eq8 is here

[coldknights (Cathy)]

EQ8 $5299.00



http://www.bintel.com.au/Mounts---Tr...oductview.aspx

[dancingononeleg (Michael)]

Our club is building an observatory and will soon be setting up an EQ8. We are currently designing a pier for it using donated and "found" materials. One of the questions we have concerns the acceptable diameter of the top plate - the one that the EQ8 will attach to. The pier diameter will probably be 9" and the current design shows that the top plate will be the same, this is 2" greater than the standard tripod top plate diameter (7"). Will this extra inch restrict our ability to slew to the zenith or past the meridian?
Thanks
Michael

[AstroJunk (Jonathan)]

Originally Posted by dancingononeleg

Our club is building an observatory and will soon be setting up an EQ8. We are currently designing a pier for it using donated and "found" materials. One of the questions we have concerns the acceptable diameter of the top plate - the one that the EQ8 will attach to. The pier diameter will probably be 9" and the current design shows that the top plate will be the same, this is 2" greater than the standard tripod top plate diameter (7"). Will this extra inch restrict our ability to slew to the zenith or past the meridian?
Thanks
Michael

Yes, but in all likelyhood, not enough to worry about. More of a problem if you are mounting an SCT rather than a newtonian/refractor, that latter would tend to strike the pier before the flange.

And if it is an issue, its nothing that an angle grinder can't sort out

[h0ughy (David)]

now on to more pressing matters – the eq8!!!!!!! simply saying this - IT IS BLOODY UNREAL!!!

First night – rms of 0.02 – this was witnessed by several people and was guiding at f6.3 through the c11 I was using. the Weeks average was 0.06 – 0.11 with the exception for Thursday as the seeing week pear shape for a short while and the rms was 0.33 guiding through a 60mm guidescope and a lodestar

simply put we worked out the two star alignment procedure and then adjusted the offset to find the SCP – two iterations for me and it was done – I never touched it for the rest of the week. But – and there is a big but – I hate the pier – its a mongrel to setup and level – but in saying that its very stable.


I will wright up more later but in a nutshell it goes to object very very well from a 1 star alignment. absolutely no backlash, however I do think that there is a bug in the 3.35 version of the software - those that had that on eq6's alt eq6 and the other eq8 had the same bug - a jump in the tracking at a regular interval

[jcm (John)]

I assume if you use EQMOD (miss out the hand controller completely) the jump in tracking should not be a problem.

John

[h0ughy (David)]

Originally Posted by jcm

I assume if you use EQMOD (miss out the hand controller completely) the jump in tracking should not be a problem.

John

dont know - yet to test that? I am not familiar with eqmod so it would be a steep learning curve

[Germ]

I have started using my EQ8 and have also noticed the sudden jump on the RA. This only happens using the Hand controller it doesn't seem to do it with EQMOD.

[AstroJunk (Jonathan)]

The Pier is in!

Its a beaut

[h0ughy (David)]

Originally Posted by AstroJunk

The Pier is in!

Its a beaut

does look good

[DavidTrap (David)]

Cable management looks just like Houghy's!

DT

[h0ughy (David)]

Originally Posted by DavidTrap

Cable management looks just like Houghy's!

DT

well that could be taken badly

[AstroJunk (Jonathan)]

It's lucky that the EQ8 slews in a tidy way - it always lifts its bum in the air first to avoid snagging

[h0ughy (David)]

ok might not have been exactly polar aligned but - look at the graph and the data, there is a clear spike created - why? Aparently those using EQmod didn t have these issues. V3.35 of hand controller. here is a sample

Analysis covers 11:48 PM to 12:15 AM
Guiding errors





Guider px
Arcsecs
Image px

RA peak error
10.46
69.25
48.31

RA RMS error
0.65
4.32
3.01

DEC peak error
1.01
6.69
4.66

DEC RMS error
0.14
0.96
0.67

Combined peak error
10.50
69.49
48.47

Combined RMS error
0.67
4.42
3.09




Correction drive analysis





RA
DEC

Frames with correction
13.9%
30.0%

Corrections at max
0.0%
0.0%

Average percent of max corr.
4.9%
8.8%



Periodic errors in RA




Top 5 periodic components in RA error, showing period & amplitude. Amplitude is relative to the DC offset.






