VintageBigBlue.org

 

Re: Polar alignment protocol (revised)


Jul 1, 2002

 


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

#10787 Jul 1, 2002

We're approaching the New Moon and I'd like dsc users to check out

this protocol and see how it works for them.



1. Align using polar scope.

2. Do 1-star alignment on Vega (for example).

3. Swing to M82 or some other bright object fairly far from Vega.

4. The second object must not be too far N, and it must be fairly far

to the W (if you aligned on a star in the E). I shall explain below.

5. If the object is within ten minutes or so of center, celebrate,

you are polar aligned and shouldn't toucha thing.

6. If it is outside the fov, or off to the edge, center it USING

AZIMUTH AND ALTITUDE ADJUSTMENTS ON THE MOUNT. Basically the amount

you are off this second object is a measurement of your error in

polar alignment.

7. Turn off the computer.

8. Go back to Vega and do a 1-star realignment.



NOW LISTEN UP! I've had HUGE PROBLEMS with this protocol for two

reasons:



1. Following the NGC Max computer polaris protocol, I kept going to

Polaris as a second star. Sound obvious? It is. BUT the problem is

that you can center Polaris in the field of view from a fairly wide

range of positions and therefore you introduce a large RA error that

gets fed to the computer. You are a victim of the GEM HOLE.



2. This one is even better! When I first tried the alignment

protocol, I did a small movement from vega to M57 and tried to

adjust. WHAT WAS THE PROBLEM? Huge movements in alt and az to get

small movements of the object. Indeed, azimuth seemed to move the

scope in almost the same direction as altitude????



WHAT WAS GOING ON????



Just this, folks. I was in the dob hole. Vega was very high and I

was moving in altitude and azimuth. Huge corrections to get small

movements which totally screwed everything up. Just like a dob mount

at zenith.



My revised recommendation is to try this adjusmtnet process nearer to

the celestial equator and AWAY FROM ZENITH!!!!



I had good results for several hours running, in fact, some of the

most accurate dsc performance I've ever had.



Pleae email me in person if you try this and let me know how it

worked out. In theory, it should work even if you don't use a polar

scope.



Regards,



Greg Nowell



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

#10789 Jul 1, 2002

--- In Losmandy_users@y..., "gnowellsct" gnowell@n...> wrote: > We're approaching the New Moon and I'd like dsc users to check out

> this protocol and see how it works for them.

>

> 1. Align using polar scope.

> 2. Do 1-star alignment on Vega (for example).

> 3. Swing to M82 or some other bright object fairly far from Vega.

> 4. The second object must not be too far N, and it must be fairly far

> to the W (if you aligned on a star in the E). I shall explain below.

> 5. If the object is within ten minutes or so of center, celebrate,

> you are polar aligned and shouldn't toucha thing.

> 6. If it is outside the fov, or off to the edge, center it USING

> AZIMUTH AND ALTITUDE ADJUSTMENTS ON THE MOUNT. Basically the amount

> you are off this second object is a measurement of your error in

> polar alignment.

> 7. Turn off the computer.

> 8. Go back to Vega and do a 1-star realignment.

>

> NOW LISTEN UP! I've had HUGE PROBLEMS with this protocol for two

> reasons:

>

> 1. Following the NGC Max computer polaris protocol, I kept going to

> Polaris as a second star. Sound obvious? It is. BUT the problem is

> that you can center Polaris in the field of view from a fairly wide

> range of positions and therefore you introduce a large RA error that

> gets fed to the computer. You are a victim of the GEM HOLE.

>

> 2. This one is even better! When I first tried the alignment

> protocol, I did a small movement from vega to M57 and tried to

> adjust. WHAT WAS THE PROBLEM? Huge movements in alt and az to get

> small movements of the object. Indeed, azimuth seemed to move the

> scope in almost the same direction as altitude????

>

> WHAT WAS GOING ON????

>

> Just this, folks. I was in the dob hole. Vega was very high and I

> was moving in altitude and azimuth. Huge corrections to get small

> movements which totally screwed everything up. Just like a dob mount

> at zenith.

