Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Inexpensive Digital Altitude and Azimuth for Dob Solutions

  • Please log in to reply
16 replies to this topic

#1 skitron

skitron

    Sputnik

  • -----
  • topic starter
  • Posts: 44
  • Joined: 18 Oct 2019

Posted 14 November 2019 - 11:17 PM

For altitude, this one on Amazon (as well as a bunch of different branded, two button, two AAA cell, white graphics on black) is low priced and very suitable. The white graphics are active, meaning they do emit light which is a good thing when you turn them red with standard photographic flash gels (i.e. plastic sheets) like these. Just double the gel to darken if needed.

 

Accuracy is very good with my copy and lol the graphics even includes a quadrant indicator that looks just like a dob! Magnet is plenty strong. Auto-off works great if left motionless. Great battery life. You can probably find the same stuff on EBAY direct from China for about half the price....

 

For azimuth I found this Android app and loaded it on an older phone no longer used for calling. The compass in this app has excellent damping characteristics making it particularly suitable, while others I tried were not damped and super jittery, virtually impossible to use. I just lay the phone on the dob base against one of the uprights and get instant proper orientation of the compass with the scope tube. Again, use some red gel (plastic sheet) material to make it night ready. I contacted the dev and asked for a red, large font heading data screen, maybe they add it. Play Store also has all sorts of bubble level apps if you need to ensure the base is level.

 

Note that you can get a single large sheet of red gel for more $$ if you have several things to cover (like flashlight lenses) or want to share.

 

 

 

 


Edited by skitron, 14 November 2019 - 11:27 PM.

  • Frank.Z likes this

#2 junomike

junomike

    Hubble

  • *****
  • Moderators
  • Posts: 17269
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 15 November 2019 - 07:18 AM

IME the GPS (i.e. Az) isn't accurate to fins anything one couldn't estimate on your own.

Setting Circles is the easiest (and probably cheapest) route.



#3 skitron

skitron

    Sputnik

  • -----
  • topic starter
  • Posts: 44
  • Joined: 18 Oct 2019

Posted 15 November 2019 - 11:57 PM

IME the GPS (i.e. Az) isn't accurate to fins anything one couldn't estimate on your own.

Setting Circles is the easiest (and probably cheapest) route.

My initial test for azimuth seemed fine, but trying tonight was not good, very unstable, so degree circle it is. The angle finder for altitude works perfectly.



#4 clearwaterdave

clearwaterdave

    Skylab

  • ****-
  • Posts: 4100
  • Joined: 27 May 2014
  • Loc: Western Maine

Posted 16 November 2019 - 01:26 AM

You can diy.,these work very well and cost very little to make.,

Attached Thumbnails

  • 20180825_172109.jpg.jpg
  • 20140116_152851.jpg.jpg.jpg

  • Joe1950 likes this

#5 skitron

skitron

    Sputnik

  • -----
  • topic starter
  • Posts: 44
  • Joined: 18 Oct 2019

Posted 16 November 2019 - 12:42 PM

You can diy.,these work very well and cost very little to make.,

I found the thread about printing degree circles, got the file to print, and will do that. Fortunately I have some self adhesive plastic sheets that are laser printable and water proof that I can use, though they will have to be done as four segments and pieced together.

 

The reason I was trying to find an alternative is that on my XT8 the lower platter is more triangular in shape as opposed to round. That means the degree circle has to go on the top platter and the pointer must mount on one of the corners of the triangular lower platter. This means that the pointer, relative to the tube, "moves" when sweeping azimuth, as opposed to seeing a window (or pointer in your setup) that is fixed relative to the tube, and changing degrees displayed while sweeping azimuth...

 

Also, I found some position based digital protractors on Amazon that appear to have the needed accuracy and if they do, I have a scheme in mind to mount them and allow for easy display. I'll post more here when I try it out.


  • clearwaterdave and Joe1950 like this

#6 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 15908
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 18 November 2019 - 08:49 AM

I'm inclined to get one. Rim_Shot.gif


  • Joe1950 and lakland5 like this

#7 Sky_LO

Sky_LO

    Explorer 1

  • -----
  • Posts: 80
  • Joined: 22 Dec 2018
  • Loc: Oregon USA

Posted 18 November 2019 - 02:25 PM

The reason I was trying to find an alternative is that on my XT8 the lower platter is more triangular in shape as opposed to round. That means the degree circle has to go on the top platter and the pointer must mount on one of the corners of the triangular lower platter. This means that the pointer, relative to the tube, "moves" when sweeping azimuth, as opposed to seeing a window (or pointer in your setup) that is fixed relative to the tube, and changing degrees displayed while sweeping azimuth..."

