Barn door star tracker

[Russman]

My prototype barn door star tracker, with pivot bolts. About to head out and give it a trial run.

I have some black machinable plastic I am going to use but I decided to perfect my timber prototype before I start drilling holes in it. The timber was free, the plastic I paid for. :)


Continuation of thread I posted in wrong category Click this Link (http://www.iceinspace.com.au/forum/showthread.php?t=109064)

[Merlin66]

Very nice!
I have a Trott double arm design I built almost 20 years ago. Aluminium sections and a small stepper motor drive.
Used to work well - I need to set it up again.....

[Russman]

Well that didn't work too well! lol The stars were doing little wobbles, I think the thread I tapped through the brass bolt was a little wonky.
So I went back to basics and built another (in 15mins lol).

Photos: Barn door tracker prototype #3 & a 2min exposure from trial run last night.

Once I get more confident I'll take a drive out into the darkness, try and get away from this light pollution!

I've been using my Android Compass App and Protractor app to align the tracker.

[Russman]

I went out to use my barn door tracker on Saturday night, in Smiths Gully, Vic. Had to get up on a hill to get above the fog.

This is a 5 x 2min exposures image stack. I'm hooked!!!! It wasn't long before the dew covered my lens, so I went home :(

Next project. lens heater!

[Merlin66]

Very nice result - you should be pleased!
Well done.

[Chris.B]

Well done, nice job.
Was quite foggy Saturday night(I'm in Eltham North).
considering how close to town you were great job.

Will have to start taking more pics.

[Russman]

Thanks guys! I am very pleased with my results! :D

The fog was very thick in lower areas, once above it though, it was crystal clear!
I saw a big bright white meteor (possibly space junk?) that broke up into a couple of pieces at the end, just before I turned my camera on :(

I can't wait to go out again! I want to motorise the tracker soon, as I find myself staring at the timer instead of enjoying the sky.

[bojan]

Russman,
If you are thinking about motorising, consider this:
http://www.ebay.com.au/itm/130867919130?ssPageName=STRK:MEWNX: IT&_trksid=p3984.m1439.l2649

Some time ago, I made a controller for this motor, using microprocessor, that generates the necessary sequence to drive this motor with minimal current consumption (see here (http://www.iceinspace.com.au/forum/showthread.php?t=45079&highlight=eq3+driver))... the firmware is very simple, just a program loop with specific number of passes to keep exact timing (it does't have to be 1rpm, it could be anything)
If you are handy with this kind of stuff, there are very cheap options available - for example, you can get Microchip controller from Jaycar and program it to drive the above mentioned motor.

Then again, if you are handy, you already know about this anyway..

[Russman]

Thanks Bojan,

I am quite handy, I do get a bit lost when it comes to the complicated side of motor controls, wiring schematics and definitely programming lol. I can nut out all basic stuff though! :D

I'm making another tracker now, so far it is coming along pretty well, I am spending allot more time on this one, hopefully it will look and perform better! Tossing up between, Isosceles mount or curved rod mount. :shrug:

I'll upload a progress photo later tonight if I get the opportunity. :)

[Merlin66]

Russ,
have a good look at the Trott double arm versions before locking in your design.....
http://home.comcast.net/~w7apd/barndoor.html

[bojan]

And, be aware that SoundStepper corrects for NPE (Non Periodic Error) introduced by straight screw and single arm .. ..
However, curved screw rod is very easy to make.

[Russman]

I have seen the double arms in my internet browsing before, they look a little bit more complicated to make, I am a newbie so I thought I'd stick to the basics. I'll continue making my single arm for now, I'll make a double arm for my next project when I'm a little more experienced. :)

Any idea on what the radius of my M6 all thread needs to be shaped into? I have 229mm from the center of the hinge pin to the center of my drive bolt. Am I right to just divide that by 2 to get my radius?

Thanks

[bojan]

No need for division.. this IS the radius (http://www.google.com.au/imgres?client=firefox-a&hs=rRs&sa=X&rls=org.mozilla:en-GB:official&biw=1823&bih=853&tbm=isch&tbnid=zhx5RkLcsc1FSM:&imgrefurl=http://commons.wikimedia.org/wiki/File:Curved_rod_mount.png&docid=xgYxQdIuvc-ZpM&imgurl=http://upload.wikimedia.org/wikipedia/commons/4/4f/Curved_rod_mount.png&w=728&h=462&ei=VkTSUcPGComjkQXfv4HgCw&zoom=1&ved=1t:3588,r:0,s:0,i:79&iact=rc&page=1&tbnh=174&tbnw=276&start=0&ndsp=31&tx=109&ty=76) of curvature you will need.

[Chris.B]

Not the same as DIY, but what about a cheap EQ mount with a battery drive?

[Russman]

:) I was reading someones else's notes on another website, I think it confused me. lol :confuse2: I got it now!

[Russman]

I'll look into that! I like building things though! :)

[Russman]

Here's my latest barn door tracker & a couple of 5x image stacks I just took out Strathewen, Vic. 10mm ISO3200 & 22mm ISO2300 2 to 3min exposures.

Made it out of recycled timber. Just went out to give it a trial run before I get onto sanding and varnishing.

[Merlin66]

Found some images of the Trott - aluminium sections, double arm Barndoor mount....may be of interest.

[Russman]

Awesome! They'll come in handy in my designing. I'm starting to get a good collection of plastic off cut, in some good lengths, I'll see what I can do with those soon! :)

Cheers :thumbsup:

[rcheshire]

It's a lot of fun.

This is one of the neatest little designs I have seen. Well described on Gary Seronik's site.
http://garyseronik.com/?q=node/52

[Russman]

Thanks Roland,

It is a neat little design isn't it?!

I cant wait until I finish my motorised tracker! & then my motorised double arm! :D

I think I am also going to have to make some sort of pan/tilt head for my tripod tracker mount, a nice rigid one! I don't like having a ball head underneath my tracker, it's not as solid as I would like it to be, and its harder to align my tracker as it moves in all directions! sometimes I get a bit :mad2: using it

best get to work now! :lol:

[Poita]

Jeez, under $3? What a bargain! I just grabbed a couple to play with.

[rcheshire]

I made a plywood adjustable equatorial wedge, fixed to an inexpensive flat topped tripod. It works quite well.

[Russman]

Here is my final manually operated barn door tracker that I will be using until I have made my motorised tracker. I have all of the parts I need (I think). I just have to make one trip to Jaycar to purchase a small gear kit and then I'm set to start building it.

