Side of pier firmware vs software, who wins?

In continuing with my try to understand side of pier behavior. I made an observation recently that has me scratching my head.

My mount, a Celestron CGX-L is capable of tracking some 20 degrees past the meridian. I have the RA limits disabled. The mount can also be programmed for a ‘prefered’ side of pier. I have that set for East. I tried setting RA limits but the sequence kept getting into the slew limits and aborting.

Also I have SGP configured to allow tracking up to 10 minutes past merdian. That’s only about 2 or 3 degrees I think.

I had a target M2 set to start very early in the evening 8:00 pm edt. At that time M2 is about 15-18 degrees east of the meridian. M2 crosses the meridian to the south at around 9:20pm. I live in North Florida Tallahassee to be specific if you want to confirm that in your software. Oh the date was 10/20/2017.

The sequence triggers and the mount slews to the target and centers but on the west side of the pier!! ??? (yes weights on west side OTA on east side tracking west).

Now thats fine I could image M2 all the way down to the horizon without a flip if I wanted to. Although the balance is off (set for east heavy). But if I have the mount set for East side preferred and the target is a good 15 degrees east of the meridian why does it slew to the west side? Is SGP over riding the ‘firmware’ for the mount?

I’m new to the CGX-L (one month in and one clear sky so far), but I think I’m interpreting the favour-east and favour-west settings opposite to you. You’ve set favour-east which will place the OTA on the west side of the mount pointing east of the meridian when looking south. So if you slew to a target which is, say, 15 degrees east of the meridian you will have about 35 degrees (3 hours) of trackability before you flip or hit the 20 degree past meridian limit of the mount. However, if you had favour-west this would put the OTA on the east side of the mount and you could track continuously without a flip or limit problem. I think your mount is doing what you told it to, it favoured-east and put the OTA on the west side, looking east. If I’ve got this right then I think favour east is the setting you would use if you lived in the southern hemisphere. But as I said, I’m new to this.

You are correct, perhaps I did not word it correctly.

I have “Favor East” set which would put the weights out on the east side with the OTA on the west side.

However when SGP started the sequence with M2 on the east side of the meridian it slewed to “West” with the weights out on the west side and the OTA on the east side.

Opposite of what would be expected. The weight bar is tilted a good ways above horizontal and the ‘bias’ weight in the wrong direction (West).

OK - I’m still a bit unsure as to why you would want to favour east as this gives you limited tracking time, but I’m sure you have your reasons.
I think though, the problems you are having may be nothing to do with favour-east or west. I have just checked my mount (even though it is daylight and raining) but if I slew to a target which is 16 degrees or less east of the meridian then my favour-west setting works - the OTA goes to the east side and the weights are high on the west side. However, if I slew to a target which is 16.2 degrees east of the meridian then the mount ignores favour-west and goes the other way. I know the mount can go 20 degrees beyond the meridian but I guess the ‘favour’ setting has a more limited range.
Looking at Stellarium at 8.00 pm M2 looks to be only 12 degrees east of the meridian so on my mount favour west would work fine. Your setting of favour-east should also have worked so I don’t know why it went west. Maybe it has something to do with disabling the RA limits.
All I can suggest is you re-set your meridian setting and put the RA limits back on and see if things change.

Because my little opening in the trees to the south 2/3 of the sky is to the east and the mount is balanced east heavy in that orientation. On the west side it ends up balanced west heavy which is ‘wrong’. My sequences run all night long not attended so that’s an issue. I tried neutral balance but the mount defanitly prefers east heavy.

I have tried setting RA limits but SGP kept getting into the slew limits and halting the sequence. Even though the slew limits were set to 5 degrees past and SGP was set for 10 minutes past (about 3 degrees). Which is part of what has brought me to this quandary.

In fact I had to switch to the newt OTA as my APO refractor was constantly crashing into the tripod legs. Slew limits of -10 was required on each side creating almost 1/2 hour of dead zone.

A pier extension would be nice but as of now one is not available.

As I thought - you have good reasons, I’m afraid some of your explanation, and your quandary is above my pay grade. I don’t yet know enough about the mount or SGP to be able to offer any other suggestions.
Hope you get it resolved.

@UlteriorModem

A couple of points – when talking “side of pier” there is always confusion as to the meaning. That is, are we talking about which side of the pier the OTA is on or the side of the pier the counter weights are on. Reading the ASCOM documentation is also a bit confusing to me.

Also, SGP does not talk to the mount; SGP doesn’t even really know what kind of mount you are using. It is just sending your ASCOM driver move commands and SGP assumes the ASCOM driver knows how to control your mount.

You set your mount to “favor the east” and this put the OTA on the east side with the counter weights high while pointing at a target that is still east of the meridian. When SGP issued the slew to M2, it just told the ASCOM driver the RA and DEC to slew to. Your mount’s driver saw the current position of M2 as allowing your mount to “favor east” and it slewed to the counter weight high position. This was a decision your ASCOM driver made – not SGP.

After that SGP could see (based on the pierSide info from your ASCOM driver) that it did not need to do a meridian flip when M2 actually crossed the meridian, so the second slew command (the one to cause a meridian flip) was never issued.

The “favor the east” or “meridian delay” option can be very useful in that it can eliminate the need for a meridian flip – as long as the target is close enough to the meridian to fit into the “favor the east” limitation when doing the initial slew.

My AP1100GTO has the feature “Meridian Delay” that defines how far east of the meridian the target can be acquired using the counter weight up positioning. I keep my driver set for -1 hour. So when SGP slews to a target, if the target is less than one hour east of the meridian, my scope slews to the counter weight up position and that eliminates the need to do a meridian flip.

Charlie

A good explanation. However, you are right about the confusion. On the CGX-L, favour-east puts the OTA on the West side pointing east. As per the manual:
“Favor East – If the target object is accessible from both
sides of the mount, selecting “Favor East” instructs the
mount to point to the object as if it were on the east side
of the meridian. The optical tube will then be positioned on
the west side of the mount and pointing east.”

@Buggs

This is confusing – putting the OTA on the west side of the pier when acquiring a target that is east of the meridian is the default behavior for all German Equatorial mounts. So it would seems that “Favor East” doesn’t really do anything.

@UlteriorModem indicated that the “Favor East” option put his scope on the east side of the pier pointing at a target that was east of the meridian.

I wonder if this is indicates the documentation is wrong?

Charlie

Two points. Firstly, my mount is set to favour-west and it does what the manual says and puts the OTA on the east side (with the weights well above horizontal on the west side). Second, by setting up this way I can point at a target which is as much as 16 degrees east of the meridian and then follow it all night without the need to flip once the target passes the meridian. So it seems to me that this utilises the capability of the CGX-L (and the CGX which does the same) where the mount can track up to 20 degrees beyond the meridian. Though I’m still learning and may have it wrong, my interpretation of this feature is that you would use the favour-east option if you were in the southern hemisphere. As UlteriorModem explained, he uses it to avoid obstacles in his location.

Thanks everyone really good input and a lot to think about. I think what was said about SGP not caring about what preference is set in the mount’s firmware and choosing what will give the ‘maximum’ amount of time on target without a flip makes sense. As that is exactly how it is acting.

I might just go back and change the meridian settings to their defaults of zero and no preference and see how it acts. But it will be a couple of days of course :slight_smile: