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Author Topic: Is this back lash ?  (Read 1452 times)

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Online Roger B

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Is this back lash ?
« on: 11:37:31, 28 February, 2016 »
When I'm calibrating with PHD2 I have noticed that when it say " Clearing backlash" my guide star moves north,  then it starts to calibrate north but struggles to bring it back to the original starting point south & has to take a extra 3 "south nudges" to centre it again.

I'm not that bothered TBH as my guiding seems to be very good ATM but it's just one of those things that bug me.


Roger
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Offline Nomis Elfactem

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Re: Is this back lash ?
« Reply #1 on: 12:10:33, 28 February, 2016 »
Mine does that too Rog (but usually needs more than three nudges to re-centre)... I concluded yes, it's the amount of backlash in the system being taken out and isn't anything to "worry" about !?

Be interested to know if that isn't the case though.

S.
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Offline tomhow

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Re: Is this back lash ?
« Reply #2 on: 12:30:45, 28 February, 2016 »
Part of the point of guider calibration is to quantify the backlash in the DEC so the guider can account for it. Otherwise you get that drift-drift-drift-JERK pattern in the dec guiding when it reverses. That's the point of those "only dec guide north" settings: To try and keep backlash out of the equation.

That said, things like backlash come riddled with hysteresis so trying to minimise it in the mechanical domain (i.e. by fiddling with the mount) can only help the guider.

RA guiding is a whole lot easier as the motor is always running so backlash ain't an issue.
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Online Roger B

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Re: Is this back lash ?
« Reply #3 on: 12:38:03, 28 February, 2016 »
Mine does that too Rog (but usually needs more than three nudges to re-centre)... I concluded yes, it's the amount of backlash in the system being taken out and isn't anything to "worry" about !?

Be interested to know if that isn't the case though.

S.

ok,  good to know it's not just me,  may be a tad of adjustment is needed in the dec to minimise the north movement

Rog
Scopes - TS65q, W/O 110 Triplet
Mount - EQ6 PRO via  Eqmod,  Rowan belt modded
Cameras - SX694, QSI583WSG,Lodestar Guidecam, GP-Cam, QHY5II.
TS 9mm OAG
Quantum 7x1.25 EFW, Baader LRGB,Ha,OIII,SII Filters 
Quark chromo

SGPro, Pixinsight.

************AND NO TIME TO USE IT************

Offline Starlight

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Re: Is this back lash ?
« Reply #4 on: 16:58:20, 28 February, 2016 »
Rog
I seem to remember reading somewhere that its best not to have it "exactly" set up to minimise declination drift as then it tends to oscillate when guiding. Once you figure out which way its drifting then set dec guiding in just the one direction.
Don
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Online Roger B

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Re: Is this back lash ?
« Reply #5 on: 17:16:40, 28 February, 2016 »
Rog
I seem to remember reading somewhere that its best not to have it "exactly" set up to minimise declination drift as then it tends to oscillate when guiding. Once you figure out which way its drifting then set dec guiding in just the one direction.
Don

cheers Don,

I best leave it TBH as I said my guiding is pretty good at the mo,   it just was bugging me when calibrating,  But as Si has the same issue I know it's not my setup.    ( If its not broke don't fix it )

Roger
Scopes - TS65q, W/O 110 Triplet
Mount - EQ6 PRO via  Eqmod,  Rowan belt modded
Cameras - SX694, QSI583WSG,Lodestar Guidecam, GP-Cam, QHY5II.
TS 9mm OAG
Quantum 7x1.25 EFW, Baader LRGB,Ha,OIII,SII Filters 
Quark chromo

SGPro, Pixinsight.

************AND NO TIME TO USE IT************

 

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