Re: 900GTO Polar Star Alignment Procedure Misunderstandings


Aug 23, 2001

 


----------------------------

#7007 Aug 23, 2001

Last night was my first attempt to polar star align the 900GTO system.

After going throught the manual first, I became confused about two

things.



Firstly, the manual says not to use Arcturus as a second alignment star

after using Polaris since the RA is nearly the same for these two. In

my star atlas, Polaris shows an RA of 2hr30min and Arcturus is at

approx. 14hr RA. So, the RA's between these two stars is 'not' close to

being the same.



Secondly, the manual asks that I polar align the mount using my polar

axis scope, and then get Polaris into the field of view of the

telescope by adjusting the RA and DEC axis of the mount, again. If I

re-adjust the mount's RA and DEC to make the Polaris visible in the

scope's eyepiece, the mount's polar axis will not be pointing at the

pole anymore, but will now be pointed at Polaris which is off of the

pole by a degree or so. Anyway, after doing this procedure and choosing

Vega as the second alignment star, a quick press of the GoTo button

brought the scope a few degrees off of the targeted M13. I'll try again

on Saturday night, my next time out observing



What am I misunderstanding?



Peter Natscher

peter@...



----------------------------

#7008 Aug 23, 2001

----- Original Message -----

From: "Peter Natscher" natscher@...>



> What am I misunderstanding?



Hi Peter,

Not if software has slewed the telescope to where it thinks POLARIS, not the

pole, should be. Right?



----------------------------

#7009 Aug 23, 2001

--- Peter Natscher natscher@...> wrote: > Last night was my first attempt to polar star align

> the 900GTO system.

> After going throught the manual first, I became

> confused about two

> things.

>

> Firstly, the manual says not to use Arcturus as a

> second alignment star

> after using Polaris since the RA is nearly the same

> for these two. In

> my star atlas, Polaris shows an RA of 2hr30min and

> Arcturus is at

> approx. 14hr RA. So, the RA's between these two

> stars is 'not' close to

> being the same.



Add 12 hrs to Polaris...When you are at the poles, the

mount will actually swing past the 90 degrees to get

to polaris on the other side without a RA movement. If

the mount does a RA movement (which it won't) the

scope may end up under the mount 180 degrees in RA

from the Arcturus.

> Secondly, the manual asks that I polar align the

> mount using my polar

> axis scope, and then get Polaris into the field of

> view of the

> telescope by adjusting the RA and DEC axis of the

> mount, again. If I

> re-adjust the mount's RA and DEC to make the Polaris

> visible in the

> scope's eyepiece, the mount's polar axis will not be

> pointing at the

> pole anymore, but will now be pointed at Polaris

> which is off of the

> pole by a degree or so. Anyway, after doing this

> procedure and choosing

> Vega as the second alignment star, a quick press of

> the GoTo button

> brought the scope a few degrees off of the targeted

> M13. I'll try again

> on Saturday night, my next time out observing

>

> What am I misunderstanding?

>

> Peter Natscher

> peter@...



When using the Polar Scope only Adjust the Alt/Az.

What you may be refering to is that on the 600e and

400 the polar scope turns with the RA shaft. Also, you

have to turn the DEC to see thru the hole in the

shaft, the instructions may be refering this.



Hope this helps.



Tim

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----------------------------

#7011 Aug 23, 2001

I did notice that when I pushed the GoTo button and the scope slewed back to

Polaris, it pointed about the same degree off as Polaris is from the true pole.

This might have been because of my leaving the scope ponting to the true pole

rather than Polaris when asked to point the scope to Polaris by the hand

controller. I'm realizing now that the true pole has no meaning here, just the

two stars in the two-star alignmennt procedure are important.



Peter



"Jeffrey D. Gortatowsky" wrote:

> ----- Original Message -----

> From: "Peter Natscher" natscher@...>

>

> > What am I misunderstanding?

>

> Hi Peter,

> Not if software has slewed the telescope to where it thinks POLARIS, not the

> pole, should be. Right?

>

> To UNSUBSCRIBE, or for general information on the ap-ug list

> see groups.yahoo.com/group/ap-ug

>

> Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/



----------------------------

#7012 Aug 23, 2001

Thanks, Tim.



