meridian limits


Paul Kirk
 

Hi - I installed 0.91a last year, but never got to use it due to extensive cloud cover for most of the winter. I have a MESU mount and a c11 on it. 


I have read the config help but don't understand the meaning of 'over pole' and 'under pole' features and what values to put in for the limits.


I understand that with scope on west and CW horizontal that's the zero point so I put on 0 degrees into the config for the eastern limit is that right?


Then for the western limit i put in Minus 180 ???


I can't contemplate trying to track past meridian as My brain won't cope with that.


Any help with what values to put in and which boxes to put them in greatly appreciated. Just want basic setting that will let the mount work.


thanks

Paul Kirk


Dan Gray
 

Hi Paul,

Check out the following screenshot.
This has the settings from SiTechExe/Config/ChangeConfig/MountTab/
imbedded in the picture, so if you study the green and blue lines, and
also the settings, maybe it will help you get a handle on this

http://siderealtechnology.com/MeridianOverlapInEastWithSettings.jpg

Also, this is a copy/paste of the help file:
Dan

New Meridian Overlap Settings.

Lucas from the Mesu mounts had a suggestion that would place the meridian
overlap area, somewhere else entirely. This is also very helpful on the
Ealing mounts, such as the one from the Wallace Observatory from MIT.

Now there are separate OVER POLE settings, and also UNDER POLE settings,
and they don't have to be around the meridian.

So, keep in mind that the value of the angle starts at the Southern
meridian as ZERO. As you go WEST, it increases. As you go East, it
Decreases to a negative number. If you keep going east, you will
eventually hit the Northern meridian. At the Northern meridian, the angle
is 180 degs (or -180 degrees if even a fraction of an arc second East of
the North Meridian Horizon).

If you're EAST of the Northern meridian (From Northern Horizon) by 1
degree, it would be -179. If you're WEST of the Northern meridian (From
Northern Horizon) by 1 degree, it will be 179.

Now keep in mind that the East and West in the above sentence is stated as
related to the due north on horizon. In a GEM mount, when tracking
"West", it will move to the EAST side of due NORTH horizon! Now that is
confusing, but if you read carefully, about 5 times, then it might make
sense!

So, when we are refering to the Meridian Limit West Under Pole, this would
normally be on the EAST side of due North Azimuth. This value would
normally be -175 or so, depending on your wishes.

In addition, when we are refering to the Meridian Limit East Under Pole,
this would normally be on the WEST side of due North Azimuth. This value
would normally be 175 or so, depending on your wishes.

Let's say you want standard settings of 5 degrees past the meridian at all
locations, and you want to track 3 degrees past the western limit. Your
numbers should look like this:
OVER POLE UNDER POLE
05:00:00 ---Meridian Limit West (Degs)--- -175:00:00
-05:00:00 ---Meridian Limit East (Degs)--- 175:00:00
03:00:00 Track Past Meridian Overlap
Your meridian overlap lines are drawn on the SkyView screen if you have a
GEM.

Let's say you have an Ealing mount, (we have our brushless controller on
this one):
http://web.mit.edu/wallace/
So, you normally can see all of the sky with the scope in the "Looking
West" position, but there is a small portion of the sky where you want to
do a meridian flip.
Here's some appropriate settings:
OVER POLE UNDER POLE
-80:00:00 ---Meridian Limit West (Degs)--- -170:00:00
-100:00:00 ---Meridian Limit East (Degs)--- 170:00:00
03:00:00 Track Past Meridian Overlap
With these settings, SkyView looks like this:
http://siderealtechnology.com/MeridianOverlapInEastWithSettings.jpg

Keep in mind that the software will keep you from entering numbers that
cross, ie, OverPole Meridian Limit East ALWAYS has to be less than
Meridian Limit OverPole West. You may have to enter your most negative
number first in the meridian Limit East textbox before you are able to
enter your desired Meridian Limit West number.

New Track Past Setting:
This works on the OVER Pole settings and also the UNDER Pole settings.
So, if you're "Looking East", and your mount is tracking, and it goes past
the Southern meridian to the Over Pole Meridian Limit West setting, it
will continue tracking until it hits the Meridian Limit West PLUS the
Track Past Setting.

Now that was hard to make it work correctly, and it seems, even harder to
describe!
Have I mentioned that I really don't like GEM's!

Hi - I installed 0.91a last year, but never got to use it due to extensive
cloud cover for most of the winter. I have a MESU mount and a c11 on it.


