During dusk, haul things out of the house and do other simple tasks:
- Carry out Mount (put it on the pier, check level. I have a cement pier, which spares me having to lug out the field tripod.)
- Carry out Work table (unfold and set up)
- Carry out Counterweight and counterweight shaft (attach to mount)
- Carry out Telescope assembly (put it on the mount)
- Carry out Two deep cycle batteries (one for laptop and dew preventers, the other for the mount and CCD. I choose to run from batteries in preparation for setting up at remote sites without AC power.)
- Carry out Tackle box with cables, etc.
- connect Autoguider with Mount
- connect Mount to Battery
- Temporarily put CCD on telescope
- Balance the load
- Replace CCD with diagonal and illuminated eyepiece
- If using dew preventers, put them on the telescopes and connect to battery
- Adjust mount to bring Polaris into view in Polar Axis bore.
- Align finder with imaging scope
- Turn on mount and do two-star align, augmented with two more calibration stars
- Do software Polar align (If I were patient, I would do a drift align here; at this point I should repeat the two-star align with calibration stars, but usually I don't--goto is reasonably accurate.)
- Turn on dew preventers (if needed)
- Connect laptop to battery and turn on
- Swap out diagonal and illuminated eyepiece used during alignment for CCD
- Connect CCD to battery
- Connect CCD to laptop
- Start software for CCD control, turn on cooling
- Slew to bright star (be careful of CCD-to-laptop cable)
- Connect Autoguider to laptop
- Focus CCD with narrowband filter
- Slew to target (be careful of CCD-to-laptop cable)
- Compose the image frame using luminosity filter (do NOT refocus)
- Connect Autoguider to laptop
- Start PHD
- Select guide star and calibrate PHD
- While PHD is calibrating, switch to narrowband filter and expose a test frame for desired exposure time
- Check that CCD cooling is correct.
- If test frame is OK (composition is correct, etc.) aside from star streaking caused by PHD calibration and PHD is done and locked on the guide star, begin shooting light frames.
- Periodically recheck progress, watching for any irregularities in the latest light frame. Also check PHD for uncorrected drift
If you don't have dark and bias frames for this temperature and exposure time, shoot them at the end of the evening. If I shoot flat frames, it's usually the next day. So far I've not seen the need to shoot sky flats. I would were I using LRGB filters.
When all imaging is completed:
- Return mount to home position
- Power off mount
- Turn off CCD cooling and disconnect from software
- Disconnect CCD and Autoguider from laptop
- Disconnect Autoguider from mount
- Shut down laptop, disconnect from battery
- Carry in laptop
- Disconnect CCD from battery
- Stow cables in tackle box and carry in
- Carry in batteries and telescope assembly
- Carry in telescope assembly
- If the weather will be OK, leave the mount on the pier and cover it.
- If bad weather is on the way, remove the counterweight and counterweight shaft and carry in. Take down the work table and carry in
The most difficult part for me is the two-star alignment with calibration stars followed by polar alignment, because I can't see the western part of the sky.
I also tend to spend quite a bit of time on image composition, trying to get it "just right."
Also time-consuming is focusing because of how stars are dimmed by a narrowband filter. I have tried using Jupiter for focusing to good effect. I've also used a Bahtinov mask a few tunes, but so far it doesn't save that much time or improve image quality any over what I can do with my camera control software's focus utility. I need to work with the mask more.
If you have an observatory you can pretty much skip the entire "During dusk..." section. That's where I hope to be by the end of next summer!
Next Time: Image Processing
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