I'm making it from the following parts/components list.

2 x pieces of Black Nylon
1 x 2RPM motor 12V DC
1 x M6 x 1.0 pitch threaded rod
2 x plastic hinges
1 x gear kit to gear down to 1RPM
1 x Spotting scope


I am going to make some kind of EQ mount for the tracker that can be easily converted and used as a Pano mount.

I am also going to drill and tap and secure a couple of small blocks of nylon to the side of the arms so it can be converted to a double arm tracker (at a later date).

I'll post photos as I progress with my build.

Thanks for reading, and following my thread! :thumbsup:

[RAJAH235]

Here's my curved rod camera tracker that I made up a few years ago.
I used an old (modified) servo & pulley's for the drive.
> http://s2.photobucket.com/user/RAJAH235/media/Tracker/IMG0001.jpg.html?sort=3&o=0#/user/RAJAH235/media/Tracker/IMG0001.jpg.html?sort=3&o=0&_suid=13748490254030145834557083519 44
> http://s2.photobucket.com/user/RAJAH235/media/Tracker/IMG0002.jpg.html?sort=3&o=1#/user/RAJAH235/media/Tracker/IMG0002.jpg.html?sort=3&o=1&_suid=13748490343960180099810332959 85
> http://s2.photobucket.com/user/RAJAH235/media/Tracker/Tracker.jpg.html?sort=3&o=4#/user/RAJAH235/media/Tracker/Tracker.jpg.html?sort=3&o=4&_suid=13748490429770660544547886118 2

I attached a 2nd hand 4 x 20, T'scopic sight to align it.
The main thing, is that I used brass hinges. Ain't no play in them babies.
Works well.

[Russman]

Looks great!

I made some real progress on building a motorised tracker last night. Just have to head out to find a little plastic enclosure to hide the motor and the circuitry then I'm set! These plastic hinges (http://www.nei.com.au/product_info.php?products_id=345&osCsid=7a24238985991921fa9fb09139c5 a4c0) I used when doubled up have no play as all! I'm really happy with my latest creation! :)

[bojan]

Looks good !
OK, now we want to see some astro-photos!

[Russman]

Here is my first wide angle image's of the Milky Way using my motorised barn door before my lens dewed up! :(

Anyone know what type of resistors and how many I need to make a lens heater? for a canon 10-22mm wide angle? a link to another thread will do.

I'm going to read up on dark/light frames & using deep sky stacker (I think that's the program I have), and also post editing on Photoshop (star colours etc.) My current goal is to create very clean and clear photos of the milky way, once that goal is accomplished I'll start zooming in on things! :D

The first pic is stacked on Photoshop, noise reduction, level adjustments, saturation etc.

The second is stacked using deep sky stacker, and then tweaked in PS.

Any hints or tips will be appreciated, or just keep doing what I'm doing!?!
:thumbsup:

[bojan]

Very nice pictures!

As for dew, try first with a tube made of black paper or plastic (from folders on sale in K-Mart).. It will have to be wide enough not to interfere with filed of view...
A couple of wounds of kanthal wire around that tube (and low voltage, 0.5V/100mA or less... might be tricky because lowest battery voltage is 1.2V) would be sufficient - you just need it to be warm, couple of degrees above environment should suffice.

[Russman]

Thanks Bojan,

I'll look into that, however, I was thinking of something that I can use 12v DC then I can just tap into my power source that I use to drive the motor.

[bojan]

A couple of resistors in series then.. so that the total resistance is 150-220ohms . Say 10x 15-22ohms.
Resistors could be rated at 1/8W.
http://www.cosam.org/astronomy/equipment/dewheater.html
http://www.togastro.com/ozzzy/heaters.html

BTW, I just found something on this forum:
http://www.iceinspace.com.au/63-292-0-0-1-0.html

[Poita]

I just put a long black cardboard tube on the end of the lens, keeps stray light and dew away and I haven't needed heaters yet.

[Russman]

Thanks Poita, the problem I have with that is I am using a wide angle lens at the moment, I can't even screw 2 of ND filters onto it without seeing them in the photos. That method might work for my 50mm lens and zoom lenses though! :)

[Russman]

I took my home built motorised barn door tracker out last night with DIY lens warmer.

Needs a few mods so it is easier to align, I need a third hand at the moment which can be quite frustrating.

Having some issues with DSS, I'll upload the results when I can figure out why my stacked images are black and white.

[Russman]

Here's a 35 x 30 second image smart object median stacked in photoshopCC.
Images taken with Canon 6D 50mm f1.4 on the barn door star tracker.

I've probably got a bit to learn with processing images in photoshop. I tried to use DSS but having issues with that at the moment.

[Russman]

I made a few more mods to my tracker as it was very frustrating & hard to align while trying to hold my smart phone (compass and protractor apps) against it in one hand and then make adjustments with other hand whilst holding it with my head :mad2: lol.. So I screwed on a small compass. I also changed the vertical part for latitude adjustment to a metal part as the plastic was no good, kept slipping! Its a lot more rigid now too which is awesome!

Also leveled it all up in the lounge and set the latitude to my location and made some markings, so when I head out next it should be very quick for me to set up! I even put a cheap eBay spotting scope on it which was probably not worth the $30 but hopefully it helps with finer adjustments.. Also going to put an elastic band from the camera platform to the drive board to give it some constant tension. I've also been studying my nightscape photos, I should be able to find the celestial pole with ease, hopefully!

I was really looking forward to using it tonight as the skies were supposed to be 'mostly clear' according to weatherzone.......... Maybe tomorrow night will be clear? Fingers crossed! I cant wait to take some shots and share my results!:)

[elfinke]

Thanks for keeping this thread updated Russ, it's been a pleasure following along. I've recently converted my old shed into a workshop and, combined with this thread, I've been inspired to rebuild my poor mans dual arm barndoor. I've got a Pentax K30 with the astrotracer add-on, which I hoped would work in conjunction with one another to allow for some pretty great results.

I'll be sure to post up any results as soon as it warms up and clears!

[Russman]

:thumbsup:

No probs elfinke, thanks for following my post!! Good luck with your barndoor! I was thinking of making a double arm but I thought I might perfect my single arm tracker first :)

I'm looking forward to seeing some pics of your barndoor!

p.s. I'm hoping to head out in a couple of hours to give mine another whirl! Hopefully the clouds stay away! :)

[Russman]

I snuck out last night, I feel I have improved on my methods, but cars kept coming past so I think that's why the left/lower left part of the image is brighter than the rest, the 2nd image has been processed in Photoshop, maybe too heavily? I don't know? I'll find my way soon enough!

