What have I done wrong!?

[Willarnold]

With being busy at work, and the rubbish weather it's been a while.

Great clear night tonight, so set up for some observing.

I set the Synscan for 2 start alignment. First start was Betelgeuse (scope way out, but these seams normal), slewed and centred.

Then chose Alnitak, nearly spot on. First choice was M42, perfect right in the centre of view, alignment successful

It all went downhill from there. I chose the Pleiadies, the scope took the scenic route and way way out, along with everything else.

I've obviously done something wrong, any ideas?

Is it better to chose stars that are not so close to each other?

Thanks in advance

[Slangers]

You should ideally choose stars that are further apart. Also, have you made sure that the scope is level when you set up?

[msinclairinork]

ditto the above. plus I think you can do a 3 star alignment and that would greatly improve the acuracy.

But defently sounds like it has just been a case of they are to close togeather, as it firstly worked for M42 and then not.

Michael

[Skylook123]

With being busy at work, and the rubbish weather it's been a while.

Great clear night tonight, so set up for some observing.

I set the Synscan for 2 start alignment. First start was Betelgeuse (scope way out, but these seams normal), slewed and centred.

Then chose Alnitak, nearly spot on. First choice was M42, perfect right in the centre of view, alignment successful

It all went downhill from there. I chose the Pleiadies, the scope took the scenic route and way way out, along with everything else.

I've obviously done something wrong, any ideas?

Is it better to chose stars that are not so close to each other?

Thanks in advance

I'll try to provide a stream of consciousness gained from six years with the Orion Atlas EQ-G, which uses the same SynScan firmware.

First, let me recommend the EQ6 Yahoo! User's Group. A friendly, very helpful bunch dedicated to the EQ5/HEQ5/EQ6/NEQ6 and the equivalent Orion clones, all running Synta's SynScan. The files section has a world of information, and the participants are great at helping.

EQ6 : Atlas, EQ6, SkyScan & SynTrek Mounts

The preliminaries of setting up are fairly important to success with SynScan. It can't hurt to have a good setup to start, so my process is to first set the mount as close to North aligned as I can by compass. Level the tripod as best as possible. Adding the mount head, I set the latitude by using an inclinometer (a tool like a large protractor used to measure the angles of walls and shelves; mine was about $7US at a local builders store. Then I install the telescope to the mount. I set a good home position by rolling the mount in RA until the counterweight bar is level using a bulls-eye level. Leave it locked in this position with the cw shaft horizontal, and set the RA setting circle to a number that you will remember, like "0" or "6".

With the cw shaft level, now loosen the DEC clutch and level the OTA. Lock the DEC clutch, and set the DEC setting circle to your latitude such that when you later point the mount to north, it will move toward "0". With the RA and DEC setting circles locked down, loosen the clutches and returh the mount head to pointing North and counterweights down. Set the RA to 6 hours different from level, and the DEC to zero. This is now your home position.

When you start the mount, there may be some cone error (misalignment between the optical axis and the RA rotation axis). Synta firmware uses a three star alignment to correct for cone error. But first, it does help somewhat to be truly polar aligned. I use what is called the iterative method. The short explanation is that you start with a 1-star alignment to a star that is at least four hours RA away from Polaris. Complete the 1-star alignment. Then execute a GOTO Polaris. It will probably not be very close. Take out half to 3/4 of the error with the mount manual az-el adjustment. More than half to 3/4 correction and you can get into hysteresis and be chasing Polaris all night; you need to sneak up on it. Now redo the 1-star alignment. Then execute a GOTO Polaris, which should be much closer. Again, adjust out half of the offset with the mechanicals. Repeat until you get close.

Synta mounts tend to be shipped with the mount needing to point about 45 degrees away from Polaris to open the polar scope path. Some of us have loosened the top plate with the three tiny grub screws at the top, and turned the plate so that it points North-Soutn when the polar scope path is open. Or, East West for dual side-by-side saddles. This lets you stop the iterative alignment after one or two cycles and complete polar alignment using the Polar scope. The hand controller will give the polar angle as part of the information when you set up; put Polaris in that clock position on the big circle and ignore the little circle.

Once you have a good polar position with a leveled mount and a good Home position, start the stellar alignment. 1-star can work if your setup is spot on, because Polaris fixes your RA axis on one star will define the sky. A two star alignment , with both stars on one side of the meridian (north south line overhead) will not suffer due to cone error; one on each side may end up with a warped sky. So, if you suspect cone error, either do a two star on one side of the meridian, or do a three star with the first two on the same side. Synta is unusual in that a three star is not just a better two star; it is intended to correct for cone error so if you have little or no cone error, a three star can be worse behaving than a two star as it tries to fix something that isn't there.

These are my hints for getting a reasonable performing alignment and GOTO. What you saw when you chose M45 after the Orion work was that the mount was likely making a meridian transition where it does not go directly to the target, but it takes a route to manage the CW shaft or prevent cable wrap. Orion is one of my first observing areas this time of year, and it is close to the meridian early on at night, so when I use Rigel as the last alignment star and GOTO Alnitak to look at The Flame or The Horsehead nebulae, it goes around the world to get there.

And, to echo comments above, it is best practice to pick stars at least 4 hours RA and 45 degrees separated in DEC, not below about 30 degrees to avoid atmospheric refraction, and hopefully a generous difference in azimut and elevation as well for the mount's solution. And, if the telescope is an SCT, do not change focus throughout the process or the mirror shift will warp the sky. Finally, my success greatly improved when I went to a reticle eyepiece for consistency. Also, I use a moderately defocused star as it's easier to center a doughnut than a pinpoint.

Sorry to ramble...just relating five or six nights per month experience setting up at a different school each night.

Good Luck!

[Willarnold]

Thanks guys!!!!!

You all never fail to part with your experiance, much apricated

Kind regards