GOTO probs - Meade

[CowboyJane]

Hi

I've had my Meade 105 for a few months now, and while I've enjoyed using it manually, the GOTO is a continual frustration for me. I can never get it align properly.

Is there anyone out there with experience of the Meade who can offer a few tips?

I've tried changing the site (I'm in Bournemouth) from Plymouth to Oxford (which are the 2 nearest cities listed), I've tried entering precise co-ordinates, I've tried most things. And yes, I've done both the home position and the one which a quarter turn to align it with the fork.

I'm thinking that if I want to use a GOTO I might be better selling it and upgrading to a Celestron 5 or 6, which I believe has moon align - so I might stand a better chance for some of the time! (But I'm not sure if they are as portable as the Meade, or as quiet while slewing...?)

Any tips would be appreciated

Sue

[Deneb]

Hi

Not to intimidate you, Have you checked the batteries to see that they have enough juice ? as they do run low quite quickly as I remember with my old ETX 90PE, What Model do you have - is it the LNT Model ?

[proflight2000]

Hi Sue

Firstly, dont change city stuff, go to google, type in your area and ask google for coordinates, at worse, download a copy of google earth and put the mouse over your house, look in the bottom left and you will see the coordinates there. Place the scope and mount outside where you want it, make sure you know where north is. Now do the following:

I dont have an etx with me but you also have to release the clutches and turn the scope all the way to the right, then you turn it back until the front of the scope is directly over the electrical area where you turn it on. Once there lock the clutches. Now pick the whole scope up and turn it so that the leg on the mount with an N on it is facing north. Dont worry what way the scope itself faces. Now see if it will align, see if that helps.

[AJSullivan]

Hi

Not to intimidate you, Have you checked the batteries to see that they have enough juice ? as they do run low quite quickly as I remember with my old ETX 90PE, What Model do you have - is it the LNT Model ?

I think you mean "Not to patronise"

Sorry couldn't help myself

[ottUp]

One thing often overlooked is the importance, when centering your alignment stars, of always approaching the star from the same direction to eliminate errors caused by gear backlash.

Pick a pair of directions: Up&Left, or Down&Right, and ensure that these are the last direction keys you touch when centering your star for alignment. If the star is on the "other side" of center, requiring that you use keys other than your selected pair, then over-shoot the center and back up.

If you don't do this -- if you center the alignment star with both the Up and Down keys, or both the Left and Right keys -- then your alignment is subject to the error caused by the backlash in your drive gears, which is an unpredictable amount. This may make a small or a big difference depending on your circumstances. Try this out next time out, you may find better alignment.

- Richard

[Jeff RV]

Try "Calibrate Sensors / Train Drives" this should make a difference, also daylight savings should be set to off.

http://www.weasner.com/etx/archive/mar07/etx-pe.html

Jeff.

[CowboyJane]

Hi

Thanks for the replies. It's the Meade ETX 105.

I know about setting the counterclockwise home position for automatic align - and tried the added 180 degrees back with 1 or 2 star align. No joy either way.

The only other thing I can think of is the level is out???- I try and make sure the tripod legs are fully extended each way to ensure it's as level as poss. I guess I need to find a tiny spirit level? (I think the Celestrons come with an inbuilt one, don't they?)

But I'll try again tomorrow or this week when we get some clear skies with the tips so far. Try the drive train too.

[Astro_Baby]

Not sure if the bigger Celestrons come with a level built in - my little Nexstar 4SE came with a tiny bubble level thats as much use as a chocolate tea pot. Its so tiny its like something from a christmas cracker.

Lucky I already had one of these they are cheap enough off ebay.

[astro_dt]

Hi Sue

I have an ETX125 and the critical settings are usually the location, time+daylight savings (=N right now) and levelling the scope. I have written up instructions on the technical section of my website.

Hope it helps

Danny

[rusirius]

Cowboyjane, although you've said you are having difficulty aligning the scope, you haven't said specifically what the problem is. I have an Meade LX90 which has the same GOTO and which initially for me was also a pain to set up, so I understand the frustration. Its worth persevering though and once you crack it, you will enjoy using the GOTO capability of your scope. Most of the points to remember have already been mentioned however to summarise;

1. Make sure that your tripod is level - a spirit level will help here. You need to be as level as you can get it.

2. Set the correct time and date. To the nearest minute is fine.

3. For Winter, ensure that Daylight Savings is Off. When the clocks go forward in the Spring it will need to be set to On, and when they go back in the Autumn, it will need to be set to Off again. (An error here will put the GOTO out by 15deg in RA).