I just returned from another trip but the lens warmer slipped and turned the focusing ring on my lens a tiny bit, what a waste of time, out of focus images do not look very good! :( At least next time I know to check the warmer!

:)

[pelu]

An idea from many years ago:

If you replace the solid steel axis of the barn door for a steel pipe, you will obtain a hole that can be used as a polar finder.

I my wood traking toy (I made it for the Hale-Boop ...) I use, instead a barn door, two wahsers in order the angle I can see trought them is the same that the circle that Polaris have. Placing Polaris in the adequate border of the second washer I achieve a very precise Polar alignment, enough for a 300mm. telelens.

With the apropiate distance between the M6 screw to washers for to need a complete tour each minute and a clock glued in the know I can have a good traking simply moving the know for to have all the time the ¿second arrow :shrug:? of the clock pointing to me.

https://lh4.googleusercontent.com/-bsG-C6NVVNc/VAxLeI5bqaI/AAAAAAAAH14/2H2NHXH5STo/w261-h396-no/58soporte.jpg


Easiest, but not so funny to do :P is the use of half Superpolaris mount.

https://lh3.googleusercontent.com/-n8zpkDgZg_o/VAxI340YD9I/AAAAAAAAH1g/jyhsAQxFA0w/w346-h461-no/mont-eclpse.jpg

[Russman]

Just an update; I'm making some mods to the mount for my barn door so it is easier to setup when i'm out in the dark. Currently need 3 hands to set it up accurately. Its probably going to look bulky but it will be very sturdy, I hope.

Also Im going to have to re-make the arms on the tracker as the plastic I used is bending and twisting! :(

I'll try and post more pics later tonight!

[OzEclipse]

Russ,
Why don't you build a double arm tracker? Much more accurate and much longer working time than a single arm.

Joe

[Russman]

Hi Joe. Thats the next project. I'll get the mount sorted and start making one.

[Russman]

Just some progress shots of the mount I was making over the weekend.

[Russman]

A few more progress shots of the mount I've been working on for my barn door tracker.

I've used a ball lock bolt for azimuth adjustment (pic 2). By tightening the star grip (pic 4) a holding force of 5.3 kN can be achieved! Massive!!! By loosening the star grip the ball lock bolt can be removed and the mount then separated from the base plate (pic 1 & 2). The mount does not yet have a screw for fine azimuth adjustments, something I may work on soon if needed.

It also has an articulated joint which the tracker is mounted for elevation adjustment (these are usually used with aluminium profile). There is a star grip for fine adjustment (pic 3). The articulated joint can be locked into place with the indexing lever on the side after adjustments have been made.

Now I need some clear skies so I can put it into action with my single arm barn door tracker. Don't know how I will go without a polar finder scope, I may need to purchase one to help when making fine adjustments.

I'll be working on a double arm tracker soon and will post up progress shots.

[OzEclipse]

Hi Russ,

What are those two pieces you've used for the elevation adjuster? Are they aluminium and are they off the shelf or custom made?
Look like a great build. Who needs a commercial drive.


Joe

[Russman]

Hi Joe. They are an off the shelf item. They are an accessory for aluminium profile modular systems. If you Google aluminium profile joint you'll see. I can get some prices if you are interested. I can order them through work. I was lucky to get mine for free off a local engineer though so not sure how much they are.

[OzEclipse]

Russ,

Thanks, I've been looking for something like that for my lightweight eclipse mounting and my Polarie. I've been thinking about custom making one for some time. Thanks for the hint. I found a possible supplier (Profilium) on line. I'll give them a try first rather than put you to the trouble of having to freight the stuff to me.

When you make that double arm drive, get in touch. I have an excel spreadsheet for optimizing the dimensions and modelling the error profiles of the type 4 isosceles platforms. It isn't very user friendly. I didn't make it for distribution so it needs a fair bit of driving.

Many years ago, I came up with a modification to the type 4 that greatly increases the drive time to almost 4 hours with theoretical ±1 arc sec drive error, plot also attached. I have my doubts that it would be quite that accurate unless you were very precise with the construction but even if you fall a bit short it would be pretty amazing.

I would be happy to optimize a set of construction dimensions and produce an error plot for you. I've attached a couple of examples of the sort of performance you can get from a type 4.

cheers

Joe

[Russman]

No probs! :thumbsup:

I am working out what materials I should use, I might use aluminium. Do you have optimised dimensions for M6 x 1.0P threaded rod? Running @ 1RPM? That would be awesome if its not too much to ask! :)

[elfinke]

Thanks for keeping this updated, Russ.

[OzEclipse]

I am working out what materials I should use, I might use aluminium. Do you have optimised dimensions for M6 x 1.0P threaded rod? Running @ 1RPM? That would be awesome if its not too much to ask! [/QUOTE]


No probs! Happy to help Russ.

The parameters I'm giving you assume that you are building the type 4 Trott, with the two boards starting parallel and pushing apart. It's not for my mod. My mod involves building something that starts at a negative angle, passes through parallel, then heads out the other way. Easy to mathematically model, easy to say not so easy to make.

You can also use the type 4 principle but make a double tangent arm drive instead of a hinged board type. When I designed the bisymmetric double arm , it was to build it as a high precision 4hr tangent for the RA axis on my old mount. It would end up looking like a complicated Astrotrac arm.

I never built it, I was getting more and more into eclipse chasing and instead my time went in to build a very lightweight EQ mount to carry in my luggage to solar eclipses around the world. Eventually I bought an iEQ45 mount for home observing.

Assuming you are going to build the easier Trott Type 4 with the boards starting parallel and pushing apart, I've optimized the design parameters for that. I have guessed because you asked for M6 and 1rpm that you have a fixed 1 rpm motor/gearbox- perhaps a synchronous motor?

If you saddle yourself with a fixed motor speed, the dimensions need to be very very precise or the errors will blow out really quickly.
An error of 0.025mm on the radius arm will push the error out to 8 arc sec over 2 hrs.
An error of 0.25mm will push the error out to 80 arc sec over 2 hrs.

A variable speed drive will let you fine tune to cancel out any minor construction errors.

