Could Feature tracking follow a comet?

[chongo228]

I was reading another forum talking about tracking a comet. It seems to not be easy.....a dance between CDC and PHD2 is one of the easier methods being talked about.

If put an old version of SC on my guide camera and turned feature tracking on could I collect images with another version of SC open on the main camera? Would a comet and guide camera give the feature tracking the contrast or image quality needed to follow a comet?

If not this seems like a possible feature for down the road...from what I know there isn't another program that will just follow a comet easily once centered.

[admin]

Hi,

I think it's more likely that the feature tracking would pick up on the stars in the background as the most promising things in the image to track and therefore wouldn't track the comet (the comet is more likely to be fuzzy and not be picked up as something worth trying to track).

It's a long time since I tried this but I seem to recall that there was a way to make your mount run at the cometary tracking rate – I can't remember if this was with CDC or using EQMOD though.

Cheers, Robin

[chongo228]

With all the photos of NEOWISE showing up I was thinking about this more...

Would it be possible to add another feature tracking option for comets in that you put an ROI field over the comet so SC wouldn't pay attention to stars, set a black level to tell SC the edge of the comet from the background or light pollution/dome, and then let it take over controlling the mount? I'm thinking a similar set up for your focusing tool for planets (edge/contrast detection tool). Could you just add an ROI selection to the current feature tracking tool? Testing this might be hard as comets don't come around often.

Even if there was a little rotation or error between frames stacking would align the frames in post processing.

[admin]

Hi,

SharpCap 3.3 has a mode where it will track the centre of brightness of the image instead of feature points – if the comet is definitely the brightest thing in view then this might work without needing the ROI. However I'm not sure if it would work properly during the calibration procedure as the comet is moving.

Cheers, Robin

[oopfan]

Given that the comet won't be around much longer I recommend going "old school". Use SC for frame capture but DSS for image stacking. DSS has a "comet mode" where it asks you to draw a box around the comet's nucleus. This works fine unless you have an alt-azimuth mount and therefore image rotation becomes a problem. As far as exposure goes. Stay under 30 seconds. If your background is washed-out at 30 seconds then cut to 20 seconds. Reduce exposure until the sky background is below 5000 ADU. You will probably be imaging during twilight so the sky will be darkening fast. (You can see it in the histogram.) You may want to consider a 3-minute image run, then pausing to increase exposure, followed by another 3-minute run. Try to keep your sky background ADU approximately the same from one run to the next. This way you should be able to stack all images together. As far as calibration frames, capture flats and bias as usual, but for darks use the average light exposure, for example if you made three runs at 10 seconds, 20 seconds, and 30 seconds, then capture your darks using a 20-second exposure.

Brian