in a sidereal day which is the length of time the Earth takes to rotate 360° or 239.434469 (original calc showed as 234.34469 sec) sec per 1° = 3.989078 mins per 1° rotation

3.989078 mins per 1° rotation  then 360° = 1,436.06808 mins for 360°

If your motor does 200 steps per min. Then for 360° rotation = 1,436.06808 x 200 = 207,213.616 steps per sidereal day

Sorry about the typo

 

@fwm891 I think I found another typo.... 1,436.06808 x 200 = 287,213.616 not 207,213.616 steps / sidereal day

@fwm891 lol...no worries, all good  I am currently documenting all my work as to upload to my website...

16 hours ago, fwm891 said:

Total = 86,164.0905 seconds in a sidereal day which is the length of time the Earth takes to rotate 360° or 234.34469 sec per 1° = 3.989078 mins per 1° rotation

Your stepper motor will give 200 steps per minute = 47,868.9391666 steps

@fwm891 I need to ask where you came up with 47,868.9391666 steps?  If I divide 47,868.9391666 by 200 steps/min, I get 239.344696 which I assume should be 234.344696 sec/deg.  Please clarify for me

Bill

I am in the design phase of building a horseshoe mount.  End result I want to achieve is a motorized control / goto type system.  I would like to utilize a raspberry pi to be the brains but will not rule out a 2560 Mega.  So far, I have collected the following information:

Nema 17 stepper will make 200 steps per full revolution

Shaft diameter is 5 mm

Earth rotates 360 degrees in 23h 56m 04s or 15.041085 degrees per hour.

Armed with this minimal amount of information, first: is there software that already exists for horseshoes so I do not have to go through all the math?

Second: If not, how would I find out how many steps / revolutions would it take to equal 15.041085 degrees?

Third: How different is solar tracking from "regular" tracking?

The refractor I have built is to be used for solar observing as the optics are only school laboratory grade, 2 scratches on the main objective.  I'm not very far into this journey and while I am more engineer than computer whiz...I still try.  Help appreciated

I'm going to try the above directions on a 5 year old Gateway (Acer) laptop and see if I can get the same or similar results.  I have an Orion 10 inch setup in my observatory and with my Pi 2B currently monitoring conditions and controlling the vitals of the observatory...I think the laptop will be a better fit for me (DS, Planetary, Solar imaging)...fingers crossed