Tpoint Mapping Run using Images and Image Link
- Be sure your mount is polar aligned and locked down unless you are doing the mapping run to perform a polar alignmnet. Then establish initial pointing of the mount to known star and synch the mount to that star using the hand control.
- Establish a link from the scope to TheSky - TheSky should show that you are pointed to the star selected above. Next, if possible, use image link as described below to do an initial precision synch on the star.
- If your selected star has at least 5 other stars around it that are shown in TheSky and within the FOV of your camera, then you can use image link to do a precision synch on this area to start your Tpoint run.
- Perform steps 4-10 below on the initial star area. Then select the Telescope tab on the image information box as shown in figure 1. Be sure "Image Link Information" is selected from the drop down box and then click the "synch" button. Your scope should now be precision initialized in TheSky and you are ready to proceed with a Tpoint mapping run. Proceed to step three below. It is important to remember that you do NOT map the initial synch point nor do you synch during the later mappings.
- If you are unable to find six stars in the initial FOV, then you can micro-slew the scope using either TheSky motion controls or the mount's hand paddle until the star is centered in the image. Then synch on that point by placing the cursor on the star in TheSky and using the telescope tab again but synching on the cursor ("cursor position" in the drop down box) or the star itself (object listing in the drop down box) instead of "Image Link Information". This is a bit less accurate but should be fine.
Zoom in with the chip FOV shown and find an area that is where you want to map which has enough stars (6+ displayed in TheSky) to image link well and then slew to that area. Be sure to uncheck "always keep telescope crosshairs on screen" in the telescope setup dialog box or you will not be able to zoom on a different area than where the telescope is currently pointed.
Take an image and be sure that the exposure is long enough to show enough stars (6+ stars)
Be sure image scale (pixel scale) is set correctly (arcsec/pixel) in TheSky image link setup.
Close the information dialog box in TheSky.
Scale the image with the histogram to display all the stars well then copy the image to the clipboard and paste it into TheSky
Rotate, size, and shift TheSky to as closely as possible match the image to the displayed chip FOV.
- "I" toggles the image on and off
- Arrow keys alone move large amounts
- Arrow keys and Control move a smaller amount
- Arrow keys and Shift/Control move very small amounts
- Rotate tool rotates TheSky display as required
- As shown below in figure 2, to align the image with TheSky, you can also Shift/click on a known star (TheSky displayed) and then drag to the same star on the image you have pasted over TheSky - as you do this, a green arrow will appear as shown below. Once you have the arrow on the star in your image, click and TheSky will shift to align as shown below in figure 3. Note that the FOV needs to be scaled to approximate the image size for this to make sense.
Run image link to match the image to TheSky. Accept the link results if it appears correct and the pixel scale displayed in the "accept results?" box matches the expected value.
Reactivate the image information box and select "Image Link Information" from drop down box as shown in figure 4.
Select the "Map" icon (red target-like icon) at the bottom right of the image information box to map the position to Tpoint.
Zoom out and select the next star or object to slew to.
Go back to step 3 and repeat steps 3-11 as often as needed for the desired modeling.
Final Note: The model starts to improve pointing only after 6 points are mapped. At that time one should select the "Fit" command and check the data to verify that it makes sense.
Copyright William McLaughlin
Copyright willmclaughlin.astrodigitals.com .