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Old 16-07-2018, 09:46 PM
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gregbradley
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Is there a way to use TPoint to flip the mount to the exact spot?

I use The Sky X and Tpoint. Is there a way to use these to mark the spot where you are currently imaging so when you do a meridian flip it goes back to the same exact spot (plate solve) so you can continue imaging quickly?

I currently have to reframe the image even if it goes to the target its not the same framing.

I was thinking if you add a point to a tpoint model it can mark it as a spot on the Sky X sky map. Then you could select it and slew to that spot?

It would save me some time.

Greg.
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Old 16-07-2018, 10:37 PM
rally
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Greg,

Tpoint and the Paramount handle meridian flips really well
No need for fudging it !

You would do your normal Tpoint mapping for Polar Alignemt reporting using 6 plus stars within a few degrees of each other on the same side of meridian.
Then once you have used the Polar alignment report to adjust for a good Polar Alignment (you might do 2 quick iterations to get it down into the +/- 10 arc second range for both axiis)
Once you have a good PA on one side of Meridian, then generate a new calibration run which has about 40 mapped points on both sides of meridian and have them +80 and -80 degrees declination and some around the celestial equator.

This will produce a Tpoint model that should have you within about a stars diameter anywhere in the sky.

You need to do that as the manual states to differentiate between the different term errors that can be caused by different things - "This is so that TPoint can distinguish between the HA sync error, IH, and the OTA/declination non-perpendicularity, CH."
Doing the mapping on both sides of meridian ensure that Tpoint can correctly identify the sources of those errors and correct them.

I assume you are using TheSkyX and can so a Super Model and you are doing your Tpoint mapping using the camera rather than swapping between visual and camera

There is a good discussion of this in the Tpoint Add On manual available online.

Rally
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Old 17-07-2018, 11:12 AM
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Quote:
Originally Posted by rally View Post
Greg,

Tpoint and the Paramount handle meridian flips really well
No need for fudging it !

You would do your normal Tpoint mapping for Polar Alignemt reporting using 6 plus stars within a few degrees of each other on the same side of meridian.
Then once you have used the Polar alignment report to adjust for a good Polar Alignment (you might do 2 quick iterations to get it down into the +/- 10 arc second range for both axiis)
Once you have a good PA on one side of Meridian, then generate a new calibration run which has about 40 mapped points on both sides of meridian and have them +80 and -80 degrees declination and some around the celestial equator.

This will produce a Tpoint model that should have you within about a stars diameter anywhere in the sky.

You need to do that as the manual states to differentiate between the different term errors that can be caused by different things - "This is so that TPoint can distinguish between the HA sync error, IH, and the OTA/declination non-perpendicularity, CH."
Doing the mapping on both sides of meridian ensure that Tpoint can correctly identify the sources of those errors and correct them.

I assume you are using TheSkyX and can so a Super Model and you are doing your Tpoint mapping using the camera rather than swapping between visual and camera

There is a good discussion of this in the Tpoint Add On manual available online.

Rally
Thanks for the reply Rally. Its not what I was asking though. I do use TPoint and supermodels and polar alignment and yes it does a fantastic job.

But here is an example of what I mean. I am imaging NGC6188 so I do closed loop slew to NGC6188 that puts it exactly in the centre of the image.
I don't want that as its not framed nicely so I move it until I like the framing. Now later I need to do a merdian flip. If I do closed loop slew I am back to NGC6188 being in the middle of the image again and I have to remove it to frame it the same as I was just imaging on the other side of the meridian.

I was wanting to know if there is a way to plate solve the framing so when you flip it goes to that exact framing not just putting the object in the middle of the image requiring moving it again to frame it the same.

I have noticed if you add a point after a plate solve it can be displayed on the map. Then closed loop slewing may go to that point rather than the middle of the object? Not sure. The flip mount tool in Sky X does not put the object in the same position of the image. That's the problem.

Greg.
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Old 17-07-2018, 01:58 PM
brisen (Brian)
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Greg

Have you tried image link in the Sky X to solve to a frame that you have taken prior to the meridian flip as opposed to using the closed loop slew and then have to reframe the image?

I am hoping to use this approach tonight to pick up where I left off last night, I usually use closed loop slew to centre the target and then have to reframe as well.

Brian
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Old 17-07-2018, 02:09 PM
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Greg

Have you tried image link in the Sky X to solve to a frame that you have taken prior to the meridian flip as opposed to using the closed loop slew and then have to reframe the image?

I am hoping to use this approach tonight to pick up where I left off last night, I usually use closed loop slew to centre the target and then have to reframe as well.

Brian
Hi Brian,


So plate solve using image link the image you last took you want to flip the mount to (but reversed). Then how do you get it to go to that plate solved image? Enter it as a Tpoint point in a model? I will play around with this as I have seen it display a marker on the map when you enter a tpoint plate solved point and then you may be able to tell it to go to that point?


Greg.
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Old 17-07-2018, 04:56 PM
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Quote:
Originally Posted by gregbradley View Post
Hi Brian,


So plate solve using image link the image you last took you want to flip the mount to (but reversed). Then how do you get it to go to that plate solved image? Enter it as a Tpoint point in a model? I will play around with this as I have seen it display a marker on the map when you enter a tpoint plate solved point and then you may be able to tell it to go to that point?


