Re: [ap-gto] 900 GTO & PE & Unguided exposures


Dec 2, 2002

 


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

#6164 Dec 2, 2002

Hello,

I a have been using Roland's technique of polar aligning with a CCD

adn CCDOPS track and error. I have the dec down to less 1/3 of a

pixel drift or 0.46 arcsec/pixel over a 5 minute tracking time.



My PE is down from 5.0 arcsec error to about 2.5 arcsec error with

the PEM correction on, again over a 5 minutes tracking time.



With this numbers I am still gettin a tad of drift in the RA with a 5

and 10 minute unguided exposure...



Could this be explained on the basis of seeing?



Any other factors?



I have already checked scope balance, and scope is an observatory so

wind should not be a factor.



TIA



Joe Marietta



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

#6165 Dec 2, 2002

Joe,



More likely, these are due to refraction in the atmosphere. As you probably

know, the atmosphere causes stars to move at different rates when they are

at different elevations. This is very pronounced near the horizon but still

occurs everywhere in the sky. Such small numbers of PE may be due to these

refractive effects.



Steve...

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

From: "Joe Marietta" jmarietta@...>

To: ap-gto@yahoogroups.com>

Sent: Monday, December 02, 2002 8:25 AM

Subject: [ap-gto] 900 GTO & PE & Unguided exposures





> Hello,

> I a have been using Roland's technique of polar aligning with a CCD

> adn CCDOPS track and error. I have the dec down to less 1/3 of a

> pixel drift or 0.46 arcsec/pixel over a 5 minute tracking time.

>

> My PE is down from 5.0 arcsec error to about 2.5 arcsec error with

> the PEM correction on, again over a 5 minutes tracking time.

>

> With this numbers I am still gettin a tad of drift in the RA with a 5

> and 10 minute unguided exposure...

>

> Could this be explained on the basis of seeing?

>

> Any other factors?

>

> I have already checked scope balance, and scope is an observatory so

> wind should not be a factor.

>

> TIA

>

> Joe Marietta

>

>

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

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

>

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

>

>

>



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

#6166 Dec 2, 2002

You didn't mention whether you shimmed the rings.



Bob K.





Joe Marietta wrote:

> Hello,

> I a have been using Roland's technique of polar aligning with a CCD

> adn CCDOPS track and error. I have the dec down to less 1/3 of a

> pixel drift or 0.46 arcsec/pixel over a 5 minute tracking time.

>

> My PE is down from 5.0 arcsec error to about 2.5 arcsec error with

> the PEM correction on, again over a 5 minutes tracking time.

>

> With this numbers I am still gettin a tad of drift in the RA with a 5

> and 10 minute unguided exposure...

>

> Could this be explained on the basis of seeing?

>

> Any other factors?

>

> I have already checked scope balance, and scope is an observatory so

> wind should not be a factor.

>

> TIA

>

> Joe Marietta

>

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

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

>

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



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

#6167 Dec 3, 2002

Hi Bob,

Nope I did not shim the rings. I have an AP 155 with AP rings on a

losmandy dove tail plate.



I read Roland's procedure on how to check fo orthrogonality but it

sounded difficult.



How do you shim the rings while the scope is mounted in the rigns?

How do you pick the correct ring to shim?



Roland writes: "simply shim up one of the tube rings to bring the star

half way towards the crosshair".



How would you loosen the tube ring to do this while the scope is

secured in the ring?



Is it still important for polar alignment t have the scope in perfect

orthogonality if you use stars away from the pole to do the polar

alignment?



In the manual, Roland writes:



"when the scope has an orthrogonal error, it is useless to try to polar

align using polaris"



If I use non-polar stars, can I get good polar alignment using

"non-polar" stars?



Thanks



Joe











On Monday, December 2, 2002, at 11:34 PM, Robert Kuberek wrote:



> You didn't mention whether you shimmed the rings.

>

> Bob K.

>

>

> Joe Marietta wrote:

>

>> Hello,

>> I a have been using Roland's technique of polar aligning with a CCD

>> adn CCDOPS track and error. I have the dec down to less 1/3 of a

>> pixel drift or 0.46 arcsec/pixel over a 5 minute tracking time.

>>

>> My PE is down from 5.0 arcsec error to about 2.5 arcsec error with

>> the PEM correction on, again over a 5 minutes tracking time.

>>

>> With this numbers I am still gettin a tad of drift in the RA with a 5

>> and 10 minute unguided exposure...

>>

>> Could this be explained on the basis of seeing?

>>

>> Any other factors?

>>

>> I have already checked scope balance, and scope is an observatory so

>> wind should not be a factor.

>>

>> TIA

>>

>> Joe Marietta

>>

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

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

>>

>> Your use of Yahoo! Groups is subject to

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

>

>

>

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

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

>

> Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

>

>







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

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