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Equipment Discussions >> Equipment

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Fireball
professor emeritus


Reged: 03/24/06

Re: Degree Circles new [Re: rnabholz]
      #940000 - 05/03/06 05:21 PM

Quote:

Carol,

Imagine a piece of thin steel - the steel strapping used on lumber or pallets would work great. You simply attach, say, 6 inches of that to the edge of your groundboard with a couple of screws.

Then attach your pointer to a small magnet, and stick it to the center of the steel strip.

When you need to tweak your calibration you simply slide the pointer along this strip of steel strapping until it matches the computer's azimuth setting and you are good to go.

Let me know if that is clear as mud and I will try again.

Rod




Sounds interesting and simple.
Is it possible to show a picture of this set-up ?
That would make everything very clear.
Thanks !


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csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: Degree Circles new [Re: Fireball]
      #940013 - 05/03/06 05:37 PM

Fireball: Go to top of this post, my first picture.
On the outer side edge of the lower circular base, the metal strip will be affixed there, completely around the base; then where the pointer is,(screwed in), I now will have the pointer glued to a small magnet that I can now move anywhere on the degree circle, to get set up.
Carol


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csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: Degree Circles new [Re: SkyArcher]
      #940019 - 05/03/06 05:43 PM

Ron: Just downloaded trial PC version, & am ordering PC & PDA version. This is a great program, just what I was looking for. Now, I'm going to try to find a good price on the Axim. Again, thanks for all your help, couldn't have done it without your kindness & expertise!
Carol


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Curt B
sage
*****

Reged: 08/02/05

Loc: Regina, Canada
Re: Degree Circles new [Re: csa/montana]
      #940116 - 05/03/06 06:52 PM

Here is the link for Pleiadatlas

http://astro.isi.edu/pleiadatlas/

and Planetarium

http://www.aho.ch/pilotplanets/

Edited by Curt B (05/03/06 06:53 PM)


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rnabholz
scholastic sledgehammer
*****

Reged: 07/25/04

Loc: Iowa
Re: Degree Circles new [Re: csa/montana]
      #940389 - 05/03/06 09:59 PM

Carol,

Of course the call is yours to make, but if it were me, I wouldn't bother to make the strip go all the way around.

6-12" of strapping would give you around 30 to 45 degrees of adjustment, plenty for even a casual initial polar alignment.

Just another two cents - making my total to date $3.08.............Sorry.


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csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: Degree Circles new [Re: rnabholz]
      #940401 - 05/03/06 10:19 PM

Rod: Again, thanks! Didn't realize this. It will save me a lot of work. Can tell I'm an amateur at this, huh? I've got the "0" degree mark on the left side, so a short strip running each way of this would be good?
Carol (p.s. you have a credit of many thousands of $, so I can pick your brain a lot, at 2cents a question, I'm gonna keep you verrrry busy!)


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rnabholz
scholastic sledgehammer
*****

Reged: 07/25/04

Loc: Iowa
Re: Degree Circles new [Re: csa/montana]
      #940454 - 05/03/06 11:07 PM

Exactly, just a few inches on both sides of zero will do the trick.

Glad to help.


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AtLarge
super member


Reged: 08/22/05

Loc: 868 Ft. Above Sea Level
Re: Degree Circles new [Re: rnabholz]
      #943553 - 05/06/06 12:51 AM

Quote:

Exactly, just a few inches on both sides of zero will do the trick.

Glad to help.




This is very informative but let me make sure I have this straight.

The pointer is on the bottom base.
The pointer is aligned with Polaris and the base leveled.
The steel band with magnet on pointer allow for adjustments so you can tweak that alignment by moving the pointer after you test on some known objects. (without having to keep moving the entire bottom base)

If the markings are on the top board and are stationary with the OTA where do you set the gradients to begin with? The zero / zero goes directly below the center of the OTA at the front of the scope? That way you always begin with the scope pointed at the Polar North.

You then match the Azm:159 and Alt:+38 as per your favorite program (my settings at the moment for Jupiter) and your on target or at least in the neighborhood.

Am I keeping up here or did I miss something?


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rnabholz
scholastic sledgehammer
*****

Reged: 07/25/04

Loc: Iowa
Re: Degree Circles new [Re: AtLarge]
      #943758 - 05/06/06 07:55 AM Attachment (746 downloads)

You have it.

In Carol's pictures you can see that she set zero at 90 degrees from the tube, but it really doesn't matter that the scale match the actual azimuth direction, only that the scale and pointer indicate properly. Her approach makes it convenient to see when at the eyepiece when the scope is pointed north.

Using the approach where the scale is attached to the rocker means that you will have to leave the eyepiece position at times to line up the pointer. The approach I used is to put the scale on the groundboard and build some adjustability into the scale rather than the pointer. That allows the pointer, attached to the rocker, to be visible from the eyepiece at all times, a little handier set up, but a little more complicated build.

Let me know if you have other questions.

Clear Skies


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csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: Degree Circles new [Re: rnabholz]
      #943900 - 05/06/06 10:17 AM

See my new post here "my $12 Go-To" test drive
Carol


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SkyArcher
Postmaster
*****

Reged: 04/12/06

Loc: 9545' in Colorado
Re: Degree Circles new [Re: csa/montana]
      #944499 - 05/06/06 07:52 PM Attachment (1609 downloads)

In case any wants it, I've attached the pdf of the file I used to make the degree circle. You can take the pdf to your local "Kinkos" copy center and have them print it out on 24x36 paper. Also while you're there, have them laminate the degree circles.

