VintageBigBlue.org

 

RE: [Losmandy_users] Re: Losmandy GM8 periodic error


Dec 19, 2003

 


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

#18345 Dec 19, 2003

Could somebody tell me what is the periodic error of the GM8?



Juan Flores



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

#18356 Dec 19, 2003

Juan,

I'm getting about +/- 8-10 arcseconds of PE with my GM-8 without

guiding. This is with the standard worm. I haven't checked it for

a while, but can auto-guide pretty well at 900 mm with it.



See the following image for an example of 10 minute images self-

guided with an ST-7XME:



my.execpc.com/~philsch/Astrophotos/PicturePage3.htm#Horsehead



Phil S.



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

juanfloresjuanflores@y...> wrote: > Could somebody tell me what is the periodic error of the GM8?

>

> Juan Flores



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

#18362 Dec 20, 2003

Dear Juan,

with a portable mount of reasonable price (as Losmandy mounts or

high end Vixen) is difficult to make better than +/- 6/8 asec with

good repeatibility over the different nights.



Sometines, with particularly lucky mounts, You could measure +/- 4

asec (especially with G11) but in fact several factors do affect the

PE performances: worm own features (not always the same for standard

worms), worm-wheel coupling (that is not the same for any AR

position of the telescope!!!), scope balancing, clutches'

tightening, dust on worm/wheel and so on.



At least this is my feeling...



Clear skies.

PAOLO



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

#18365 Dec 21, 2003

Dear Paolo,



Can you please explain the method you used to measure the periodic

error of your GM8?



Thank you so much.



Juan Flores





--- In Losmandy_users@yahoogroups.com, "albireo71" mail@l...> wrote:

> Dear Juan,

> with a portable mount of reasonable price (as Losmandy mounts or

> high end Vixen) is difficult to make better than +/- 6/8 asec with

> good repeatibility over the different nights.

>

> Sometines, with particularly lucky mounts, You could measure +/- 4

> asec (especially with G11) but in fact several factors do affect

the

> PE performances: worm own features (not always the same for

standard

> worms), worm-wheel coupling (that is not the same for any AR

> position of the telescope!!!), scope balancing, clutches'

> tightening, dust on worm/wheel and so on.

>

> At least this is my feeling...

>

> Clear skies.

> PAOLO



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

#18366 Dec 21, 2003

Dear Paolo,



Can you please explain the method you used to measure the periodic

error of your GM8?



Thank you so much.



Juan Flores





--- In Losmandy_users@yahoogroups.com, "albireo71" mail@l...> wrote:

> Dear Juan,

> with a portable mount of reasonable price (as Losmandy mounts or

> high end Vixen) is difficult to make better than +/- 6/8 asec with

> good repeatibility over the different nights.

>

> Sometines, with particularly lucky mounts, You could measure +/- 4

> asec (especially with G11) but in fact several factors do affect

the

> PE performances: worm own features (not always the same for

standard

> worms), worm-wheel coupling (that is not the same for any AR

> position of the telescope!!!), scope balancing, clutches'

> tightening, dust on worm/wheel and so on.

>

> At least this is my feeling...

>

> Clear skies.

> PAOLO



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

#18383 Dec 22, 2003

Dear juan, mine is a Losmandy G11 but the method of measuring the PE

is of general use.



Personally I find very useful the use my CCD camera and MaximDL/CCD,

that is a state of the art software for CCD managemnt and digital

processig. Unfortunately is quite expensive (>350 USD).



My method is the following, set-up the CCD in autoguider mode, that

means tracking a star by sending corrections to the mount over the

serial port. During such autoguiding MaximDL creates a kind of log

file that contains the tracking error detected by the CCD.



These errors are expressed in pixel (es: -0.25 pixel) and by means of

the focal length of the guiding scope and the size of your pixels

(approx 10. um) you can derive the depointing error in arcseconds.



For a 500 mm refractor and a SX Mx5c CCD you have about 4 asec pixel.



What you have to do is simply unplug the autoguider plug from the

mount while autoguiding. This means that the tracking will start

experiencing the PE + the other tracking errors. The sofware will

detect such depointing errors, along AR and DEC, and will write them

on the log file.