4. Make sure that the scope is correctly set in its home position. I think this may be different for the ETX series but your manual should tell you exactly how to position it. For my LX series, it needs to be set pointing celestial north (not magnetic) and horizontal (Alt 0 deg). (I usually point it at Polaris and then lower it to the horizontal position - this is sufficient for visual observing).

5. Do a two star align.

It took me a while to get this process exactly right but once I cracked I found that I can usually get my GOTOs accurate enough to place an object in a 12mm eyepiece (x166) - this would equate to a 9mm on the ETX105, but I'm not sure how accurate the gears on the ETX are when compared to the LX so this might be somehwat optimistic. Maybe 12mm is a more realistic target for the ETX. Intially, though, I would expect your GOTO to place objects within a 20 or 26mm eyepiece.

If you have the Autostar #497 handset, then you should also be able to do a 'Sync' on a couple of stars which makes the GOTO more accurate. Don't try this until you get the alignment process right though as synchronising when significantly out of alignment only makes things worse.

As an ETX owner, you might want to have a look as Wesners ETX site. It can be found at http://www.weasner.com/etx/menu.html and has lots of useful information particularly for ETX owners although I found it a useful resource for my LX scope too. For example, this tutorial might be of some help: http://www.weasner.com/etx/tutorials/aligning.html

[Jeff RV]

Once you have aligned, you can as rusirus suggest "do a sync" but remember this will only be accurate on that part of the sky, quite a few people put this method to good use.

Jeff.

[RobH]

Hello Sue,

One thing that completely stumped me when I first had my old 10 inch LX200 was that it turns out that you have to put the date in the american way....MM/DD/YY.

I couldn't work out for the life of me what was going on until Mrs H had a look and figured it out!!

Regarding time....you don't need to worry about the daylight saving bit. Just enter the time in GMT and leave daylight saving off.

If you get stuck I'm only in Weymouth so just half an hour or so's drive away.

Cheers

Rob

[CowboyJane]

Hi

Thanks - I'll give all the advice a go - once the clouds disappear!

The only other thing I need to check is - on the handset for site, there is also 'time zone'. It's currently set at 0 - but I'm not sure about this setting?

No probs with the date - the month appears in Dec/Jan etc form. Batteries are at 100%.

One thing that intrigues me is pointing the scope north to start with. I was advised to keep it just slightly off north for align, as it doesn't like starting exactly north, and will do an almost full rotation to get this part of the alignment. If that's the case, and it does this almost full rotation, why is pointing it north from the start so important? Even if it's pointing south in the home position, won't it still find north itself?

The problem is - when it asks me in automatic align to check the brightest star, its pointing somehwere where there are quite a few stars and none of them are that bright, and the brightest stars in that part of the sky seem quite a way out of line...(and it doesn't name which star it is its referring to). When I try and just accept what it does, by aligning with the 'brightest' star in the area it's pointing and then GOTO an object I can identify, it's no where near.

I guess it just means lots of practice with the above advice, maybe trying with 1 star align - but I am still wondering if the Meade 105 is really suitable for a numpty beginner, and whether a Moon align one might be better GOTO bet for a beginner with basic sky navigation skills. (I have a PhD, but not in anything useful or scientific!)

[astro_dt]

Hi Sue

The reason it needs to point North is that the scope calculates how far it needs to travel from North to the first alignment star. I point mine at Polaris and that seems to work.

The GOTO should tell you the star it using for alignment. Sometimes it easier to align earlier in the evening before too many stars are showing. Also you can get a map and list of stars that Meade use here http://www.weasner.com/etx/buyer-newuser-tips/starcharts.html This should help you navigate, it's worth perservering as it is quite easy once you get used to it.

Good luck

Danny

[rusirius]

Sue, the first star will always be a little off and often outside of the eyepiece FOV. The second is usually much closer and usually within the FOV. If you do an Auto-align then it doesn't tell you with star it is expecting, just asks you to point at the brightest star, but if you do a 2-star align, you then actually get a list of alignment stars to select from, but then you need to know where to find them.

If you are not sure with star is which then maybe a planetarium program something like the free Stellarium or Cârtes du Cièl might be some help.

Stellarium:

http://www.stellarium.org/

Cârtes du Cièl:

http://www.stargazing.net/astropc/

[CowboyJane]

Hi Sue

The reason it needs to point North is that the scope calculates how far it needs to travel from North to the first alignment star. I point mine at Polaris and that seems to work.

