Star-tracking camera mount: Why it works and how to build one

In this video, I explain (using a bunch of timelapses) why "polar tracker" or "star tracker" camera mounts allow you to take long exposures of the sky without streaking. I also show off my polar tracking rig, which is my most recent piece of homebuilt photography equiment. It uses a door hinge and a curved lead screw to slowly rotate the camera (approximately 0.25 degrees per minute) and eliminate streaking in astrophotogrphy images.
Based on the design by Gary Seronik:
garyseronik.com/build-a-hinge-...
My parts:
Motor: www.amazon.com/gp/product/B00...
Gears: www.amazon.com/gp/product/B00...
Battery: www.amazon.com/gp/product/B00...
lead screw: #8 threaded rod from Home Depot
Hinge: 8"x8" strap hinge from Home Depot
Controller: LM317 configured as voltage source
Any USB battery will work - this is just the one I have for my phone.
If I re-built the design now I would probably print or lasercut the two necessary gears to save money and have more customizability.
Music in this video:
I dunno by grapes, is licensed under a Creative Commons: Attribution License (creativecommons.org/licenses/...)
Source: ccmixter.org/files/grapes/16626

[@luukdeboer1974]

The animation of your barndoor tracker hinge aligned with Polaris shown by that red line was particularly helpful and brilliantly done. Couldn't get my head around that by just reading alone until I saw that animation 👍. The confusing point for me was that we're making a circle around the poles with a certain radius depending on your location on the globe. Theoretically that means that we're also shifting (circular) relative to the sky on a plane perpendicular to the earth's axis. But that's negligible of course on astronomical scale 🙃

[@ronkrzyzewski8072]

take the infrared filter out of your camera and you'll pick up nebulosity way better. It's blocking the reds

[@controlerg]

Fantastic job! Not on just the tracker motor and design... but also the tutorial! Thank you for the genius tip.

[@mj12345671000]

One of the simplest and best explanation I have seen along with very cool build!

[@sharpnr445]

It's amazing that you can shoot multiple shots of the same image (if that's what stacking is) and "register" your system to exactly the same position and angle without loosing sharp edge resolution. Well done!

[@robertYTB78g]

Awesome explanation of how this works, something I didn't deeply understand until now. Also cannot wait to build one. Thanks for posting.

[@rmf11699]

Simple design that seems to work fantastically!

[@Anonymous-pm7qc]

Awesome build and final resulting pics of the nebulas. The Orion Nebula looks pretty awesome!

[@AlphaPhoenixChannel]

Thanks! Glad you like it!

[@ultrametric9317]

Great job! I was a subscriber to Sky & Telescope when the Seronik platform was published. You don't even need a motor - you can use a cable (to avoid shakes) and turn a screw by hand at a fixed rate.

[@amirk45]

Amazingly clear and concise information. This video answers so many questions about astrophotography! Thank you!

[@cpirius]

Great information, thank you. I appreciate the explanation.

[@justincace5517]

I'm building my own 8" Newtonian telescope. I was searching for ideas on how to make an equatorial mount. Tada.... Thanks a LOT for the barn door hinge idea! Your name is going on the finished product.

[@explorelearnshare8222]

I'm impressed with your result! Especially at that focal length. FWIW, I can just make out the horse head in your pic. Also impressive as your DSLR's IR cut filter is working against you there. Pretty awesome, and I'm sure satisfying, to be able to accomplish this with a homebuilt rig! Well done! Recently found your channel and have been enjoying your content and especially your enthusiasm...thank you!

[@alexsilva-mz8fe]

awesome design loved it!

[@nikoligogle3153]

Now that is quality content! 🔭

[@robertpendergast2620]

VERY good presentation

[@AstroLaVista]

Excellent video!

[@ixamraxi]

Seems like an elegant solution thats ripe for improvements and modifications. :D

[@JerHetrick]

Very impressive, Im now in the process of disassembling an old vinyl cutter for the stepper motor and possibly even the board. I may be able to use that to control the feed

[@AlphaPhoenixChannel]

Thanks- glad you like it! And yeah, with a stepper motor hard-coded to a specific speed you can get awesome precision - it'd be a lot easier to tune with a keyboard than my screwdriver-and-trimpot method... There's someone I know that actually just finished a barn door with a stepper so I know it works!

[@citylimitsphoto]

Hi Brian. Great video. Can you please update your list of suppliers and parts of the equipment you used to build this. Two of the Amazon links are dead.

[@SarbjitSingh-ed1el]

Fantastic Job

[@GS-hg9cl]

Gut gemacht. Einfach, erschwinglich, funktioniert 👍🏻

[@NickMoore]

Great build! Using USB is a good idea, I have started using 5v as often as possible. Do you have a way to quickly rewind when you get to the end of the rod?