If you have a variable speed stepper driver, then you can make fine adjustments to the motor speed to trim out any construction errors at the end.

The construction parameters and error curve are on the excel zip file. The diagrams from the original articles in S&T and show which parameters r, b & c are.

cheers

joe

[Steve_C]

Hi all,

Just joined the site. I am planning on building a barn door tracker as per
http://www.garyseronik.com/?q=node/52.

Does anyone know where I can get similar parts in Australia?

I can get all these parts from the supplier indicated, but would prefer to buy in Oz

Regards,

Steve

[mswhin63]

Hi Steve, will be able to buy most if not all parts from various suppliers, Wood hinges from hardware. For the gears etc, www.smallparts.com.au comes to mind although there is quite possibly more around. Just a bit of digging.

[bojan]

Sometimes the best supply of such parts are thrown away printers, photocopiers, scanners..
Just pay attention to what pople are leaving on the streets over weekends..

[Steve_C]

I am not familiar with how to drive stepper motors, although I do have an extensive knowledge of general electronics. I would assume a stepper motor is not ideal for a barn door as the earth does not rotate in steps but smoothly. Is my assumption correct?

Steve

[Merlin66]

If the geared stepper ratio is sufficient, the "steps" won't be seen in the image.

[Steve_C]

What would be considered sufficient?

Also, in a two arm design, how do you stop the threaded rod drive gear from moving vertically?

Steve

[Merlin66]

Assuming you have the "usual" 1rpm requirement to give sidereal rate.
This gives a rate of 15 arc sec/ sec time with an input of 1 rev (360 degrees/ 60 sec) = 6 degrees of screw rotation every sec. Giving 2.5 arc sec/ degree rotation.
For the standard camera lens normally used on the Barndoor mount, a resolution of 10 arc sec would be allowable. (Users to verify)

The stepper motors are usually (basic) 1.8 degree per pulse.
if attached directly to the screw you need 6/1.8 (3.33 pulses) per sec to maintain the tracking rate and each pulse would only move the mount 1.8 * 2.5 arc sec = 6 arc sec. Well below the 10 arc sec limit.

Hope this makes sense.

[Steve_C]

Is there any advantage using a stepper motor vs a constant speed motor that is powered by a voltage regualted source?

[Merlin66]

No, not really.
Comes down to availability....
Frequency control of small motor drives was very popular with amateurs in the 70's but fell out of favour.

[Russman]

No probs! Happy to help Russ.

The parameters I'm giving you assume that you are building the type 4 Trott, with the two boards starting parallel and pushing apart. It's not for my mod. My mod involves building something that starts at a negative angle, passes through parallel, then heads out the other way. Easy to mathematically model, easy to say not so easy to make.

You can also use the type 4 principle but make a double tangent arm drive instead of a hinged board type. When I designed the bisymmetric double arm , it was to build it as a high precision 4hr tangent for the RA axis on my old mount. It would end up looking like a complicated Astrotrac arm.

I never built it, I was getting more and more into eclipse chasing and instead my time went in to build a very lightweight EQ mount to carry in my luggage to solar eclipses around the world. Eventually I bought an iEQ45 mount for home observing.

Assuming you are going to build the easier Trott Type 4 with the boards starting parallel and pushing apart, I've optimized the design parameters for that. I have guessed because you asked for M6 and 1rpm that you have a fixed 1 rpm motor/gearbox- perhaps a synchronous motor?

If you saddle yourself with a fixed motor speed, the dimensions need to be very very precise or the errors will blow out really quickly.
An error of 0.025mm on the radius arm will push the error out to 8 arc sec over 2 hrs.
An error of 0.25mm will push the error out to 80 arc sec over 2 hrs.

A variable speed drive will let you fine tune to cancel out any minor construction errors.

If you have a variable speed stepper driver, then you can make fine adjustments to the motor speed to trim out any construction errors at the end.

The construction parameters and error curve are on the excel zip file. The diagrams from the original articles in S&T and show which parameters r, b & c are.

cheers

joe[/QUOTE]

Thanks heaps Joe, appreciate you time & efforts, love the astro community, everyone seems willing to help out each other! :thumbsup:

[Russman]

Ive ordered these off ebay, hoping they will be the right ones and do the job to drive mine!

http://www.ebay.com.au/itm/191492110623?_trksid=p2057872.m2749 .l2649&ssPageName=STRK%3AMEBIDX%3AIT


http://www.ebay.com.au/itm/171703594516?_trksid=p2057872.m2749 .l2649&ssPageName=STRK%3AMEBIDX%3AIT

as for other items such as gears etc, jaycar might be an option?

http://www.jaycar.com.au/PRODUCTS/Electromechanical-Components/Mechatronics/Gears-%26-Pulleys/Worm-Drive-Set/p/YG2632

http://www.jaycar.com.au/PRODUCTS/Electromechanical-Components/Mechatronics/Drive-Train-Components/Worm-Drive-Set/p/YG2736

Threaded rod is easily sourced from your local nut & bolt shop. and hinges from hardware. :)

[Russman]

As far as I am aware the stepper motors offers a far more accurate drive than a constant speed, less variances. :)

[OzEclipse]

Most constant speed motors, synchronous or dc, need to turn at > 1000 rpm, usually 2000-3000 rpm to have sufficient torque. They then need very high reduction gear boxes(read expensive) to get down to the sort of speeds required for these trackers or worm drives.

You can buy small stepper motors with integral 64:1 gearboxes (sufficient for a 200mm tracker radius arm) and PCB's with drive circuits for them for under ten dollars each on ebay. You can also buy power supply cards. If you are good with electronics then it'll be childs play. It's just a matter of putting them in a box and connecting the power to the drive and the drive to the motor through a connector. There are two types of stepper, bipolar and unipolar and the drive circuits for each are different, just make sure you get the right type of drive.

While Bojan is correct that discard printers etc do have motors, I have pulled a few apart found it a but hit and miss in the past with motors with strange characteristics or high voltages 24V. Also, many printer motors may not have gearboxes.


You also asked

Also, in a two arm design, how do you stop the threaded rod drive gear from moving vertically?

If I understand your Q, you are talking about the curved threaded rod type in Gary's article. The weight of the camera and top board holds the gear down. The rod is not attached to the lower board. There is a large hole there that the curved rod just passes through. It's actually a single arm tracker not a two arm.

Incidentally, we call the type with two boards a single arm and the type with three boards a double arm tracker. Naming is somewhat historical based on the original magazine articles written in the 1980's.