I have read the config help but don't understand the meaning of 'over
pole' and 'under pole' features and what values to put in for the
limits.


I understand that with scope on west and CW horizontal that's the zero
point so I put on 0 degrees into the config for the eastern limit is that
right?


Then for the western limit i put in Minus 180 ???


I can't contemplate trying to track past meridian as My brain won't cope
with that.


Any help with what values to put in and which boxes to put them in
greatly appreciated. Just want basic setting that will let the mount
work.


thanks
Paul Kirk


Paul Kirk
 

thanks Dan - what does 'under pole' mean please?

best wishes
Paul


Dan Gray
 

any coordinate that is higher thab the north pole (for those of us 'up
over') is "Over Pole". Anything below the north pole is "below" pole.
Take a look at the screenshot again:
http://siderealtechnology.com/MeridianOverlapInEastWithSettings.jpg

You'll see the blue line, and the green lines up at the top, just below
where it says "north". Those lines are the "Under Pole" lines.
Dan

thanks Dan - what does 'under pole' mean please?

best wishes
Paul


Wayne Rosing
 

There are probably more than one definition but generally this means a star whose altitude is less than Polaris, or where the hour angle of the telescope is greater that 6 or less than -6. 

With a German mount you can also define to be counterweight is above the telescope.

Cirumpolar stars can be visible through 360 degrees, were it not for the Sun.

So getting to those stars means some gymnastics with German mounts because things do not always clear the pier -- cameras, eyepieces on the floor, cables severed.  Ugly unless prepared for.

Folks tend not to go there beause the objects are low altitude, high airmass and things physically can interfere.

But if there is a great comet or speedy asteroid... you try if you can.

W


On Jul 31, 2016 5:46 PM, "paulskirk53@... [SiTechservo]" <SiTechservo@...> wrote:
 

thanks Dan - what does 'under pole' mean please?


best wishes
Paul


Paul Kirk
 

thanks Dan - sorry I can't understand this. Are there any default values I can put in? Or is there a process I can follow which informs the values I should use for my equipment?

I appreciate your help, as you say GEM is confusing and I can't understand it.

best wishes,
Paul


Paul Kirk
 

Hi Dan,

In my limited knowledge of all this meridian limits stuff, I have a suggestion which might help those of us who can't work out what to do. The suggestion is based on the Gemini II controller and Losmandy Gem mount which I previously owned. In order to set the east and west limits, the controller software asked the user to use the hand controller to position the mount at a limit - this was defined by 'as far as you can go and still rotate the scope in Dec without hitting the pier'. You could then click a button which said 'set limit here'.

So for example to set the western limit, use the HC to move the scope to the western side of pier as far as it would go without the scope hitting the pier when rotated in Dec. Click 'set limit here' and the software filled in the value. Now do same for eastern limit.

For meridian overlap, you just filled in a value id Degrees as per sitech controller.

I hope this may help for the future.

best wishes
Paul


Reinhold Friedrich Auer <auer.reinhold@...>
 

Hi Dan and Paul,
I also have a big problem to understand the sense of OVER and UNDER pole. Don Westergard and Dan tried to explain me, I also studied carefully the help file and this communication, but still I cannot fully understand the new parameters. 
My equatorial mounts is a special one, where meridian flip is not necessary anymore. So from the very much EAST to the WEST I do not have to make a meridian flip. And I have big problems to find the right parameters.
Is there a possibility to use ASCOM telescope simulator for that purpose?
RFA

paulskirk53@... [SiTechservo] <SiTechservo@...> schrieb am Mo., 1. Aug. 2016 um 06:32 Uhr:

 

Hi Dan,


In my limited knowledge of all this meridian limits stuff, I have a suggestion which might help those of us who can't work out what to do. The suggestion is based on the Gemini II controller and Losmandy Gem mount which I previously owned. In order to set the east and west limits, the controller software asked the user to use the hand controller to position the mount at a limit - this was defined by 'as far as you can go and still rotate the scope in Dec without hitting the pier'. You could then click a button which said 'set limit here'.

So for example to set the western limit, use the HC to move the scope to the western side of pier as far as it would go without the scope hitting the pier when rotated in Dec. Click 'set limit here' and the software filled in the value. Now do same for eastern limit.

For meridian overlap, you just filled in a value id Degrees as per sitech controller.