Assuming a correct polar alignment, the DEC error should ne

negligible (only the random effect of seeing).



The AR error will be the sum of the PE + seeing error (turbulence).



By importing the data in Excel, Lotus or whatever, You can convert

the data in arcsecs and plot the AR error Vs. time in a chart.



An oscillating bahaviour should be evident, indicating the presence

of periodic error. The expected period for GM8 is 8 min (4 min for

G11).



By measuring the peak to valley amplitude of such sinusoid, you have

your PE. Higher frequency fluctuation will be present, indicating the

effect of seeing.



I suggest You to monitor at least 3 worm periods, that means 24 min

data gathering. In this way it is easier to recognise the effect of

seeing (that is random) from the PE itself, that is some cases can

have also sudden variations due to patologic imperfections of

worm/wheel.



Besides a minor drift of the AR sinusoid could be evident, indicating

a not perfect tracking speed or a not perfect polar alignment.

Neglect any mean value drift in you sinusoid for the aim of PE

estimation.



If you don't have a CCD, take an eyepiece with a lighted reticle,

align the eyepiece so that the AR motion is parallel to one axis of

the reticle, compute the size of the guiding box in asec (by knowning

telescope data and eyepiece data) and try to monitor the oscillation

of a bright star in the reticle. By comparing it to the size of the

guiding box You should be able of estimating the PE with a decent

confidence.



Kind regards, paolo



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

juanfloresjuanflores@y...> wrote: > Dear Paolo,

>

> Can you please explain the method you used to measure the periodic

> error of your GM8?

>

> Thank you so much.

>

> Juan Flores

>

>

>

> --- In Losmandy_users@yahoogroups.com, "albireo71" mail@l...>

wrote: > > Dear Juan,

> > with a portable mount of reasonable price (as Losmandy mounts or

> > high end Vixen) is difficult to make better than +/- 6/8 asec

with > > good repeatibility over the different nights.

> >

> > Sometines, with particularly lucky mounts, You could measure +/-

4 > > asec (especially with G11) but in fact several factors do affect

> the

> > PE performances: worm own features (not always the same for

> standard

> > worms), worm-wheel coupling (that is not the same for any AR

> > position of the telescope!!!), scope balancing, clutches'

> > tightening, dust on worm/wheel and so on.

> >

> > At least this is my feeling...

> >

> > Clear skies.

> > PAOLO







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

#18384 Dec 22, 2003

I wrote a visual basic program that plots the RA and DEC error in real time

as well as displaying other relevant information about how your guiding is

performing. It is free and available at:



www.ccdargo.com/vbtrack.htm



Tom Carrico

www.ccdargo.com ----- Original Message -----

From: "albireo71" mail@...>

To: Losmandy_users@yahoogroups.com>

Sent: Monday, December 22, 2003 5:49 AM

Subject: [Losmandy_users] Re: GM8 Periodic Error





> Dear juan, mine is a Losmandy G11 but the method of measuring the PE

> is of general use.

>

> Personally I find very useful the use my CCD camera and MaximDL/CCD,

> that is a state of the art software for CCD managemnt and digital

> processig. Unfortunately is quite expensive (>350 USD).

>

> My method is the following, set-up the CCD in autoguider mode, that

> means tracking a star by sending corrections to the mount over the

> serial port. During such autoguiding MaximDL creates a kind of log

> file that contains the tracking error detected by the CCD.

>

> These errors are expressed in pixel (es: -0.25 pixel) and by means of

> the focal length of the guiding scope and the size of your pixels

> (approx 10. um) you can derive the depointing error in arcseconds.

>

> For a 500 mm refractor and a SX Mx5c CCD you have about 4 asec pixel.

>

> What you have to do is simply unplug the autoguider plug from the

> mount while autoguiding. This means that the tracking will start

> experiencing the PE + the other tracking errors. The sofware will

> detect such depointing errors, along AR and DEC, and will write them

> on the log file.

>

> Assuming a correct polar alignment, the DEC error should ne

> negligible (only the random effect of seeing).

>

> The AR error will be the sum of the PE + seeing error (turbulence).

>

> By importing the data in Excel, Lotus or whatever, You can convert

> the data in arcsecs and plot the AR error Vs. time in a chart.