Guider px
Arcsecs
Image px

DC offset
-0.00
-0.01
-0.01

6.57 seconds
0.08
0.54
0.38

3.6 minutes
0.08
0.53
0.37

5.00 seconds
0.08
0.51
0.36

5.12 seconds
0.08
0.51
0.36

7.06 seconds
0.08
0.51
0.36


Drift estimate





Guider px
Arcsecs
Image px

DEC drift / minute
0.52
3.43
2.39

Std error of drift mean
0.10
0.67
0.47


Estimated polar-alignment error: 18.54 arcmins, based on specified guide-star declination of 45º. Experimental estimate for non-drift-check events.

Field rotation




Estimated maximum field-rotation per minute at farthest edge of imaging field for various guider-to-imager alignment offsets in multiples of imager FOV. Guidestar-to-edge angles in arcmins.





Alignment
Guidestar-edge ∆
Image px

Concentric:
81.9
0.11

Offset 0.5 FOV:
131.7
0.18

Offset 1 FOV:
181.4
0.25

Offset 1.5 FOV:
231.1
0.32

[AndrewJ]

Gday Houghy

Whilst i have no experience with the EQ8 mount/hbx etc
what you are seeing there is exactly what we have been looking at
recently with LX200GPS scopes in polar.
I dont know if you have ever played with an LX200 GPS in polar
and manually operated the DEC slomo ( do it carefully and with a very light grip ). The scope knows where it "should" be pointing, and if it gets too far off track, it arbitrarily returns to that spot, and it does it very rapidly.

We havent fully tracked it down but we do know several things can happen.
First guess is something is going on where the scope keeps 2 ideas of where it is pointing. Your scope is drifting in DEC and at some point, the system may say, whoops, too far off target, and then just arbitrarily slews back, which invokes backlash application which creates a jump???
Just a thought

Andrew

[h0ughy (David)]

Originally Posted by AndrewJ

Gday Houghy

Whilst i have no experience with the EQ8 mount/hbx etc
what you are seeing there is exactly what we have been looking at
recently with LX200GPS scopes in polar.
I dont know if you have ever played with an LX200 GPS in polar
and manually operated the DEC slomo ( do it carefully and with a very light grip ). The scope knows where it "should" be pointing, and if it gets too far off track, it arbitrarily returns to that spot, and it does it very rapidly.

We havent fully tracked it down but we do know several things can happen.
First guess is something is going on where the scope keeps 2 ideas of where it is pointing. Your scope is drifting in DEC and at some point, the system may say, whoops, too far off target, and then just arbitrarily slews back, which invokes backlash application which creates a jump???
Just a thought

Andrew

not a bad thought

[AndrewJ]

Gday Houghy

Just found one plot of what we see.
The green is the internal "float" value that the scope uses when reversing.
Ie whilst in that region, the encoders move but the "axle" position doesnt change.
The blue plot is the raw encoder count.
You will see that when guiding, every now and then it gets too far off position and violently reverses. Even after the lash is fully accounted for, It then keeps going in the opposite direction for a while then swings back again, almost like it is getting confused as to where its really pointing when being guided.

Andrew

[jcm (John)]

There is now an update to the motor controller firmware to solve the problem of the "spikes" during guiding. ( Sky Watcher downloads section)

Yahoo Groups "SkywatcherEQ8" also has the updates in the files section.

Changes made in the EQ8 motor controller firmware version 2.09:
1. Fixed a bug which might cause random spikes during autoguiding via the autoguider port.
2. By default, use full torque to drive the mount when the motor slews in low speed.
3. Provide the ability to allow the user to choose driving torque in low speed; this feature will be availiable in the next SynScan hand control firmware release.
We would like to thank Hamish Thava from Australia who reported the problem and helped us to test this version of firmware.

John

[h0ughy (David)]

Originally Posted by jcm

There is now an update to the motor controller firmware to solve the problem of the "spikes" during guiding. ( Sky Watcher downloads section)

Yahoo Groups "SkywatcherEQ8" also has the updates in the files section.

Changes made in the EQ8 motor controller firmware version 2.09:
1. Fixed a bug which might cause random spikes during autoguiding via the autoguider port.
2. By default, use full torque to drive the mount when the motor slews in low speed.
3. Provide the ability to allow the user to choose driving torque in low speed; this feature will be availiable in the next SynScan hand control firmware release.
We would like to thank Hamish Thava from Australia who reported the problem and helped us to test this version of firmware.

John

so just a question - are we better off waiting for the 3.35plus a bit firmware update for that?

[Tandum (Robin)]

Just another reason to use eqmod.

They certainly don't seem to want to thank them

[jcm (John)]

There may be a problem with this update.( motor controller )
Posted on Yahoo SkywatcherEQ8 group:-

http://tech.groups.yahoo.com/group/S...EQ8/message/94


John