A tip for getting really good EQMOD alignment and go-to

[Breakintheclouds]

So I've been doing some experimentation on improving my EQMOD go-to performance after generally finding the go-tos were a little too far off-target for my taste. They weren't bad, but I wondered if it could be better, especially for imaging where it's a pain if the target doesn't land in the middle of the camera sensor. I hit upon this series of steps that made a big difference to the quality of my EQMOD alignment: go-to targets now land right in the middle of a small (20x17 arcminute) CCD view every time.

The idea is to redefine your mount's park position, using EQMOD to get it absolutely spot-on. This gives you a much better starting point for doing your alignment.

1. Connect to the telescope and activate EQMOD in your usual way
   
2. Unpark the scope. Turn off tracking
   
3. In EQMOD, click once on the little button beneath the ASCOM logo (it has a window and a plus-sign). The display changes to the two rings
   
4. The aim now is to re-define your parking place as EXACTLY level and pointing EXACTLY north. Use the N, S, E, W controls, or your game controller, until the number beneath the left-hand ring is 06:00:00 and the number beneath the right-hand ring is 90:00:00. Take the time to get these numbers exact. Your mount is now sitting in the perfect parking place. The remaining steps are to tell EQMOD that this is now its parking place for the mount.
   
5. Do not park the scope.
   
6. Shutdown EQMOD (in SkyTools I use the "disconnect telescope" option to do this)
   
7. Turn off the mount's power
   
8. Power the mount on again
   
9. Restart EQMOD. It'll report that the mount is unparked
   
10. Press park (the mount won't move, and your new, perfectly central position will be recorded as the new park position)
    

This then gives you the perfect starting place for star alignment, and that seems to make a big difference to how well the alignment works. The first two go-tos I made last night were off-target, as usual, and I had to use the finder to get them on target (as usual). But after registering just two alignment stars, my go-tos became almost impeccable. Registering some more alignment stars in EQMOD was quick (as the go-tos were so close to their targets). I'm now VERY happy with my go-tos landing within just one or two arcminutes of the target every time.

[chrisshillito]

Sorry, but that doesn't make much sense to me. The position you are moving to manually by watching the dials is the home position and you could have just parked to home and unparked. When you power cycle the mount the software encoders are reset to the home position so I really can't see that you've actually changed anything.

The method many folks use to initially fine tune the mounts home position is:

1. Make sure the mount is polar aligned.

2. Make sure the EQMODs site coords are correct.

3. Make sure the PC time is correct

4. Clear all alignment and sync data.

5. Goto a star.

6. Slacken the clutches and manually centre the star in a reticule eyepiece.

Chris.

[Breakintheclouds]

Hi Chris

Okay, that's weird. Your method makes a lot of sense, I guess. But I'm puzzled why mine seemed to work so well last night. Certainly I don't think that parking to the home position initially was getting those numbers to the exact 06 and 90 positions. I suppose it might depend if those numbers come from the encoders or EQMOD itself

[kookoo_gr]

i agree with chris's steps but i also want to add that the quality of the service of your mount will affect the goto accuracy

as for finding the home position here is what i do when i setup my equipment

1. level mount, and polar align it

2. without any eqipment on i load the counterweights and slacken the RA clutch, gravity will rotate the mout vertical to the ground whicj is what we want, the RA axis vertical to the ground, then i tighten the clutch.

3. using a level i rotate the dec axis until it is level to the gorund and then i rotate the dec ring until i have it at 0. then i rotate the dec axis until it is at 90. and that is the home position

i have done these steps at my house during acloudy night and i have marked these positions with a marker.

[swag72]

I use the method that Chris suggests and it works well. After the first manual clutch adjustment, the next lot of alignment stars are very close to the centre. I also make sure that I do alignment stars near to or around the target. Then using CdC (if it's too faint on the camera chip) I can work out star patterns to get it bang on where I want it in the frame.

[malc-c]

The only flaw in the OP is that whilst it may set the encoders in the true home position, the mount could be off due to the process of locking the clutches in what the user determines as the correct home position. for example you could unlock the DEC and have the OTA pointing East/west but the mount will think its pointing north.

To accurately set the mount you need a know reference point such as a star, as per Chris's post.

[Breakintheclouds]

Ah well. I've clearly got this wrong, and have ended up getting it aligned by accident. But I don't care - my go-tos are spot on and that's all that matters!

[cotterless45]

Well said! I tend to follow a routine that involves tripping over everything , then losing my glasses,

Nick.

[BrendanC]

On 04/09/2012 at 14:49, cotterless45 said:

Well said! I tend to follow a routine that involves tripping over everything , then losing my glasses,

Nick.

Sorry, I know this is a very old thread, but this quote made me giggle.

[Starflyer]

There is a way to get an accurate home position with EQMOD in daylight, using a spirit level.

It's been a while since I did it, but it goes something like this.

Click once on the little button beneath the ASCOM logo (it has a window and a plus-sign). The display changes to the two rings

Unpark, rotate RA so it shows 12:00:00 or 00:00:00, choose whichever gives you a flat surface on your mount casing. Place your spirit level on your now (almost) horizontal mount, unlock the clutch, set it level and lock the clutch again.

Park, unpark and then slew DEC to 180:00:00 or 270:00:00, choose whichever gives you a flat surface on your scope. Place your spirit level on your now (almost) horizontal scope, unlock the clutch, set it level and lock the clutch again.

Park, clear any alignment data and you're good to go. I used this for years before changing to a mount where I can't use EQMOD any longer. If your PA is good, your location and time is correct and you set an accurate home position your life will be much easier, well your alignment anyway 😃