I hope this may help for the future.

best wishes
Paul

--
Reinhold Friedrich AUER Dipl. Ing. (FH)
Chudčice 273, CZ - 664 71 Veverská Bityška
tel.   +420 605 553 852


Dan Gray
 

Sounds like a good idea, I'll put it on the list....
Dan

Hi Dan,

In my limited knowledge of all this meridian limits stuff, I have a
suggestion which might help those of us who can't work out what to do.
The suggestion is based on the Gemini II controller and Losmandy Gem
mount which I previously owned. In order to set the east and west limits,
the controller software asked the user to use the hand controller to
position the mount at a limit - this was defined by 'as far as you can go
and still rotate the scope in Dec without hitting the pier'. You could
then click a button which said 'set limit here'.


So for example to set the western limit, use the HC to move the scope to
the western side of pier as far as it would go without the scope hitting
the pier when rotated in Dec. Click 'set limit here' and the software
filled in the value. Now do same for eastern limit.


For meridian overlap, you just filled in a value id Degrees as per sitech
controller.


I hope this may help for the future.


best wishes
Paul


Paul Kirk
 

thanks Dan - much appreciated, 
best wishes 

Paul


Albert
 

Hi Dan,

I'm confused after reading this thread a few times and I can't figure out what to do.
Could you tell me exactly which limit the blue and green dashed lines represent? (which color is what?)

What does the "Track past meridian overlap" exactly do?

I'm experiencing strange behavior when using my MesuMount GEM in combination with ACP.
I set ACP in a way that it flips immediately at the meridan, and it can track 20 minutes past meridian.
And it will wait with a GoTo until 2 minutes after passing the meridian.



And I set the Sitech settings like this:



This results in the mount flipping back and forth about 5 degrees past the meridian.

What I would like to happen:
The mount should immediately flip when a GoTo is performed after the meridian has been passed.
An image acquisition can be started, even a few minutes before the meridian is reached, the mount can track 5 degrees or 20 minutes past the meridian.
This image acquisition will be finished within 20 minutes after passing the meridian.
After the image is downloaded, ACP will perform a Goto, so the mount should flip immediately at that point.

Should I set the Sitech settings like this to accomplish that? (I can't test this at the moment due to the bad weather)



Thanks for any insights!

Regards,
Albert


Albert
 

I need to add that these ACP settings worked perfectly for my previous 10Micron GM2000 GEM mount.
That way I never lost any time around the meridian, and would like to have the same behavior with the Sitech controller.


Don W
 

Hi Paul,

I will try to explain what "Under the Pole" is.  Where ever you are on Earth except at the equator you can see a POLE, either the North Pole or the South Pole.  When you look at the Pole, you can see stars and SDO's above and maybe below the Pole.  For instance I live in San Diego at latitude 32°.  So when I look at the Pole, it is 32° above the North Horizon.  I can see many stars below the pole and a lot more above the Pole.

For me, I know that atmospheric refraction is very small above 30° above the horizon, so I do not image below 30° local altitude.  That means I never image "Below the Pole".  So I completely ignore the "Under the Pole" settings.  Mine are set to -178° Meridian Limit West and 178° Meridian Limit East.  Since I never move my telescope at a target below the pole, these don't ever do anything.

OK, If I lived way up north (or way south) close to the Artic Circle (Dec = 66°) I might be tempted to look at targets below the Pole.  However when you look at the distribution of DSO targets there are very few close to the North Pole.  No Solar system planets, but sometimes a comet.  All the targets under the pole will be above the pole in the next half year (except maybe comets).  So I can wait a few months.

Don W


Don W
 

Hi Albert,

OK, I will try to explain the settings for Meridian Flips in ChangeConfig/Mount Parms.

Meridian Flips only apply to GEMs.  So to use these settings, you must first tell SiTech it is a GEM.  You have two additional settings that tells the mount whether to auto Flip on GOTO's and on Tracking.  If you don't choose one or both of these settings, the mount will never meridian flip automatically.

Below those settings are the controls that set the meridian limits.  When the mount is tracking, it only goes west, so only the Meridian Limit West applies.  Lets only look at settings Over Pole.  You can set the Meridian Limit to 10° and that means the limit is 10 degrees past the Meridian.  The mount will Auto Flip on GOTO's past this limit (whether East or West by your settings).

The Meridian Limit East allows you to move the telescope east of the meridian while the scope is "Looking West", this allows more tracking time for some targets.