Peter



Tim Khan wrote:

> --- Peter Natscher natscher@...> wrote:

> > Last night was my first attempt to polar star align

> > the 900GTO system.

> > After going throught the manual first, I became

> > confused about two

> > things.

> >

> > Firstly, the manual says not to use Arcturus as a

> > second alignment star

> > after using Polaris since the RA is nearly the same

> > for these two. In

> > my star atlas, Polaris shows an RA of 2hr30min and

> > Arcturus is at

> > approx. 14hr RA. So, the RA's between these two

> > stars is 'not' close to

> > being the same.

>

> Add 12 hrs to Polaris...When you are at the poles, the

> mount will actually swing past the 90 degrees to get

> to polaris on the other side without a RA movement. If

> the mount does a RA movement (which it won't) the

> scope may end up under the mount 180 degrees in RA

> from the Arcturus.

>

> > Secondly, the manual asks that I polar align the

> > mount using my polar

> > axis scope, and then get Polaris into the field of

> > view of the

> > telescope by adjusting the RA and DEC axis of the

> > mount, again. If I

> > re-adjust the mount's RA and DEC to make the Polaris

> > visible in the

> > scope's eyepiece, the mount's polar axis will not be

> > pointing at the

> > pole anymore, but will now be pointed at Polaris

> > which is off of the

> > pole by a degree or so. Anyway, after doing this

> > procedure and choosing

> > Vega as the second alignment star, a quick press of

> > the GoTo button

> > brought the scope a few degrees off of the targeted

> > M13. I'll try again

> > on Saturday night, my next time out observing

> >

> > What am I misunderstanding?

> >

> > Peter Natscher

> > peter@...

>

> When using the Polar Scope only Adjust the Alt/Az.

> What you may be refering to is that on the 600e and

> 400 the polar scope turns with the RA shaft. Also, you

> have to turn the DEC to see thru the hole in the

> shaft, the instructions may be refering this.

>

> Hope this helps.

>

> Tim

>

> >

> > To UNSUBSCRIBE, or for general information on the

> > ap-ug list

> > see groups.yahoo.com/group/ap-ug

> >

> > Your use of Yahoo! Groups is subject to

> > docs.yahoo.com/info/terms/

> >

> >

>

---------------

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----------------------------

#7013 Aug 23, 2001

On 8/23/01 8:12 AM Peter Natscher wrote:

> What am I misunderstanding?



There was a discussion on the ap-gto list about the polar routine. See:

"[ap-gto] Re: Polar Alignment one more time". You might find that discussion

worthwhile. I'll forward one of the most enlightening messages offlist.



In short, Roland was recommending NOT using the polar routine and was

considering removing it in the future. The two star routine was recommended.



Regards,

Robin



Astro Accessories by Robin Casady

Stainless Steel Weights & Dovetail Saddles

www.CarmelCoast.com/Astro/sales.html



Casady & Greene, Inc.

www.casadyg.com



----------------------------

#7018 Aug 23, 2001

Roland said: >

> Way 1: use one of the alignment routines in the keypad at startup.

> Way 2: use a Pole scope

> Way 3: do a drift alignment

> Way 4: use a carpenter's level and set the scope up per the instructions in

> the manual using the Reference Park positions. This is also a good way to

> polar align the scope in the daytime.

>

> Way 5: Does anyone know of any other way?



.The only other way I've heard of involves a chicken, 2 goats,

a congressman from Idaho and 3 lbs of spinach. >:-)



--Kit







--

Kit Cosper cosper@...



----------------------------

#7020 Aug 23, 2001

--- In ap-ug@y..., Robin Casady rcasady@c...> wrote: >

> In short, Roland was recommending NOT using the polar routine

>

> Regards,

> Robin





In about 10,000 years or so Polaris will be far away enough from the

pole to make it usable. I think the AP mounts will last that long

also.



Tim Povlick

San Juan Capistrano, CA



----------------------------

#7024 Aug 23, 2001

Peter Natscher wrote:

> Last night was my first attempt to polar star align the 900GTO system.

> After going throught the manual first, I became confused about two

> things.

