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Re: Periodic Error---averages? -- CORRECTION


Mar 21, 2004

 


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

#19624 Mar 21, 2004

I've been reading about periodic error in the G-11's and find that

+/- 10 arcseconds seems to be the general consensus (from what I've

found). This is with the older worms, not the newer high-precision

worm.



I was measuring mine tonight and using a reticle ep on Jupiter I was

getting a drift back and forth of about 1/5 of the diameter of

Jupiter. With Jupiter being about 43 arcseconds right now, I figure

I'm getting about +/- 8 or 9 arc seconds of error.



What size of error are others getting?



Thanks,



Todd



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

#19626 Mar 22, 2004

Todd,



I have the newer worms. When I upgraded, initially my error was 9

arcseconds peak-to-peak (+/-4.5"). At one point I swapped the RA and

DEC worms, and found that my error is now +/-3" (6" peak-to-peak).

These were measured with a ccd.



+/-10" is not bad, as long as the error is smooth, with no sudden

jumps.



Regards,



-Paul

--- In Losmandy_users@yahoogroups.com, "Todd" tdcarls@a...> wrote:

> I've been reading about periodic error in the G-11's and find that

> +/- 10 arcseconds seems to be the general consensus (from what I've

> found). This is with the older worms, not the newer high-precision

> worm.

>

> I was measuring mine tonight and using a reticle ep on Jupiter I

was

> getting a drift back and forth of about 1/5 of the diameter of

> Jupiter. With Jupiter being about 43 arcseconds right now, I

figure

> I'm getting about +/- 8 or 9 arc seconds of error.

>

> What size of error are others getting?

>

> Thanks,

>

> Todd



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

#19627 Mar 22, 2004

Hi Paul,



I had just a slow but smooth drifting of Jupiter back and forth

across my crosshairs last night. I watched it for about 10 minutes

and there didn't seem to be any quick movements. It was basically

an hypnotic slow but steady oscillation back and forth.



Maybe I'll think about switching the worms to see if that makes a

difference although I'm probably just being anal about it. One of

these nights I'll get my autoguider attached to it too.



The previous owner had a C14 and C11 on it and now I'm either

mounting a 4" Vixen apo or a TV76. Big difference in weight!



Todd



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

#19628 Mar 22, 2004

Slow and hypnotic is good ;-) The autoguider should easily take care

of this.



I'd suggest you test the mount with the autoguider, and if it can

handle the PE well, there's really no reason to swap the worms: you

never know if what you'll get will be an improvement.



Regards,



-Paul

--- In Losmandy_users@yahoogroups.com, "Todd" tdcarls@a...> wrote:

> Hi Paul,

>

> I had just a slow but smooth drifting of Jupiter back and forth

> across my crosshairs last night. I watched it for about 10 minutes

> and there didn't seem to be any quick movements. It was basically

> an hypnotic slow but steady oscillation back and forth.

>

> Maybe I'll think about switching the worms to see if that makes a

> difference although I'm probably just being anal about it. One of

> these nights I'll get my autoguider attached to it too.

>

> The previous owner had a C14 and C11 on it and now I'm either

> mounting a 4" Vixen apo or a TV76. Big difference in weight!

>

> Todd



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

#19630 Mar 22, 2004

By the way, Jupiter is probably not the best object to use to measure

tracking, as it does not move at Sidereal rate. There will be some

drift in the eyepiece, even with the most precise worm. SkyMap Pro

reports the Jupiter RA drift at nearly 16 arcseconds per 10 minutes.



It's better to use a bright star for this purpose.



Regards,



-Paul



--- In Losmandy_users@yahoogroups.com, "Todd" tdcarls@a...> wrote:

> Hi Paul,

>

> I had just a slow but smooth drifting of Jupiter back and forth

> across my crosshairs last night. I watched it for about 10 minutes

> and there didn't seem to be any quick movements. It was basically

> an hypnotic slow but steady oscillation back and forth.

>

> Maybe I'll think about switching the worms to see if that makes a

> difference although I'm probably just being anal about it. One of

> these nights I'll get my autoguider attached to it too.

>

> The previous owner had a C14 and C11 on it and now I'm either

> mounting a 4" Vixen apo or a TV76. Big difference in weight!

>

> Todd



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

#19632 Mar 22, 2004

Very interesting on the natural drift of Jupiter. I did not consider

this. I suppose the same happens with Saturn.



--- In Losmandy_users@yahoogroups.com, "Paul K" pkane2001@h...>

wrote: > By the way, Jupiter is probably not the best object to use to

measure > tracking, as it does not move at Sidereal rate. There will be some

> drift in the eyepiece, even with the most precise worm. SkyMap Pro

> reports the Jupiter RA drift at nearly 16 arcseconds per 10 minutes.

>

> It's better to use a bright star for this purpose.

>

> Regards,

>

> -Paul

>

>

> --- In Losmandy_users@yahoogroups.com, "Todd" tdcarls@a...> wrote:

> > Hi Paul,

> >

> > I had just a slow but smooth drifting of Jupiter back and forth

> > across my crosshairs last night. I watched it for about 10

minutes > > and there didn't seem to be any quick movements. It was

basically > > an hypnotic slow but steady oscillation back and forth.

