Topics

One object tracking goes well, the other gives startrails #iEXOS-100 #polaralignment #ExploreStars #astrophotography


Koen M.
 

I had in once before and yesterday i had it again.
I setup my iEXOS100, polar align it and 3 start sync it.

After that i made it slew to NGC6611 and it worked perfectly.
I took the pictures i needed, parked the mount again and then i gave it the order to slew to M3, took the first test picture and it did not track the object (startrails)
So i parked the mount again slewed back to M3 and the same problem occurred.
Parked again, slewed to M4, and it tracked perfectly again.
After that i tried M3 again, and again the star trails appeared.

So it looks to me that everything south/southeast of Polaris went good, but everything West/southwest failed with tracking.
I have however no idea what i am doing wrong...

So if anyone can explain to me how to fix this, i would realy like that :D

Regards
Koen




Wes Mcdonald
 

Koen

Remind us all how you are set up.  Iexos.  Guide camera and guide scope?  PhD?  Unguided?

1.  If you are guiding I have found differences occur in guide quality dependent upon where you are.  Think about this.  If you were imaging the NCP and you had RA motion the object would not move in the FOV... similarly any object near North does not move much in the image frame with tracking error.  But if you look east movement in RA is much more apparent.

2.  When you are looking south east the counterbalance weight is on one aide.  When you look south west you flip the mount and the counterbalance weight is on the other side.  This  changes the way the weight bias, if there is some, acts against backlash.

3.  When you look at high elevation angles the Dec axis receives no gear loading from your camera weight bias.  Most have found you should bias the Dec axis with the camera end heavy.  This keeps the Dec backlash engaged.  Except when you are imaging something high in the sky.  The camera hangs down along the gravity vector and provides little to no buas in Dec.  This leave the Dec axis able to "blow in the wind" across its backlash.

How bad are the star trails?  How high in your sky were these objects.  Do you have weight bias?  Does any of this apply to your set up?

Wes



--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired


Koen M.
 

Hi Wes.

My sertup is the iEXOX100 with a DSLR camera on top of it. No extra guiding whatsoever.
Isnt balancing the setup taking care of the weight bias?
Objects i wanted to slew to where about in a 35) angle from my viewing point.
Picture added is a 20sec exposure of the one with the startrails
The other picture is where it went good (also 20sec exposure)
Still need to work a bit on my focussing and stuff like that, but that cant be the trailing problems fault :p


Wes Mcdonald
 

Koen

It looks like the one with the trails was zoomed in.  Are you using a telephoto lens?  What focal length are the two pictures taken at?

The iexos cannot be use unguided very well at long focal lengths.  At short focal length no problem. 

Please state the AZ and EL for each photo also.

Wes.


--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired


Koen M.
 

Hi Wes,

They where taken with a 18-200 lens.

The one with the trails on 200mm the other one on 18mm.
However i dont think thats the problem, because i also took pictures on 200mm on the side where the tracking did work and those have no startrails.

As for the AZ and EL for the photo's i haven no idea where to find that information, and i did not write them down (is a good tip to starting to write those down tough)
I did however look them up in Stellarium (i went back to the future or something like that :p )
This is the data Stellarium gives me on the "succesfull one"


And this is the data it gives me on the one with trails