skyx pro: The astrometric solution failed.Error=655

[konstantinos75]

Hi


I tried to use the automatic calibration in skyx pro with tpoint addon.
First I captured a image with the camera addon, then I go to imagelink.
When I press the button "Find Astrometric Solution" I get this error

"The astrometric solution failed.Error=655"

I attach the fits image I loaded in the imagelink.

I cannot explain why I get this error. Any help would be appreciated.

Please rename the attached file vega.txt to vega.fit in order to pass it to imagelink skyx.

Thank you

[cfranks]

Hi,
Tried AllSky Blind search. Your ImageLink may have the wrong 'arcseconds/pixel' set.

Charles

******** ASTROMETRIC SOLUTION RESULTS ********
Center RA: 18h 35m 58.41s
Center Dec: +38° 46' 57.3"
Scale: 10.85 arcseconds/pixel
Size (pixels): 533 x 400
Angular Size: 1° 36' 22" x 1° 12' 19"
Position Angle: 123° 58' from North
RMS: 1.24 (X: 0.69 Y: 1.03)
Number of Stars Used in Solution: 13 (100%)
FWHM: 1.55 pixels, 16.86 arcseconds
*********************************** ************

...All Sky Image Link Succeeded. Found solution in Lyra.

[gregbradley]

Ah yes that famous error message. I have seen it many times, way too many times that is!

First you need to know accurately your image scale. You can use the free Wodaski CCD image scale calculator from New Astronomy Press.

You also need to set your camera up well. I found my Proline 16803 worked well with 2x2 binning, 5 second exposures and luminance filter.

But my Trius 694 often did not do well. I think it often did not get enough stars. Also if the moon is bright you may get that error as there are not enough bright stars in the image. But when it did work I used 10 second exposures 1x1 binning.

The other thing to set is the north angle. What I do is if that image scale finder does not work I take an image in CCDsoft, save it then click on research astronometric (something or other). It usually works and gives me the north position angle. You have to tell it your image scale though.

Now I put that in the Sky X and it usually works.

It could also mean your polar alignment is off and the image you took is a fair way off the coordinates in the Sky X where it should be. So I think you need a rough polar alignment done first.

Greg.

[konstantinos75]

Hi

It is solved by setting the "bad pointing sample criterion choice" to 5.
Default value for "bad pointing sample criterion choice"=0.5 degrees

Now I have realized why this error message appeared.

My setup includes:
- Skywatcher HEQ5 mount
- Vixen ED81s
- SBIG ST2000xm camera

I performed a draft polar alignment with the mount polar scope. After connecting the mount via ASCOM, I slew to Vega.
I noticed the telescope was pointing some degrees away. Since Vega was not in the camera field of view, I moved the mouse in RA/DEC with the gamepad controller in order to bring Vega in the camera field of view. I captured a image of Vega with the skyx camera addon. In the fits header of the file I sent to you you can see

OBJCTRA='18 22 25.562'
OBJCTDEC='+34 15 58.26'


After finding the astrometric solution of the image with skyx you can see

Center RA: 18h 35m 58.41s
Center Dec: +38° 46' 57.3"

The angular separation between these two positions is more than 0.5 degrees.
This is why Image Link is failing.

So I guess I need to have a good polar alignment next time. Perform a synchronization of the mount in the first time.
After that proceed with the image link.

Thank you

[konstantinos75]

and now my second question related to this topic.

If a perform an automatic calibration in Tpoint, in case image link fails then the skyx will proceed with all sky image link?

Thank you

[gregbradley]

I had been using Tpoint successfully with my FLI Proline 16803.

Then the next time I wanted to do one it kept failing no matter what I did. I gave up for that night. I went back at it another night. That box "all sky image link" was checked for some reason.I unchecked and everything worked fine. So my experience is the opposite. I am not even sure what that box even means (sometimes SB labelling is too esoteric, known only to them).

It may mean it checks the whole sky for a link but I can't imagine it does that as surely that would use a tremendous amount of computer power.

For what its worth, if you manage to plate solve the first time it usually continues to work without a hitch. The only issue I get is the slew limits. Sky X seems bugged on software set sky limits. They seem to need to be set every time you start the program (unless I am doing something wrong). If you don't set them to allow to go a bit past the meridian you can get software slew limit errors even though the mount is nowhere near the pier.

Greg.

[Atmos]

Pretty sure it just means that it sends it off to astrometry.net and it gets run through their servers.

[cfranks]

No. If you have the 'Use All Sky Image Link for automated pointing runs' box checked, image link will always use the AllSky database. I have no problems finding a solution for pointing samples with mine set up like that and usually less than 2 seconds for the solution.

Charles

[frolinmod]

No, it solves them locally and in not much more time than a regular image link. It does not require much in the way of resources either. Just the use of a special datafile that is a few gigabytes in size. It works extremely well.

By the way, TheSkyX image link apparently doesn't handle fields of view over 10 degrees wide, but the all-sky image link can be made to automatically crop images so that this isn't a problem. They do need to be FITS format images though.