On this page, I collect further experiences with and some information about my new Celestron StarSense AutoAlign for Sky-Watcher module (ordered on February 1, from Teleskop-Spezialisten, arrived on February 7, 2018), which I will call "StarSense module" for short in the following. After the acquisition of a GoTo controller, this module is the final step towards "complete astronomical incompetence"...
On this page, I want investigate, how I can increase the positioning accuracy, avoid cable wrap, ... (other things to come later...)
When I bought the StarSense module I had two main expectations:
*) I am not completely unwilling to learn in this respect and created a list of alignment stars as well as printed out a corresponding map (see page Sky-Watcher Star Discovery AZ GoTo-Mount - Named and Alignment Stars). But when you are a bit under time pressure and the hand box confronts you with stars, of which you have no idea where they are located in the sky, this is quite an unpleasant situation (of course, you can go to the computer and have the star shown to you, but this takes time...). Now that I prepared the list, this should go faster...
With respect to the first item, I can tell at least so much: Once one has mastered the initial hurdles, then the "creep under the scope problem" is a thing of the past.
The second item is a little more complicated: First of all, the alignment has to be successful before you can talk about improvements in accuracy. And unfortunately, the automatic alignment fails for me more often than I had expected. In the case that the automatic alignment is successful, it can still happen that the accuracy of the positioning leaves a lot to be desired. To my knowledge, the following can then be done in this case:
And if nothing helps, a new calibration is necessary...
In the following, I would like to discuss these methods briefly, as far as I am already able to write something about them...
Photos: StarSense on Explorer 150PDS and Star Discovery AZ GoTo mount
The first thing to do if the alignment fails or is insufficient is certainly to repeat the automatic alignment, especially if it was perhaps still too bright for the alignment. Sometimes, however, I have already experienced that things got worse and worse, and that the automatic alignment became more and more "misaligned".
If I want to align automatically again or align manually, I always switch the mount off and on again first, because I have experienced so far that the mount aligned "somewhere" when it was aligned another time without switching it off (unfortunately, I then also have to reactivate "Cordwrap"...). Maybe someone will write me what my mistake is...
The manual alignment is especially intended and suitable for the case that parts of the sky are covered. According to the manual, the positioning is less accurate than with automatic alignment, but quite good for the part of the sky for which the alignment was done. So you should only observe in that sky region.
I have only performed the manual alignment for a few times. I therefore cannot tell whether the accuracy of the alignment is better for me than for the automatic alignment (I cannot see the whole sky).
I added additional alignment points only once up to now, and was not able to see any positive effects of this (I approached the same target after each new reference point and checked its position in the viewfinder). Nevertheless, this method should have a positive effect. The manual points out that additional reference points improve the GoTo model, even in the case of deflections or other mechanical sources of error.
When you synchronize to a star, the GoTo model is re-aligned to that star, which improves the accuracy in the vicinity of it. Since you cannot undo synchronization to the star with StarSense (if you want to change the sky position), Michael Swanson advises against using this feature in his NextStar book and advises using additional reference points instead.
The manual also suggests the use of this function in the event that you hit the telescope or that an axle clamp has loosened.
According to the manual, the HELP button is intended to improve the positioning accuracy if bright targets cannot be positioned in the eyepiece or can only be positioned poorly. This should be applicable especially for manual alignment.
My own experiments with this function did not yield any results, and Michael Swanson does not mention this function in his book at all...
If nothing helps, a new calibration seems to me to be the "ultima ratio" for me, especially since one cannot (or I cannot...) check whether the calibration is still OK. I have not recalibrated my module up to now.
At the moment, this list is a compilation of possibilities in order to keep them in mind. I have not been able to report on practical experiences so far. After all, I already know that I should better do without the SYNC function - and perhaps also without the HELP function...
StarSense relay box
StarSense relay box and handbox at the mount
StarSense relay box, seen more from below
StarSense relay box and handbox at the mount - positions exchanged for less cable clutter
Photos: StarSense at Explorer 150PDS and Star Discovery AZ GoTo mount
If you mount the StarSense module on the telescope, which in turn sits on a mount, then you have to connect some devices with cables:
When an automatic alignment is started, the telescope may rotate once around its own axis during the alignment procedure and begin to "wind up" some of the connecting cables. Considering their limited length, this, of course, quickly gets to its limits! And if you approach certain targets after the alignment, it can happen that the situation worsens. I have often been on the verge of disconnecting and reconnecting the plugs of cables, but you are certainly losing your alignment when you do so. So I refrained from doing so and tried to pull the cables a little by hand. Fortunately, it has not yet happened to me that the mount's movement was stopped by the cable during alignment or GoTo movements...
Overall, however, this situation is unsatisfactory. And it does not seem to have completely escaped Celestron either, because there is a "Cordwrap" function somewhere buries in the handbox menu, which is supposed to prevent the wrapping of cables. In the English manual, this functio is shown in the "menu tree" at "Menu > StarSense Manual > Cordwrap", but with my equipment it is "Menu > Telescope > Cordwrap." The function is, of course, not documented, and in my German manual it is completely missing (in some English manuals this function does not appear either)...
I called this function once and did not understand the instructions given by the handbox. That is why I had not used it until then. At the beginning of April 2018, I finally searched the Internet for this function and found the following hints in a Cloudy Nights discussion given by Michael Swanson, who also wrote the book The NexStar User's Guide II (already in the second edition) on Celestron telescopes.
Cordwrap: Michael Swanson (link) - from my book):
Now I at least understand the instructions that the hand box gives me. I ordered the book and hope to learn a little more from it and that the StarSense chapter justifies the almost 30 EUR...
In the meantime, I tried to follow the instructions for the Cordwrap function, but the results are not yet clear to me... When aligning automatically, the mount clearly exceeded the limit once. Perhaps the limit is not valid for the alignment...
Obviously you have to reactivate (set to On) the Cordwrap function every time the Starsense module (and the GoTo control) is switched on. I find this quite annoying, because so far I do not get the alignment right away, and I have to switch off the control to start a new alignment (otherwise the telescope points somewhere...).
I have also found a German and English manual for the Celestron SkyProdigy telescope, which describes the Cordwrap function as follows:
According to this text, this function would be activated by default, which is not the case with my StarSense module. It is also points out that the telescope sometimes has to travel long distances when this function is activated.
This is just a collection of topics and more or less preliminary...