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how set the seting circles

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#1 De Lorme

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Posted 28 December 2012 - 02:49 AM

Hi, If someone could confirm if I'm doing this right I sure would appreciate it. I'm getting ready to install the ra setting circle on a old 17.5" Odessey. I made a round circle out of plywood and installed a lazy susan on which the base will sit. Assuming RA starts at 0, do I align 0 with {magnetic} north?
Then have a pointer centered {and starting at zero, magnetic north} at the bottom of the base to which would guide me from 0 to 360 degrees. Is my thinking correct? Thanks for letting me know. De Lorme

#2 vsteblina

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Posted 28 December 2012 - 08:24 AM

I assume you are going to use this with a computer readout. I did this about 30 years ago with a c-64.

If I remember right it was backwards. this was in the days of fido net and some guy with Bell Labs pointed out my mistake. Sorry if I am not as smart as him.

Try it with some paper circles, before doing something peer ament.

BTW it worked great until I got encoders.

#3 rmollise

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Posted 28 December 2012 - 08:49 AM

Hi, If someone could confirm if I'm doing this right I sure would appreciate it. I'm getting ready to install the ra setting circle on a old 17.5" Odessey. I made a round circle out of plywood and installed a lazy susan on which the base will sit. Assuming RA starts at 0, do I align 0 with {magnetic} north?
Then have a pointer centered {and starting at zero, magnetic north} at the bottom of the base to which would guide me from 0 to 360 degrees. Is my thinking correct? Thanks for letting me know. De Lorme


Negative. You align the azimuth (there is no R.A. with an alt-az mount) with true north, Polaris. Center Polaris in the main scope and set the circle to 0. Also be advised that for this to work well, the scope's mount needs to be as level as you can get it.

;)

#4 De Lorme

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Posted 28 December 2012 - 06:00 PM

Hi Rod, When I set my CGEM up I pointed the front tripod leg
North using a compass. Since it's close to Polaris why can't I do this with this dob. Also do the numbers run
{ if your standing behind the telescope, starting 0-360}clockwise or counter? Thanks for the help. De Lorme
clockwise

#5 DaveJ

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Posted 28 December 2012 - 06:09 PM

Hi Rod, When I set my CGEM up I pointed the front tripod leg
North using a compass. Since it's close to Polaris why can't I do this with this dob. Also do the numbers run
{ if your standing behind the telescope, starting 0-360}clockwise or counter? Thanks for the help. De Lorme
clockwise


I'm not Uncle Rod, but I can answer your question. Clockwise. In other words, due east is 90, south is 180, west is 270 and back to north at 0. Magnetic deviation can be fairly large depending on your location. Here, it's 8 degrees off from true north. True north (within 2/3 degree of Polaris) is where you want your "0" setting to be.

#6 rmollise

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Posted 28 December 2012 - 06:31 PM

Hi Rod, When I set my CGEM up I pointed the front tripod leg
North using a compass. Since it's close to Polaris why can't I do this with this dob. Also do the numbers run
{ if your standing behind the telescope, starting 0-360}clockwise or counter? Thanks for the help. De Lorme
clockwise


Because for the alt-az setting circle idea to work acceptably you have to be dead on to the Celestial Pole, as close as possible, not magnetic north, unless the magnetic deviation in your area is 0. How hard is it to point the scope at Polaris and move the setting circle under the pointer till it reads 0? You did make it adjustable, I hope...

#7 De Lorme

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Posted 28 December 2012 - 07:07 PM

Hi Rod. I mounted the bottom of the lazy susan{stationary
side}to the round board. I had planned on mounting the lazy susan to the base today{movable side} than I reliazed I cannot put the setting cirlces on as the base would sqeeze it tight. any idea how to mount the setting circles with a lazy susan? Oh! I hope so.
Thanks for your help. De Lorme

#8 De Lorme

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Posted 28 December 2012 - 10:19 PM

Hi Rod, Fixed the setting circle lazy susan problem.
I made a setting circle from Robert Willet.com and I'm not sure the numbers are going the right way. When I look at the circle facing me with 0/360 at three oclock,the next
number toward me is 350 and away from me 10. Is this correct? If not do you know of another setting circle program? Thanks for the help again. De Lorme

#9 SkipW

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Posted 28 December 2012 - 11:08 PM

When the telescope is pointing due north, the circle should indicate 0 or 360. When the telescope is pointing east, the circle should indicate 90.

#10 De Lorme

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Posted 29 December 2012 - 01:12 AM

Thanks for your pateince Rod. When I was making the setting
circle I over looked draw numbers clockwise. That caused my
confusion. I'll just have to make another.
Many Thanks, De Lorme

#11 archer1960

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Posted 29 December 2012 - 01:23 PM

And when you get picky about it, even Polaris isn't necessarily true north, but is rather about 2/3 of a degree off the celestial pole.