>

> Firstly, the manual says not to use Arcturus as a second alignment star

> after using Polaris since the RA is nearly the same for these two. In

> my star atlas, Polaris shows an RA of 2hr30min and Arcturus is at

> approx. 14hr RA. So, the RA's between these two stars is 'not' close to

> being the same.



It's off by almost exactly 12 hours. I can definitely attest to the fact

that Arcturus is not a good star to use.

>

>

> Secondly, the manual asks that I polar align the mount using my polar

> axis scope, and then get Polaris into the field of view of the

> telescope by adjusting the RA and DEC axis of the mount, again. If I



You shouldn't have to use a polar scope, except maybe to get

reasonably close on the first run.



Bob K.



----------------------------

#7027 Aug 24, 2001

I'm not sure why there is a problem. I have used the polar star method

for aligning my 600 GOTO mount for years now and have had no problem.

On the other hand when I tried to use the 2 star method I HAVE had

problems. As I recall in one instruction manual using the 2 star

method you were suppose to make the correction after the scope slewed

to the 2nd star with the alt. Az, control on the mount and in the

other manual you were instructed to make only ONE-HALF correction.

That's much more confusing to me. Which is correct?



Jim



>

> > What am I misunderstanding?

>

> There was a discussion on the ap-gto list about the polar routine.

See: > "[ap-gto] Re: Polar Alignment one more time". You might find that

discussion > worthwhile. I'll forward one of the most enlightening messages

offlist. >

> In short, Roland was recommending NOT using the polar routine and

was > considering removing it in the future. The two star routine was

recommended. >

> Regards,

> Robin

>

> Astro Accessories by Robin Casady

> Stainless Steel Weights & Dovetail Saddles

> www.CarmelCoast.com/Astro/sales.html

>

> Casady & Greene, Inc.

> www.casadyg.com



----------------------------

#7031 Aug 24, 2001

Hi Jim,



I just tried the 2 start alignment last night, and although it took many

iterations to get it right, the AP1200 was dead on. I continually checked

the pointing accuracy over the entire sky for several hours and was

astonished to find it was always within 3 arc minutes. From Vega to

Fomalhaut to Algenib, I usually got 1-2 arc minutes, but never worse than

3. I have always used the one start alignment before and gotten usable but

not nearly as good results. No more though. I'm sold on the 2 star approach.



As regards the procedure, my manual says to use the keypad for the first

pass on the two stars, then use half keypad and half alt-az controls for

each succeeding star alignment. That makes it more tedious, but the results

for me have been very good.



Cheers,



Andy Thompson





At 03:15 PM 8/24/01 +0000, you wrote: >I'm not sure why there is a problem. I have used the polar star method

>for aligning my 600 GOTO mount for years now and have had no problem.

>On the other hand when I tried to use the 2 star method I HAVE had

>problems. As I recall in one instruction manual using the 2 star

>method you were suppose to make the correction after the scope slewed

>to the 2nd star with the alt. Az, control on the mount and in the

>other manual you were instructed to make only ONE-HALF correction.

>That's much more confusing to me. Which is correct?

>

> Jim

>

>

> >

> > > What am I misunderstanding?

> >

> > There was a discussion on the ap-gto list about the polar routine.

>See:

> > "[ap-gto] Re: Polar Alignment one more time". You might find that

>discussion

> > worthwhile. I'll forward one of the most enlightening messages

>offlist.

> >

> > In short, Roland was recommending NOT using the polar routine and

>was

> > considering removing it in the future. The two star routine was

>recommended.

> >

> > Regards,

> > Robin

> >

> > Astro Accessories by Robin Casady

> > Stainless Steel Weights & Dovetail Saddles

> > www.CarmelCoast.com/Astro/sales.html

> >

> > Casady & Greene, Inc.

> > www.casadyg.com

>

>

>

>To UNSUBSCRIBE, or for general information on the ap-ug list

>see groups.yahoo.com/group/ap-ug

>

>Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/







----------------------------

#7032 Aug 24, 2001

Thanks Andy,

I'm definately going to have to learn the two star method. I'm

thinking of replacing the mount in my observatory with a 1200 QMD. I

first have to find rings that will hold my AP 9" F/15 Folded Tube

assembly and attach to a 1200 mounting plate. I'm thinking Parallax

(Is that the right name?). I then have to figure some other things out

like how to get the old mount out. And, if I get all that done I will

have to use the two star method because Polaris will be directly

behind my 3rd floor. My observatory was built over a one story

outbuilding (now Kitchen) on the South side of a 3 story Rowhouse

(Brownstone). You can't see the northern sky.



