• SessionCraft and Meridian Flip

SessionCraft and Meridian Flip

The SessionCraft is accessible from Tools tab
or with F9 key.
Session Craft is designed to monitor various events and to control imaging session. It works even when the window is closed. The first feature from this tool is "Automated Meridian Flip". APT can be configured to track the object position during the imaging and when it closes the celestial meridian passing to flip telescope position to prevent physical damage or bad guiding. After that flip the imaging process continues from the interruption moment, aiming to the exact same place of the sky.
To achieve this goal of Automated and Unattended Meridian Flip, APT follows the next scenario:
1. If there is running plan, before every exposure is checked if there is enough time take a new image before the need to make flip. If there is no running plan the check is running in real-time
2. If the "Flip Moment" occurs or there is no enough time to take another exposure, Session Craft determines the exact position of the current target via PointCraft taking a short exposure
3. Pauses for user defined time, disables the tracking and guiding giving time the object to pass the meridian or the scope position to be safe after flipping the pier/tripod side
4. Once pause is elapsed, it enables the tracking and flips the scope position
5. Makes GoTo++ to the target in order to frame the object by the very same way as before the flip
6. Enables the guiding by selecting a new guiding star and making re-calibration if needed
7. Resumes the imaging plan
Because these operations could be dangerous for your setup, in case of smallest problem for security reasons APT leaves the scope with disabled tracking, disabled guiding and stops the imaging plan. In every moment you can press the Stop button in Session Craft, the Stop button in Gear Tab or by pressing F12 key to stop all movements and actions.
The default Meridian Flip settings should work out of the box for virtually every setup. It will stop 5 minutes before the celestial meridian passing, will wait 5 minutes after the actual passing through the meridian (total pause of 10 minutes) and after that will flip the scope position. Every step of the process is logged in the Log panel. During the flip the SessionCraft windows will be displayed automatically if it was closed.
However you must to prepare your setup, learn it behavior and observe the first few flips to be sure that everything is fine and safe. We do provide the automation, but you are using it by your own decision and you are taking the whole care for your scope! Keep eye on your setup during the first few flips!!!
Here are the most important checks to make before enabling Make Automatic Flip:
1. After preparing your setup and connecting all cables make "dry" manual flips moving the scope by hand from the both sides of the pier/tripod to make sure that all cables are free. Make these checks near the Zenith, but also above South and North points of horizon. It is very important! Short cables or short cable travel can cause serious damages to connectors, ports or to pull computer form table!!!
2. If you are using CCD/CMOS and usually there is needing Histogram stretching in order to solve the images keep the Histogram open.
3. Make sure that you have configured PointCraft correctly. It is used to determine the exact position before the flip and to reach the same position after the flip. We suggest to configure both PS2 and ASPS and for the first flips to use blind solving for target centering. We also suggest to define Default exposure in PointCraft Settings which is long enough to get few stars with all of your filters. If defined by Blind solving ASPS will be used only for the first step of the GoTo++
4. Check the usual time PS2 takes to solve an image from your scope. If it is more that 1-2 minutes increase the Flip Moment.
5. Make sure that you are using PHD2 or MGen for guiding and that Control Guiding is enabled. Meridian flip is also possible when your mount doesn't need guiding.
6. Make sure that you are using dark frames in PHD2 to avoid selection of hot pixels during guiding star auto-selection.
7. It is advisable to confirm the limits of your setup. Once the scope is aligned move it to position East from celestial meridian near Zenith via the handset, control panel of your driver or Gear Tab. Start making fine movements towards meridian and keep an eye on Meridian Flip Clock. See if the default limit of 5 minutes before meridian passing is safe for your kit. If not increase Flip Moment to a value that fits better. Move the scope from the other side of the tripod/pier and close it to meridian. Meridian Flip Clock will show values close to 720 minutes (this is the time of next meridian passing - the lowest object position). If the position that shows 715 is not safe see the value that fits better and subtract it from 720, set the result as Delay Flip Move. For example if the safe position is 713 minutes the needed delay is 720-713 = 7 minutes.
The points 1 and 2 have to be checked on every session. The other point are needed in the first time or after scope change. You can skip point 7 only if you are trying the default settings and you are keeping an eye on the process!!!
SessionCraft and Meridian Flip


1. Status
This area show the Session Craft status. If Make Automatic Flip is unchecked Session Craft will not make any actions. During the flip process it shows the current step or the remaining time of pause defined by Delay Flip Move.

