Star Alignment - Not Sure This Is Right

[AlistairW]

Hello,

My scope is pretty well polar aligned, there is certainly no more that 2 arc seconds of error, and it is on a permanent pier. But my question is this :

> With my scope parked at the home position, I can see Polaris well enough on a Live View on my DSLR. It is well off centre of the frame but that is to be expected right ?

> Now I have my scope connected to the computer with Stellarium, and I can slew to a preferred Star via selecting it in Stellarium, - and off the scope goes.

> When the scope finished slewing, I find I need to give the scope a final 3 second bust at full slew speed in the East direction for my preferred star to come in to display. And then it is pretty much centre.

> Now the above is not a problem as I know that this needs to be done each time I switch on my scope\mount\computer. And once I have done a one star alignment, then finding any other star\galaxy\nebula is perfectly fine.

My question is: Should I have to slew to the East for 3 seconds just to find my first star ? - or do I have something set up wrong ? - Also is there anyway to save the 1 star align - so that when I switch the scope\mount\computer back on it remembers the configuration ? (I am using EQMOD). I have to repeat this process each time I switch everything back on.

 

Thanks

 

Alistair

[Freddie]

Doesn't sound right at all. Do you have the correct time set in the mount/software as it is just an East movement you need to make?

[ultranova]

A good call Freddie made, it does sound like its  time / date/ issue

somewhere.

Paul

 

[Owmuchonomy]

Just to confirm as I'm sure you aware Polar Alignment and Star Alignment are different things.  One does not necessarily guarantee the other.  Polar alignment is aligning your mount.  Star alignment (GoTo) is aligning your scope and mapping the night sky from your location.  Once you have done both accurately the scope can be parked at home or even a custom position.  As long as it remains untouched, when you start your next session, as long as the parameters you enter are correct, as described above it should all be fine.

[Paul M]

As above, 

The park position has no relevance unless after last use the fully goto aligned scope was "parked"  at the end of the session and left untouched. 

The park function simply records the encoder positions in nonvolatile memory.  

Because my scope isn't permanently sited I can't use Park. My first alignment star is often nowhere near until I manually center it and accept it. The second star is usually very near if not within the field of view. 

[Gazabone]

Have you tried a 2 star align? Not sure if will help but maybe worth a try. Hope you get it working spot on. 

[AlistairW]

This is where it is weird. I will check the date time one last time, but I am pretty sure it is not that. Once a single star align is done all is fine, but the initial slew from the parked home position is way off. The only thing I do use is JNOW rather than J2000, but I would not think that makes any difference.

Ownmuchmoney, I can't seem to get the home position to work in the way you describe. I start Stellarium and Stellarium Scope etc and carry out my one star align. At which point I see an entry in EQMOD saying I have added a point. That's all good. But once I park the scope and turn off all the applications then the next time I use it, I still have to do the alignment. Is there not a way to save the alignment points I have done, so that when I start the system up, I simply have to load the pointing model I have, and the scope knows where to go. (Assuming I park to home each time).

So back to the original question, my initial slew should not be so far off then ?

Thanks

Alistair.

 

 

[Dazzyt66]

28 minutes ago, Paul M said:

As above, 

The park position has no relevance unless after last use the fully goto aligned scope was "parked"  at the end of the session and left untouched. 

The park function simply records the encoder positions in nonvolatile memory.  

Because my scope isn't permanently sited I can't use Park. My first alignment star is often nowhere near until I manually center it and accept it. The second star is usually very near if not within the field of view. 

I'm a newbie to GOTO (so new that it was my first time setting up the other night). As such, I read everything 50 times (at least) before starting. As said earlier polar align just aligns your mount - it doesn't even have to be that accurate to then use star alignment. I know this cos I couldn't figure out how the use the polar scope properly so I just went for an approximate line up (as I would've with my eq1) and then star aligned - mainly to see how the GOTO worked. I only did single star alignment but each time the star was in the FOV of both finder and scope (I'd set them up earlier) and only took a minor adjustment to centre and accept. I'd also checked (and re-checked) all data before entering so I know polar align isn't really critical. Was BST set correctly as I didn't bother with it I just entered the actual time?

[ngwillym]

I'm also thinking its a daylight saving time not being set (or being set when it shouldn't be) with the handset - ~3- 4secs at max slew speed for an HEQ5 (~3.5 deg/sec) is getting close to 15 degrees = 1 hr of RA = DST offset??

 

Regards

Neil

[AlistairW]

I understood about the handset comments, but this is all via EQMOD and I don't use the handset, the PC takes the time and date from the system clock, hence why I am not sure its anything to do with BST in this instance. Does feel like it is something like though I agree.

[AlistairW]

I am thinking this is what I need ....

http://welshdragoncomputing.ca/eqmod/doku.php?id=saving_n-point_alignment_data

So I can save and load my alignment. So I only have to do it once.