Jim



> Hi Jim,

>

> I just tried the 2 start alignment last night, and although it took

many > iterations to get it right, the AP1200 was dead on. I continually

checked > the pointing accuracy over the entire sky for several hours and was

> astonished to find it was always within 3 arc minutes. From Vega to

> Fomalhaut to Algenib, I usually got 1-2 arc minutes, but never worse

than > 3. I have always used the one start alignment before and gotten

usable but > not nearly as good results. No more though. I'm sold on the 2 star

approach. >

> As regards the procedure, my manual says to use the keypad for the

first > pass on the two stars, then use half keypad and half alt-az controls

for > each succeeding star alignment. That makes it more tedious, but the

results > for me have been very good.

>

> Cheers,

>

> Andy Thompson

>

>

> At 03:15 PM 8/24/01 +0000, you wrote:

> >I'm not sure why there is a problem. I have used the polar star

method > >for aligning my 600 GOTO mount for years now and have had no

problem. > >On the other hand when I tried to use the 2 star method I HAVE had

> >problems. As I recall in one instruction manual using the 2 star

> >method you were suppose to make the correction after the scope

slewed > >to the 2nd star with the alt. Az, control on the mount and in the

> >other manual you were instructed to make only ONE-HALF correction.

> >That's much more confusing to me. Which is correct?

> >

> > Jim

> >

> >

> > >

> > > > What am I misunderstanding?

> > >

> > > There was a discussion on the ap-gto list about the polar

routine. > >See:

> > > "[ap-gto] Re: Polar Alignment one more time". You might find

that > >discussion

> > > worthwhile. I'll forward one of the most enlightening messages

> >offlist.

> > >

> > > In short, Roland was recommending NOT using the polar routine

and > >was

> > > considering removing it in the future. The two star routine was

> >recommended.

> > >

> > > Regards,

> > > Robin

> > >

> > > Astro Accessories by Robin Casady

> > > Stainless Steel Weights & Dovetail Saddles

> > > www.CarmelCoast.com/Astro/sales.html

> > >

> > > Casady & Greene, Inc.

> > > www.casadyg.com

> >

> >

> >

> >To UNSUBSCRIBE, or for general information on the ap-ug list

> >see groups.yahoo.com/group/ap-ug

> >

> >Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/



----------------------------

#7033 Aug 24, 2001

On 8/24/01 10:21 AM thefamily@... wrote:

> I'm definately going to have to learn the two star method. I'm

> thinking of replacing the mount in my observatory with a 1200 QMD.



I thought the two star method was a goto routine. How can you do it with a

QMD?



Regards,

Robin



Astro Accessories by Robin Casady

Stainless Steel Weights & Dovetail Saddles

www.CarmelCoast.com/Astro/sales.html



Casady & Greene, Inc.

www.casadyg.com



----------------------------

#7052 Aug 26, 2001

Andy,

Can you describe in detail the drift alignment method? When I get

my 1200 QMD mount in place I'd like to get it as accurately alighned

as possible and I understand when you get close, very close, using

other methods , the drift method will get you right on. Thanks.



Jim

>

> Andy,

>

> You probably didn't try this, but I would be real curious if the

drift > alignment of you mount was right on the money after you go thru this

> excercise.

>

> Tim Povlick

> San Juan Capistrano, CA

>

> --- In ap-ug@y..., Andy Thompson support@s...> wrote:

> >

> > I just tried the 2 start alignment last night, and although it

took > many

> > iterations to get it right, the AP1200 was dead on. I continually

> checked

> > the pointing accuracy over the entire sky for several hours and

was > > astonished to find it was always within 3 arc minutes. From Vega

to > > Fomalhaut to Algenib, I usually got 1-2 arc minutes, but never

worse > than

> > 3. I have always used the one start alignment before and gotten

> usable but

> > not nearly as good results. No more though. I'm sold on the 2 star

> approach.

