I have inherited an ETX 90 with autostar from a relative who has 
upgraded. I'm having fun playing with it and I've read lots of stuff 
about using it on the web but....

After spending time calibrating, setting it up pointing north, 
horizontal and putting in accurate location and time, when I do an
align the target is never in the eyepiece and is well off in the finder 
(some times not in).
After aligning it the target is again almost never in the eyepiece but 
usually reasonably close to the finder center - usually within 1/3 of 
the field of view of the center.

Is this as good as it gets in terms of goto accuracy?
mikej

On Mon, 21 Jan 2008 09:01:02 GMT, Mike James wrote:

> I have inherited an ETX 90 with autostar from a relative who has 
> upgraded. I'm having fun playing with it and I've read lots of
> stuff about using it on the web but....
> 
> After spending time calibrating, setting it up pointing north, 
> horizontal and putting in accurate location and time, when I do an
> align the target is never in the eyepiece and is well off in the
> finder (some times not in).
> After aligning it the target is again almost never in the eyepiece
> but usually reasonably close to the finder center - usually within
> 1/3 of the field of view of the center.
> 
> Is this as good as it gets in terms of goto accuracy?
> mikej
> 

No, you can make them much more accurate by re-training the drive, 
though this takes patience. There are instructions on how to do this 
in the manual.

What I also found was that even with maximum adjustment of the 
screws, the smartfinder wasn't anywhere near in line with the 
eyepiece, so ended up having to wedge a bit of paper in underneath 
the plastic collar holding the finder on the main tube.

Give retraining a go first though. Personally I always found manual 
alignment the best - especially when I started using mine in 
equatorial mode. I don't have mine anymore though, as I sold it some 
months ago after lack of use - really want a larger aperture, so was 
going to get a cheaper dobsonian. Didn't really need all that 
electronics and tracking for my purposes, and couldn't get the hang 
of astrophotography with my kit.

On Mon, 21 Jan 2008 09:01:02 +0000, Mike James
 wrote:

>I have inherited an ETX 90 with autostar from a relative who has 
>upgraded. I'm having fun playing with it and I've read lots of stuff 
>about using it on the web but....
>
>After spending time calibrating, setting it up pointing north, 
>horizontal and putting in accurate location and time, when I do an
>align the target is never in the eyepiece and is well off in the finder 
>(some times not in).
>After aligning it the target is again almost never in the eyepiece but 
>usually reasonably close to the finder center - usually within 1/3 of 
>the field of view of the center.
>
>Is this as good as it gets in terms of goto accuracy?
>mikej

No, it should be far better than that. You may have daylight saving
time set (you don't need it at this time of year); that's quite a
common problem. Also, train the drives on a terrestial target very
accurately following the instructions exactly. In particular, if, when
you are appraching you target, you overshoot it, don't reverse the
'scope but start the training all over again. 

The finder should align with the 'scope itself and this can be done by
pointing the 'scope at a star and then adjust the finder so that the
same star is centred in the finder. Polaris is good for this but any
star can be used when your drives are running.

- Mike

Mike Murphy wrote:
> On Mon, 21 Jan 2008 09:01:02 +0000, Mike James
>  wrote:
..
>> Is this as good as it gets in terms of goto accuracy?
>> mikej
> 
> No, it should be far better than that. 

Any clue as to how good? Do you expect to see the object in the eyepiece 
most of the time?

>You may have daylight saving
> time set (you don't need it at this time of year); that's quite a
> common problem. 

Checked this one.

>Also, train the drives on a terrestial target very
> accurately following the instructions exactly. In particular, if, when
> you are appraching you target, you overshoot it, don't reverse the
> 'scope but start the training all over again. 

Ah.... I've been moving back and forth over the correct position till it 
looked right - I'll try that.

> The finder should align with the 'scope itself and this can be done by
> pointing the 'scope at a star and then adjust the finder so that the
> same star is centred in the finder. Polaris is good for this but any
> star can be used when your drives are running.