Joe

[OzEclipse]

No problem. If you want to change any construction parameters, let me know. Do PM me. I get busy at time and don't always check IIS.

It's very quick to re-run the optimization on any of the primary parameters - primary radius, motor speed etc and spit out the results. As explained in the Feb 88 S&T article, the ratio of the hinge separation to the slide contact length b/c is critical to the stability and works best kept at 2.186 so I keep that ratio fixed.

Also remember that no matter how accurate you make it, you will need to tune out the construction errors by trimming the motor speed at the end.

I contacted Profilium today about those hinge fittings. Thanks for the heads up on that. Is that the brand you use? how solid are the screw clamped joints you use? Do the boards bounce much? There a fair cantilever there.

cheers

Joe

[Steve_C]

The Ebay stuff looks right, Jaycar gears not so sure. The smaller doesn't appear to have any shaft and grub screw to mount. The larger one would need to be drilled out to take the rod. Littlebird seems to have the relevant gears, but the larger one from them would need a hub, which they have. Re the ebay controller, you would want to possibly replace the pot with a trim pot so you don't accidentally bump the setting.

I do have some RC servos I might be able to press into service, although I doubt they would have the torque.

I have already looked into other nuts and bolts source, one thing I found out is that a 5mm (M5) brass rod is 32TPI, so fits Gary's design well. I do know you can change dimensions to suit different tpi.

I qualified as an electronic tech in the 1960's, but have never played with this newer stuff, been out of the game for around 10 years.

This is a long term, (months) project for me.

[Russman]

I ventured out into the yard to give my single arm barndoor and new DIY mount a go. It was pretty easy to get it aligned, hardest part was adjusting the speed of my motor, eventually got it as close as I could to 1rpm and was happy with results so I started taking shots. Unfortunately some thin cloud started to roll in so I called it quits and came inside.

3rd photo is a shot of my DIY setup in action. 1st is a quick edit in Nebulosity of approx 12 images total exposure time 16mins with darks & flats subtracted, and a bit of processing in Neb and PS. I will need to get some more practice in on Nebulosity as I am pretty new to it, I like the program a lot, a little bit time consuming but with some patience and some good stock images I think it will produce amazing pictures.. 2nd shot is a 5min 26 sec exposure @ 50mm to show example of trailing.

Must goto bed now, my eyes are sore! :)

[bojan]

I think there is.. especially if used with longer lenses, because the speed is controlled by crystal, which is more accurate.

Also, if you are using processor to drive the stepper motor (via appropriate drivers of course), you can pre-program the motor speed such that you go not need anything more that basic barndoor mechanic.

Also, have a look at Sounstepper (at sourceforge), this app can do this (it is running on PC)

[Steve_C]

You would need a stepper motor driver module as well wouldn't you?

I don't have the necessary tools at home to make an accurate device, however a new Men's Shed will be opening up near me in September, so hopefully I will have access to some decent machinery.

Regards,

Steve

[Russman]

:thumbsup:

I think mine came from RCS Products, not too sure though as I these were given to me. Once clamp lever is tightened they lock up very well, I can not make it move when I apply force. The boards are pretty solid, I haven't used a telephoto lens yet, that'll show how solid it is. My cousin has a 300mm f2.8 I might try on it tonight if he lets me borrow it!

[Russman]

One of the links is a stepper motor controller, as far as I am aware that's all I need. I don't really know much about this stuff, but I am quite cluey so I'll nut it out..

:D

[Steve_C]

If you look further down the controller link page, it mentions you need another board. That is basically what I am referring to. I am new to this as well and also quite cluey. I can't see where on the one pcb you would connect the motor.

I think this would be better, a number of sellers have them.

http://www.ebay.com.au/itm/Stepper-Motor-Speed-Pulse-Controller-and-Driver-Board-/330549567534?pt=LH_DefaultDomain_15&hash=item4cf64a202e

Maybe someone else here can help?

[mswhin63]

If you are going to look for a board for Astro purposes, alwys consider Micro-stepping capability. The drive board in the link does not have micro-steeping in the description.

It may still work but is always a better option for both smoother operation plus can reduce the speed even further if required.

[rcheshire]

Not sure if this is the type of info you need. You will need a board to generate the stepping pulse and forward/reverse logic, such as a microprocessor or 555 timer. These signals are sent to a driver board (such as an eady driver) which provides the correct voltage and energises the coils sequentially. The step and direction inputs are marked on the board - hook these up to the logic outputs.

A microprocessor can be used in two ways. 1. Send individual coil pulses to a darlington array, such as a ULN2008, which becomes the driver board (very small footprint) 2. Send a single stepping pulse and direction logic to a driver board, such as an easy driver.

[Steve_C]

Maybe I'm reading this controller spec wrong, but it seems to me it has one mode which generates the pulse and drives the motor. It does have a 4Mhz crystal on board, why would it have that if not to generate the pulse? It also seems to have a mode where you can use an external pulse. I found a more detailed spec sheet, http://www.kc-kwan.com/supports/menu/menu_pc_board_stepper_motor_control ler_01.jpg. Biggest issue is if it can generate the correct speed. Price is around $16, so not much out of pocket if it does not work.

I still might go with Gary's original design, using a gearmotor driven through an LM317 regulator. The regulator will compensate for minor variations in input voltage and should provide good output voltage regulation as long as input/output voltage ratio is high enough. There will of course be variations due to temperature. I'll have to see how that goes. I don't particularly want to fiddle with Arduino or microprocessors. Unless the pulse is generated by a crystal, I doubt if would be any more accurate than the regulated motor method, especially as the motor is geared down from a higher rpm. I might be missing some basics here, I haven't fiddled with electronics at this level for a long time.

[rcheshire]

Starting again - perhaps I pitched my comments a bit low. It sounds like you know what your about.

If speed control is the only consideration then microprocessors might just be personal preference.

Most, if not all tangent arm builders will use a DSLR or similar, and staggering shots by turning the drive off for a few seconds between images, a sort of dithering, is very beneficial with significant gains in image quality.

Using the microprocessor as an intervalometer can be a nice way of automating the whole thing, along with the short delays between images. A neat level of sophistication.

Not being an electronics expert a microprocessor was the simplest route. A ULN2008 makes a simple interface for unipolar motors and an L298 for bipolars, with some flyback protection if necessary.