Greg.
Hi Greg

I don't have T Point so not sure about it, I am not sure if it works with an EQ 6 mount as they don't have encoders.

Image Link will solve to the image and rotate the Sky X to fit it, I am going to give it a go myself tonight - I have tried it ages ago but haven't used it lately. I started on the Eagle after it crossed the meridian last night and want to try and start it much earlier tonight so I am hoping it plays nicely and just works as it is on the other side to where I started last night.

Brian
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Old 17-07-2018, 06:50 PM
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Perhaps once the dso has been framed it needs to be plate solved and then this coordinates need to be assigned to this sequence. That's how it works in SGP anyway - once an image gets plate solved (after framing) SGP asks if the user wants to use this as a reference for the active sequence.
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Old 17-07-2018, 07:23 PM
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Quote:
Originally Posted by brisen View Post
Greg

Have you tried image link in the Sky X to solve to a frame that you have taken prior to the meridian flip as opposed to using the closed loop slew and then have to reframe the image?

I am hoping to use this approach tonight to pick up where I left off last night, I usually use closed loop slew to centre the target and then have to reframe as well.

Brian
Quote:
Originally Posted by Slawomir View Post
Perhaps once the dso has been framed it needs to be plate solved and then this coordinates need to be assigned to this sequence. That's how it works in SGP anyway - once an image gets plate solved (after framing) SGP asks if the user wants to use this as a reference for the active sequence.
That's what I thought would have to occur.

Greg.
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Old 17-07-2018, 07:38 PM
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Hi Greg.
The way to do this is with a closed loop slew. It will get you where you want to be every time within a few pixels. You need to be able to plateslove the photographed image, then TSX will compare the offset and do a final minor slew to whereyou want to be. No guess work. This is what i do. You don't even need to be using a Tpoint model as far as i am aware.



Josh
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Old 18-07-2018, 05:23 PM
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First plate solve the position you intend to flip to.


Then drag the meridian flip line so that when you CLS to the plate solved image it will be forced to flip. In other words, do not use the Flip Now command. It's a pity that there isn't a sub menu under Flip that allows for a selection to flip to the exact position being vacated (but, this would require a plate solve prior to the move...similar to what FocusMax does when it goes to a focus star and then returns).



Peter
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Old 18-07-2018, 07:21 PM
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Originally Posted by Joshua Bunn View Post
Hi Greg.
The way to do this is with a closed loop slew. It will get you where you want to be every time within a few pixels. You need to be able to plateslove the photographed image, then TSX will compare the offset and do a final minor slew to whereyou want to be. No guess work. This is what i do. You don't even need to be using a Tpoint model as far as i am aware.



Josh
Thanks Josh.

So to be clear you:

1. Plate solve using Image Link the current image you last took you want to flip to on the other side of the meridian when the mount is hovering in the meridian zone on the map.
2. Sky X automatically registers that image as a the target to go to.
3. Click closed loop slew and it will go to the plate solved image on the other side of the meridian.

Greg.
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Old 18-07-2018, 07:22 PM
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Originally Posted by PRejto View Post
First plate solve the position you intend to flip to.


Then drag the meridian flip line so that when you CLS to the plate solved image it will be forced to flip. In other words, do not use the Flip Now command. It's a pity that there isn't a sub menu under Flip that allows for a selection to flip to the exact position being vacated (but, this would require a plate solve prior to the move...similar to what FocusMax does when it goes to a focus star and then returns).



Peter
Thanks Peter that sounds the same as Josh's except for the dragging of the meridian line if the mount is not already in that zone (the purple zone).

Thanks guys, I'll try that out probably tonight!

Greg.
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Old 18-07-2018, 07:59 PM
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Hi Greg

I tried the image link with an image from the west side of the meridian captured a couple of nights ago when I was able to image, to start on the east side tonight using all sky survey in the Sky X. It solved easily, I right mouse clicked over the solved image on the chart and then selected Closed Loop Slew from the list that this opened. The mount slewed, had a think, and then centred exactly on the image where it was on the other side of the meridian a couple of nights ago.

Much easier and quicker then just a CLS to the image and as you say then having to spend time reframing which is what I had also been doing.

Brian
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Old 18-07-2018, 08:07 PM
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Greg,


Have a think about this. If you plate solve the image before the mount flips and you CLS to the image the mount will not flip. This will happen even if you are within the purple zone. By moving the flip line the mount will have no choice except to flip!


Peter
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Old 18-07-2018, 10:19 PM
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Let us know how you go Greg.
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Old 18-07-2018, 10:33 PM
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Although I don't use TSX for meridian flips I have found that the best way to deal with this kind of thing generally is that when you find the framing you like you centre on a star that best represents the centre of the frame that you want. Your image centre will likely be something like HD34853489573.

Plate Solving your image to begin with is certainly another way but it doesn't work as well when you're photographing several objects in the sky that are crossing meridian.
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Old 19-07-2018, 10:13 AM
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FWIW I have TSX and use CLS but for fine positioning I like using Maxim as after a plate solve you can click on any part of the image and just tell it to center on that point and save it as a bookmark . It handles flips as it goes
also in my APCC software (not relavent here ) I can specify a time to do the meridian flip which is very handy.
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