Skywatcher 16 !!!

[CraigS]

From Noswonky:

It does have an issue with some looseness or 'play' in the azimuth axis. A few others have mentioned this but I haven't yet seen anyone claim to have solved it. Someone said that you can 'tighten the gears' etc. But how do you get access to them???? Has anyone actually done it?

Rob288 (from NZ) on 1st August in this link said the following about a SW 12 inch Goto:

This dealer http://www.nztelescopes.co.nz has been selling the auto tracking dobs with the AZ GOTO hand set for over a year now, I have one and it works well, using Frmware 3.07 at present.

The only issue is some back slash in the RA gear, no matter how much you tighten the clutch, apparently some people have fixed it withTeflon bushes, but have not been able to find any direct info.

That's the closest I've heard of anyone addressing/resolving this problem.

Cheers & Rgds

[noswonky (Peter)]

Originally Posted by noswonky

Well that's very strange indeed!

I have the 12" SW Collapsible also. Mine is Auto Tracking (not go-to).
It does not have the problem you describe. It can be pushed around to point at targets just like a regular (non-motorised) dob. You can even do this while it's tracking and it just continues tracking the new target.

Further to that, see this video on Skywatcher's YouTube Channel which refers to the goto version of the scope...

http://www.youtube.com/watch?v=XW8nRe_-LyE

At 1:26 it says:

"The patented dual-encoder design allows you to manually move the telescope anytime and to anywhere you wish - with no need for re-allignment. Slewing to an object on the opposite side of the night sky no longer feels like watching a pot boil. Simply push the tube close to the object and let the computer do the rest of the work."

[CraigS]

Hmm .. Peter;

So now I'm wondering how much power one night's observing might take ? I'd love to get out of having to manage the charging & transportation of that battery pack. Do you reckon you could scale down the power supply if you stick to 'push to' for long distance slewing ?

Cheers

[Louwai (Bryan)]

Originally Posted by noswonky

Further to that, see this video on Skywatcher's YouTube Channel which refers to the goto version of the scope...

http://www.youtube.com/watch?v=XW8nRe_-LyE

At 1:26 it says:

"The patented dual-encoder design allows you to manually move the telescope anytime and to anywhere you wish - with no need for re-allignment. Slewing to an object on the opposite side of the night sky no longer feels like watching a pot boil. Simply push the tube close to the object and let the computer do the rest of the work."

Peter,
Haven't looked at the link. (can't access youtube from work).
I hear what you are saying, but I'd need to look at the specs of the individual scopes to make an informed comment / comparison.
I am only making comment on the actual scope that I have. (which is the unit that I recently won in the Qld Astrofest raffle)

My 12" has drive motors which are permenantly locked in. Manually pushing the scope will force the motors to spin. As the motors are designed for tracking, the gearing is very high & so the scope is reasonably stiff to manually push due to the resistance from the motors. If you push fast, the motors literally scream as they are spinning so fast.

The instructions which came with the scope advise to use the hand ctrl & drive the scope when needing to move manually, even to the alignment stars during initial alignment.

So from what I know about my 12" & from what you have said about yours, it seems that we may be trying to compare 2 different models of the same base unit.

Cheers, B

[Louwai (Bryan)]

Originally Posted by CraigS

Hmm .. Peter;

So now I'm wondering how much power one night's observing might take ? I'd love to get out of having to manage the charging & transportation of that battery pack. Do you reckon you could scale down the power supply if you stick to 'push to' for long distance slewing ?

Cheers

The 12" that I have came with a battery pack to hold 8 x 'D' size batteries. Although I have not used this battery pack, I'm assuming that it would give at least 3 to 4hrs of motor use.

Also I found that the scope didn't actually come with a power cord that could be used with a std cig lighter socket. The ONLY power cord was that which was attached to the battery pack noted above.
I happened to have another cord which is suitable & can be used from a cig socket.

B

(my mistake - Yes 'D' size batteries)

[noswonky (Peter)]

Originally Posted by CraigS

Hmm .. Peter;

So now I'm wondering how much power one night's observing might take ? I'd love to get out of having to manage the charging & transportation of that battery pack. Do you reckon you could scale down the power supply if you stick to 'push to' for long distance slewing ?

Cheers

I've only had the auto-tracking scope about a month, so I'm not yet sure how much power it uses.

It came with a battery pack which takes 8 'D' size batteries (producing 12V) and I'm using heavy duty batteries.

I've probably run it on one set of batteries for at least 8 hours (possibly more) in total - tracking most of that time - and the batteries still seemed ok. However, I don't use the motors for slewing more than a few degrees.

I did change the batteries after that to avoid them going flat during a star party, so I'm not sure how much power they had left.

But my feeling is that it doesn't seem to use much power. I would expect the go-to version to use more power due to the more sophisticated hand controller and the greater use of motorised slewing.

[CraigS]

Originally Posted by noswonky

I've only had the auto-tracking scope about a month, so I'm not yet sure how much power it uses.

It came with a battery pack which takes 8 'D' size batteries (producing 12V) and I'm using heavy duty batteries.

I've probably run it on one set of batteries for at least 8 hours (possibly more) in total - tracking most of that time - and the batteries still seemed ok. However, I don't use the motors for slewing more than a few degrees.

I did change the batteries after that to avoid them going flat during a star party, so I'm not sure how much power they had left.

But my feeling is that it doesn't seem to use much power. I would expect the go-to version to use more power due to the more sophisticated hand controller and the greater use of motorised slewing.