[@AlphaPhoenixChannel]

+Nick Moore I just lift the hinge so the gears unmesh and spin it back by hand... any back-driven-motor solution would have been a serious pain, and I wanted to keep as few components in the circuit as possible (as you can see by my abuse of that LM317 with only a single trimmer attached) So yeah, I cheat and do it manually!

[@NickMoore]

Nothing wrong with keeping it simple. Thanks for putting this together!

[@tomasdahuabe]

I think it would be useful to attach one of those cheap green astronomical laser pointers parallel to the axis of the hinge to make it easier to point it to Polaris

[@keteperez6512]

Muchas gracias, acabo de sacar buenas ideas de tu trabajo.

[@nicolapiubel]

Great build, where do you have bought the motor and the gears?

[@blakenancarrow5239]

I really enjoyed your barn door video. I particularly like your annotations for Polaris. Well done. Heh. Meta. A time-lapse of a time-lapse. :-D

[@AdrianGonzalezBlogs]

Thanks so much, very usefull information!

[@AlphaPhoenixChannel]

+Adrian Gonzalez glad it was informative!

[@stgogarcia]

Gracias por compartir tu conocimiento! Es muy valioso

[@maximus7947]

Formula for f=speed of Motor in revolutions per minute: r1 = hinge radius r2 = big wheel radius r3 = small wheel radius Z = the amount of spins you need to travel 1m on your lead screw. You can just count the notches per 10cm and multiply it by 10. (r1*r2*Z)/(r3*1440*π)=f

[@utubevind]

It depends on the number of teeth on gear (gear ratio). Going by radius would be wrong. But your approach is right !

[@thepolymathedu]

@@utubevind how would you compensate for the gear ratio?

[@paolobottari6672]

@AlphaPhoenix This is a very nice video for POLARE. Thank you again! 💪🏻 Before I didn't understand how polar works. 👌🏻

[@sebastiandelamaza8440]

dude you are smart as hell, great video

[@tharukasiriwardana4612]

Thank you very much !! 👍👍

[@jbflores01]

you're a genius! Plain an simple!

[@gsegallis]

I don't care about the video, your logo animation is awesome!!! :-)

[@Joshua.26]

Thank you so much. I like the video

[@Bolydark]

do you take dark frames and flat and bias??? this will improve your stacking

[@mm-tm4qt]

Very good

[@shivamnegi7149]

great contraption. Is it available for sale?

[@alphaphotoandvideo]

Have you tried the one made by omegon it is like $130

[@subhadeepreaditassubhodeep6161]

Kudos to you DIY people

[@raymondzhao9557]

pretty interesting

[@alisaandra05]

awesome

[@alphaphotoandvideo]

Ur good with tools👍

[@deangawler9727]

I haven't checked your other videos yet, but did you come back and re-shoot the Orion Nebula and the Horse Head Nebula? Good results from a simple setup!

[@AlphaPhoenixChannel]

Unfortunately I have not yet. I was going to this Orion season with a 100mm refractor but it has yet to arrive what with covid and international shipping...

[@scottwilliams895]

Excellent video! I'm looking to build a DIY open source astrophotography camera tracker, and look who has a video on that very subject... @AlphaPhoenix FTW!

[@_P.K.]

Super.. Can we buy the barndoors with motor?

[@bobharris7458]

I thought I'd give this build a try. Unfortunately, the link to the motor Amazon shows currently unavailable. What alternative motor do you recommend? Thanks!

[@billkaroly]

Would you be willing to update the parts listings in the description? Mainly the motor you used.

[@hemamapari8887]

Does the rate at which the hinge rotates depend on the length of the arm of the hinge from the joint to the thread rod?

[@uppermech7153]

So, is it possible to get precise speed control with DC motor and LM317?

[@whereswa11y]

Very nice idea. I will make one, I might just add a ESP8266 for wifi control of on/off/speed.

[@kevhatch1252]

Does it matter what size hinge or where the holes go for the pivot rod? I thought there was some formula needed for distance from hinge to the pivot rod.

[@AlphaPhoenixChannel]

+Kev Hatchett yes the distance from the pivot to the center of the hinge will change how fast the upper hinge tilts, but because I was adjusting my motor speed by hand with an analog trimpot, getting distances perfect didn't matter - I picked up the slop when I tuned the speed. That process itself isn't fun - I stood outside with my at-the-time longest lens and took minute or two minute exposures, looking for streaks, and would very slightly adjust the trimpot between tests until I got the streaks as short as possible.