 

The easy peasy alternative setup for the XT8 - given the triangular part....is to mount the setting circle atop the central nut

INSIDE the dob base.   I used an old saw blade (with the az setting circle on thin cardboard over that) placed over the central nut and a heavy rubber washer to hold it in place.   Then glue something to the side as a pointer.    

 

To align you simply point the OTA of the scope to Polaris, then adjust the center disc until your pointer says zero / north.  The rubber washer holds the saw blade disc steady, but allows you to move it for alignment.  

 

The advantage is a fast/ easy setup.   The slight disadvantage in using it is you have to use your red flashlight to look down inside the dob base while turning the scope to set the AZ direction.       Really works well and is a fast easy setup.  

 

I got very good at the alt/ az finding method and like it a lot.   

I have since upgraded to the xt 10i

 

-Lauren 


Edited by Sky_LO, 18 November 2019 - 02:33 PM.


#8 skitron

skitron

    Sputnik

  • -----
  • topic starter
  • Posts: 44
  • Joined: 18 Oct 2019

Posted 18 November 2019 - 11:47 PM

The easy peasy alternative setup for the XT8 - given the triangular part....is to mount the setting circle atop the central nut

INSIDE the dob base.   I used an old saw blade (with the az setting circle on thin cardboard over that) placed over the central nut and a heavy rubber washer to hold it in place.   Then glue something to the side as a pointer. 

I have a digital protractor coming tomorrow, and plan on doing something very similar with respect to mounting on the center bolt. Plus if it works, cut a viewing port in the dob upright on the eyepiece side, and maybe mount a red led in there with a switch to light it since the readout is not lit.


  • Sky_LO likes this

#9 clearwaterdave

clearwaterdave

    Skylab

  • ****-
  • Posts: 4100
  • Joined: 27 May 2014
  • Loc: Western Maine

Posted 19 November 2019 - 07:59 AM

I would put a backing on your circle so it can go in between the bases.,If you make it so one or the other.,( the circle or the pointer) or both can be adjusted it makes it easy to get aligned.,good luck.,



#10 mic1970

mic1970

    Viking 1

  • -----
  • Posts: 903
  • Joined: 09 Aug 2018
  • Loc: St. Louis Metro Area

Posted 19 November 2019 - 08:27 AM

Do you happen to have a pic of your old setup?

The reason I was trying to find an alternative is that on my XT8 the lower platter is more triangular in shape as opposed to round. That means the degree circle has to go on the top platter and the pointer must mount on one of the corners of the triangular lower platter. This means that the pointer, relative to the tube, "moves" when sweeping azimuth, as opposed to seeing a window (or pointer in your setup) that is fixed relative to the tube, and changing degrees displayed while sweeping azimuth..."

 

The easy peasy alternative setup for the XT8 - given the triangular part....is to mount the setting circle atop the central nut

INSIDE the dob base.   I used an old saw blade (with the az setting circle on thin cardboard over that) placed over the central nut and a heavy rubber washer to hold it in place.   Then glue something to the side as a pointer.    

 

To align you simply point the OTA of the scope to Polaris, then adjust the center disc until your pointer says zero / north.  The rubber washer holds the saw blade disc steady, but allows you to move it for alignment.  

 

The advantage is a fast/ easy setup.   The slight disadvantage in using it is you have to use your red flashlight to look down inside the dob base while turning the scope to set the AZ direction.       Really works well and is a fast easy setup.  

 

I got very good at the alt/ az finding method and like it a lot.   

I have since upgraded to the xt 10i

 

-Lauren 

 



#11 Sky_LO

Sky_LO

    Explorer 1

  • -----
  • Posts: 80
  • Joined: 22 Dec 2018
  • Loc: Oregon USA

Posted 19 November 2019 - 01:43 PM

Here is a photo.  

 

It's an easier approach for sure. 

Put the setting circle on the inside of the dob base rather than around the outside.