#12 rmollise

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Posted 29 December 2012 - 02:48 PM

That's why I said "Celestial Pole," but in my experience "Polaris" is sufficient to provide acceptable pointing accuracy without having to resort to trying to aim at the true pole. ;)

#13 rmollise

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Posted 29 December 2012 - 02:49 PM

Thanks for your pateince Rod. When I was making the setting
circle I over looked draw numbers clockwise. That caused my
confusion. I'll just have to make another.
Many Thanks, De Lorme


Yep, but that's OK...MK II is usually better. ;)

#14 De Lorme

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Posted 29 December 2012 - 02:51 PM

When I set up my CGEM in the rool off roof I put the front tripod leg North{magnetic}. I do a 2 star alignment and 2 more too it.
I realize that where just using the coordiates of a given
object but isn't that what the computor uses to locate
anything. I'm going to give it a try and put the base North and go from there. If I cannot find say M42 than I'll go back to aligning with a star first. If I cannot find Polaris,because the sky is bad can I use any star? For example Belteguese.
Thanks for the great help, Really appreciate it! De Lorme

#15 De Lorme

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Posted 29 December 2012 - 02:53 PM

Rod, What is Mk11? Your beloved humble sevant.LOL De Lorme

#16 DaveJ

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Posted 29 December 2012 - 05:44 PM

And when you get picky about it, even Polaris isn't necessarily true north, but is rather about 2/3 of a degree off the celestial pole.


Yes, it's true that Polaris is approximately 2/3 degree from the NCP (North Celestial Pole), but from my location at -81.427333 longitude, Polaris will be straight up from the NCP tonight at exactly 8:22:55pm. If I were trying to set up an ALT/AZ mount with setting circles, I'd aim the scope directly at Polaris at that time and set the AZ to zero. The 2/3 degree offset wouldn't come into play at all then. :grin: Incidentally, the "Mk II" to which Rod referred means the second version of your setting circles - and that they'll be "more better" than the first version.

#17 De Lorme

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Posted 29 December 2012 - 11:35 PM

Hi Dave,:question:If I put the center of the dob base on the magnetic deviation line for my area would I not be at true North? I'll be putting this in my rool off roof so it will not be moved. I'm trying to by pass having to center Polaris or any star and just start observing. Thanks for
your pateince and help. De Lorme

#18 rmollise

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Posted 30 December 2012 - 11:17 AM

Rod, What is Mk11? Your beloved humble sevant.LOL De Lorme


Your second attempt at doing an azimuth circle. ;)

BTW, don't reinvent the wheel...the Equipment forum has PDF degree circles ready for printing.

#19 De Lorme

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Posted 30 December 2012 - 06:27 PM

Could you give me your opinion about lining up with true north by ajusting to{the differanc between magnetic north and true north} the magnetic deviaton line and than starting the 0 from there? To be able to go to the cordinates of the first object with no star alingment would be of great conveince. Better to make sure than to "I should have ask".
Thanks for your patience, and help, De Lorme

#20 rmollise

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Posted 30 December 2012 - 06:59 PM

Why not just sight Polaris, adjust your circle and move on ;)? Certainly if you no the precise magnetic deviation for your area you can use a compass. If the compass is accurate. If it's not disturbed by nearby metal, etc.

#21 beatlejuice

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Posted 30 December 2012 - 07:40 PM

I think you are over complicating things, as Rod said,
just get polaris in the center of a high power eyepiece and set the AZ to zero. For slightly more improved accuracy find the AZ of polaris(planetarium software) for the time that you are setting up(this will be approximately between + or - 1/2 degree on either side of zero. Set your AZ for this slight difference from zero and your set. Dont forget to level the scope as best you can.

Eric

#22 De Lorme

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Posted 30 December 2012 - 07:46 PM

If I could by pass Polaris,go to 0 and then any object I wish it would be easier. I would have to ajust the magnetic
deviation once a year though. Taking a minute every time I go out to do a star alignment would be to me another step that's not necessary. This is an idea only as you said if it's done accurately and no metal interferance.
I'm looking into a really good large compass. Any advice is
really appreciated. I know I stand on the head of giants here. I look forward to reading what everybody has to
say. Thanks for the help. De Lorme

#23 beatlejuice

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Posted 30 December 2012 - 10:02 PM

I am wondering if you have read this thread degree circles If not, take a good look at it. It's long, but contains just about anything you want to know about them.

Eric

#24 rmollise

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Posted 31 December 2012 - 10:07 AM

If I could by pass Polaris,go to 0 and then any object I wish it would be easier. I would have to ajust the magnetic
deviation once a year though. Taking a minute every time I go out to do a star alignment would be to me another step that's not necessary. This is an idea only as you said if it's done accurately and no metal interferance.
I'm looking into a really good large compass. Any advice is
really appreciated. I know I stand on the head of giants here. I look forward to reading what everybody has to
say. Thanks for the help. De Lorme


Help us to understand why you have a problem centering Polaris, which will be much more accurate than what you are proposing. To recap:

Center Polaris in the field.
Set circile to 0.
You are done.

;)

#25 De Lorme

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Posted 31 December 2012 - 02:41 PM

I made a mistake on the design. I attached the lazy susan to
the base with a board the same size of the laze attached to it. I then made a larger board on with the setting cirlce
would sit. I thought if I put a spacer between them it would allow the setting circle board to turn. All it do
though was to make the base wooble. I could not find a
solution until I came across the ajustment with magnetic
declination. I thought my prayer had been answered.
I read that the magnetic declination moves approximately 40
miles per year. Perhaps if I do an ajustment once a month
it will work. If not there is SkyScout. OR mabey someone here has an answere to my problem of which I would gladly
give a BONUS! I eagerly await your reply. De Lorme BTW Thanks for the help.






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