[@SackyX]

Too bad those parts are not around on some of the links, I really need a star tracker. Any suggestions on sourcing the parts again would be great! Thanks in advance.

[@janbaranovski4850]

Well mate. Subscribed after 3 minutes )

[@AlphaPhoenixChannel]

Thanks! Glad you liked it!

[@troypointerphotography]

Troy great video anyway exactly how did you edit them in the right room group because obviously you need exposure night photography so stop blurring in the video

[@ben1969350able]

If that works you could use a 12v liner actuator and larger hinge to lift a heavier telescope and camera assembly.

[@pinakoza]

Very nice & informative video. My Hinge mount is almost ready, but I have a question. I see that you have used 15 RPM motor that requires 12 volts (as per your link to motor on amazon), but you are running on 5 volts USB pack further reduced to around 2.5 volts (as you mentioned in video)! So my questions are: 1. Will such a low voltage (2.5 volts) still run 12 volt rated motor? Is there any extra benefit of such setup? 2. What gear ratio you have used, and what is the final RPM of shaft (rod) itself? 1 RPM?? 3. Can I use motor rated at 3 volts with 4 RPM, and reduced to 1 RPM using 40 teeth and 10 teeth gears? I will highly appreciate if you reply my questions, please. Last but not least, many thanks for sharing :-)

[@AlphaPhoenixChannel]

dc motors are pretty much linear until you get to very low voltages, so running a 12vmotor at 6v would make it go about half as fast as the rating. I just went to go count teeth, and my (plastic gear) ratio is 2:5. The threaded rod I used is 8x32 so it moves 1 inch for every 32 rotations of the big gear. As for your last question, I see no reason that wouldn't work with the same 5v->lm317 setup, as long as you never feed the motor more voltage than it's peak rating (as in, don't plug a 3v motor straight into the 5v supply and expect no damage). The last important value you didn't list is the distance between the hinge axis and the threaded rod you're pushing. As long as you leave yourself some variability in speed, you should be able to tune in what you need!

[@pinakoza]

Thank you so much for detailed answer :-). I have used the hinge that has 182mm distance from axis to center of rod. I still need to do some calculations to select proper gears (from those available on amazon). You cleared my doubts on selecting motor :-)

[@fotogmike303]

is there a break down or parts list of what you used to make this or do u have video up of you making this racker?

[@AlphaPhoenixChannel]

I kinda threw this together in a hurry (to take to an event at Joshua Tree where it ended up being cloudy...) so There was never a cohesive design or time to film it. However I added a parts list to the description so I hope that helps! Most can be substituted for similar items - the only thing you have to be careful of is that the motor is capable of spinning slow enough to rotate with the speed of earth after passing through the gear reduction and the lead-screw reduction.

[@aerosoulzx]

I wouldn't mind a full parts list too. I can see the obvious items like the motor, etc, but no listing for some of the bits like the pot. Also, does anyone have an exhaustive build guide, please? :)

[@spook_dad]

I’m struggling to find an 8/32 threaded nut is there another size I can use and would I then need to run the motor at a different speed to account for the different number and f threads with in the nut?

[@christianbenoit2519]

Me too, cannot find that specific rod. Is a #8 threaded rod same as a 3/8 or 5/8 ?

[@gp414]

Would this track the moon properly as well? I'd like to do photos and video of the moon. Cheers.

[@AlphaPhoenixChannel]

Yes it does! the moon actually moves at a slightly different apparent speed than the stars, but over the course of one picture, it's not noticeable (certainly within the precision of this janky mounting). Normally, however, the moon is so bright I can actually take pictures of it handheld - no need for long exposures. A while back when there was an eclipse and the moon was really faint, I did use this mount and had pretty good results!

[@gp414]

Ok, thanks.

[@hozefadaginawala4838]

Hey, does the barndoor work well for telephoto lens' also?

[@AlphaPhoenixChannel]

Yeah the Orion shot was with a 210x1.5

[@chavakano54]

Hi, question, the Amazon gear kit has 5 gears, it's hard to see which pair you used T50, T40, T30, T20 or T10, can you let us know please, so far the circuit is working on a breadboard.... thanks !!!

[@AlphaPhoenixChannel]

I’m not sure which set of gears you’ll need - it depends on the threaded rod you use and the motor rpm

[@eduardoteodoro1135]

I didn't understand why you used a startracker to get a shot with 30" exposure with 12mm and 1600 ISO (500/18=27" exposure maximum without stars trails). Would make more sense to make a 9 minutes exposure with 100 ISO mounted on star tracker to get the same amount of light with less grainy.

