Comet tracking

franco

Any tips on how to identify the comet in the guide scope image so that it can be selected for guiding?

Last night I got my first chance to image the green comet as it climbs above the roof of my house and although I got some quite nice single images, I wanted to try guiding on the comet as other people have done. I was guiding ok on the stars but couldn't tell which of the tiny points of light was the comet itself.

I will try again tonight using a different telescope with a guide scope and camera that can plate solve but if anyone knows of a better way, it would be great to know for future reference.

I did try upping the exposure time on the guide scope camera but it's limited to 5 seconds. In hindsight I should have swapped the main and guide camera in the Air but it only occurred to me after I'd packed up.

[Edit]

It's just dawned on me that the comet might not have been in the FOV of the guide scope, I keep forgetting that the short FL of the scope is negated by the tiny guide camera chip.

w7ay

franco It's just dawned on me that the comet might not have been in the FOV of the guide scope, I keep forgetting that the short FL of the scope is negated by the tiny guide camera chip.

If your guide scope is mounted on a set of rings, you can get the two cameras to point very close to one another by first centering a star and plate solving the main OTA first, and then plate solve the guide scope to adjust the rings until you can get the star into the FOV, and after that just use video mode in the guide window to center that star.

Much easier with plate solving than using visual guessing :-).

Chen

franco

w7ay this is my old Newtonian that only has a finder shoe but I do plan to add another dovetail bar along the top.

I wasn't sure how big or bright the comet would be.

I do wish ZWO would allow you to use the same tools you have for the main camera with the guide camera without having to switch devices.

w7ay

franco I wasn't sure how big or bright the comet would be.

Don't worry,there will be another bright one at some point. :-).

You can look at the Magnitudes of the Comets. Roughly speaking if they are as bright as a Magnitude 6 star, you just need to be able to see the 6 magnitude star (if both are spread out to the same number of pixels due to optics and seeing, to the same number of pixels).

C/2022 E3 is currently at Magnitude +6.2, so with plate scale where the comet head is inside, say a 2x2 or 3x3 pixel area (typical size of an imaged star), then you can simply check if your current optics can guide with +6.2 stars.

Chen

franco

w7ay after switching to a bigger guide scope pointing at the same patch of sky as the main scope, tracking the comet turned out to be quite easy. Can't say it was worth waiting 40,000 years for!

Got bored of looking at the green smudge so pointed my telescope in the opposite direction to image NGC1672 and was amazed at how much better the guiding is when the target is closer to the SCP, was getting around .25". I can't normally image to the south because we are on a big hill.