I was reading up on temperature compensation in SGP and hope I have this correct. Based on what I read my understanding of temperature compensation is that a refocus will only be initiated based on the compensation curve and at the END of the image currently being taken. If I am wrong on this feel free to correct me.
Since SGP can generate a log with curve as a session is progressing, is it possible to have SGP dynamically focus while an image is being taken? I Imagine this would be similar to IF ONAG’ s Focus Sharp software. Unfortunately, that $100 software package requires the IF ONAG and in some cases you are limited by your available back focus. I have the IF ONAG on my AGO scope and it is a fantastic piece of equipment. Problem of it is the price: about $1300 plus adapters. I do not use the focusing software, as the AGO has a pretty stable focus throughout the evening. My Tak FSQ is another story. It frequently requires refocus and dynamic focus (DynaFocus) would be a nice feature for this and other refractors.
I’m not a script writer nor someone familiar with focus theory, so this may be pie in the sky thinking. Would it be possible to accomplish dynamic focus using something like a change in HFR (delta HFR) and delta time? There is a graph with the temperature compensation in SGP that I have seen.
I just starting looking into the Arduino boards and scripting using the Arduino IDE. I plan on building my own weather station for the wife’s birthday and that is what turned on the light bulb in my brain for DynaFocus. Don’t know if this would be a project that is both feasible and at the same time, something the developers would find interesting to pursue. Of course it would be an add on ($$)…Gunny
As I understand it, SGP will only perform temp. compensation focusing at the end of the image. I believe that they have adopted a policy not to move the focuser during image acquisition.
Some focus controllers allow internal temperature compensation that performs the compensation on-the-fly while collecting an image. SGP can, in theory, use autofocus at the same time that the focus controller is using internal temp. compensation. The controller exposes an ASCOM property called TempComp (I think) that can be turned on and off. So, TempComp can be running during image acquisition and SGP will turn it off at the end of an image to perform autofocus.
I say “in theory” because I have never actually tried it nor have I read of anyone else actually using it. My controller (Rigel nStep) allows internal temp. compensation, but best I can tell, it does not expose the ASCOM property so it cannot be turned off by SGP. They can’t bboth be running at the same time. I’ve been looking at other controllers and am having a hard time finding one that does internal temp. comp. and also exposes the ASCOM property.
I would support a feature request to have the SGP developers reconsider using SGP-controlled temp. comp. during image acquisition, though I understand that they have other priorities.
All the Optec focusers support TC implemented in the ASCOM driver. I always enable automatic TC in the ASCOM driver so it runs continuously. When SGP does an auto focus, it turns off TC in the ASCOM driver; performs the auto focus; and then re-enables TC in the ASCOM driver.
I do not have the TC option in SGP enabled as it is not needed. Also, I believe when TC is enabled in SGP, it performs the TC adjustment of the focuser prior to starting the next sub and before it attempts an auto focus.
You’re correct that SGP does wait until the conclusion of the current image in a sequence. Not so sure what you are saying with regard to Optec tc. My understanding is that it is not a dynamic focus algorithm. I’ll need to speak to Jeff about that.
I did find this in SGP: TempComp control - Accepted Unplanned - Main Sequence Software. I’m not really understanding the logic of the developers due to " rough focusers" that may cause oscillations. Seems like it would be a matter up to the individual to decide whether to refocus during the time allocated for a sequence of images. With my focuser (fbII), I can easily adjust 25 steps manually without screwing up the image while it is being exposed. I’ve done this as an experiment with my fsq and the fbII. Step size is roughly 3um for my focuser/scope combo.
I’ll be the first to admit that I’m not the brightest bulb in the box when it comes to focusing and all the theory behind it. The developers may have a valid reason for not implementing this. I just don’t know and I’ve thrown it out there as a " can this be done?" This is one of the few forums where I don’t see a bunch of fighting, so please don’t turn this into a a big deal. It’s not my intent to slam the developers. Just a guy asking a question and not wanting to ruffle fur>>>>>>Gunny
This is true. That said, it is also our policy to respect your focuser’s settings for external temperature compensation (from your driver) if you want to turn that on during a sequence.