[Steve_C]

I'm TAFE qualified in electronics (1969) and have an Advanced class amateur radio licence. I have not played with electronics much in recent years, my career moved in a different direction.

[Russman]

Hi Steve, Thanks for pointing that out! I will have to get that as well! :thumbsup:

[Steve_C]

I think I am going to give up on the stepper motor design and stick with DC voltage controlled for now. Most research I have done seems to indicate it will work well. Also look at http://www.ronsongears.com.au/ for gears. Best I have found so far and reasonably priced.

For accurate polar alignment, I think I can use a compass and an inclinometer app to set elevation = to latitude. Saves fiddling trying to line up with a non existent point in the sky.

[N1]

Would an egg timer have enough torque :lol: to drive this thing?

[Steve_C]

I did see a design using an egg timer! It used a length of fishing line to drive the arm from the timer, using the weight of the camera to provide tension on the fishing line! I doubt it would be accurate enough and you would have no way of making minor adjustments.

See http://www.mpas.asn.au/Astro/Tips/dingaling/dingaling.htm

[Steve_C]

The link I gave has a microcontroller chip with on board memory, as well as a motor driver chip capable of delivering up to 4A. If it can produce the correct pulse frequency, I think it would work well.

[Steve_C]

Where did you get the gears for your mount, and what motor did you use?

Plans for my single arm barn door are coming together, slowly. 32 TPI rod seems to be hard to get at a reasonable price, however I can get 1/4" BSW rod (20TPI) at Bunnings, along with appropriate nuts. Will this work? I realise the radius will need to be bigger as will the arm. I could use 3/16 rod at 24 TPI, but Bunnings don't seem to have 3/16 nuts available without screws, perhaps the 3/16 rod would be too thin. Thoughts?

[OzEclipse]

Hi Steve,

If you re-read my post earlier in this thread where I replied to your Q about motors, I stated that DC motors are difficult to gear down. It's because of their high native output speed.

Let's say you build a tracker with a 20TPI 1/4" whitworth rod and a 10 inch arm radius, every turn of the nut advances the arm by

206265 ÷ 20 TPI ÷10 inch = 1031 arc sec per turn of the nut. But the sky only moves at 15.04 arc sec per sec. So you need to turn the nut at 1 turn every 68.6 seconds.

If you were to order this 6rpm motor.

http://www.ebay.com/itm/12V-6RPM-Ouput-Speed-Geared-Gearhead-Box-DC-Motor-High-Torque-Output-Heavy-Duty-/181775778754?pt=LH_DefaultDomain_0&hash=item2a52ae43c2

You will need approximately 6:1 gear reduction in between the motor gearhead output and the gear that turns the shaft.

You could make the required reduction a bit less by making or buying a pulse width modulated DC motor speed controller but if you reduce the motor speed too much, you'll eventually lose torque.


I realize that steppers are a slightly more difficult to control electronically but they are far far easier to deal with on the mechanical side. If you use one of the Arduino steppers with 64:1 gear box that are available on ebay, you can drive the nut with a simple pulley or 1:1 gear. No reduction required.

The stepper controller mentioned earlier in this thread will run the arduino motors. If the speed adjustment on the circuit is too course, send in a pulse from a 555 timer board. Replace the timing capacitor with a polyester capacitor, they are much more temperature stable. When you have the right resistance, remove the course potentiometer and replace it with a metal film resistor and a small range trimpot to allow fine tuning of the motor speed.

Cheers

Joe

[OzEclipse]

An afterthought, I think those PWM DC speed controllers will give decent torque at 1/6 speed reduction. I don't know how stable or accurate the speed control is when using these controllers. Using 1/6th of the rated voltage will kill the torque although the 6rpm motors have such a high reduction already, the loss of torque may not be an issue.

Joe

[Russman]

I got my motor from ebay, gears from jaycar and other stuff from work. I work in a nut and bolt shop. PS threaded rod is very cheap, I'd stick to M6 as its easier conversions etc. I'll try and put together a detailed description of how I made mine over the next couple of days. :) PS. i'd stay away from anything lesser diameter than 6mm, I think it might be too flimsy.

[pixelsaurus]

You mean something like this?

http://www.instructables.com/id/Standalone-mount-for-astro-photography/

[Steve_C]

One nut and bolt shop near me wants $41 per meter for M5. I can get 1/4 20tpi (steel or brass) from Bunnings for $7.50. Do you know of a cheap source for M5 or M6 rod?

[Steve_C]

Surely if I got a 4rpm o/p motor off ebay and used 4:1 gearing that would work as per Gary's article?



I need to understand the maths for this, long time since I studied math! Gary's article mentions a formula R= rpm/(.004375*tpi) to get the rod radius and rod position from the hinge, but I don't understand where the .004375 constant comes from.



I understand that, and it is fairly easy to do. I plan to go with a stepper, either a28BYJ-48 or a Nema 17 format, using the driver / controller board I mentioned previously. Just need to get the arm radius and arm postion calculations correct. I'll look at the spreadsheet mentioned elsewhere. I haven't decided on motor voltage yet, I have some spare 11.1V li-pol batteries from some Rc gear I can use, I'll probably regulate them down to around 6V.

[Steve_C]

Where does the figure of 206265 come from?

[N1]

Ingenious in a way but does not support a DSLR according to the comments further down.

[Russman]

:mad2: That's a joke! A 1 meter length of M6 Zinc all thread shouldn't cost more than $10 I'd probably sell Zinc for $5 & brass for $10 over the counter at work.

I used the following items on my barn door;
http://www.ebay.com.au/itm/12V-DC-2RPM-Replacement-Torque-Gear-Box-Motor-/260793497840?pt=LH_DefaultDomain_15&hash=item3cb880f8f0

http://www.jaycar.com.au/PRODUCTS/Electromechanical-Components/Mechatronics/Gears-%26-Pulleys/Worm-Drive-Set/p/YG2632
Used the 2:1 gears

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcS8RNLAGiUnoFqZtx Kpi9BPa-BFVE9UqArJKtzJkde4tkSNXKFzQ6hswg

The M6 flange nut was pressed into the larger gear and I drilled a hole in the bottom board of the barn door to match the OD of the flange nut which locates the gear into position and keeps it engaged with the smaller drive gear.

I also used a control knob (think its called a potentiometer) to fine tune the speed as I found that the 2rpm motor from china wasn't very accurate, might have something to do with my voltage supply??. I drew a white dot on one of the gear teeth and a dot on the board, turn it on, set a timer and adjust to 1rpm. I can get it pretty accurate to within +- within 1 second.