The setting for Track Past Meridian only applies to the Meridian West Limit.  It allows the mount to track past the setting you set for the Western Limit.  If this is set to zero, then the SkyView will only show the Blue dashed limit line, superimposed on the the green line (hidden).  The Blue line is actually the track past meridian.

The Green line shows the setting for the Meridian Limit (West and/or East).  If the the tracking limits is zero, the green line is hidden.

Don W


Che
 

I am not familiar with ACP but if I understand correctly, you are trying to set up a meridian flip in both ACP and Sitech.  I think only one should command the flip.  If I am misunderstanding, I appologize
Che


Albert
 

Thanks a lot Don,

I think it has become a little bit clearer to me.

As far as I can deduce now, it  may not be possible to manage flips the way I want to.
For that to work, Sitech should be able to track past the meridian some 10-20 minutes, but when a GoTo is issued in that zone the mount should flip immediately.
But when I read it correctly, all I can do is shift the flipping point to the west.

Regards,
Albert


Albert
 

Hi Che,

Thanks for your reply.
I had ACP working perfectly with my old mount this way.

The flipping point is set right to the meridian in both ACP and Sitech.
But when I tell Sitech to be able to track past the meridan, it seems to also shift the flip point, so it won't flip on a GoTo.
When I tell Sitech to track past the meridian, ACP also has to know that it can image some time past the meridian.

Regards,
Albert


Ross Salinger
 

I don't use ACP, I use CCDAP but Che is correct, in my experience. You
need to turn off the automated flip in SiTech for ACP to control the
flip. I don't image past the meridian but my settings are to have the
auto flip turned off and they work. Remember that an ASCOM "flip"
command doesn't exist. All that happens in ACP or CCDAP is that a slew
command is issued by the imaging software. At that point the mount
driver checks to see if the required slew is east or west of the slew
limit and then either flips the mount or doesn't based on (as I
understand it) "Side of Pier". So, I'd recommend turning that setting
off and setting ACP to flip at the meridian. Then make sure that the
time is correct everywhere and you should see the flip work. If that
happens properly then you can experiment and see how to make it flip
early or late.

Rgrds-Ross

On 1/12/2020 6:35 AM, Albert wrote:
Hi Che,

Thanks for your reply.
I had ACP working perfectly with my old mount this way.

The flipping point is set right to the meridian in both ACP and Sitech.
But when I tell Sitech to be able to track past the meridan, it seems
to also shift the flip point, so it won't flip on a GoTo.
When I tell Sitech to track past the meridian, ACP also has to know
that it can image some time past the meridian.

Regards,
Albert





Albert
 

Thanks for your input Ross,

I'm going to try that, thought I had to choose one option for auto flip in the Sitech driver.

Unfortunately the weather doesn't want to cooperate at the moment...
I post here when I have tested.

Regards,
Albert

On 1/12/20 4:45 PM, Ross Salinger wrote:
I don't use ACP, I use CCDAP but Che is correct, in my experience. You
need to turn off the automated flip in SiTech for ACP to control the
flip. I don't image past the meridian but my settings are to have the
auto flip turned off and they work. Remember that an ASCOM "flip"
command doesn't exist. All that happens in ACP or CCDAP is that a slew
command is issued by the imaging software. At that point the mount
driver checks to see if the required slew is east or west of the slew
limit and then either flips the mount or doesn't based on (as I
understand it) "Side of Pier". So, I'd recommend turning that setting
off and setting ACP to flip at the meridian. Then make sure that the
time is correct everywhere and you should see the flip work. If that
happens properly then you can experiment and see how to make it flip
early or late.

Rgrds-Ross

On 1/12/2020 6:35 AM, Albert wrote:
Hi Che,

Thanks for your reply.
I had ACP working perfectly with my old mount this way.

The flipping point is set right to the meridian in both ACP and Sitech.
But when I tell Sitech to be able to track past the meridan, it seems
to also shift the flip point, so it won't flip on a GoTo.
When I tell Sitech to track past the meridian, ACP also has to know
that it can image some time past the meridian.

Regards,
Albert





Eric Walden
 

Albert,

I'll follow up here as well to see if you found a solution for the meridian flip with the Mesu. I'm using NINA, but the same or similar command checks should be used regardless of platform to poll the ST settings to command the flip.

Were you able to find a combination of settings that allowed for consistent slews and flips?

Thanks, hope the skies have cleared for you!

Eric