Nothing except for auto continue. Your V should be the same if you did not change any AF params. The one thing that is exactly the same about 2.3 and 2.4 is that we move out by half of (steps * size) take an image grade it, then move in by steps, take an image repeat. In 2.3 we would stop when we reached your steps value and make a best guess at focus, now 2.4 will continue if it wants more data on the “left” side of the “V”. This is really the only difference. Unfortunately, when you continue, you may see the HFR dip back down because the HFR of the circumference of donut stars is smaller than that of big fat stars.
Because of this, we might add an option to disable auto continue (and expand) for folks with gear like yours.
Got it – thanks Ken. I’ll pay closer attention to this when I can get out and try to run some tests while saving the data this time. It seemed like the AF was picking much fewer stars than before, but that could be due to any number of things.
I still have 2.3 running on my little Venue 8 Pro (no perf beast but really great as an astro mini controller!) so I’ll try to do a quick comparison for sanity sake. I just need clouds to break (feature request).
I will add that I think that autofocus for my SCT has become more of a problem with 2.4. It was always a bit tricky but unless I’m watching it now I can’t rely on it.
Changes I’ve noticed in AF behavior are:
the new AF sample size slider - this doesn’t seem to have an effect on anything that I can tell. I’ve tried changing from min to max and anywhere in between and it doesn’t change star detection. I’ve seen this with both my small refractor and the SCT.
Far fewer stars detected and used in AF. I have also noticed this with my AT65 where AF works beautifully. I get no more than 20 stars detected in any frame, even in a dense star field, less with the SCT. SGP 2.3 had a problem of detecting too many hot pixels as stars and putting HFR values very low. Now it seems to not use enough stars in the field. My focus curve bottoms out around 5-6 with the SCT, max is around 7 so the curve is really flat. Any larger step size and the stars go to circles and HFR values go to very low, turning V into sort of an M. I have nebulosity rejection set to weak (full left).
The “use same stars” check box appears to be gone. Maybe it would help the SCT’s to use the same stars every time, especially if the sample size is smaller? Changing to different stars every time may alter the results, depending on the stars chosen?
Is this AF problem limited only to SCT’s or do other long focal length scopes have the same issue? Pardon my ignorance but why does the central obstruction matter? It can’t be seen in the frame. Does it change the way stars look when out of focus?
I’ve never had much trouble with my (non-Edge) C11 and SGP 2.3, but I haven’t tried 2.4 yet. I do have one suggestion, from a rare bad AF run the other night. In that run (which happened at 3 am, so this is from the logs), the number of stars detected suddenly dropped from 25 to 5, just as HFR dramatically improved. I assume SGP switched from using stars to using donut edges.
If that “discontinuity” is typical, perhaps SGP can be instructed to back out farther and repeat the focus run when it encounters this? At least if the user has told SGP that the scope is an SCT.
BTW, does autocontinue in 2.4 only address situations where HFR continuously declines, rather than continuously rises? Can it be made to deal with the latter situation?
I just verified that this does have an effect on AF. Here is a sample AF frame using M13 with the slider on 15:
Here is the same frame with the slider on 100:
As you can see from the screen shots above (from 2.4), AF will select as many stars as you allow it to. Are you certain that your sample size slider was allowing enough stars to be selected? Maybe you need to increase exposure time in that area?
The bottom line is that we cannot really help you without logs and focus packs… everything you or I say without them is just speculation.
Very interesting. Are there any negative side effects if the slider value is too large (i.e. 15 vs 100)? In other words, how would we know what’s the correct slider value for different images?
I’ll save some autofocus packs, I forgot to turn that on again. I have the AF slider on 100 all the time. I have never seen that many stars selected in 2.4. I have my AF exposures set to 30 sec at iso6400. There are lots of stars around but only a few are selected by SGP.
Anyway, I’ll try to get some AF packs saved tonight if its clear.
You adjust the slider only to remove inclusion of hot pixels and noise in the HFR calculation. If no hot pixels or noise is detected, leave the sample size at 100. Otherwise, leave it as high as possible.
I have some data here – not quite sure if it will be helpful. I went back and forth between 2.3 and 2.4 with my SCT using the same settings. It is quite gusty right now so there are spurious points here and there. Even so, there are some trends.
2.4 seems to find fewer stars and, looking at the AF graph only, the HFR is much higher. My best HFR on v2.4 was between 3.5 and 4, and on v2.3 was between 2.5 and 3.
For example, v2.3 screenshot, showing a typical curve I’d get trying to keep the step size a bit on the narrow side – not perfect but a good selection of stars:
Now, a v2.4 screenshot – this was a successful run! – the curve actually looks not too bad, but it just doesn’t seem to find as many stars in general:
Or this one (v2.4), found more stars by the graph is quite flat:
At any rate, I did have some success with 2.4 tonight. I’m not sure why the HFRs are so different, and the number of stars detected seems to vary so much.
Here are logs, full sized screenshots, and AF images for a few runs:
Thanks. That is certainly helpful and exactly the kind of data we need to be of assistance. In the 2.4 runs, what was your sample size set to? Did you actually move the slider to another value or just leave it at the default 100?
The HFRs are different because we have decided to prioritize larger stars for the HFR mean as opposed to 2.3 which prioritizes higher intensity stars, regardless of size.
Sample size was set to 100 across the board – I even tried bringing it down and then back up, in case it just needed a kick (if that makes sense).
That’s good to know about the HFR differences. The exposures were all 25s I believe – though I’ve tried a bit less at some point. Maybe they are oversaturating?
Ok… Well I am not sure about the star detection delta. That is one thing that did not change from 2.3 to 2.4… just the way in which we order them. I’ll take a look at some of your sample data.
Here is a run from tonight. Honestly I have not seen a curve that smooth before tonight. I included the log file in the dropbox folder. Nebulosity rejection is full weak and AF sample size is at 100.
One of the benefits of having star packs is that I can run the same exact data through both versions of SGPro and look for anomalies and unexpected deltas. I used the AF packs you sent over (thank you) and validated that there is no difference at all in terms of star detection (between 2.3 and 2.4). For AF pack 5 (originally captured in 2.4), both 2.3 and 2.4 found stars as:
13,15,15,22,37,35,29,39,14,19,15,15
AF Pack 2 (originally captured with 2.3) found stars in 2.3 and 2.4 as:
29,45,42,58,60,48,33
It appears as though the number of stars found and used for calculations is not version dependent, but is only differentiated by data.
One thing I might recommend… In your 30 sec exposures, some have significant trails. If you cannot avoid this during AF, you should either guide or reduce the exposure time. These frames introduce bad data into the algorithm and while SGPro can recover from a few of these, too many will come to a bad focus position.
It’s not a problem… and also, just as a note, the sample slider will have no effect for you unless you keep it very low… there are just not a lot of “good” stars. We reject stars that may look good to the eye, but will likely provide poor HFR data. You probably don’t need to use this slider at all. It is meant for people that have 20 or 30 good stars and then 70 parts noise and hot pixels that overwhelm the HFR calculation. In this case you would set the value to 30 and the other junk would get ignored.
An interesting thread - I use an 8" RC at it’s native 1600m and I am finding the auto focusing routine inaccurate compared to a bahtinov mask. I hope that the developers can work on the longer focal length focusing as it really can be a deal breaker I think.
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