Thanks Peter.

So, the next question, (not for you 'cause this is a 'goto' question), would be does the SkyScan (SS) controller get feedback from the encoders in the Autotracking mechanism ?

If yes, then you could still push the scope to the approximate position and then use the SS to do the fine adjustments (thereby saving battery power).

Also, I think I read in the SS technical manual that the SS controller remembers the position if the power is removed (without the need for re-alignment). From memory, I think this feature only works if you park the scope in the vertical position before disconnecting the power (??). - I'll have to read up on that again.

Interesting.

Cheers & Rgds.

[noswonky (Peter)]

Originally Posted by CraigS

Also, I think I read in the SS technical manual that the SS controller remembers the position if the power is removed (without the need for re-alignment). From memory, I think this feature only works if you park the scope in the vertical position before disconnecting the power (??). - I'll have to read up on that again.

Interesting.

Cheers & Rgds.

In the case of the auto-tracker, it remembers your latitude setting when powered off - so you only have to set latitude once, not once per observing session.

The alignment at the start of a session involves simply pointing the scope at the northern horizon (ie zero degrees azimuth and zero degrees elevation) and powering it off and on. How you find north is up to the user.

[Steffen]

Originally Posted by noswonky

I have the 12" SW Collapsible also. Mine is Auto Tracking (not go-to).

But that's the difference, for mere tracking the scope just needs to be aligned (the tracking computer needs to know which way the mount is oriented), it doesn't need to know where it's pointing right now, like a goto mount does. EDIT Sorry, strike that, I forgot for a moment that Dobs are alt-az…

I never quite understood why encoders in goto mounts are always put into (or near) the motors?? They should be placed near the pivots, like you'd find with DSCs. That way it wouldn't matter if the tube gets unclutched from the motors, the computer would always know where it's pointing.

To take this slightly off-topic, I found a curious behaviour with my new HEQ5Pro mount. Without proper polar alignment of the mount I can still perform a 3-star align and goto accuracy would be quite good. However, tracking gets worse with sloppier polar alignment. It appears that while the computer takes the actual mount orientation into account for goto it will track by simply turning in RA at the siderial rate. If that's the case it seems like an odd limitation of the software…

Cheers
Steffen.

[CraigS]

Originally Posted by Steffen

But that's the difference, for mere tracking the scope just needs to be aligned (the tracking computer needs to know which way the mount is oriented), it doesn't need to know where it's pointing right now, like a goto mount does. EDIT Sorry, strike that, I forgot for a moment that Dobs are alt-az…

I never quite understood why encoders in goto mounts are always put into (or near) the motors?? They should be placed near the pivots, like you'd find with DSCs. That way it wouldn't matter if the tube gets unclutched from the motors, the computer would always know where it's pointing.

To take this slightly off-topic, I found a curious behaviour with my new HEQ5Pro mount. Without proper polar alignment of the mount I can still perform a 3-star align and goto accuracy would be quite good. However, tracking gets worse with sloppier polar alignment. It appears that while the computer takes the actual mount orientation into account for goto it will track by simply turning in RA at the siderial rate. If that's the case it seems like an odd limitation of the software…

Cheers
Steffen.

Hi Steffen;

i) Would that suggest that the Goto software doesn't get involved in the tracking (??) but only gets involved in the pointing (??) (Am I reading you right here ?)

ii) I believe, (read somewhere), that on a GEM, non-orthogonality between the Dec and Optical axes is quite common but analysis using three stars only
is not adequate to compensate for RA to Dec non-orthogonality. Some GEM controllers apparently only offer three star alignment to compensate for this error.

Perhaps what you're pointing out maybe answered by (i) or (ii) above.
Not sure, though.
Interesting.

Cheers & Rgds

[Steffen]

Originally Posted by CraigS

i) Would that suggest that the Goto software doesn't get involved in the tracking (??) but only gets involved in the pointing (??) (Am I reading you right here ?)

That appears to be the case. I can use goto to slew to an object, watch it drift out of the field and then get it back by simply pressing enter again on the hand controller to initiate a new goto to the same object.

This indicates to me that the "intelligence" gathered during alignment is available to the goto function but disregarded for the purpose of tracking. Weird.

ii) I believe, (read somewhere), that on a GEM, non-orthogonality between the Dec and Optical axes is quite common but analysis using three stars only
is not adequate to compensate for RA to Dec non-orthogonality. Some GEM controllers apparently only offer three star alignment to compensate for this error.

Isn't that what's known as "cone error"? I believe some scope control software can detect and compensate for cone error, not sure about SynScan at the moment. Gotta read the manual when I get home

Cheers
Steffen.

[CraigS]

Originally Posted by Steffen

That appears to be the case. I can use goto to slew to an object, watch it drift out of the field and then get it back by simply pressing enter again on the hand controller to initiate a new goto to the same object.

This indicates to me that the "intelligence" gathered during alignment is available to the goto function but disregarded for the purpose of tracking. Weird.

Or the controller simply isn't compensating for a systematic pointing error which only manifests itself as the scope moves. (?) (As opposed to during the alignment process).

Isn't that what's known as "cone error"? I believe some scope control software can detect and compensate for cone error, not sure about SynScan at the moment. Gotta read the manual when I get home

Perhaps this error correction is only 'crude' and is based solely on calculations based on the three star alignment at the outset (?).

- Don't know .. but we'd have to delve into the software to find out !

Cheers & Rgds