I'll take some photos and post them up soon. :D

If you want to PM me and we can discuss posting to you. Ive got a fair collection of threaded bits and pieces in my workshop! :thumbsup:

[OzEclipse]

Hi Steve

It's the number of arc seconds in a radian.

60 x 60 x 180 ÷ pi

Using radian measure for small angle trig allows really simple calcs that are just as precise as using trig functions because the tan and sin functions of small angles are the same as their radian angle value.

The rest of the calc is just working out the fraction of a radian.

Joe

[OzEclipse]

I had often wondered that myself. I have worked it out. Turns out, he's using the same radian measure trig shortcut that I am.

The angle the board moves through is RPM ÷ { TPI x R(inches) }

In one minute the board has to move
60s x 15.04 arc seconds per second = 902.4 arc sec
902.4 ÷ 206265 (arc sec per radian) = 0.004375 radians.

0.004375 = RPM ÷ { TPI x R(inches) }

rearranging

R(inches) = RPM ÷ { TPI x 0.004375 }

If you want to go down the dc motor route, I'd be tempted to use a 6rpm motor and a 4:1 gear. Then use a PWM dc motor speed controller to achieve the 2/3 speed reduction.




It should work if everything is made VERY precisely. It will work. If not, you really need some motor speed adjustment to trim out the construction errors.




The spreadsheet referred to is mine. I ran my spreadsheet for Russ based on some of the construction parameters he wanted to use. Then I created a second output spreadsheet to display the results. I don't mind giving the spreadsheet out but it's not user friendly. I think I'd spend more time explaining it or fielding complaints if people run it the wrong way and build their drive on wrong parameters than I would if I just run it and give constructors the output and error chart. Happy to do the same for you.


Hope this helps

Cheers

Joe

[OzEclipse]

Suggest you just change the radius to suit the 20TPI 1/4" - 11.43 inches

[Steve_C]

That's what I plan to do, just makes it a bit longer. The 1/4 rod at Bunnings seemed to bend fairly easily too.

[Steve_C]

Joe,

I plan on using a stepper motor now, just working out the voltage/current requirements. I'm going to get the motor and electronics first, to get that working before I do the mechanics.

If I went with a DC motor, the voltage would be made adjustable to fine tune speed.

For some reason the forum is not letting me quote posts that have been quoted by me before.

[Howard]

Can't argue with the previously posted photo's using a DC motor. Great results.
However, for those who do still wish to pursue stepper motors ... I have never tried this, but the following webpage is a guy who built a DIY HiFi turntable. About half way down the page he drives a stepper motor by two 90 degree offset sine waves created on pc with free software. The motor is hooked up to amp/audio card output and when you 'play' the sine wave(s) apparently it drives the stepper motor at whatever the frequency you put into the sine waves. If you have a pc in the field it might work, but all the faffing around might be just as tough to do as find/buy those pcb boards off eBay?
For what its worth the link is an interesting read though ...
http://www.altmann.haan.de/turntable/

[OzEclipse]

Howard, It's a good idea. The only downside I see is that you are stuck with needing a laptop which reduces portability and increases setup time.

However, once tuned, the frequencies could be stored to a sound file on an MP3 player, smartphone etc You'd only need to install a battery, power supply and two channel power amplifier card in the base of the barndoor to drive the stepper. joe

[Steve_C]

Thanks, I have plenty of bits and pieces as well, just no threaded rod.

I remembered another place in Sydney where I have bought stuff from before, I'll see if they have the rod at a reasonable price.

Steve

[Steve_C]

Russ, did you drill the larger gear out to accept the nut and the smaller gear to take the 6mm shaft?

Did you just put the potentiometer in series with the motor or did you use a voltage regulator? Without a regulator the speed would not be constant.

Steve

[Russman]

Hi Steve,

I drilled the large gear so as the hex of the nut was a tight press fit, I also used a strong adhesive to hold it in place.

I purchased a 12v DC motor speed controller & a 12v DC 2RPM motor off eBay. The gears were from Jaycar. I got the M6 brass rod from work and bent it to get a curved radius.

The last photo was taken with my barn door on 23rd July with my 6D & canon 50mm f1.4 lens @ f3.2 ISO 3200. Approx 30 exposures ranging from 10 to 60 seconds.

[Steve_C]

Stacked in DSS or Nebulosity I assume?

Thanks, what is the cable on the left side?

[Russman]

I stacked using Nebulosity 3, I found it much more user friendly than DSS.

The cable is a spring to hold the finder scope on.

[Steve_C]

Russ,

What battery did you use? Do you find you have to recalibrate motor speed every time you use it?

TIA
Steve

[Russman]

At the moment I am using my car jump starter. I like to re-calibrate it each time anyway. I might order a speed controller with an LCD speed display soon. :)

[Steve_C]

Maybe a stupid question, bear in mind I am a newbie.

All I have read re barn doors is they need to be aligned with a ref point, north or south celestial pole. As we don't have a definite sky ref to do this, how do we do it?

Elevation seems to be easy, just use a protractor with a pointer set up on the barn door. Aiming south is a little more difficult. I have seen some suggest a compass and correct for magentic deviation, but any ferrous metal in the barn door would affect the compass. If the rod and hinges are brass, maybe no problem. However, the motor will have a magnetic field, as will the wires going to it. Hence I guess the need for a ref point in the sky. Am I on the right track here?

[Steve_C]

Thanks.

[RAJAH235]

Steve_C,
I use a 2nd hand, 4 X telescopic sight from the local gun shop.

It's attached via a (slide scope in), Aluminium bracket, adjacent to the brass hinges & is very accurate once set up.

Using a SCP finder chart, it's relatively easy to find it.
Might take a little while to "fine-tune-it-in" but it works well.

For the elevation/latitude, I had 2 hardwood wedges made up.
One "large variety" under the bottom plate on the tripod & a smaller one for the camera ball mount.

Piccies are in Post #25 on the 2nd page of this thread.
;)

[rcheshire]

I have used Google Earth/ map to work out true south in relation to the orientation of a fence line. Measure the angle between south and the fence lay it out with a string line and point the hinge in that direction. Helpful for ball park alignment and if you can't see the SCP. In that case I drift align my double arm drive

[Steve_C]

Any logical reason it can't be done using the southern cross 4 1/2 times long axis method?

