Ekos

[Hy Murveit]

Yes, A-P can vary the tracking rate in both RA and DEC. this kind of thing
only really makes sense for high-end mounts, and even for A-P I think only
makes sense for their encoder mounts. you’d also need good control of your
periodic error. I actually started a project to implement this in ekos a
year or two ago, but gave it up. Perhaps I’ll get back to it someday. I
thought dealing with some of this might ease the load on guiding. It would
be a feature that only applied to mounts where you can control the guiding
rates on both axes, but as I said, I gave it up.

BTW, I do believe the underlying software may use TPoint.
Hy

On Wed, Feb 19, 2025 at 8:29 PM Jasem Mutlaq <mutlaqja at ikarustech.com>
wrote:

> Thank you for sharing the details Hy! I actually thought that folks used
> it for accurate slewing, much like TPoint and thought Why? Platesolving is
> already much easier than to model the whole sky. I didn't know that its
> primary purpose today is accurate tracking without guiding.
>
> We have a similar solution in INDI with INDI Alignment Subsystem, but this
> is purely used for GOTOs and not adjusting RA/DE tracking on the sky. I
> don't even recall if the AP command sets include such a command to adjust
> tracking rate, and most mounts do not support this. It can be done with
> SkyWatcher and Celestron mounts nevertheless.
>
> However, it seems to be a niche requirement given that guiding is working
> well for most people. Definitely adding support to this at the INDI layer
> would be beneficial but it requires a lot of time and effort.
>
> --
> Best Regards,
> Jasem Mutlaq
>
>
>
> On Wed, Feb 19, 2025 at 6:44 PM Hy Murveit <murveit at gmail.com> wrote:
>
>> Let me be a little more specific. SPCC does sky modeling, that is, it
>> (along with a companion program) captures images of the sky every degree or
>> two in a square grid, plate solves all those images, and computes a
>> function comparing where the mount thinks it is vs where it actually is.
>> This allows it to vary the tracking rates in RA and DEC, so that things
>> like refraction, and tube bending, and polar alignment error etc can be
>> compensated for, and folks can image for many minutes without guiding (at
>> least on scopes with optical absolute encoders that remove all periodic
>> error). This process takes, I believe, about an hour or so (though you can
>> shortcut it by just modeling the DEC arc you plan to image tonight). People
>> with permanent installations do it and forget about it. People who move
>> their scopes to dark sites every time they use them need to do this
>> modeling every night--though you can start before it is astronomically dark.
>>
>> So, my A-P 1100 mount without absolute encoders and without SPCC is
>> similar to yours (John) in that it has basically the same capabilities,
>> except perhaps better materials/workmanship so it tracks a little better
>> and handles more weighty loads. Add in SPCC and it can do the same or
>> better without guiding.
>>
>> So, Wolfgang, sky modeling is needed for those folks who like to image
>> without guiding. The A-P clientele are definitely in that category--at
>> least the ones that buy SPCC. Sky modeling for big telescopes was used for
>> more accurate slewing, but now for amateur imaging telescopes is used for
>> guiding-free imaging.
>>
>> However, guiding works--at least to some level--well enough for many
>> people to think the modeling is not needed. I suppose it's nice not to have
>> to guide etc.
>>
>> Hy
>>
>
>>>>
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