> >

> > As regards the procedure, my manual says to use the keypad for the

> first

> > pass on the two stars, then use half keypad and half alt-az

controls > for

> > each succeeding star alignment. That makes it more tedious, but

the > results

> > for me have been very good.

> >

> > Cheers,

> >

> > Andy Thompson

> >

> >







----------------------------

#7081 Aug 27, 2001

Andy,

Thanks very much. I got out my NGC Max manual today and there is

no two star method for aligning the polar axis accurately. Only the

one star method that requires being able to see Polaris. I called JMI

and confirmed that. The gentleman I spoke to Faxed a copy of the star

drift method. I think you have it just right. Thanks!



Jim



> Hi Jim,

>

> I did try the drift alignment to check the 2-start method and saw

very > little drift after about one hour ( 5"" for azimuth and 15" for

> altitude). I have little experience in the drift method so I'm not

sure I > was doing it right, but I think I did. I have only tried the 2-star

> alignment once, so maybe I just got lucky the first time and hit it

dead on. >

> Here is my understanding of the drift alignment procedure.

>

> Part 1: Azimuth adjustments:

> 1. Aim the scope at a star near the celestial equator, somewhat

south of > the zenith.

> 2. Align one of the reticle axes with the telescope's NS axis.

> 3. Center the star in the reticle.

> 4. After 15 minutes check the NS drift. Ignore the EW drift. If

there is no > drift, you're done. If the star has drifted north, the scope is

pointed too > far west. If it has drifted south, it is too far east. Adjust the

azimuth > controls on the mount accordingly.

>

>

> Part 2: Altitude adjustments:

> 1. Aim the scope at a star near the celestial equator, as far east

as > possible.

> 2. Align one of the reticle axes with the telescope's NS axis.

> 3. Center the star in the reticle.

> 4. After 15 minutes check the NS drift. Ignore the EW drift. If

there is no > drift, you're done. If the star has drifted north, the scope is

pointed too > high. If it has drifted south, it is too low. Adjust the altitude

controls > on the mount accordingly.

>

> That is my understanding of the drift alignment procedure. I didn't

> actually make any adjustments. I only noted the drift after one

hour and > concluded it was pretty good. There is another good description at

> www.aa6g.org/Astronomy/Articles/drift_align.html and another

at > www.darkskyimages.com/quick.html.

>

> Cheers,

>

> Andy Thompson

>

> At 11:46 AM 8/26/2001 -0000, you wrote:

> >Andy,

> > Can you describe in detail the drift alignment method? When I

get > >my 1200 QMD mount in place I'd like to get it as accurately

alighned > >as possible and I understand when you get close, very close, using

> >other methods , the drift method will get you right on. Thanks.

> >

> >Jim

> >

> >>

> >> Andy,

> >>

> >> You probably didn't try this, but I would be real curious if the

> >drift

> >> alignment of you mount was right on the money after you go thru

this > >> excercise.

> >>

> >> Tim Povlick

> >> San Juan Capistrano, CA

> >>

> >> --- In ap-ug@y..., Andy Thompson support@s...> wrote:

> >> >

> >> > I just tried the 2 start alignment last night, and although it

> >took

> >> many

> >> > iterations to get it right, the AP1200 was dead on. I

continually > >> checked

> >> > the pointing accuracy over the entire sky for several hours

and > >was

> >> > astonished to find it was always within 3 arc minutes. From

Vega > >to

> >> > Fomalhaut to Algenib, I usually got 1-2 arc minutes, but never

> >worse

> >> than

> >> > 3. I have always used the one start alignment before and gotten

> >> usable but

> >> > not nearly as good results. No more though. I'm sold on the 2

star > >> approach.

> >> >

> >> > As regards the procedure, my manual says to use the keypad for

the > >> first

> >> > pass on the two stars, then use half keypad and half alt-az

> >controls

> >> for

> >> > each succeeding star alignment. That makes it more tedious,

but > >the

> >> results

> >> > for me have been very good.

> >> >

> >> > Cheers,

> >> >

> >> > Andy Thompson

> >> >

> >> >

> >

> >

> >

> >To UNSUBSCRIBE, or for general information on the ap-ug list

> >see groups.yahoo.com/group/ap-ug

> >

> >Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/ > >

> >

> >



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