Meridian management


KHursh
 

I now have my Mach2 humming along pretty well. I have set up APPC Pro with horizons and meridians and a pointing and tracking model. Where I am stuck is with meridian behavior. I know that my mount can handle tracking past the meridian up to a point depending on where it is relative to my safety limits. My question is, with NINA or even SGPro, I have to tell the software, how long past the meridian to wait to flip so how do I predict this based on the Dec position of object I am imaging? Am I overthinking this? Should I just pick a relatively safe time, like 45 minutes, and flip there for all objects? TIA

Kevin


Andrea Lucchetti
 

Hi Kevin, there is a similar thread from me about 1-2 weeks ago. I don’t comment here because I still have to practice what I have learnt. 
But if you are imaging with sgp I assume your problem is just to avoid loosing time at th meridian. If your frames are 600s, I think that a delay of 600s is enough to finish a frame and flip.


KHursh
 

Thanks Andrea,

I am doing something slightly different, I think. I am trying to predict when the flip might occur so I can tell my imaging software what to do. APCC is set to flip at the meridian limits set in APCC, but that time will differ according to the DEC of the object I am imaging. You (I think) have already decided on a 45 minute delay, which is what I may ultimately do, but if my object is at a lowish declination I may not have to flip at all. I can play with my setup during the day and watch what it does at various declinations and write down when it approaches my limits (I should have done this when I set up my limits), but I am trying to ask if there is another way to predict the behavior


Marcelo Figueroa
 

What I do and it works perfectly well is to turn off the meridian limits in ACPP and let SGP take over. I usually use about 10 or 15 minutes past the meridian and ensure that the wait for meridian option is activated.
 


Joel Short
 

With SGP you don't have to worry about "minutes past meridian to flip"  SGP will never stop an exposure for something and will wait until the exposure is finished to issue a flip.  So in SGP just set your "Minutes past meridian to flip" to 0.  Let's say your exposures are 10min.  If the mount crosses the meridian at minute 2, the mount will track past the meridian for the remaining 8mins and after the exposure is complete SGP will issue the meridian flip.  Works perfectly and I've never done anything else.  
joel


Dale Ghent
 

Hi Kevin,

As others have pointed out, you manage this by specifying a slightly wider "window" of flip time in your sequencing app so that it orchestrates the flip prior to the driver's programmed limits being hit and it either stop tracking or initiating another response, usually one that is incompatible with your imaging ;) In this case, you can think of the driver being a safety stop for your mount - if the sequencer fails to do the flip for some reason, the driver will force it when the mount sails into its limits there.

Amongst the NINA devs, we have been toying around lately with the idea of meridian and horizon limits, a la what you would find in APCC. I think this kind of tight integration between mount driver and sequencing app is important. In the case of horizon limits, it would allow the sequencer to manage a "gappy" session for a target. This is useful in the cases where the target might be obstructed temporarily by a tall tree or other object and guiding and imaging must be suspended while the object is occluded, or if you want to image something up from or down to the horizon, but the horizon line at your site is very irregular. In the case of meridian limits, the app would be able to optimize exposure times around the meridian based on the clearance map that was specified, allowing a flip to be done within a varying window of space rather than a hard set limit no matter which orientation the OTA is in.

This is all in the conceptual phase at the moment, but once a design is settled on, I would like to be able to get APCC hooked into that, via published API or other means. We'll see what the future brings once we all figure it out :)

On Dec 5, 2020, at 09:41, KHursh via groups.io <khursh=yahoo.com@groups.io> wrote:

I now have my Mach2 humming along pretty well. I have set up APPC Pro with horizons and meridians and a pointing and tracking model. Where I am stuck is with meridian behavior. I know that my mount can handle tracking past the meridian up to a point depending on where it is relative to my safety limits. My question is, with NINA or even SGPro, I have to tell the software, how long past the meridian to wait to flip so how do I predict this based on the Dec position of object I am imaging? Am I overthinking this? Should I just pick a relatively safe time, like 45 minutes, and flip there for all objects? TIA

Kevin


KHursh
 

Thanks for chiming in Dale. This is exactly what I am looking for. I am in need of understanding 1.11 builds of NINA as I am still using 1.10. Getting the astrophotography capture software to interact with APCC is my holy grail.