>

> An oscillating bahaviour should be evident, indicating the presence

> of periodic error. The expected period for GM8 is 8 min (4 min for

> G11).

>

> By measuring the peak to valley amplitude of such sinusoid, you have

> your PE. Higher frequency fluctuation will be present, indicating the

> effect of seeing.

>

> I suggest You to monitor at least 3 worm periods, that means 24 min

> data gathering. In this way it is easier to recognise the effect of

> seeing (that is random) from the PE itself, that is some cases can

> have also sudden variations due to patologic imperfections of

> worm/wheel.

>

> Besides a minor drift of the AR sinusoid could be evident, indicating

> a not perfect tracking speed or a not perfect polar alignment.

> Neglect any mean value drift in you sinusoid for the aim of PE

> estimation.

>

> If you don't have a CCD, take an eyepiece with a lighted reticle,

> align the eyepiece so that the AR motion is parallel to one axis of

> the reticle, compute the size of the guiding box in asec (by knowning

> telescope data and eyepiece data) and try to monitor the oscillation

> of a bright star in the reticle. By comparing it to the size of the

> guiding box You should be able of estimating the PE with a decent

> confidence.

>

> Kind regards, paolo

>

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

> juanfloresjuanflores@y...> wrote:

> > Dear Paolo,

> >

> > Can you please explain the method you used to measure the periodic

> > error of your GM8?

> >

> > Thank you so much.

> >

> > Juan Flores

> >

> >

> >

> > --- In Losmandy_users@yahoogroups.com, "albireo71" mail@l...>

> wrote:

> > > Dear Juan,

> > > with a portable mount of reasonable price (as Losmandy mounts or

> > > high end Vixen) is difficult to make better than +/- 6/8 asec

> with

> > > good repeatibility over the different nights.

> > >

> > > Sometines, with particularly lucky mounts, You could measure +/-

> 4

> > > asec (especially with G11) but in fact several factors do affect

> > the

> > > PE performances: worm own features (not always the same for

> > standard

> > > worms), worm-wheel coupling (that is not the same for any AR

> > > position of the telescope!!!), scope balancing, clutches'

> > > tightening, dust on worm/wheel and so on.

> > >

> > > At least this is my feeling...

> > >

> > > Clear skies.

> > > PAOLO

>

>

> To unsubscribe from this group, send an email to:

> Losmandy_users-unsubscribe@egroups.com

>

>

>

> Yahoo! Groups Links

>

> To visit your group on the web, go to:

> groups.yahoo.com/group/Losmandy_users/

>

> To unsubscribe from this group, send an email to:

> Losmandy_users-unsubscribe@yahoogroups.com

>

> Your use of Yahoo! Groups is subject to:

> docs.yahoo.com/info/terms/

>

>







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

#18389 Dec 23, 2003

Dear Tom, VERY NICE. I'll try your smart utility.



King regards and happy Xmas, happy new year.



Paolo



--- In Losmandy_users@yahoogroups.com, "Tom Carrico" tom@c...> wrote:

> I wrote a visual basic program that plots the RA and DEC error in

real time

> as well as displaying other relevant information about how your

guiding is

> performing. It is free and available at:

>

> www.ccdargo.com/vbtrack.htm

>

> Tom Carrico

> www.ccdargo.com

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

> From: "albireo71" mail@l...>

> To: Losmandy_users@yahoogroups.com>

> Sent: Monday, December 22, 2003 5:49 AM

> Subject: [Losmandy_users] Re: GM8 Periodic Error

>

>

> > Dear juan, mine is a Losmandy G11 but the method of measuring the

PE

> > is of general use.

> >

> > Personally I find very useful the use my CCD camera and

MaximDL/CCD,

> > that is a state of the art software for CCD managemnt and digital

> > processig. Unfortunately is quite expensive (>350 USD).

> >

> > My method is the following, set-up the CCD in autoguider mode,

that

> > means tracking a star by sending corrections to the mount over the

> > serial port. During such autoguiding MaximDL creates a kind of log

> > file that contains the tracking error detected by the CCD.