>

> My revised recommendation is to try this adjusmtnet process nearer to

> the celestial equator and AWAY FROM ZENITH!!!!

>

> I had good results for several hours running, in fact, some of the

> most accurate dsc performance I've ever had.



I've tried this same thing with lining up an AP-900 GOTO and had some

trouble. One is, don't use Polaris (which I think you also say) as

the lines of RA converge there. In making the adjustments, one only

goes half the distance with the alt-az screws. As far as a star at

the Zenith, Rowland mentioned this case and I think he said don't

adjust the ALT axis,only AZ. And to I dare say it, the mount/scope

has to be orthogonal for this to have any hopes of working. This can

be done, but most times I've tried it, I walked the mount further and

further away from the true pole. If it use the Polar Alignment scope,

to get back on track, I was able to bring it right into convergence.

In the end, I will probably stick to a well aligned PAS and drift align.



Nice to have you back Greg, misses your helpful posts.





Tim Povlick

San Juan Capistrano, CA






now zero>

>

> Pleae email me in person if you try this and let me know how it

> worked out. In theory, it should work even if you don't use a polar

> scope.

>

> Regards,

>

> Greg Nowell







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

#10790 Jul 1, 2002

Nice to be here Mr Povnick, and thank you. See below...

--- In Losmandy_users@y..., "limunary" potentate@h...> wrote:



> I've tried this same thing with lining up an AP-900 GOTO and had

some

> trouble. One is, don't use Polaris (which I think you also say) as

> the lines of RA converge there. In making the adjustments, one only

> goes half the distance with the alt-az screws.



I'm not sure of this 1/2 business. I can "see" it when going side to

side to align on Polaris (when shimming, for example), but

conceptually I don't see it here. You're off by what you're off, not

by 1/2 what you're off. When you have a full moon and nothing better

to do, let me know how it works for you (I guess you already did, but

really, there is no *theoretical* reason this shouldn't work).





>As far as a star at

> the Zenith, Rowland mentioned this case and I think he said don't

> adjust the ALT axis,only AZ.



I would avoid zenith altogether. For the simple reason that alt AND

az adjustments may be needed.



>And to I dare say it, the mount/scope

> has to be orthogonal for this to have any hopes of working. This

can

> be done, but most times I've tried it, I walked the mount further

and

> further away from the true pole.



Yeah, you walk the mount and get nowhere. Lots of cranking and

nothing to show for it.



>If it use the Polar Alignment scope,

> to get back on track, I was able to bring it right into

convergence.



My guess is that you would actually get maximal precision in this

adjustment by using a star or dso on the celestial equator,

preferably below 45 degrees altitude, to get the most accurate

performance. I'm not sure whether orthagonality would count, but

lord knows I've tried in that department. Working within a 15 degree

error diameterthe other night was something of a triumph.



> In the end, I will probably stick to a well aligned PAS and drift

align.



Banish drift alignment!

--regards,

Greg Nowell



> Nice to have you back Greg, misses your helpful posts.

>

>

> Tim Povlick

> San Juan Capistrano, CA

>

>

>
is

> now zero>

>

> >

> > Pleae email me in person if you try this and let me know how it

> > worked out. In theory, it should work even if you don't use a

polar

> > scope.

> >

> > Regards,

> >

> > Greg Nowell



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

#10793 Jul 1, 2002

--- In Losmandy_users@y..., "gnowellsct" gnowell@n...> wrote: >



I should also say that when moving the alt/az axis halfway to the

target star, the hand control buttons should be used to exactly zero

in on the target star, and then recalibrate or sync to the star.

As to orthogonality, when I had mine right on the money, it made doing

this procedure easier, otherwise you have to 'see' how much off you

are in orthogonality. >

> > In the end, I will probably stick to a well aligned PAS and drift

> align.

>

> Banish drift alignment!



Agreed - with a large observatory in a dark sky site where the wx is

warm and the skies are clear....





----

Tim



Contact Us
This Site's Privacy Policy
Google's privacy policies

S
e
n
i
o
r
T
u
b
e
.
o
r
g