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INDI Library v1.8.4 Released

Minor bugfix release with some highlights:

Figuring out a meridian flip?

1 week 1 day ago
mpaul73
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Figuring out a meridian flip? #50986
In the simplest explanation possible, please help me to understand when I need to do a meridian flip and how to set it in Ekos so it happens when it's needed. I watched the module video but am still confused. Thank you.

Equipment: Skywatcher HEQ5 - Stellarvue 80mm access - Canon 6D (unmodified) - Stellarvue 50mm Guide Scope - ZWO ASI290MM Mini - Rasp Pi4

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1 week 1 day ago
hy
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Figuring out a meridian flip? #50990
OK, I'll take a stab at it to start you off.

I believe your Skywatcher HEQ5 is a german equatorial mount (GEM). That is, you point it roughly at the north star when you set up (or at southern pole in the southern hemisphere). This process is called polar alignment and you need to learn to do that if you haven't already. For mounts like that, if you were to start tracking an object on the Eastern half of the sky, eventually it will cross the Meridian (though it's possible it will do that after dawn). In the northern hemisphere, the Meridian is the imaginary line running from the North Star heading towards the Southern Pole going through the Zenith, the high-point in the sky overhead. When your object crosses the Meridian, the front of your telescope will be pointing mostly up, and the back end where your camera is would be pointing mostly down (you have a refractor, so the camera is on the back end). After the object crosses the Meridian, your telescope, still tracking the object would start pointing at lower altitudes. The problem is, the back-end/camera would start going underneath your mount, into your tripod, and the camera will probably will hit something down there, causing the motion to stall, and potentially breaking or mis-aligning your mount, and certainly ruining your imaging session. To get around that, instead of continuing to track the object smoothly after the object crosses the Meridian, (usually after a little delay) the telescope switches to the other side of the mount (the back of your telescope would move to the east side, the front toward the west side), and as it tracks, now the bottom will be moving away from the tripod, instead of towards it. That switching of sides is called a Meridian Flip.

Jasem has posted a few videos on how to set up Ekos to do a Meridian Flip, e.g.
and there's plenty of discussion of it in the forum
and on YouTube and CloudyNights and elsewhere.
My 2 cents would be to simply check the box in the Mount tab which says "Flip if HA > ___" and fill in the value with something like 0.20 hours.
Start your imaging session. Use KStars or stellarium or other planitarium software to see if and when your object will be crossing the Meridian.
If it wil, don't trust the automated flip the first time, or until you've been successful with a few times. That is, instead be there watching/supervising it,
and be prepared to stop things if it looks like it going to crash, and/or if doesn't do the flip at all (and will eventually crash into the tripod).

When the session is running, while your object is East of the Meridian, the Indi Control Panel's mount tab, main control should indicate
"West (pointing East)", and after the flip it should say "East (Pointing West)". The Ekos mount tab should tell you how many hours and minutes
it is before the meridian flip will occur. If your mount is "West (Pointing East)" according to the Indi Control Panel, the mount tab it should NOT say Meridian Flip disabled.
You can also verify by eye that the telescope/mount is correctly labeled as "West (Pointing East)" or "East (Pointing West)".

Before you start, make sure your cables won't catch on anything, loosen the clutches and make sure the mount is able to move around freely then tighten them,
set up, and see if you can get the flip to succeed. It took me a while to get it to work reliably, but now I'd say it works pretty well.

This was all "off the cuff", please watch the videos to learn more, but you should be able to accomplish this.
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1 week 1 day ago
hy
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Figuring out a meridian flip? #50991
Also, FWIW, here's a screenshot of my Ekos Mount Tab right now: photos.app.goo.gl/ieY2mLgo8j4MZR5q7
You can see that a Meridian Flip is planned in 46 minutes. Really, it should happen when the next image capture completes after 46 minutes.
You can see the hour angle (HA) is -34 minutes, which means, in 34 minutes the telescope will be pointing at the Meridian, but I've told it
to perform the flip 0.2 hours after that, so it won't flip for 46 minutes.
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1 week 1 day ago
TallFurryMan
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Figuring out a meridian flip? #50993
In the Mount tab, you can set at which time offset around the meridian you want the flip to occur, in RA hours.

If you want the mount flip to occur when the object you are tracking crossed the meridian half an hour ago, type 0.5 in.

It is important to remember that there is no "do a flip" procedure. Ekos will simply ask the mount to slew to the target again, and the mount driver will choose the right orientation based on the current object position in the sky.

Because the mount may not be perfectly polar aligned, or the geographical position may not be precise enough, it is important to provide a RA delay that is large enough. If it isn't, in the general case, Ekos would ask a slew but the mount would retain the original orientation per its own sidereal time calculation. Afterwards, no further slew would be requested and there would be a risk that the scope hit the pier.

-Eric

HEQ5-Pro - Atik 314E - Orion ED80T - DMK21 on Orion 50mm
DIY 3D-printed Moonlite and FWheel RGB/LPR
KStars and indiserver on two Atom 1.6GHz 1GB RAM Linux, VPN remote access
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