Help please - Meade Autostar/EQ5 align

[erick (Eric)]

I've got the Meade Autostar (#497) connected to my EQ5 mount. It's taken me a little work to get to where I am. One of the two motors I attached was "skipping" internally. But I had a spare and it seems to not have that problem. It took a while to align the drive wheels so all turned smoothly. Then I had the Dec motor colliding with the Dec clutch lever. Built a new version of the lever allowing sufficient clearance. The RA drive seems to counteract the earth's rotation quite well. I can slew the scope well in Dec and RA.

So now, to alignment.

I cannot get anything like reasonable alignment. I think it knows that it is on a GEM rather than a Alt/Azi, or a polar aligned fork mount, but I'm not absolutely sure.

The manual I have been working from is:-

http://www.meade.com/manuals/Telesco...497english.pdf

which is a bit sparse on information. I also notice that my 497 has a few more menu options than this manual lists. I have set date and time right and location to Melbourne (yes, in Australia - close enough).

It gives me four options for align - "Easy", "One Star", "Two Star" and "Three Star". I've tried the first three. It starts with me pointing to the polar home position and it says "German South". So I'm hoping that means that it thinks I have a GEM pointing at the SCP.

Then I select ACRUX - It slews somewhat close and I centre it and press enter, then I choose Sirius. It slews to vaguely that general direction (within about 20 deg!!) and I centre and press enter. It says it is happy but gives me some strange directions to the pole. If I tell it to goto ACRUX it sets off on a wild chase.

OK, I'm missing something here. Can anyone with experience of an Autostar on an EQ5 tell me, so I can slap my forehead and go away and fix it.

Thanks
Eric

[tbothy]

Hi Eric
Ive had a bit of experience with autostar and meade mounts,I used to run a LXD55, try training the Autostar as per page 6 of the manual you quoted this will get the gear ratio's for the motor system.

"It says it is happy but gives me some strange directions to the pole"

Yes this is pretty much what that means, the vees or arrows give arcminutes where the pole is relative to the current calibration, they are quite handy and I wished the SynScan had the same feature.

Is the autostar connected to a meade mount or a different brand mount?

Cheers
Tim

[erick (Eric)]

Thanks Tim

I had trained the Autostar against the motors previously, but I'd better do it again. And best I do it the afternoon before I try to align and leave the mount/scope in place and Autostar on to reduce opportunities for problems.

If I just do the training as directed, it saves away the ratios it calculates? I don't have to enter anything in those fields??

It's an EQ5 mount. Secondhand, with nothing to suggest its vintage - probably one of the Chinese made clones.

[AndrewJ]

Gday Erick

Have you set the ratios correctly?? ( both value and sign )
What firmware is loaded?? ( that will also confirm model

I havent read your manual, but the Autostar system is very flexible
and does work well with retrofits, but it also depends on toothcount
of the wormwheel and total gear reduction being accounted for
correctly before it works.
ref http://groups.yahoo.com/group/RoboScope/
as a group dedicated to retrofitting scopes with controllers
and most use the 497 autostar.

If it reports German South, then it knows its a GEM.
What scope model did you select??? as that will auto select
several std settings re ratios, slew rates, slew limits etc.
If you also load patched firmware, lots more stuff can be made available for tweaking.

As to location, after selecting Melb, you can edit the name and Lat Long to suit what you want

Andrew

[AndrewJ]

Gday Erick

Re

If I just do the training as directed, it saves away the ratios it calculates? I don't have to enter anything in those fields??

The ratios tell the motor what the geartrain "ratio" is.
It is a value that represents the arcsecs of OTA movement per tick of the encoder ( mounted on the motor ), and the direction of that move.

This ratio is specific to the geartrain, and doesnt change with training.
What training does is determine how much slop there is in the geartrain when reversing.
The correct procedure to setup is
1) Start scope
2) Enter correct ratio (incl sign) for your specific setup.
This only has to be done once
3) Calibrate "motors" This sets the encoder illumination and should be
run on each remote setup, as it tweaks the encoder lightsources to
suit the current power supply voltage
4) Train Drives. This only has to be done once every six months or so,
and after any bumps/work done on the gearboxes or their mountings.

After that, and correct date/time entry, it should just work.

Andrew

[toc (Tim)]

Hi Erik just for reference, I think the ratios are: 3.28533. That is for 144 toothed mounts like the CG5 and Vixen GP.

[erick (Eric)]

Thanks guys. I've just realised that I changed the telescope model AFTER I had trained the drives - Duh! It was set to an ETX-125 I think and I changed it to some Meade scope that looked (on Google) to be a GEM.

You've given me plenty to work on. Thanks again.

(Thanks Tim - I am enjoying having the Autostar connected rather than the previous simple dual axis drives.)

[Karls48 (Karl)]

Hi Eric.
Have look on this link http://www.data-plumber.com/autostarupgrade.htm
I had EQ3 mount fitted with Autostar for about two year. It worked great until the mount seize and stripped the gears.

[erick (Eric)]

Thanks Karl, I'll check that out.

