Orion with astrotracer miscalibration fix

Started Dec 10, 2017 | Discussions thread
chris gunn
chris gunn Veteran Member • Posts: 8,606
Re: Some more tests

Polacofede wrote:

This time i wanted to test the DA*60-250.

First I tried to compensate for -15º but results were not good, after some tests i decided to use just the magnetic declination value for the place -8º and it worked very well imho.

In desperation, resort to reading the manual.....

Page 8 of the manual: "Calibration is the operation to get the electronic compass to work accurately"

Page 11: "0 deg is based on True North, not Magnetic North"

Page 19: "Accuracy +- 5deg (precise calibration)"

So, it is supposed to sort out the declination somehow.

If it doesn't work well with iron adjustment for 0 deg error, probably a new calibration is required, which would be impossible using rod?

Still interesting results! Try for partial correction only! Testing thoroughly will be time consuming...

barely noticeable, Flame & Horse Head, da*@250mm iso1600 f4 100s ( max value allowed by astrotracer for 250mm and that orientation )

Bit of spherical aberration. And you managed max exposure! You pro!

I submit a single shot just to show the movement quality achieved when i compensate my K3II compass.

Something i noticed again is that, if i leave the rod in a fixed position ( sticking it to the camera top ) to apply the compensation at certain camera orientation and then i turn the camera then the effect caused by the rod is not the same. This has sense to me as after re orientating the camera the way the rod "interacts" with the magnetic field and hence the compass is not the same.

Yes, I would expect that.

So, applying a workaround like this requires a bit of work on each shot, i did that by leaving the camera screen in compass mode.


18 shots f4 250mm 100secs shots stacked (dss average)

As I had some shots I considered stacking them as it was for free. Nothing to be proud but I think astroacer can be a much more amazing tool.

So, 30min @f4. Not bad! You need a lot of light to get the Horsehead.

IMHO all this leads me to thing that, if Pentax would add the option to enter by some way the compensation value, that simple thing ( no technical excuses here ), would turn Astrotracer in a piece of cake and give it much much better accuracy, hands down.


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