VintageBigBlue.org

 

Re: polar alignment accuracy with G-11


May 4, 2005

 


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

#25381 May 4, 2005

Group

I am disappointed by my GM-8 azimuth and elevation wiggle (I am

refering to the large play with the knobs)which makes it pretty much

impossible to achieve polar alignment accuracy of below 5' for both

A an E. Doing a PAC often makes it worse (!) due to the wiggle.

The end result is a polar alignment of between 5 and 10' - which is

unacceptable to me.

I have decided to return the GM-8 to the dealer (he will give me a

95% refund) and buy either the G-11 or the Takahashi EM-200

instead. Having visited the Takahashi group and having had a number

of discussions with various folks, the preliminary conclusion is

that the Takahashi EM-200 is probably superior to the G-11,

especially when it comes to polar alignment. The PEC performance is

probably similar even though Takahashi claims they are better.

I am biased in favor of the G-11 because of the greater load it can

bear, and also because I like Gemini. The Temma II seems to be

clearly inferior to the Gemini unless you run it directly from a

notebook computer with the respective S/W support. I don't want to

always depend on the notebook...

By the way, I have eliminated the Titan as an option since it's

simply too heavy for me to log around.



My question to the group:

Is the azimuth/elevation control on the G-11 a lot better than on

the GM-8? What REALISTIC A and E values can I expect to achieve?

Anyone who has both the GM-8 and G-11 mounts and can compare? How

about polar alignment of G-11 versus EM-200?

Thanks in advance for your inputs. This user group has already been

extremely helpful to me just by reading the many postings. :)))

tom



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

#25382 May 4, 2005

Tom,

I wonder if perhaps there's something loose with your GM-8 if you

have excessive play in the azimuth and elevation adjustments. I

have had both a GM-8 and G-11 and both have been pretty easy to

adjust. My G-11 was an older model, and the elevation was somewhat

difficult to adjust because of the single bolt. However, as long as

I came at if from the right direction, I got pretty good results

(A&E numbers between 0 and 2, usually around 1). My GM-8 is a more

recent vintage with 2 bolts on the elevation adjustment, and it's

been just a breeze to align. Again, A&E numbers around 1.



The GM-8 and G-11 use nearly identical (as far as I can tell)

mechanisms to adjust the elevation and azimuth. Do you have anyone

else near you with either a GM-8 or G-11 that you can look at?

There may be something you can tighten up on yours to get better

accuracy in your adjustments.



Dave S.



--- In Losmandy_users@yahoogroups.com, "primecounter"

primecounter@y...> wrote: > Group

> I am disappointed by my GM-8 azimuth and elevation wiggle (I am

> refering to the large play with the knobs)which makes it pretty

much > impossible to achieve polar alignment accuracy of below 5' for

both > A an E. Doing a PAC often makes it worse (!) due to the wiggle.

> The end result is a polar alignment of between 5 and 10' - which

is > unacceptable to me.

> I have decided to return the GM-8 to the dealer (he will give me a

> 95% refund) and buy either the G-11 or the Takahashi EM-200

> instead. Having visited the Takahashi group and having had a

number > of discussions with various folks, the preliminary conclusion is

> that the Takahashi EM-200 is probably superior to the G-11,

> especially when it comes to polar alignment. The PEC performance

is > probably similar even though Takahashi claims they are better.

> I am biased in favor of the G-11 because of the greater load it

can > bear, and also because I like Gemini. The Temma II seems to be

> clearly inferior to the Gemini unless you run it directly from a

> notebook computer with the respective S/W support. I don't want

to > always depend on the notebook...

> By the way, I have eliminated the Titan as an option since it's

> simply too heavy for me to log around.

>

> My question to the group:

> Is the azimuth/elevation control on the G-11 a lot better than on

> the GM-8? What REALISTIC A and E values can I expect to achieve?

> Anyone who has both the GM-8 and G-11 mounts and can compare? How

> about polar alignment of G-11 versus EM-200?

> Thanks in advance for your inputs. This user group has already

been > extremely helpful to me just by reading the many postings. :)))

> tom



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

#25384 May 5, 2005

Am I just looking at this chain wrong? For me the polar scope

(Losmandy) gets my G-11 really close; for visual it is perfect. For

short exposure shots usually close enough. For long exposures you have

to do a drift alignment. Unless you are on a pier, you need to fine-

tune the alignment every time you set up for long exposures.



Good pictures take time, Precise alignment, Practice, Patients,

Persistence and some times Planetary alignment.



Chris



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

#25385 May 5, 2005

Tom, don't know about GM8 or EM200, but I can achieve sub-arcminute

polar aignment with my G11 on a regular basis with PoleAlignMax

(have done it four times now).



PAC will get you close but not as close, and depends on the accuracy

of the model you've built prior to doing it.



5 arcminutes sounds reasonable for a PAC run. I used to do two PAC

runs in a row, each moving the mount 3/4 of the way instead of

completely centering the star each time. My results were under 3

arcminutes error. Just make sure that the adjustments are made in

the same direction each time, this way you'll avoid any slop in the

El/Az adjusters.