> >

> > Maybe I'll think about switching the worms to see if that makes a

> > difference although I'm probably just being anal about it. One

of > > these nights I'll get my autoguider attached to it too.

> >

> > The previous owner had a C14 and C11 on it and now I'm either

> > mounting a 4" Vixen apo or a TV76. Big difference in weight!

> >

> > Todd







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

#19634 Mar 22, 2004

OOOPS! SORRY, MY MISTAKE!



I should've looked more carefully: the drift for Jupiter was actually

0.16 arcsec/10min in RA last night, and about 1 arcsec/10 min in DEC!

For Saturn it was less than 0.05 arcsecs/10 minutes in both, RA and

DEC.



These values change over time, but for now, it don't think this drift

will introduce too large of an error into PE measurement :-}



Regards,



-Paul

--- In Losmandy_users@yahoogroups.com, "ejrobau" ejr@c...> wrote:

> Very interesting on the natural drift of Jupiter. I did not

consider

> this. I suppose the same happens with Saturn.

>

> --- In Losmandy_users@yahoogroups.com, "Paul K" pkane2001@h...>

> wrote:

> > By the way, Jupiter is probably not the best object to use to

> measure

> > tracking, as it does not move at Sidereal rate. There will be

some

> > drift in the eyepiece, even with the most precise worm. SkyMap

Pro

> > reports the Jupiter RA drift at nearly 16 arcseconds per 10

minutes.

> >

> > It's better to use a bright star for this purpose.

> >

> > Regards,

> >

> > -Paul

> >

> >

> > --- In Losmandy_users@yahoogroups.com, "Todd" tdcarls@a...>

wrote:

> > > Hi Paul,

> > >

> > > I had just a slow but smooth drifting of Jupiter back and forth

> > > across my crosshairs last night. I watched it for about 10

> minutes

> > > and there didn't seem to be any quick movements. It was

> basically

> > > an hypnotic slow but steady oscillation back and forth.

> > >

> > > Maybe I'll think about switching the worms to see if that makes

a

> > > difference although I'm probably just being anal about it. One

> of

> > > these nights I'll get my autoguider attached to it too.

> > >

> > > The previous owner had a C14 and C11 on it and now I'm either

> > > mounting a 4" Vixen apo or a TV76. Big difference in weight!

> > >

> > > Todd



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

#19639 Mar 22, 2004

Shoot,



Back go my fast mount issue.



I have measured my periodic error that ranges from 0.5 arc-seconds to

about 2.5 or so arc-seconds. When I verify this several times I will

post a plot of the error and the time variation. When I guide with

my st8e at three seconds the guiding is great it starts to wear off

at 5 seconds or so. Wind is the biggest issue for me right now. I

need an observatory.







--- In Losmandy_users@yahoogroups.com, "Paul K" pkane2001@h...>

wrote: > OOOPS! SORRY, MY MISTAKE!

>

> I should've looked more carefully: the drift for Jupiter was

actually > 0.16 arcsec/10min in RA last night, and about 1 arcsec/10 min in

DEC! > For Saturn it was less than 0.05 arcsecs/10 minutes in both, RA and

> DEC.

>

> These values change over time, but for now, it don't think this

drift > will introduce too large of an error into PE measurement :-}

>

> Regards,

>

> -Paul

>

> --- In Losmandy_users@yahoogroups.com, "ejrobau" ejr@c...> wrote:

> > Very interesting on the natural drift of Jupiter. I did not

> consider

> > this. I suppose the same happens with Saturn.

> >

> > --- In Losmandy_users@yahoogroups.com, "Paul K" pkane2001@h...>

> > wrote:

> > > By the way, Jupiter is probably not the best object to use to

> > measure

> > > tracking, as it does not move at Sidereal rate. There will be

> some

> > > drift in the eyepiece, even with the most precise worm. SkyMap

> Pro

> > > reports the Jupiter RA drift at nearly 16 arcseconds per 10

> minutes.

> > >

> > > It's better to use a bright star for this purpose.

> > >

> > > Regards,

> > >

> > > -Paul

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com, "Todd" tdcarls@a...>

> wrote:

> > > > Hi Paul,

> > > >

> > > > I had just a slow but smooth drifting of Jupiter back and

forth > > > > across my crosshairs last night. I watched it for about 10

> > minutes

> > > > and there didn't seem to be any quick movements. It was

> > basically

> > > > an hypnotic slow but steady oscillation back and forth.

> > > >

> > > > Maybe I'll think about switching the worms to see if that

makes > a

> > > > difference although I'm probably just being anal about it.

One > > of

> > > > these nights I'll get my autoguider attached to it too.

> > > >

> > > > The previous owner had a C14 and C11 on it and now I'm either

> > > > mounting a 4" Vixen apo or a TV76. Big difference in weight!

> > > >

> > > > Todd



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