> >

> > These errors are expressed in pixel (es: -0.25 pixel) and by

means of

> > the focal length of the guiding scope and the size of your pixels

> > (approx 10. um) you can derive the depointing error in arcseconds.

> >

> > For a 500 mm refractor and a SX Mx5c CCD you have about 4 asec

pixel.

> >

> > What you have to do is simply unplug the autoguider plug from the

> > mount while autoguiding. This means that the tracking will start

> > experiencing the PE + the other tracking errors. The sofware will

> > detect such depointing errors, along AR and DEC, and will write

them

> > on the log file.

> >

> > Assuming a correct polar alignment, the DEC error should ne

> > negligible (only the random effect of seeing).

> >

> > The AR error will be the sum of the PE + seeing error

(turbulence).

> >

> > By importing the data in Excel, Lotus or whatever, You can convert

> > the data in arcsecs and plot the AR error Vs. time in a chart.

> >

> > An oscillating bahaviour should be evident, indicating the

presence

> > of periodic error. The expected period for GM8 is 8 min (4 min for

> > G11).

> >

> > By measuring the peak to valley amplitude of such sinusoid, you

have

> > your PE. Higher frequency fluctuation will be present, indicating

the

> > effect of seeing.

> >

> > I suggest You to monitor at least 3 worm periods, that means 24

min

> > data gathering. In this way it is easier to recognise the effect

of

> > seeing (that is random) from the PE itself, that is some cases can

> > have also sudden variations due to patologic imperfections of

> > worm/wheel.

> >

> > Besides a minor drift of the AR sinusoid could be evident,

indicating

> > a not perfect tracking speed or a not perfect polar alignment.

> > Neglect any mean value drift in you sinusoid for the aim of PE

> > estimation.

> >

> > If you don't have a CCD, take an eyepiece with a lighted reticle,

> > align the eyepiece so that the AR motion is parallel to one axis

of

> > the reticle, compute the size of the guiding box in asec (by

knowning

> > telescope data and eyepiece data) and try to monitor the

oscillation

> > of a bright star in the reticle. By comparing it to the size of

the

> > guiding box You should be able of estimating the PE with a decent

> > confidence.

> >

> > Kind regards, paolo

> >

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

> > juanfloresjuanflores@y...> wrote:

> > > Dear Paolo,

> > >

> > > Can you please explain the method you used to measure the

periodic

> > > error of your GM8?

> > >

> > > Thank you so much.

> > >

> > > Juan Flores

> > >

> > >

> > >

> > > --- In Losmandy_users@yahoogroups.com, "albireo71" mail@l...>

> > wrote:

> > > > Dear Juan,

> > > > with a portable mount of reasonable price (as Losmandy mounts

or

> > > > high end Vixen) is difficult to make better than +/- 6/8 asec

> > with

> > > > good repeatibility over the different nights.

> > > >

> > > > Sometines, with particularly lucky mounts, You could measure

+/-

> > 4

> > > > asec (especially with G11) but in fact several factors do

affect

> > > the

> > > > PE performances: worm own features (not always the same for

> > > standard

> > > > worms), worm-wheel coupling (that is not the same for any AR

> > > > position of the telescope!!!), scope balancing, clutches'

> > > > tightening, dust on worm/wheel and so on.

> > > >

> > > > At least this is my feeling...

> > > >

> > > > Clear skies.

> > > > PAOLO

> >

> >

> > To unsubscribe from this group, send an email to:

> > Losmandy_users-unsubscribe@egroups.com

> >

> >

> >

> > Yahoo! Groups Links

> >

> > To visit your group on the web, go to:

> > groups.yahoo.com/group/Losmandy_users/

> >

> > To unsubscribe from this group, send an email to:

> > Losmandy_users-unsubscribe@yahoogroups.com

> >

> > Your use of Yahoo! Groups is subject to:

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

> >

> >







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

#60725 Jan 19

Hi guys,







This is my first post on this group. Sorry for my english, I.m not a native speaker.







I have an old GM8 mount which I want to improve. The actual periodic error is about 54 arc/sec peak to peak. I have the steel worms and two block design. I.ve attached a picture with PECPrep graphs.







My questions are:







1) Can I improve the actual error using the steel worm?