Got the finder fairly well aligned - but I have to say it isn't easy to use.
Thanks
mikej

On Wed, 23 Jan 2008 18:03:19 GMT, Mike James wrote:

>>> Is this as good as it gets in terms of goto accuracy?
>>> mikej
>> 
>> No, it should be far better than that. 
> 
> Any clue as to how good? Do you expect to see the object in the
> eyepiece most of the time?

Once correctly aligned, it should at least be in the eyepiece or 
very close. It should at least be within view in the smartfinder.

When the dot is over a star in the smartfinder, you should expect 
the star to be within at least 50% of the centre of the viewing 
field in the eyepiece.

As previously suggested, try aligning the smartfinder with a 
terrestrial target - at least then you can see what you're doing, 
then try training the drives.
Getting the time and location right are key points to remember also. 
I'd never had a great deal of luck with automatic alignments and 
only found the two-star alignment to be any good.

Being relatively new to astronomy, I didn't always know which stars 
it was intending to point at, so I manually cycled through to ones I 
knew and used those as the reference points.

-- 
http://www.rexx.co.uk
To email me, visit the site.

http://www.rexx.co.uk/runes/ - personal online rune readings

Rexx Magnus wrote:
> On Wed, 23 Jan 2008 18:03:19 GMT, Mike James wrote:
> 
>>>> Is this as good as it gets in terms of goto accuracy?
>>>> mikej
>>> No, it should be far better than that. 

>> Any clue as to how good? Do you expect to see the object in the
>> eyepiece most of the time?
> 
> Once correctly aligned, it should at least be in the eyepiece or 
> very close. It should at least be within view in the smartfinder.

ok - only one problem - smartfinder?
I have a finder with no magnification and a cross-hair.

> When the dot is over a star in the smartfinder, 

dot?

you should expect
> the star to be within at least 50% of the centre of the viewing 
> field in the eyepiece.
> 
> As previously suggested, try aligning the smartfinder with a 
> terrestrial target - at least then you can see what you're doing, 
> then try training the drives.
> Getting the time and location right are key points to remember also. 
> I'd never had a great deal of luck with automatic alignments and 
> only found the two-star alignment to be any good.

> Being relatively new to astronomy, I didn't always know which stars 
> it was intending to point at, so I manually cycled through to ones I 
> knew and used those as the reference points.

Good idea - I sometimes have to guess which star it is I'm aiming at.
Thanks
mikej

On Thu, 24 Jan 2008 09:34:32 GMT, Mike James wrote:

>> Once correctly aligned, it should at least be in the eyepiece or 
>> very close. It should at least be within view in the smartfinder.
> 
> ok - only one problem - smartfinder?
> I have a finder with no magnification and a cross-hair.
> 
>> When the dot is over a star in the smartfinder, 
> 
> dot?
> 

Ah, sorry - you may have a different version from the one I had. I 
had the one with a little plastic lens on the side of the tube, that 
projected a flashing spot via fibre optic LED, rather than a 
finderscope.

-- 
http://www.rexx.co.uk
To email me, visit the site.

http://www.rexx.co.uk/runes/ - personal online rune readings

Rexx Magnus wrote:
> On Thu, 24 Jan 2008 09:34:32 GMT, Mike James wrote:
> 
>>> Once correctly aligned, it should at least be in the eyepiece or 
>>> very close. It should at least be within view in the smartfinder.
>> ok - only one problem - smartfinder?
>> I have a finder with no magnification and a cross-hair.
>>
>>> When the dot is over a star in the smartfinder, 
>> dot?
>>
> 
> Ah, sorry - you may have a different version from the one I had. I 
> had the one with a little plastic lens on the side of the tube, that 
> projected a flashing spot via fibre optic LED, rather than a 
> finderscope.
> 
I want one....
:-)
mikej