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Relativist
Post Laureate
*****

Reged: 10/11/03

Loc: OC, CA, USA
Re: Degree Circles new [Re: SkyArcher]
      #944714 - 05/06/06 11:08 PM

Just out of curiosity, how good is that home depot inclinometer? Could we maybe make our own that was a bit better?

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csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: Degree Circles new [Re: Relativist]
      #944767 - 05/07/06 12:10 AM

It's about 4-3/4" high (circular), with magnetic base. As Rod Nabholtz said, using the inclinometer, it's independent of the base, so no leveling is required.The scale is quite small & a little difficult to read at night, but works. During my viewing session, My Altitude degree scale matched the inclinometer with each change. The ideal one is what Rod has now; MD SmartTool digital level. It runs $100 though. I'm quite happy with my setup & accuracy.
Carol


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Relativist
Post Laureate
*****

Reged: 10/11/03

Loc: OC, CA, USA
Re: Degree Circles new [Re: csa/montana]
      #947707 - 05/09/06 02:40 AM

Ok, so let me ask this, could you use the inclinometer to "calibrate" the Altitude scale, bypassing the need to level the base? The idea would be to move the arrow as is done with the Azimuth scale.

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THESKY
scholastic sledgehammer
*****

Reged: 02/16/06

Loc: SOCAL
Re: Degree Circles new [Re: Relativist]
      #947728 - 05/09/06 03:31 AM

Boy this is such a good thread . . . thank you for all . . . especially Carol who initiate this thread. Also to Rob and SkyArcher who make the Alt/Az degree circle work.

I also plan to do the same since it is doable.
My question will be when you have a tracking platform how do you calibrate the level. When you just start tracking you will have the platform swing to the east side and then it will end as it swing all the way to the west for 60 - 80 minutes.

I guess one solution will be searching for the object while the rocker base is level and after the object is in the FOV - turn on the tracking device.

Ridwan


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rnabholz
scholastic sledgehammer
*****

Reged: 07/25/04

Loc: Iowa
Re: Degree Circles new [Re: Relativist]
      #947818 - 05/09/06 06:47 AM

Curtis,

Using a scale without a level base is problematic because while you can always set the scale to match an inclinometer determined setting, when you turn the rocker on the base, the scale reading will be off immediately and will not be exactly accurate until you return it to the same azimuth you set it at.

Now, depending in the degree of deviation from level, this error could be small, but it could also be very large and make finding things in a one degree or so field of view very difficult.

The inclinometer takes away the possibility of this error, and so makes it the choice for me. The analog inclinometer mentioned in this thread is about $10, a cheap efficient solution.

Of course leveling the scope is another option, and actually, I do both to make things as accurate as possible.

Edited by rnabholz (05/09/06 10:39 AM)


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rnabholz
scholastic sledgehammer
*****

Reged: 07/25/04

Loc: Iowa
Re: Degree Circles new [Re: THESKY]
      #947869 - 05/09/06 08:08 AM

Ridwan,

I have given the tracking platform issue some thought, as I am conisidering building one for my scope.

I think the only approach that will work is stopping and returning the platform to level during the object acquisition process and then turning the motors on.

You would sacrifice 50% of your tracking period, but depending on the platform you would likely have 20 to 30 minutes of travel left. That would generally be enough for my purposes.


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THESKY
scholastic sledgehammer
*****

Reged: 02/16/06

Loc: SOCAL
Re: Degree Circles new [Re: rnabholz]
      #948148 - 05/09/06 11:37 AM

Rod,

That is what I thought . . . having the dob level - align to the object (Alt/Az) - then turn on the tracking. Thank you for that confirmation.

Or another idea would be . . . calculating the difference between a leveled platform and a maximum swing platform. Then we can use this different to a Alt/Az value from the pocket star.

What do you think about that one?


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rnabholz
scholastic sledgehammer
*****

Reged: 07/25/04

Loc: Iowa
Re: Degree Circles [Re: THESKY]
      #948202 - 05/09/06 12:12 PM

Quote:


Or another idea would be . . . calculating the difference between a leveled platform and a maximum swing platform. Then we can use this different to a Alt/Az value from the pocket star.

What do you think about that one?




Well, here is what I have come up with as I have pondered using a platform.

Remember that if you adopt my strongly preferred approach for altitude - an inclinometer, not a scale, the tube reading is always read independent of the base. So even on a platform the altitude reading will be accurate.

It is the azimuth that is vexing. Visualizing the base and the azimuth scale and the different possible orientations of that scale to the tilt of the platform, it seems to me that you would have an infinitely variable factor to consider.

For example, consider the scope pointing precisely perpendicular to the axis of platform rotation or pointing precisely parallel to the axis of rotation. In these cases, your azimuth is likely to be pretty accurate.

Now consider the scope pointing in between those points. It seems to me that depending on the degree of the platform tilt, you would compromise the accuracy of the scale because you have in effect compressed the spacing of the degree marks by tilting the scale.

If my visualizations are correct (and PLEASE, anybody who sees this differently please let me know your thoughts) you would have a very difficult time quantifying the deviation and therefore could probably not easily adjust for it.

Edited by rnabholz (05/09/06 12:28 PM)


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SkyArcher
Postmaster
*****

Reged: 04/12/06

Loc: 9545' in Colorado
Re: Degree Circles [Re: rnabholz]
      #948402 - 05/09/06 02:33 PM

Rob, I'm just having a little brain fart here, but I'm thinking that if you're using a tracking platform, wouldn't it be better to use the other set of coordinates (RA-DEC) and set up a different set of degree circles. I confess that I don't know what Ra-Dec coordinates are other than they are used on EQ mounts.

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