In the world of astrophotography, long exposures are like a magical key that opens the door to the deep universe for us. To ensure the telescope tracks the target correctly and achieves precise guiding during exposure, it is essential to perform a polar alignment for the equatorial mount.
The StellaVita astrophotography smart wireless controller provides the polar alignment function, offering an easy and fast method for astrophotography enthusiasts.
Operating Instructions
Preparations
- Ensure the time, geographic location, and focal length of the main telescope are correct.
- Adjust the RA and DEC of the equatorial mount so it points to a visible area of the sky.
- Switch the main camera to video mode, adjust the exposure and stretch parameters until the background of the image is visible. Then, use the electric focuser control panel to manually perform the main telescope coarse focusing.
- After completing coarse focusing, switch to single-frame shooting mode and set the main camera parameters appropriately. Capture and analyze the image using the single-frame shooting function. Make sure the image shows a suitable contrast with several stars that can be successfully analyzed, and synchronize the analysis results to the equatorial mount.
Note: If the above parameters or setups are incomplete, it might result in the failure of the polar alignment. During the preparation, there is no need for the main telescope to use autofocus. Just make sure that the star points in the image are analyzable. Autofocus should be done after the polar alignment to optimize equipment adjustment.
Start Polar Alignment
First, the main interface of the polar alignment function will show the operation instruction:
The polar alignment in the StellaVita App mainly consists of two steps:
- Three-point polar alignment to calculate polar axis error
- Manual adjustment and error data refresh
1. Three-Point Polar Alignment to Calculate Polar Axis Error
At the start of the polar alignment, StellaVita will first perform a three-point polar alignment to calculate the polar axis pointing error. This involves automatically capturing and analyzing three images at the initial position of the equatorial mount, 15°, and 30 ° along the RA axis. By determining the center coordinates of these images, the software can calculate the equatorial mount’s rotation center and compare it with the actual North (South) celestial pole to obtain error data.
2. Manual Adjustment and Error Data Refresh
Based on the analyzed altitude and azimuth data and the direction of adjustment, adjust the equatorial mount or tripod and then click "Refresh" until the app gives a "Ding-dong" sound and the analyzed values turn green. This indicates that the polar axis accuracy has reached a reasonable range.
There are two types of sound prompts. When both error data are less than 1 arcminute, there will be a little surprise for you!
Note:
- If the initial error during three-point polar alignment is large (greater than 1°), it is recommended to redo the polar alignment to verify the results. Multiple checks and iterations are one of the characteristics of the three-point polar alignment method.
- During polar alignment, always adjust the azimuth or altitude angle with the larger error first.
- The first polar alignment doesn’t need to be very precise. Once both data values are below 1°, you can exit the current process and start the second polar alignment for improving equipment adjustment efficiency.
- If the polar alignment takes too long, we recommend returning the equipment to its initial position and starting the polar alignment again. As celestial objects are constantly moving, it could reduce the accuracy when the polar alignment process takes an extremely long time.
FAQs
Q: Are there any special considerations for the initial pointing position of the polar alignment?
A: Yes, here are a few things to note:
1. It is recommended to avoid the azimuth positions 90° (East) and 270° (West) during polar alignment, as it is difficult to calculate altitude angle data at these positions, which may lead to incorrect results.
2. Avoid pointing directly at the zenith (overhead) for polar alignment, as it will be difficult to calculate azimuth angle data, which may lead to incorrect results.
3. Avoid using low-declination regions, as the closer the region is to the celestial equator, the tracking errors become more noticeable, especially when the initial polar axis error is large.
4. When pointing at low altitude angle areas, atmospheric refraction (air mass error) may reduce the accuracy of the polar alignment.
5. Avoid pointing near the meridian or flipping through the zenith during thepolar alignment process.
Q: Why does the error data change even though I haven’t adjusted the azimuth and altitude angles?
A: The change in error data depends on the plate resolving results, which require the equatorial mount to maintain tracking with a certain level of tracking accuracy. With longer exposure times for single-frame images, the stars may appear as trails instead of points, which reduces analysis precision and leads to changes in error data. Additionally, since the polar alignment requires tracking, tracking errors such as mechanical inaccuracies or alignment issues will also affect the analysis results. We recommend keeping the exposure time for the polar alignment between 1 to 3 seconds.
Also, don’t worry if there is a minor fluctuation in arc-seconds of error, as such fluctuations are within an acceptable range.
Q: What should I do if the polar alignment fails in StellaVita?
A: Please check the weather conditions, image exposure settings, and ensure the correct focal length is set for the main camera. You can try taking an image in single-frame mode with the same parameters and analyzing the image to ensure it can be parsed correctly. If the polar alignment still fails after these checks, try pointing at a different area of the sky and restart the polar alignment process.
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