Good luck

Danny

Thanks Danny

But I still don't understand people say it doesn't like being put directly on N, and needs placing a bit off N - and then it still finds N? If there is a lot of rotation needed to find N, is more accuracy lost in that rotation (ie a loss of accuracy corresponding to the amount of rotation needed? If that makes any sense?)

I just don't get why - if the scope finds N itself as part of the alignment - why it matters so much where you point it in the initial home position.

[Doc]

Go-to works off the triangulation theory to point to your object.

It knows where north is (One point). You tell it another star and enter it (Two points). Then by triangulation it works out it's third point in the triangle.

[Jeff RV]

As far as i remember (as i'm not with my scope at the moment), it should offer you alternative stars even when Auto Align is selected incase your line of vision is obstructed by trees etc.

You just push the Scroll up or Down key (i think) until you like the star selected.

If someone can confirm that the scroll keys are the correct keys please!.

Jeff.

[RobH]

When I aligned my LX as closely as I could to north (alt az mode), it didn't move far at all when finding north alignment. It does sound odd it going that far.

Is the home position you're using the right one? It's very easy to get wrong. I know from experience

Can you post a photo of the scope in home position, with north marked.

Cheers

Rob

[SteveP]

Sue

A few pointers to help you understand the reason behind aligning the scope in this manner -

Firstly, what the mount is trying to do is match what you tell it when you are confirming that the particular star is aligned with its own internal 'sky map' software. Once it has done that with 'north' and two more aligned stars, then the 'goto' facility will work more effectively. It is a sort of triangulation process

Secondly, The initial alignment should be with the 'celestial north pole' (CNP) which is for all practical purposes is the True North pole of the earth. This is different from Magnetic North where a compass would point to and currently is about 2 degrees west of magnetic north. That's why you may have been told to point the mount slightly away from the compass bearing. Of course, that doesn't say by how much or in which direction!

Thirdly, you may have been told as an alternative to point the scope at Polaris (aka the Pole Star). This is a star on the end of Ursa Minor and is a good proxy for the CNP. Indeed, the difference isn't worth bothering about for goto purposes at this stage

I hope this helps your understanding ... and apologies if I have been condescending!

Clear skies

[ringz]

Hi Sue,

You should go to the meade website and have a look at the videos they have there for setting up their scopes.

Try this link for your particular scope:-

http://www.meade.com/educational/etx%20videos/index.html

If I remember correctly you will need to view the site using internet explorer rather than any other browser or the videos won't run.

Regards,

Martyn

[tooth_dr]

One thing that completely stumped me when I first had my old 10 inch LX200 was that it turns out that you have to put the date in the american way....MM/DD/YY

Not much help on the topic, but when I got my SW mount I spent two hours one night wondering why everytime I picked an alignment star it slewed below the horizon Then the penny dropped and it started to get cloudy lol

[vincentnm]

One thing often overlooked is the importance, when centering your alignment stars, of always approaching the star from the same direction to eliminate errors caused by gear backlash.

Pick a pair of directions: Up&Left, or Down&Right, and ensure that these are the last direction keys you touch when centering your star for alignment. If the star is on the "other side" of center, requiring that you use keys other than your selected pair, then over-shoot the center and back up.

If you don't do this -- if you center the alignment star with both the Up and Down keys, or both the Left and Right keys -- then your alignment is subject to the error caused by the backlash in your drive gears, which is an unpredictable amount. This may make a small or a big difference depending on your circumstances. Try this out next time out, you may find better alignment.

- Richard

Thats quite an interesting bit of information. I have random goto issues, this is probably why.

Thanks,

Vincent.

[astro_dt]

[but I still don't understand people say it doesn't like being put directly on N, and needs placing a bit off N - and then it still finds N? If there is a lot of rotation needed to find N, is more accuracy lost in that rotation (ie a loss of accuracy corresponding to the amount of rotation needed? If that makes any sense?)

I just don't get why - if the scope finds N itself as part of the alignment - why it matters so much where you point it in the initial home position.

Hi Sue

I think the confusion maybe because celestial, magnetic and geographic North are all different. Bit pushed for time tonight so don't want to go into details.

BTW I have to point my scope North because it's old and doesn't find N by on its own!

Cheers

Danny

[CowboyJane]

Hi

But I still don't get why - if the scope finds north itself - why starting in any version of north matters??! The scope will override what position you've put it in...doesn't it??