Flip / Stop / Reset

2. Flip / Stop / Reset
When Session Craft is in "Monitoring" status you can use the Flip button to start the process manually.
If automatic meridian flip is in progress this button becomes Stop that will immediately stop all movements, tracking, guiding, solving and imaging.
If the last automatic meridian flip process failed or Stop button is clicked this button becomes Reset that can clear all errors and flip process can be restarted. Note that you will have to start the scope tracking manually by Tracking in Gear Tab.

Make Automatic Flip

3. Make Automatic Flip
Enables/Disables making the automatic meridian flip. On enabling SessionCraft will check the settings and will give an error message in case of problem.

Flip Moment

4. Flip Moment
Defines how many minutes before the celestial meridian passing to start the preparations for flipping the mount. On process start it will determine the current position via taking a short image and plate solving it in PointCraft. It will stop the tracking and guiding once the position is determined.
If an imaging plan is in progress and there is no time to take the next exposure before the flip moment occurring, the imaging will be paused earlier and the additional time will not be counted as delay - it is an extra pause to prevent collisions.
Flip Moment works in combination with Delay Flip Move and Delay is counted after meridian. See the notes.
If this value is negative this means that process will start after meridian passing. We suggest to investigate very carefully the behavior of your mount before using negative values! Delay is counted after meridian passing has to be unchecked.

Delay Flip Move

5. Delay Flip Move
Defines how many minutes to wait before executing the actual scope move that will flip its position according to the pier/tripod side. This delay can be counted from two moments - from the object passing through the celestial meridian (Delay is counted after meridian is checked) or from the "Flip Moment" (Delay is counted after meridian is unchecked).
During this delay the mount tracking and guiding are disabled. It gives time the object to move away from the positions where scope can hit the pier/tripod or/and to guide poorly.
Example: Let have an object that will pass through celestial meridian in 22:15. Let have Flip Moment set to 5 minutes and Delay Flip Move set to 7 minutes.
No matter if Delay is counted after meridian is checked or not, Session Craft will stop the guiding and tracking in 22:10 (or earlier if there is no time to take scheduled image, but for simplicity we will ignore that extra pause). This happens because we have set to stop 5 minutes before meridian reaching. Here are the two options depending on Delay is counted after meridian state:
1. If Delay is counted after meridian is checked - Session Craft will wait 5 minutes the object to pass the meridian in 22:15 after that will wait another 7 minutes and then will make the flip move. Total pause 5+7=12 minutes.
2. If Delay is counted after meridian is unchecked - Session Craft will wait 7 minutes after 22:10 and will make the flip move. Meridian passing is in 22:15, so the move will happen just 2 minutes after the passing. Total pause 7 minutes.
If we have running plan and there is extra pause, consider that Session Craft will be idle for X minutes till 22:10 is reached then the above calculation will be applied.
We suggest to use Option 1 because it is easier to predict the flip move and measure the scope position limits. Be careful, not all mounts can flip the scope pier/tripod position before object passing through the meridian! If the flip move is started too early is possible to be ignored by the mount and to leave the scope from the old side leading to crash! Option 1 ensures that object will be on position that can be safely used by all mounts and flip will happens!
Option 2 gives possibility for optimizing the flip process and to take the maximum of your mount, but requires very careful measurements of the Flip moment (positive or negative) and the needed delay. Also needs knowing if it is possible to make flip move before meridian. Make experiments in various parts of the celestial meridian - from Zenith to South and from Zenith to North keeping an close eye on the mount and in the messages in the Log panel.
In every moment you can press the Stop button in Session Craft, the Stop button in Gear Tab or press F12 key to stop all movements and actions.

Delay is after meridian passing

6. Delay is after meridian passing
Defines how the pre-flip delay is measured. When checked the delay is measured from the object passing through the celestial meridian. When unchecked the delay is measured from the Flip moment. See the Delay Flip Move notes!

Blind Solve

7. Blind Solve
Defines what solving method to use for the first GoTo++ step after flipping the pier/tripod scope position. When checked the first solving will be blind solving via ASPS. All other GoTo++ steps will use near solving via PS2. When unchecked only PS2 will be used.


8. Recalibrate
When checked will force PHD2 recalibration after the flip before guiding star. MGen does recalibration unconditionally.