[rcheshire]

None at all, if that part of the sky is not obscured, as it frequently is from my location.

[Steve_C]

Thanks

[Steve_C]

I live in a Nth Western Sydney suburb, so to get to a dark sky loacation takes me at least an hour. Nearest reasonable would be Bowen mountain, is anyone here a member of NSW Astronomical Society?

[Steve_C]

How accurate does the curved rod need to be? I have bent it as close as I can to the correct radius for an M6 rod, 9".

How accurate does the measurement from the hinge to the rod need to be? within 1mm, .5, 2?

TIA

steve

[OzEclipse]

Hi Steve,
A 1mm error in the radius, that is where the radius error results in a 1mm greater radius than the ideal radius will result in a drive rate error of 4 arc sec per minute. This is not significant for short exposures on wide angle lenses. Up to 2 min exposures up to 100mm lenses. Accurate polar alignment will present a bigger problem than this error.

Cheers

Joe

[Steve_C]

I can pick up a rifle scope from Ebay pretty cheap. Not sure if they are customs restricted though. How did you attach yours? They seem to have a wedge shaped mount.

Steve

[VPAstro]

A few years ago I picked this up on Gumtree here in Melbourne for $25.00
It was made in 1988 by ST Astro in Beaumont Texas USA and came with original letters between the ST Astro and the purchaser (no email back then, only snail mail), instructions and transfer receipt.
He paid $155 USD back in 1988.
It doesn't have a curved rod, but a circular cutout in the top and bottom arm, which changes angles as the arms separate. It has a tube to assist in the alignment, but is not really of any benefit here in the southern hemisphere. It runs on 12v (1 x 9v and 2 1.5v AA batteries). I have used it a few times, but have never really got it aligned well enough to prevent star trails. Anyway, I just thought I would post as an alternative to the curved rod.
Thanks
Andrew

[RAJAH235]

Steve...
The Telescopic sight fits into 2 machined < grooves in the barrel.
But, it will fit very neatly over a "T" bracket.
I made an Aluminium "T" bracket. (The Al. "T" bar that I had, was offset, as you can see.)

Screwed that on the top board, adjacent to the brass hinges.

Easy peasy.

[rcheshire]

I gave up on visual alignment and developed a drift align procedure. It is fairly straight forward.

As usual, align with TS and set latitude. With the camera pointed in the direction of the area to be imaged, with the live view screen horizontal, take a 10 second image. If the stars are round increase to 20 or 30 seconds and more until drift is evident. Corrections are made in alt and az until drift is eliminated/negligible. You only need to correct up to your maximum exposure time for the night.

This method also corrects for refraction error. Not just for the big boys toys. It works very well once mastered.

[Steve_C]

Ok,

The barn door is coming along. I am playing around with construction methods and processes to get a feel before I make my final unit.

A question I have is, is the perpendicular alignment of the hinge in relation to the longitudinal axis of the arm critical? In my experimental version and with my limited woodworking skills I can get the hinge to within 1 deg of perpindicular to the longitudinal axis of both arms of a single arm design. I can get the threaded rod arm to the correct distance from the centre of the hinge without a problem, am I making myself clear here? I plan on using arms of about 19mm x 100mm.

My motor will be 12VDC, speed controlled with a PWM controller.

TIA

Steve

[OzEclipse]

Steve,
The errors I worked out for you in an earlier post apply here.



If it isn't quite perpendicular a 1 deg error shouldn't displace the thread by 1mm so it will be less than the error quoted above

Cheers

Joe

[Steve_C]

An update on my project. I fiinally received the 2rpm motor from China, it does 2 1/2 revs/min on a fully charged 12v battery. I have decided to change the gearing to 1:1 to give me a bit more speed control a pwm controller. I also figured out a way to ensure the mount from the bottom arm to the tripod was very strong, a 1/4" t-nut held in place by a short 1/4" bolt that allowed enough thread left in the t-nut for the tripod screw.

I'll post some photos when complete, if we ever get some clear skies in Sydney again I can run some photo tests!

Regards,

Steve

[Steve_C]

Hi all, not sure whether to post this here or start a new thread, but as it is barn door related............

I have come across a method of aligning a finder scope on my BD to the hinge, by looking at a fixed object, moving the top plate and seeing if the object moves in the finder. Would someone please explain why this works?

It seems to me that moving the top plate would cause the fixed object to move out of view. What am I missing?

Steve

[OzEclipse]

If the optical axis of the finder and the rotational axis of the platform are parallel. For a distant object they are both pointing at the same point.
However, when viewing a nearby object with the finder, parallax will make the object leave the field.

Many years ago, I had an old mount that couldn't have a polar finder attached, solid 2" shaft. I tried attaching it to the outside of the shaft housing but the mount was so heavy, If I bumped anything, I lost alignment.

So I used to set up an 80mm shorty refractor on the telescope and during daylight, point it at a distant object and line up the mount with the scope by rotating the polar axis. Worked a treat.

[Steve_C]

Further update, BD is now complete. Images attached.

The left switch is power, the other switch is motor direction (not really needed). Red leds indicate motor direction green led power on. Powered by 8 AA cells. So far everything looks good, the BD top arm moves approx 0.25 deg /min which is correct, still need to fine tune that. The motor and gearing do not stall with a camera and heavy lens attached, so that is good.

Now all I need is some clear skies to test.

[Steve_C]

Is it worth adding a finder scope to my BD, especially as down under we don't have a star to align it with?

Or should I stick with my digital compass/protractor to align, then use drift align.

TIA

Steve

[ZeroID]

A simple sight tube might help in getting the first 'eyeball' alignment going.
If you are going to be using somewhere consistently like your backyard you could do a solar noon & plumb bob line on the ground. That will give you a good Nth/Sth line to start with. Probably accurate enough for widefield. I find the digital compasses on phones\tablets can be somewhat inaccurate.
Another method is to get onto Google Earth and zoom in on your site beforehand and then look for a horizon landmark as a reference point either due Sth of it or offset by some measurable amount. I used this first at home to set a line on the driveway for repeated use.
A proper hiking compass can then let you establish a pretty good Nth/Sth line using it as a protractor.
The inclinometer applications on tablets and phones seems to work quite well as long as the phone has a good straight edge to sit on.
Hey Presto SCP !!

[Steve_C]

Thanks.

I will be working in different locations, but I do have a proper hiking compass and a good inclinometer app.

Steve