[@SharkonLp]

You could also do that, but the fact that you would just take a single exposure would increase the chance of hotpixels. At least that's what I think, I'm no expert by any means :D

[@Utilisateurpasvalide]

I think the amount of total pictures you can take with that long to take just one with make it worst in the end.. a lot less data to work with in post imo

[@aBoogivogi]

It depends on the pixel error rate of the camera. if it's an isoinvariant camera then your statement might be true. However many cameras are not isoinvariant ones and even those that claim to be typically has a lower error rate at slightly higher ISO values. Hence stacking frames with fewer errors might give you far better results as opposed to taking one long exposure. It also lets you cut any images with outright issues prior to stacking as opposed to noticing after the fact that several of your long exposure shots are worthless.

[@Caboose301]

Has anyone been able to find the motor used above? Link no longer works

[@manasgadkari7883]

whats the rpm of the motor and how many teeth for each gear please help

[@1.4142]

I just discovered astrophotography but fall is when everything exciting happens- meteor showers, milky way, etc.

[@rushel4104]

At which rpm were u running the motor?

[@joranvancoillie8133]

Does it matter where you position the ball join for your camera on the top plate of the tracker or can you place it anywhere you want since the top plate moves at a constant rate?

[@AlphaPhoenixChannel]

Anywhere on top works where you think Itl balance - the angle is really all that matters

[@joranvancoillie8133]

@@AlphaPhoenixChannel Thank you so much!

[@Harish-gu3ym]

What the rotation speed should be ?

[@AlphaPhoenixChannel]

4 degrees per minute

[@Gruxxan]

im going to try to make one of these 😀 actually 2

[@albadegr8593]

"Hinge: 8"x8" strap hinge" what do you mean by this? do you mean each arm of the hinge is 8 inches long?

[@albadegr8593]

or did you mean the whole hinge is 8 inches long, TIA

[@KartikeyG]

Good tutorial, but why rush? 😊

[@nickphoto831]

Can you resend the links to the motor, gear, and battery? I opened the amazon links from your description and it says page not found.

[@keithkelly5808]

You will need a 4rpm motor a 64 tooth gear and a 16tooth gear. Run that in a 8-32 or 10-32 threaded rod and voila

[@sampson1582]

you should take the IR filter off the camera. look it up, it's not easy, but you'll get a lot better light from your stellar photography.

[@willdey1]

Thanks for the great video. Although the finite speed of light is a problem for flashing the galaxy (52 secs) the bigger problem is that the amount of energy required to capture a reflection from this flash does not exist on Earth and even if it did, would vaporise the planet and probably our sun too.

[@AlphaPhoenixChannel]

+willdey1 haha absolutely true! That'd be a seriously bright flash.

[@IMCDundee]

You did get the horsehead!

[@dennisrkb]

and ofc polaris is so far away that it doesn't matter whether you're at the north pole or the equator..both lines would basically be parallel correct?

[@AlphaPhoenixChannel]

Yep!

[@AdamH-er2uh]

So did you use the tracker while taking the stacked images? If so, how long was your sub-exposure? If you are using a tracker shouldn't you be able to get a good image without stacking?

[@AlphaPhoenixChannel]

Wind and chunkyness in the threaded rod both can cause unwanted camera motion, so some unfortunate fraction of images get thrown out even when tracking

[@AdamH-er2uh]

@@AlphaPhoenixChannel I see. Thank you for replying to my comment, hoping I can try out some nebula photos for myself soon!

[@michalaugustyniak6449]

So instead of taking one very long exposure picture you dive into hundreds of shorter ones ? How long the exposures should be of the short snapshots ?

[@AlphaPhoenixChannel]

A huge fraction of the snapshots had something wrong with them, like the mount jostled, or there was wind that shook the camera, or there were weird thermals in the sky blurring the image, or a plane or a satellite flew by. There are a lot of ways for pictures to be ruined, and the longer exposures you take, the more you risk catching one of those problems and having to throw it out. A single hour long exposure won’t look as good as 30 1-minute exposures that we’re the BEST 30 minutes from that same hour. The full hours expire gets all the good and all the bad and you can’t remove the bad. You are paying for the ability to only use the best moments in time with storage space and computational might on the stacking side. I would experiment to find the best time. If you reliably get good 2 to 5 minute exposures, awesome! But if most of those are blurry, scale back to 20 or 30 seconds and work your way up. The mount/weather/everything determines the longest exposure you can take.

[@jodomof]

Why don't you make a video of making this great cheap solution?....it would be nice !

[@aaronyeungx]

this can support how many weight?