 

Use the largest setting circle you can get, the bigger the more accurate. 

The setting circle I used just barely cleared the 3 walls inside the Dob base. 

 

I glued a brass fastener to the side wall of the dob base as the pointer.

The pointer moves around the setting circle as the scope is turned.

 

The setting circle on the central bolt stays stationary aligned with polaris

The rubber washer holds the setting circle stable, but allows it to be moved for alignment

 

It is easy to peek inside to see the setting. 

I did not consider cutting a view hole into the side of the Dob Base.

 

-Lauren

Attached Thumbnails

  • IMG_1465.JPG

Edited by Sky_LO, 19 November 2019 - 01:52 PM.

  • Joe1950 likes this

#12 skitron

skitron

    Sputnik

  • -----
  • topic starter
  • Posts: 44
  • Joined: 18 Oct 2019

Posted 26 November 2019 - 04:08 PM

Success on the digital azimuth for under $20 total. Below is information how to do it on an Orion XT8. The general idea should be adaptable to many DOBs. I did it in a way to make it as accessible to as many DIYers as possible, and getting repeatable measurements within .06 degrees!

 

I started with this plastic rule digital protractor.  I chose a plastic ruled one as opposed to stainless because the plastic is easily cut with tin snips or heavy scissors. I cut the upper rule (the one the measuring module attaches to) on the 60mm mark. The lower rule cut much shorter on the 230mm mark. Neither measurement is critical and can be off a few mm.

 

A bit about the protractor. I disassembled mine in order to see if the module can be used by itself by simply unscrewing the rules from it. It turns out that this is not possible because the lower rule has a copper encoding circle printed on it, and the upper rule serves as the bottom cover of the encoder module. But all of this plays into making this project super simple since the solution is simply cut the rules to the desired length and be done with it.

 

Next I removed the center locking knob, which when unscrewed, exposes the threaded brass hub of the device. I used a 1/8" drill (which does not cut the threads) to drill through the lower rule so the device center axis is clearly identifiable looking at the back of the device. I covered the opening where the knob screwed in with a piece of tape since it provides better sealing and protection.

 

Then I used a bit of JB Weld epoxy to glue a metric 10x1.5 nut to the bottom of the device, centered over the hole drilled above. You want to get the hole in the nut as concentric as possible with the drilled hole, but if its slightly off, its no problem.

 

After the epoxy set for 24hrs I threaded a second nut onto the protruding axle bolt of the XT8 base (after adjusting the plasti-nut for the correct platter tension). This nut will serve as a lock nut for the protractor/epoxied nut assembly.

 

Next, I flipped the DOB base upside down and rotated the triangular lower base in order to thread the protractor/epoxied nut assembly into place. Then flipped it back over, and secured it in place with the lock nut.

 

Note that if you cut the upper rule a bit shorter so it can clear the side uprights of the DOB base while threading the protractor in place, you don't have to flip the base. I would cut it shorter to avoid this hassle if I ever do this project again.

 

The final part is to secure the upper rule from rotating. For this I used a couple of right angle braces from the deck building hardware section of Home Depot. Just screw them in place with a couple of #10 x 1/2" pan head screws. Make sure there is no side to side slop between the braces and the rule. I chose this method to allow for the slop in the axle of the stock DOB base to not stress the module. Plus if your epoxy nut is a bit off center, this method will accommodate that as well.

 

Note that its a good idea to mark the drill with some tape at a little less than a 1/2" so you can avoid drilling all the way through the base when drilling the holes for the #10 x 1/2" screws to secure the brackets.

 

Super easy project for very little $ that gives great results. That said, if you already have a degree wheel installed, this is probably not worth retrofitting, but is instead an alternative to the degree wheel for people looking to add an azimuth locator.

 

Pros:

 

1) Easy to build and install.

 

1) Very accurate, and easy to situate in the field. Simply sight in the North Star and press the zero button.

 

Cons:

 

1) After zeroing, must always rotate the scope CW to get the correct degree readings (the protractor starts at zero and increments numerically upward no matter which rotational direction, and will also continue to increment past 360 degrees if continuing past one revolution).

