NASA’s JPL Horizons is a free program can help to generate ephemerise for comet or any celestial bodies
- Click this link
2. Set up traget click change traget body, key in the celestial body you want to search , for comet give their IAU name for example , C/2019 Y4, or 1P/Halley, or asteroids name.
3. Set up Observer locaiton : Geocentric
4. Set up Time span : give the dates you want to search
5. Table setting : For astrologer most important is Observer ecliptic lon. & lat. This will give you the zodiac degree (0-29 = Aries , 30 – 59 = Taurus … ), if you want Declination you can select Astrometric RA & DEC too. Than click use selected setting. I usually have Apparent AZ & EL, Visual mag. & Surface Bright, Constellation ID for stargazing.
6. Click Generate Ephemeris.. You will get the information you need.