EQDirect & EQMOD GoTo question

[IvanT]

Can someone tell me if when setting up each night does EQDirect automatically sets date and time in EQMOD and my scope control box, i.e. when using the handset you set location, date & time so that the GoTo knows how to compensate. I've noticed that my GoTo catalogue in EQMOD doesn't seem to be accurate from night to night. Am I doing something wrong?

I no longer need to Polar align each night since I went the pier route and tracking seems spot on, it's just the GoTo that is causing problems. If I spent a night finding targets and syncing using Cartes Du Ceil, do I need to do anything else each time I switch on other than load my GoTo catalogue?

Thanks

[MikeP]

Hi Ivan,

Have you seen the series of videos on YouTube by Chris Shillito who is one of the developers? Here's a link to the first one on alignment ....

If you watch all 4 alignment ones, I think it will help you understand what is going on.

Mike

[IvanT]

Cheers Mike, I'll check it out.

Busy on a Cassiopeia open cluster fest, gota make the most of a rare clear sky. Bagged NGC869 and on 884 now with M38 to finish off if the clouds hold.

Ivan

[MikeP]

This will probably help too ..... Saving N-Point Alignment Data [EQMOD]

Mike

[IvanT]

Ok, so I watched the videos and from the sound of it, there is nothing I need to do each time to get EQMOD to time-stamp the scope control box. I have my settings such that I load the alignment points on UNPARK. It may be that I have too many alignment points within close proximity to each other which it sounds like EQMOD doesn't like.

So from a very simplistic point of view, if I

a) Start with a clean alignment model on night 1

Perform a 3 star alignment, on night one, every GoTo to any of those stars is always spot on

c) Make sure I save the alignment model and PARK before power off

d) On night 2, night 1 alignment model is auto-loaded on UNPARK

e) GoTo on any of night one's stars should still be spot on

i.e EQDIR/EQMOD automatically perform date/time compensation on the model and the time stamping I'm worrying about is something that is only applicable to the synscan handset which I'm not using any more.

Thanks

[chrisshillito]

e) GoTo on any of night one's stars should still be spot on

Thanks

Don't confuse alignment points with stars. Stars appear to move across the sky - alignment points do not - you can think of them as having fixed Alt, Az positions. Just because a particular star was used to create an alignment point doesn't mean that goto's to that star will always be accurate - only gotos to the area of the sky where a particular star happened to be when you made the alignment point will be accurate.

Chris.

[IvanT]

Ah, that makes sense, thanks! I guess your point brings me back to my original question, how does the SynScan control box (or EQDIR) timestamp get set so that it can compensate for time differentials from the time the model was created to the night it is being used, i.e. would you expect a 3 point model created last year to still be valid one year on assuming static positioning of the mount?

[chrisshillito]

The EQASCOM alignment model is not time dependent in any way. It simply models the mechanical and optical characteristics of your setup and it is assumed that these do not vary with time. If you change equipment though you may invalidate the model.

If you want accurate gotos in all areas of the sky then it is best to add alignment points in all areas. Some folks go for a 6 point model with 3 points covering each side of the meridian. Personally I use 12 point model with a triangle of points in each quadrant. I also set EQASCOM to filter based upon quadrant so only those points in the quadrant of the target are used to provide goto correction.

Would I expect a 3 point model to remain valid for a year? yes, if the mount and equipment has remained totally changed, the mount has always been parked and unparked successfully, and there have been no accidental bumps that may have caused the clutches to slip etc. In reality I would suspect most folks fiddle and change things (refine the polar alignment etc.) and so re-do their alignment model from time to time.

Please note the EQDIR has no intelignece at all it simply converts RS232 (or USB) signaling levels to the TTL levels used by the mount.

Chris.

[martin_h]

I usualy start with a 3 point model each side then add to it as I go along ie sync to a near star for imaging, thus adding to the point list over time.