Regards,



-Paul





--- In Losmandy_users@yahoogroups.com, "primecounter"

primecounter@y...> wrote: > Group

> I am disappointed by my GM-8 azimuth and elevation wiggle (I am

> refering to the large play with the knobs)which makes it pretty

much > impossible to achieve polar alignment accuracy of below 5' for

both > A an E. Doing a PAC often makes it worse (!) due to the wiggle.

> The end result is a polar alignment of between 5 and 10' - which

is > unacceptable to me.

> I have decided to return the GM-8 to the dealer (he will give me a

> 95% refund) and buy either the G-11 or the Takahashi EM-200

> instead. Having visited the Takahashi group and having had a

number > of discussions with various folks, the preliminary conclusion is

> that the Takahashi EM-200 is probably superior to the G-11,

> especially when it comes to polar alignment. The PEC performance

is > probably similar even though Takahashi claims they are better.

> I am biased in favor of the G-11 because of the greater load it

can > bear, and also because I like Gemini. The Temma II seems to be

> clearly inferior to the Gemini unless you run it directly from a

> notebook computer with the respective S/W support. I don't want

to > always depend on the notebook...

> By the way, I have eliminated the Titan as an option since it's

> simply too heavy for me to log around.

>

> My question to the group:

> Is the azimuth/elevation control on the G-11 a lot better than on

> the GM-8? What REALISTIC A and E values can I expect to achieve?

> Anyone who has both the GM-8 and G-11 mounts and can compare? How

> about polar alignment of G-11 versus EM-200?

> Thanks in advance for your inputs. This user group has already

been > extremely helpful to me just by reading the many postings. :)))

> tom







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

#25386 May 5, 2005

Thanks for your and the other replies.

I am quite meticulous when building the model and when doing the

PAC. But I am not even close to getting the accuracy you guys are

achieving...

Since I am not a mechanically astute person and I don't want to take

anything apart unless I have to, is there an easy way to adjust the

play for the A and E knobs/mechanism?

thx

tom









--- In Losmandy_users@yahoogroups.com, "Dave Sandage" daves@e...>

wrote: > Tom,

> I wonder if perhaps there's something loose with your GM-8 if you

> have excessive play in the azimuth and elevation adjustments. I

> have had both a GM-8 and G-11 and both have been pretty easy to

> adjust. My G-11 was an older model, and the elevation was

somewhat > difficult to adjust because of the single bolt. However, as long

as > I came at if from the right direction, I got pretty good results

> (A&E numbers between 0 and 2, usually around 1). My GM-8 is a

more > recent vintage with 2 bolts on the elevation adjustment, and it's

> been just a breeze to align. Again, A&E numbers around 1.

>

> The GM-8 and G-11 use nearly identical (as far as I can tell)

> mechanisms to adjust the elevation and azimuth. Do you have

anyone > else near you with either a GM-8 or G-11 that you can look at?

> There may be something you can tighten up on yours to get better

> accuracy in your adjustments.

>

> Dave S.

>

> --- In Losmandy_users@yahoogroups.com, "primecounter"

> primecounter@y...> wrote:

> > Group

> > I am disappointed by my GM-8 azimuth and elevation wiggle (I am

> > refering to the large play with the knobs)which makes it pretty

> much

> > impossible to achieve polar alignment accuracy of below 5' for

> both

> > A an E. Doing a PAC often makes it worse (!) due to the

wiggle. > > The end result is a polar alignment of between 5 and 10' - which

> is

> > unacceptable to me.

> > I have decided to return the GM-8 to the dealer (he will give me

a > > 95% refund) and buy either the G-11 or the Takahashi EM-200

> > instead. Having visited the Takahashi group and having had a

> number

> > of discussions with various folks, the preliminary conclusion is

> > that the Takahashi EM-200 is probably superior to the G-11,

> > especially when it comes to polar alignment. The PEC

performance > is

> > probably similar even though Takahashi claims they are better.

> > I am biased in favor of the G-11 because of the greater load it

> can

> > bear, and also because I like Gemini. The Temma II seems to be

> > clearly inferior to the Gemini unless you run it directly from a

> > notebook computer with the respective S/W support. I don't want

> to

> > always depend on the notebook...

> > By the way, I have eliminated the Titan as an option since it's

> > simply too heavy for me to log around.

> >

> > My question to the group:

> > Is the azimuth/elevation control on the G-11 a lot better than

on > > the GM-8? What REALISTIC A and E values can I expect to achieve?

> > Anyone who has both the GM-8 and G-11 mounts and can compare?

How > > about polar alignment of G-11 versus EM-200?

> > Thanks in advance for your inputs. This user group has already

> been

> > extremely helpful to me just by reading the many postings. :)))

> > tom



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

#25393 May 6, 2005

--- In Losmandy_users@yahoogroups.com, "primecounter"

primecounter@y...> wrote:

> Since I am not a mechanically astute person and I don't want to take

> anything apart unless I have to, is there an easy way to adjust the

> play for the A and E knobs/mechanism?



What play? The weight of the equatorial head takes up the slack in the

altitude adjuster, while there never is any play in the azimuth adjuster.



Are you sure we're talking about the same thing here?



Bear in mind that you cannot simply align with the polar scope then

tighten the locking bolts all the way - you must tighten them in

increments, verifying the alignment each time you do.



Laura Halliday VE7LDH "Que les nuages soient notre

Grid: CN89mg pied a terre..."

ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte



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