[erick (Eric)]

Great stuff everyone! The Yahoo group and the site Karl suggested. Amazing how little I knew before I started fiddling with the Autostar and the EQ5!

[AndrewJ]

Gday Erick

Just for general Autostar info, you also need to visit
http://www.weasner.com/etx/menu.html
( pack a cut lunch and waterbottle )

Everything you ever wanted/needed to know re the autostar units themselves.

Andrew

[erick (Eric)]

Originally Posted by AndrewJ

Gday Erick

Have you set the ratios correctly?? ( both value and sign )

......

Andrew

Yep, ratios were wrong. Have set them correctly and been able to enter correct Lat/Long. Also calibrated and then trained the motors. If I can see any stars tonight, I'll try again.

[erick (Eric)]

Originally Posted by AndrewJ

Gday Erick

Just for general Autostar info, you also need to visit
http://www.weasner.com/etx/menu.html
( pack a cut lunch and waterbottle )

Everything you ever wanted/needed to know re the autostar units themselves.

Andrew

http://www.weasner.com/etx/autostar_info.html

[erick (Eric)]

Update! Better, but no cigar!

Set up WITH SCOPE pointing roughly at SCP, then sent it off on a two star align - first stop Rigel Kent. Fairly close - jump onto the slewing buttons. What the?? It has a mind of its own in the RA axis when I try to centre the star.

A bit of searching the paperwork and I find "rubber banding"! A bit more fiddling and I find the numerical results of the training I did. Dec - 550, OK. RA - 16,000, that's a bit more than 650!!! It looks like I can edit the value to whatever I want - but before I figured that out, I said I'll train it again. First attempt - 4,000. Second attempt - 12,000. Third attempt - 1,200. STOP right there and try two star align again. Rigel Kent, then Sirius - not too bad, close - I centred each and hit OK. It likes that alignment. OK, machine, go and find Saturn. Plenty of whirring later, it was fairly close - woo hoo! OK, try to sync on Saturn. Done. Hey M104 isn't too far away - goto M104. Miles out . Reckon something is sus' here. Sent it away to park the scope and it gets the Dec back close but RA a fair distance out.

Seems I'd better do some investigation of my RA axis mechanics.

[AndrewJ]

Gday Erick

How are you training RA????
Where/what is your target??
The numbers should be repeatable within +/-25 or so
Again, what Firmware rev have you got loaded.
( as some bugs/comments are specific to ver )

Synching on Saturn isnt good as it only uses a rough calculation
( Autostar is only an 8 bit processor ) to get planet positions.
Only synch on stars if you can, ( or use high precision mode,
which does that for you )

Just for info, drive train numbers are represented as arcsec of "OTA slop" caused by the slop in the gears.
When the scope reverses direction, the gears take up this amount
at nearly double guide speed, but only when the motor needs to reverse to start retracking.
So lets say scope tracks west and you slew west, it will just resume tracking.
If you slewed East the scope will forcibly slew back WEST by the drive train amount "BEFORE" it thinks the OTA is moving and hence resume tracking. If you are way "overtrained" ie have very high nos
the OTA starts moving quickly, but the scope still thinks its taking up gearslop.
This is why getting drive train numbers right is important.

Andrew

[erick (Eric)]

With each reply, I understand more that I didn't understand before. Thanks for your patience, people.

I've checked some information:-

Autostar reports Ver 43gg
Telescope model is set to "LXD55/75 10 New"
Mount is set to "Polar" - only one choice for that telescope model, I think.
Edit Az train:- +1224
Edit Alt train:- +569
Alt/Dec ratio:- +03.28533
Az/RA ratio:- -03.28533

The afternoon "training" of the mount/drives was on a distant tree branch. I had the RA axis turned until the counterweight bar was almost horizontal.

When I redid the training after dark when I had the ginormous "rubber banding", I went for a distant terrestrial light (again with the counterweight bar close to horizontal).

As I said, the variation in RA drive train numbers, on repeated training, suggests to me that there is something wrong in the RA mechanics. I will do more testing during the day, but with the RA set in various positions from counterweight bar horizontal one way, through "vertical" to the opposite horizontal position. But I'll do a close inspection first and then carefully observe through the eyepiece to see if I can see the large gear slop it is reporting. I haven't seen it before. Of course, this is an old EQ5 - I'm not expecting stellar performance. But if I can get it to goto targets and get them in the FOV of a widefield eyepiece, I'll be happy.
Eric

[AndrewJ]

Gday Eric

You have an old style 497 with the latest firmware so thats a good start.
I will look at the code today, as i cant remember the exact method used,
but in Polar, some versions allowed you to train on a star
and the code didnt work properly, as it didnt account for the time differential correctly.
IIRC, To correctly train RA on a GEM required it to be in "terrestrial mode"
( under tracking ) first, so that the RA motor is turned off.

Andrew

ooh forgot. When training RA, you want your DEC to be as close to 0 as possible
to maximise movement in the EP relative to rotation of the RA axis

[erick (Eric)]

Woops! Thinking of what I did, I probably had Dec closer to -90 deg for both motor training.