2) If I change to a high precision worm from Losmandy what would be the best PE I can get? How much better than now? To know what to expect.







3) Can I find the mount.s year of production by viewing the serial number? The serial number is HGM299805084.











What I want to do next to gain some improvements:







1) Change the bearings with new ABEC 5 bearings.







2) Spring washer on one bearing to tension the worm between the blocks.







3) Play with the mesh to find the hot spot.











What I did till now:







1) Clean and grease the mount.







2) I found that at transport the blocks that press the needle bearing and hold the RA axis were misaligned. So I pressed them together to a true. I.ve read about this here on the group.







3) Make a version of OPW. You can see it in the attached picture.











I.ve searched a lot on internet about performances of GM8 but very few details I found. So you are my last chance J







Any suggestions are welcome.







Catalin



















[Non-text portions of this message have been removed]



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

#60727 Jan 19

Your first big win will be very likely from the worm gear mesh adjustment, that's definitely worth doing. I got a large improvement on my mount just be doing that.



Clear skies

Dave Partridge



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

From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com]

Sent: 19 January 2018 08:19

To: Losmandy_users@yahoogroups.com

Subject: [Losmandy_users] Losmandy GM8 periodic error



Hi guys,







This is my first post on this group. Sorry for my english, I.m not a native speaker.







I have an old GM8 mount which I want to improve. The actual periodic error is about 54 arc/sec peak to peak. I have the steel worms and two block design. I.ve attached a picture with PECPrep graphs.







My questions are:







1) Can I improve the actual error using the steel worm?







2) If I change to a high precision worm from Losmandy what would be the best PE I can get? How much better than now? To know what to expect.







3) Can I find the mount.s year of production by viewing the serial number? The serial number is HGM299805084.











What I want to do next to gain some improvements:







1) Change the bearings with new ABEC 5 bearings.







2) Spring washer on one bearing to tension the worm between the blocks.







3) Play with the mesh to find the hot spot.











What I did till now:







1) Clean and grease the mount.







2) I found that at transport the blocks that press the needle bearing and hold the RA axis were misaligned. So I pressed them together to a true. I.ve read about this here on the group.







3) Make a version of OPW. You can see it in the attached picture.











I.ve searched a lot on internet about performances of GM8 but very few details I found. So you are my last chance J







Any suggestions are welcome.







Catalin



















[Non-text portions of this message have been removed]







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

Posted by: "Catalin Paduraru" catalin.paduraru@...>

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





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



Yahoo Groups Links



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

#60729 Jan 19

Hi Catalin,

If you are capable of doing the mechanical work without damaging the mount and the mount ihows no obvious damage your GM8 should be capable of pretty good tracking. With any project like this you have to be honest with yourself in recognizing your abilities and your limitations to avoid causing more harm than good. That said the basics are the most important considerations. This is what I always do with any equipment I buy new or used. Assess the baseline performance of the system in front of me to see if it meets the needs of the project or use. If the answer is yes use it as is.��

If the answer is no, document performance problems then determine what can be done to bring the system into operational condition. For a high quality mount like the GM8 this should be simple as long as there is no obvious damage, just bring the mount back to manufacturer's stock condition before chasing improved performance. To do this you need to disassemble, remove old lube fully using solvent and blow bearings and all surfaces clean and dry, inspect and assess condition of component parts, replace or repair any components that are not in top mechanical condition. Correctly lubricate (minimal fresh lube) using correct lube for expected environmental conditions and reassemble and verify correct assembly, do not rely on as received assembly order, if in doubt ask here or refer to assembly photos. Adjust worm mesh and reassess performance using the same system used for baseline data. Be sure that your measurement system is valid, if in doubt ask here or on sites that support your autoguider software and hardware.��

Once you have a good working mount and you know the mount is working correctly and is as well adjusted as possible in my experience the single largest improvement to tracking error is changing from the old silver steel colored worms to the brass colored high precision worm on the RA axis. The second option with the most impact on tracking or PE is to put that HP-worm in a one-piece worm block. Other than these two updates careful assembly and adjustment like adding Bellevue spring washers and using good clean bearings on the worms make all the difference. The most obvious issue that adversely affects every EQ mount's tracking error is polar alignment. What to you use to do your polar alignment? The best method I have seen and used is the PoleMaster camera but if you have an autoguider you can also use SharpCap 3.x which can also give you an excellent polar alignment, these two are the best of what I have used.����Chip Louie��







