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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Re:Figuring out a meridian flip?

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How do I figure out the flip point?
Equipment: Skywatcher HEQ5 - Stellarvue 80mm access - Canon 6D (unmodified) - Stellarvue 50mm Guide Scope - ZWO ASI290MM Mini - Rasp Pi4
3 years 11 months ago #52380

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You can do this manually, standing next to your telescope (that is, looking at it so you can see if it changes sides). Slew to a star that's a little before (east) of the meridian and plate-solve (align) so that you're reasonably confident about your position. One of he tabs in your mount's indi control panel should indicate "West pointing East" and you can look at your hour angle.. Now from there, slew to some position near there further west, just past the meridian. Does the mount stay on the same side? What is the hour angle now? If it didn't change sides, slew further to the west and repeat. Keep doing this until your mount decides to change sides and note the hour angle. This should give you a reasonable idea of how to set that hour-angle parameter on the Ekos "Flip if HA > " input box. Perhaps set it to a little more than that hour angles where your mount decided to flip (of course, make sure the scope wont be hitting your tripod at that hour angle).

You should make sure before you do all this that
- your computer's time is set properly to the local time,
- the entries in the indi control panel mount tab, "site management" sub tab seem right (e.g. for UTC time, UTC offset, latitude and longitude.
- You can park and slew properly -- e.g. when you start from a parked position and slew to some object, it points to within a few degrees of the object you wanted it to point to (e.g. it doesn't need to be exact, but shouldn't be e.g. 30-degrees off), and that it returns to pointing near the north star when you park.

Hy
3 years 11 months ago #52382

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I have been doing some experimenting with the meridian flip for the past few days. I have found that the meridian line on the Kstars map does not match the HA displayed in the Ekos telescope window. It can be a few minutes off. Also the telescope meridian flip point can be several degrees from the actual telescope meridian point and several degrees from the Kstars/Ekos meridian. To enable an automatic meridian flip, an object must be selected that is East of meridian for both the telescope mount and Ekos. And the flip is executed successfully only if the mount is West of the mount meridian point when the meridian flip goto command is sent to the mount.

Things to do to investigate the issue:
1) In Kstars select an object just East of the meridian line and note the HA time when that object actually crosses the line. HA = 0 is the reference time for the triggering of the goto command that causes the meridian flip. The goto command is sent to the mount when the HA>xx limit is reached.
2) Manually move the telescope with the hand controller or the Kstars telescope movement controls to the point where the counterweight bar is perfectly horizontal. The difference between the telescope location and the meridian line on the Kstars map can be determined by noting the RA position of the cursor on the map in the lower right corner of the map. This may not be the telescope meridian flip point.
3) To determine the telescope mount meridian flip point. select an object sufficiently far to the East that causes the mount to slew to that object with the telescope on the West side of the mount. Periodically press the Kstars goto button until the mount actually does the flip. Watch the HA position in the Ekos telescope window and note the HA position when the flip occurs.
3 years 10 months ago #53715

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What version of KStars are you using? Hy and I have been working on the meridian flip process recently and it will now retry if the flip falis. It also reports the pier side in the mount tab and can implement a HA limit that is intended to stop the mount tracking into the pier if it is in the wrong pointing state. This may all only be in the sources, not a released version at present. It all requires that the mount reports the pier side. If is doesn't none of this will be done.

in your section 2 some mounts report the mount axis positions. It may be worth watching the Ha or Ra axis position as the mount moves through the meridian. I would expect it to move through 180 or 0/360 degrees at that point. I would esxpect that the target pier side would change as the axis direction goes through 180 or 0.
3 years 10 months ago #53716

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Kstars: 3.4.2

My primary mount is a Celestron AVX. I don't think it reports HA or the pier side.

I have been doing the testing during the daytime without a doing an accurate alignment to real objects. Some of the differences between the mount and Kstars/Ekos should be reduced after doing a real alignment with stars.
3 years 10 months ago #53774

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The AVX definitely reports pier side. Ha is always derived from the mount Ra, the time and the longitude. I have one and made sure that the driver uses the mount pier side command.
The following user(s) said Thank You: Paul Muller
3 years 10 months ago #53787

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did you ever have success with this. I am having issues much like you list but with an ioptron cem60. it does seem to report pier side, but the meridian flip fails .
3 years 9 months ago #55654

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Also CEM60 here (EC model, as you might recall from CN...). For me, the flips really work like a charm now. Which version are you running, what are your MF settings, and where does it fail?
3 years 9 months ago #55661

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yep, thanks for trying to help me.

I think I have everything set in ekos ok, but it crashed and I couldn't capture where exactly it failed, but I remember in the telescope module it said flip failed.

does the cem60 hand control have to also be set to flip vs stop ?? if so, that may be the issue. I had set the hand control to stop, so that if it did do a meridian flip I would know it was ek0s that did it.
3 years 9 months ago #55666

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The HC/mount should probably be set to 'stop', but with a limit larger than that used for EKOS. And EKOS should be set to a value somewhat larger than zero, to make sure that the pointing is definitely past the meridian, so that the slew command EKOS sends initiates the move to the other side.
If the mount stops, or starts the flip by itself, any sequence running in EKOS will abort. So the basic idea is that EKOS acts before the mount, and it doesn't really matter what the mount would do...
3 years 9 months ago #55669

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Chris recently updated the iOptron driver that is used by the CEM60 and by the iOptronSmartEQPro+. I tested it extensively, since I also had Meridian Flip problems before. I can attest that it works great now, but it may still be available only from sources.

One other thing I learned while testing that revised driver is that the iOptron calculates sidereal time in a confusing way. So while the INDI Control Panel shows the time zone offset correctly, the hand controller may negate that, since it uses a DST setting, and if you forgot to change that when daylight savings time went into effect, your mount will be 15 degrees off and that will be enough to send it into the pier or tripod and have the flip occur at the wrong time.

I would check that first, it could fix a lot of your problems. Make sure time zone and DST settings are correct.

Embarrassingly, mine were wrong....

Jo
Last edit: 3 years 9 months ago by Jose Corazon.
3 years 9 months ago #55673

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ok thanks. I am pretty sure I am good on times, Ekos did try to start the flip but it failed. I will try setting the hand control to flip instead of stop at 15 degrees past and will set Ekos to flip at 5 degrees past and see what happens. the time Ekos says it will be until the flip seemed correct. I a, using 1.5.3 stellarmate and there are newer stable updates.
3 years 9 months ago #55676

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