Comet exposure time calculation?

[michaelmorris]

I'm hoping to get some images of Comet 41P/Tuttle–Giacobini–Kresák in the next week.  Is there a handy tool for working out the optimum sub length on comets (i.e. max exposure before motion smears image)?

Thanks

 

[happy-kat]

Are you using a tracking mount. And smears on comet or stars?

[michaelmorris]

23 minutes ago, happy-kat said:

Are you using a tracking mount. And smears on comet or stars?

Yes, It'll be on an HEQ5 pro, so hopefully mount tracking accuracy shouldn't be the limiting issue.

[Davey-T]

Which lens / scope will you be using, I took some 90 sec ISO800 exposures a couple of nights ago and there was no movement in the image.

On the other hand took some using 10"SCT and movement was visible over a few minutes.

Just been looking on Stellarium and a nifty 50mm looks like it will get 2 comets M13 and M92.

Dave

[michaelmorris]

5 minutes ago, Davey-T said:

Which lens / scope will you be using, I took some 90 sec ISO800 exposures a couple of nights ago and there was no movement in the image.

On the other hand took some using 10"SCT and movement was visible over a few minutes.

Just been looking on Stellarium and a nifty 50mm looks like it will get 2 comets M13 and M92.

Dave

I'm planning to shoot at a focal length of 510mm with 1.95 arcsec/pixel camera resolution.

[Davey-T]

1 hour ago, michaelmorris said:

I'm planning to shoot at a focal length of 510mm with 1.95 arcsec/pixel camera resolution.

When I did a timelapse of it with the SCT it only moved about 1 degree in 5 hours so doubt you'll get much smearing.

Dave

[dph1nm]

https://ssd.jpl.nasa.gov/horizons.cgi is your friend. You can use this to generate an ephemeris for the comet in, say, 1 minute, steps and see how its coordinates are changing. When I looked last week I think it was about a couple of arcseconds a minute.

NIgelM