|
|
Hi Basil, Thank you for your comments :) I have a planned change to allow to move the crosshair anywhere on the image. Maybe just adding some additional custom circle to the crosshair can help? What do you think? |
|
|
Very sorry for my delay in replying. Yes, your idea of having a movable cross hair with an adjustable circle overlay would be fine for what I was looking for. Actually I think just one circle is fine, I don't need 3. I could just use the circle to represent the outer diameter of my photometry background sky annulus, or the "warning zone". What I would probably do is use SkyChart to plot the position of the asteroid for tonight, then lock the chart onto my target asteroid, set the field of view to about 1/2 degree on a equatorial plot (not alt, azm.), then download a DSS image (Get DSS Image) to show the background stars. Then I would turn on my custom display masks (Finder Eyepiece circles set to my photometric apertures), zoom in, and increment the time by maybe 10min to see where the asteroid is heading tonight. Since the chart is locked on the asteroid, the mask circles will follow the asteroid. If it wasn't locked then the circles stay on the center of the chart as the asteroid moves with time. Follow me? -like the chart follows the asteroid, lol :) Actually, probably the very last step in the process would be to lock the chart on the asteroid as I've noticed making any changes to a chart can break that lock. When taking images I sometimes notice the asteroid is a little behind or ahead of it's predicted position - the path is good, it's the time that's off. That means I can't be exactly sure when it gets too close to a star using StarChart as I described above. So while imaging in CCDCiel, I would place the new cross hair on the bad star in the way and wait for the asteroid to get too close to the warning zone. I could then pause imaging of that asteroid and go to another, or get a cup of coffee, or read a book, or... Then take a short exposure every so often to see if the asteroid is on it's merry way through a dark background sky. Sorry if that was way too many details of my thoughts, but maybe when the new cross hair is live you could somehow condense my workflow to explain one, very specific, use of the new feature. Thank you again. |
|
|
After some thought there is one more thing that would almost be required for this to work, and it is because of tracking errors with my telescope (probably true for other people). If I placed the crosshair and circle over a star and waited for the asteroid to get too close there could be enough tracking error so the crosshair might not stay centered on the star over time. So it would almost be essential that the crosshair could lock on to the star (or asteroid ) like CCDciel does when it is doing an auto focus for example. So the code to "lock on" is already in there, it would just need to be applied to the location of the crosshair. However, I imagine there are times when someone would want the cross hair to stay located at some x,y coordinates in the image and not move. Now how would CCDciel handle a NEO flying across the field - if someone wanted to lock on to the asteroid? Maybe that's asking too much and possibly that need would rarely happen? Ugh. Hey, if this very custom feature can't handle a telescope with very poor tracking or follow some newly discovered thing flying through the Earth's neighborhood, well the program is free isn't it? (Donations are welcome) So , trying to keep things simple, there would need? to be 3 options: make the crosshair movable, have a user specified diameter for the center circle, and the ability to lock the cross hair on a point source or not. Certainly a little more complicated. Thank you for your consideration. |
|
|
Yes this can get a bit complicated. For now I start with the simple thing. Once the crosshairs is displayed it can be moved by pressing the Ctrl key and a click at the asteroid position. The position is reset to the picture center every time the crosshairs button is deactivated. Up to 3 additional circle can be defined in Preferences / Preview. You can try it by installing the version 0.9.93-3967 from https://vega.ap-i.net/pub/ccdciel/daily_build/ Automatically following the asteroid that move on every image is more complicated. This probably require to plate solve the image and get the asteroid position from the planetarium, then find a dot near this position. But this can work only in an ideal case. We have no way to be sure the selected dot is the asteroid and not a nearby star. If the telescope is guided on the asteroid the stars can be trailed and the plate solving will fail. About the precision of the position in CdC it can be interesting to always get the SPICE kernel instead of the elements, even for standard asteroid. |
|
|
Thank you the link, I will give it a try the next clear night, maybe tonight. Rethinking exactly what I am trying do do and the easiest way to do it, perhaps this sums it up: I want to know if a moving target (asteroid) is going to pass too close to a background object (star, galaxy, etc) causing photometric measurements to be invalid. To do this I would first plot the object's path for my planned observation time using CdC using an equatorial chart and a small field of view, about 1 degree. Then I download the DSS image for that FOV (usually the Skyview DSS images). I then increment the time, usually 5-10min per increment, and see where the thing is headed and note the approximate time there could be a problem from a background object. That's all the preparation work. During imaging I think this is all I would like CCDCiel to do. Place a circle on a possible background object in the way - NOT place a circle on the moving asteroid - (that should make the coding a little easier!). The circle's diameter would represent a "danger zone" where I should probably stop photometric measurements. As images are being taken the danger zone circle would (hopefully) re-center on the background object (star) to correct for any tracking errors of my mount. Note: re-centering on an extended object (galaxy) probably wont work and that's okay for my needs. I would then just watch the images as my asteroid approaches the danger zone and stop imaging if needed. Then resume imaging after the asteroid has cleared the danger zone. I would probably start closely monitoring the asteroid's path based on the time I got from CdC, keeping in mind the CdC path can be just an estimate (Not because of any error in your programming, but due to uncertainties in the asteroids orbit!) So in summary, it would helpful for me (and I hope others) to be able to place a circle, with a diameter I choose, on a fixed point source (star) in a image and have that circle recenter on the point source from image to image. I think that's it. Now if you want CCDCiel to set off some kind of alarm, a sound or whatever, if something enters the "danger zone", well I don't know if that's necessary, or even a good idea. I can see false alarms being a problem, or just interrupting a quiet, peaceful night of observing.... Sounds simple enough, right? Yeah Basil, sure it does... lol Thank you so much and sorry for another lengthily message. |
|
|
Basil, I make a change to allow what you describe. This reuse two existing functions. One to follow a star from frame to frame mainly for focusing purpose, and one to draw the crosshair with a custom size circle. To use it, install the version 0.9.94-4055 from https://vega.ap-i.net/pub/ccdciel/daily_build/ Setup the size of the circle in Preferences / Preview. Activate the crosshair using the concentric circle button in the visualization tool. Double click on the star to show the green selection box around it. The crosshair move to this star and follow it on every new image, moving the crosshair circle along. |
|
|
Sorry for my long delay in replying, I wanted to wait for a clear night to test the cross-hair circle and last night it was finally clear long enough to give it a test. Everything worked great! It was easy to follow your instructions and it was easy for the circle to follow a star and the asteroid (I tested both). The star was also pretty faint, to give it a tough test. My only thought was when I used all 3 circles, combined with the green circle and box, the whole thing got a little too much for me - 3 red circles, 1 green circle, and 1 green box all in a pretty small space on my screen. I switched to just using 1 circle and let that represent the outer diameter of my photometry aperture - the outer edge of my background sky. That seemed to work better for an occasional glance to see if anything was getting close, which I actually needed last night as my target ran directly over a star! Thank you! crosshaircircle-final.png (847,332 bytes) |
- Anonymous