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

#60730 Jan 19

Catalin, ��My experience was with a used (made around 2006 I recall ��� it has the 25 year sticker on it) G-11. I was the second or third owner. I think the first owners bought it and did not know how to adjust it properly. ��I started out in the same place with about 40 arcseconds of swing in the pattern and it included the dreaded 76 second ��(of time) spike in the pattern, which PEC can not take out. That is usually a result of miss-alignment of the bearing blocks on the worm. ��I did the following: ��Replaced the steel worm gears (I did both) with the brass high precision worms. So of course this meant I cleaned and re-greased the worm wheels as well. ��Replaced ��the worm shaft bearings with upgraded ones like you are talking about. ��I also replaced the bearing blocks (two per worm) because the prior owner had seriously over torqued the bearing blocks. Since the metal is thin and the bearing blocks were cheap I replaced them. Perhaps not necessary. ��Carefully aligned the bearing blocks by installing them with the mounting bolts finger tight. Then I clamped a metal angle bracket to them (with small soft-jaw clamps) to keep them parallel. Then I adjusted the worm to worm wheel spacing (often referred to as the ���lash���) to find the high spot on the worm and carefully tightened the worm blocks in place. This took a bit of practice but I was able to completely eliminate the 76 second problem . This was before the one-piece worm blocks were available. But I haven���t had to change it since 2007. ��Carefully mounted the motors so the Oldham couplers were square and parallel. ��By doing the above I got the PE down to about +-4 arc seconds, which put it well within range of an autoguider since the slope would be about 4arc sec/60 seconds. So during a three second guider exposure the accumulated error would be 12/60th = 0.2 arc seconds, which you���ll never see given the atmosphere. ��I hope you are not trying to image moderate to long focal lengths without guiding. ��I assume you have a non-Gemini mount. You didn���t say if it was the 492 or the Gemini drives. Some of the other responses, I think, assumed you had the Gemini since they talked about gearboxes. If you have the Gemini, of course, that is something else to worry about. ��Hope this helps you. ��Choi, ��Mark Christensen ��



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

#60731 Jan 20

Hi guys,.

Thank you for your feedback..

Chip



I think I can do all this improvements without damaging the mount. At least part of the hobby is improving my gear and I have experience over the years :).I believe.the mount has it's stock specs now. All I want to do is to improve a bit the periodic error. If I'm not happy with the results I will buy the HP worm. At least this is the plan. I don't think I need the OPWB for what I do but will see.For polar align I'm using the Losmandy polar finder. Is good enough for now. I will try SharpCap also.I couldn't find belleville washer in my country or ebay so I ordered wave washer. I hope they will do the same job.

Mark



I have the stock mount with.492 digital drive. And using the mount to do astrophotography using 600mm focal length and DSLR camera..You have good improvements with your mount..

For the next clear night I want to try and get the best mesh setup for this worm. And after this I will do the same with the DEC worm. And I have another worm from a friend and try his worm to. And see which worm performs better..

And I will return with the error to see how good it can be with steel worm, ABEC 5 bearings, wave washer and my version of OPWB..

Catalin



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

#60735 Jan 21

Hi Catalin,

Have you read Michael Herman's document in the files about how to optimize your G11 mount? It is the definitive piece for the G11 and GM8 mounts! Shoot me you mailing address and I'll send you the correct Bellevue spring washers. Wave washers are not going to work.

Chip����



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

#60736 Jan 21

Hi, ��Yes, I know the paper Michael made and that was the main reason I started modifying the mount. And I have to admit I love this part J Also because I have I friend with the same mount and we are a team on this journey J ��The hard part now is waiting for parts. ��Catalin ��__Catalin PaduraruTel: (004) 0722.22.75.94www.bikegeek.ro

��From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com] Sent: Sunday, January 21, 2018 10:47 PMTo: Losmandy_users@yahoogroups.comSubject: [Losmandy_users] Re: Losmandy GM8 periodic error



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

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