[@AlphaPhoenixChannel]

I’ve never tested anything beyond my camera, but I assume it would work for any reasonable dslr.

[@aaronyeungx]

AlphaPhoenix thanks my dslr weighed 1.6kg, idk if it can support my dslr

[@vicplasma58]

It would not be better if it went down instead of going up like that it would take less force ?

[@AlphaPhoenixChannel]

You’re right if you “lowered” it at the right speed it’d be less strain on the motor, but you’d be depending on gravity to make the thing fall at a specified rate. It’s likely to get hung up and stick-fall-stick-fall rather than lowering perfectly gradually. By pushing up continuously, I feel like it would eliminate most (but maybe not all) of that behavior because the ridiculously high gear ratio of that lead screw can push past anything getting stuck in the mechanism.

[@fsefso7587]

You didn't make darks and your final picture got very noisy. I also reccomend doing offsets and flats to make your final pictures even better

[@AlphaPhoenixChannel]

I don't remember my exact setup because it was a while back, but If I didn't take standalone dark frames to average together, I certainly would have taken in-camera darks. However I've never gone so far as to do flats and offsets with this camera. Dark frames are good for removing hot pixels that lead to salt and pepper noise, but I think most of the noise in my final image here was just white noise from very little light reaching the sensor ("effectively" averaging over not enough photons)

[@ecoreality7225]

It wasn't clear why your telephoto results were not as good as desired. Mechanical vibration? Speed variation as the centre changed position over the lead screw?

[@AlphaPhoenixChannel]

I think that vibrations (some from the mechanism but mostly wind) and a bad sky were the primary issues. If I remember right I threw out well over half in deep sky stacker.

[@oliverh1]

Yooo I live in SB

[@oliverh1]

Just got into astrophotograpgy

[@L3GiiTMango]

I have been following along with this video attempting to build something similar but ran into a snag. When i run on an external battery pack I get 5 volts for about 30 seconds before I lose power. Its almost like the battery bank I have decided not enough power was being drawn and shuts off. Any ideas how I could fix or work around this?

[@AlphaPhoenixChannel]

If your motor isn’t drawing enough juice and the power pack is too smart for its own good, you could cheat and add a small resistor in parallel in order to draw some extra current?

[@renderuthis]

Oh I thought you would need a stepper motor.

[@AlphaPhoenixChannel]

Really you should - this is very simple

[@renderuthis]

I was going to build the open tracker. I really need to learn more before I start. Now that I see how this works I say "oh!" I'm going to make a big one though I want to use a old Nikon 600 it weighs a ton. I have not tried to stack photos for 10 years, i used a cheap free software. Im excited now as the open tracker looks daunting. I can make the machine but do not know if I can learn to operate it. haha

[@renderuthis]

@@AlphaPhoenixChannel I want to spend a little more time on it. I want a compus and a level as I can not see the north star behind the mountains. I Think a 180 degrees from level sight to level sight would be nice. I have a big lens I want to try so Im thinking a removable adjustable counter weight

[@ihavecojones]

This guy ... this guy is soooo under rated. I can't believe that completely useless imbecils like Mr. Beast or PewDiePie got more traction than AlphaPhoenix or other people like him. Life... is dman cruel, man.

[@southernexposure123]

Wait for thousands of years? Well - that's too long. ((-:

[@renderuthis]

What happened to the normal flu and the normal cold!!??

[@retiche]

You're misguiding you're viewers: you don't make multiple shots to have enough "light", but but you do them because you want to increase the SNR or the signal to noise ratio. That's because real signal is always a positive number, when the noise is just a random number. If you then stack up each pixel, where you have signal the number will increase, and the noise will just cancel out. Also, M42/M43 requires multiple length of exposures because the core of the M42 is extremely bright and will burn our the core unless you do a HDR

[@friedaspyder8485]

You're funny...

[@Martinko_Pcik]

Nice ghetto star tracker. But didn't you overcomplicate it ? With 55mm lens you should be fine with up to 20sec exposures even with a static tripod. Stacking software will then align your set of 100 slightly rotated pictures. I don't think your hinge helped you much in getting those pictures.

[@AlphaPhoenixChannel]

It makes quite a difference - it’s also a lot easier to take a series to stack later if you don’t need to keep aiming

[@davidplush7960]

And if you live in a hemisphere without a North Star...

[@AlphaPhoenixChannel]

Haha it’s still completely possible, just harder to line up

[@dugy40]

Hi my freind. I live in Oklahoma. Would you be interested in making me a tracker? I own a ball head. I can tell you’re a good person so I trust you. I can PayPal you money. Please consider it. Thank you. Doug.