 

2) The auto-off feature cannot be disabled. This means the device will likely shut off at some point, and must be re-zeroed. The work around is to place a piece of tape across the upper and lower platter when sighting the North Star. Then slice it between the platters so they can move freely. This creates a reference of the North Star until the telescope is moved, and simply lining up the tape marks and pressing the zero button again is all that is needed if the auto-off comes into play.

 

In practice, the cons are worth it to me to have the luxury of simply sighting in the North Star and pressing the zero button and being good to go.

 

These photos are pretty bad, but you can get the idea. I'll try to take some better ones and repost....

 

gallery_318587_12204_744337.jpg

 

gallery_318587_12204_236338.jpg

 

This shows the locking nut and the scope tube clearance:

 

gallery_318587_12204_268813.jpg

 

...and a pic of the reference tape to be placed while sighting the North Star. Just align these marks and re-zero the protractor if the auto-off gets you:

 

gallery_318587_12204_514902.jpg


Edited by skitron, 26 November 2019 - 04:55 PM.

  • clearwaterdave and Joe1950 like this

#13 clearwaterdave

clearwaterdave

    Skylab

  • ****-
  • Posts: 4100
  • Joined: 27 May 2014
  • Loc: Western Maine

Posted 27 November 2019 - 08:29 AM

If that works in the field that is pretty cool beans.,My biggest concern to start with is in the devise itself.,is it going to last.,will it work in the cold.,how easy will it be to read with the scope mounted.,

  I hope it does pass the field test cause it is a great idea.,waytogo.gif waytogo.gif



#14 skitron

skitron

    Sputnik

  • -----
  • topic starter
  • Posts: 44
  • Joined: 18 Oct 2019

Posted 27 November 2019 - 07:07 PM

If that works in the field that is pretty cool beans.,My biggest concern to start with is in the devise itself.,is it going to last.,will it work in the cold.,how easy will it be to read with the scope mounted.,

  I hope it does pass the field test cause it is a great idea.,waytogo.gif waytogo.gif

Easy to read with the scope tube in place except when about 85 degrees or more vertical, or when about 15 or lower. In that case the tube needs to be moved a bit and azimuth located, then locate alt.

 

As for longevity of the device, it should be decent as long as it doesn't get soaked. I disassembled it and it is not a capacitive sensor like found in a digital caliper, which is a good thing. It has a printed copper encoder circle, which should lend to reliability, but only time will tell. It is very accurate and repeatable for now anyway.

 

Temp is spec'd at 0-50 C, so might be a problem for those who brave the cold, but in practice it will probably operate fine for teens F and up. I live in Houston, so cold not so much an issue here.


  • clearwaterdave likes this

#15 Sky_LO

Sky_LO

    Explorer 1

  • -----
  • Posts: 80
  • Joined: 22 Dec 2018
  • Loc: Oregon USA

Posted 29 November 2019 - 01:17 PM

very slick !



#16 junomike

junomike

    Hubble

  • *****
  • Moderators
  • Posts: 17269
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 30 November 2019 - 08:11 AM

This one here looks to work in either direction.



#17 Beeham

Beeham

    Lift Off

  • -----
  • Posts: 12
  • Joined: 08 Nov 2019

Posted 30 November 2019 - 09:44 AM

Here's an alternative, for a non-digital solution.

 

Cut a large circle out of plywood, and attach some feet to the bottom so that it won't contact the ground directly and get wet.  I like rubber hockey pucks for this use.  Call this board the "secondary ground board".

 

Use a router to cut a circular channel around it's top surface, maybe 1/4" inch in from the edge, about 1/8" deep.

 

Counterbore three holes in the top surface that match the rubber feet on your stock XT8 base.  You can now set the telescope on top of the secondary ground board in a constrained location.

 

Cut a ring out of sheet plastic, FRP panel, masonite, etc. that matches the dimensions of the groove in the secondary ground board.  The ring should be able to rotate in the groove.  Mark the ring off in degree increments.

 

Now all you need to do is put a pointer on the rotating portion of your XT8.  Align to a known star, rotate the ring so that it lines up correctly with the pointer, and you're good to go!  I did this on my base (although mine is on the ground board, without adding a secondary ground board, but I'm not using the stock XT8 base).  With a 24" ring, the degree increments end up about 1/4" apart, so it's very easy to eyeball fractional-degree positioning.

 

It looks like this when complete:

 

Azimuth Ring

  • clearwaterdave likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics