How to predict the Meridian flip?

[Russe]

Hi guys,

How can I predict When the Meridian flip will occur? I'd like to time my imaging around that time...

[lensman57]

Hi guys, How can I predict When the Meridian flip will occur? I'd like to time my imaging around that time...

Hi,

On an ordinary GEM  it seems to be unavoidable but have a look at this link anyway.

A.G

http://www.cloudynights.com/ubbarchive/showflat.php/Cat/0/Number/948415/page/106/view/collapsed/sb/6/o/all/fpart/1

[Russe]

Found a way in one of my planetarium softwares:

At least I can plan around it - have a plan in APT that stops beforehand.

My HEQ5 just stopped tracking altogether - have I clicked somewhere "prevent meridian flip"? Where do I find that in EQMOD?

[Russe]

Oh, and - when exactly does it do the flip? When the yellow line hits the target? Or slightly beforehand?

[ollypenrice]

You can often image way past the meridian without flipping, depending on the length of OTA and whether you are using a tripod or pier. Maybe 90 minutes or more in my case. The nearer the zenith you are the sooner the tube will collide with the tripod or pier. The thing is that by definition the nominal point of the flip (ie the object transiting the meridian) is the best time to catch it because it is at its highest. You don't really want to miss out on this, certainly for lower objects. A pier usually allows longer before collision and a height raiser on a tripod can have a similar effect. Worth looking into.

On any planetarium you just look at when the object reaches the meridian. In Skymap Pro you can click on any object and ask for the information window. There its transit will be shown under 'Transit.'  I would expect most planetaria to offer this information.

Olly

[Russe]

Come to think of it - wouldn't PHD prevent an automatic flip? I gotta try this out...

[Russe]

Found the transit in skysafari pro

[ollypenrice]

Found the transit in skysafari pro

Perfect. That's what you need.

Olly

[Daniel-K]

if your running ascom theres a box that stops it from flipping ive been imaging with a ED80 the past few weeks and on my pier i go way past the meridian

[Russe]

if your running ascom theres a box that stops it from flipping ive been imaging with a ED80 the past few weeks and on my pier i go way past the meridian

Do I have to tick auto meridian flip here?

[Russe]

I tried to simulate it but nothing happens when the meridian line passes over my chosen target...

[Daniel-K]

if you dont want it to flip leave it unchecked, on mine it say's enable limits i leave it unchecked and it just carry's on as normal if its checked it just stops tracking. HTH

Dan

[Russe]

Or untick "enable limits"?

[Daniel-K]

if you untick it, you can image past the meridian

[Russe]

Ah, that seems to have done it, methinks.

[chrisshillito]

if you untick it, you can image past the meridian

You can image past the meridian with it ticked - in fact that is actually the safest way to do things. What you do is first goto your target, then slew in RA past the meridian until the mount/telescope/camera is about to hit the pier/tripod, back of a bit and then set the "meridian limit" (which is really badly named and is actually a RA limit). Return back to your target and start tracking with limits applied safe in the knowledge that EQMOD will automatically stop the mount at your limit point.

Chris.

[Russe]

if you untick it, you can image past the meridian

It worked!!

How far can you go? Until the scope hits the mount?

[r3i]

You can image past the meridian with it ticked - in fact that is actually the safest way to do things. What you do is first goto your target, then slew in RA past the meridian until the mount/telescope/camera is about to hit the pier/tripod, back of a bit and then set the "meridian limit" (which is really badly named and is actually a RA limit). Return back to your target and start tracking with limits applied safe in the knowledge that EQMOD will automatically stop the mount at your limit point.

Chris.

Chris, am I right in thinking that you can also set up EQMOD to pre-empt a meridian flip?  i.e. getting it flip over to the west side before it would normally do so.

[chrisshillito]

Do I have to tick auto meridian flip here?

You can't - you haven't enabled the flip option in the setup menu - flipping in EQMOD is deliberately disabled as an option because most sane folks never want to flip and hate the thought of accidentally doing it!

Take a look at my video on meridian limits for details of how the flip works in EQMOD

Why do you want to flip? Much better to track through the meridian, or preflip before you start, or just pick something else to look at that isn't going to cause you flips (plenty up there).

Chris.

[Daniel-K]

It worked!!

How far can you go? Until the scope hits the mount?

over an hour i just keep an eye on things in my obs if it gets too close then its just a case of how bad do you want that data re slew and refocus re calibrate PHD and turn the camera round for framing.   for me i just move onto another target by the time it gets close i have around 2-3 hours worth of data any way.

[chrisshillito]

Chris, am I right in thinking that you can also set up EQMOD to pre-empt a meridian flip? i.e. getting it flip over to the west side before it would normally do so.

Yes, the is a box to check that forces the next goto EQMOD receives to be 'flipped' so that the mount ends up with it's counterweights upward. The box self clears so it is a case of checking it prior to every flipped goto you want to perform.

Chris.

[Russe]

Yeah, turning the camera and re-framing is what I forgot last time.

Not to forget though, one has to refocus too...

[ollypenrice]

Can I just say a little something here? Let's hear it for Chris Shillito whose helpfulness goes so far beyond the call of duty as to beggar belief. My own hassles with ASCOM are certainly not his fault and I'm constantly inspired by his generosity of effort. 

Olly

[Daniel-K]

Totally agree with you olly Chris helped me out with a few issues as well. Im sure he has a push notifications when ever the word ascom is used on SGL