Hi Leo
I am doing some spectroscopy work and want to be able to solve pointing at the outset and then maintain it through the night with the star on the slit under guiding control… There are a few different ways of doing this but not in a good automated fashion while I sleep.
I also note that I’m using advanced for the Robotarget feature which prevents array supporting this in some fashion currently.
I am currently planning to use a tandem pair of scopes on the same mount to support this. The second scope main camera will do the platesolving for initial pointing under Voyager#2 control with its guider managing tracking of the mount. The spectroscope would be under control of Voyager#1 for taking spectra but also has its own guide camera for monitoring the subject star with respect to the slit.
This process requires that the slit on the big scope be carefully aligned with the centre of the platesolving camera to achieve pointing and that there is no differential movement between them through the night, which in practice is a poor assumption. The slit width is 40um at 2900mm focal length which gives me about 10 pixels and 5" of pointing accuracy required, or 2.5" to account for seeing and the star being fully defined by the slit.
It occurs to me there is probably a better way to do this.
I note that PHD2 guide api can provide guide images on request which could then be platesolved. This means that while solving and guiding through the smaller scope, I could acquire slit guider images to be plate solved which could then be used to adjust the ‘sticky lock’ position of the phd2 managed guider on the smaller scope to take account of differential guide changes between the scopes.
Alternatively and better (less complex, no interaction between Voyager instances ) I could use a single instance of Voyager to point and then guide through the guide camera using the same feature of the guide api to provide sample images to plate solve.
The biggest issue is the small field of view on the guide camera - its about 8’ square at 2900mm focal length so detailed star sets are required to support this and I’m hoping that auto exposure will provide enough stars and exposure flexibility to support consistent solve capability.
Either that or solve at the start of the night on the Voyager #2 instance camera and use that as the basis for pointing solutions in the small field of Voyager 1. That will mean occasional syncs between the instances.
Can this be added as an option to the sequence for guiding please - i.e.
a, at start of imaging, that a number of frames could be acquired through the guider which can be used to platesolve and measure and publish the centre coordinates vs desired coordinates. ie. the offset from centre.
In practice a sequence would have to NOT platesolve using the main camera ( since that requires a profile change or change of config within the session) and introduce some options on guiding which is used to provide or update the initial platesolve solution.
This also begs the question whether platesolving could be supported from guide or main camera on demand (via a tickbox?) as a matter of course.
b, a guide frame is captured and plate-solved to resynchronise while guiding using the sticky lock adjustment method. This would prevent guiding to be halted, scope moved and re-settle.
Any thoughts please ?
regards
Mike