35
9.
Find another star in the new field, center it and press ENT.
You have just selected your second point.
10. Allow the mount to drift again and repeat the above procedure for as many points as you wish.
If you plan to
image 1/2 to 1 hr, two points may be enough, one point near the object and the 2nd point 1 hr west of the object.
11. Once you have enough points, select Finish=ESC.
12. Return to the Main Menu and select 8=DrftON to apply your model. At that point the mount begins to apply the
drift terms and adjusts the RA/Dec rates accordingly. If you want to see what they are, press ENT in the Main
Menu and the display will show the RA and Dec drift rates in arc seconds per hour. Now re-enter the object and
press GoTo to begin your imaging session.
13. If you wish to add points to your model at a later time,
return to window 5220 and select 4=Add to Model. Points
can be added at a later date and later session as long as the scope and mount have not been moved.
Pro Tip:
Do your modeling before dark using an H-a filter to suppress the sky background and pick a bright star
somewhere in the field along the declination of the object. You can generally be done in the hour during twilight before it
gets dark enough for imaging. Stars of up to mag 5 can be imaged even before the sun has fully set if the sky is cloud and
haze free.
If you don’t move the mount and scope between imaging sessions, the model will be accurate for any length of time
between sessions. The model will take into account drift due to polar misalignment, atmospheric refraction as well as minor
drift due to instrument flexure (if repeatable). If you wish to add another object at a future time, you can use the Add Model
routine instead of creating an entire new model. That new object can be anywhere in the sky at any declination.
If you model on a night of very high atmospheric pressure and then image on a night of low pressure, the measured
refraction drift rate may be different. The model will not fully apply and you may be limited in exposure time before drift is
detected in the image. Typically imaging times of 5 to 10 minutes will not be affected if the object is - 2 hours of the
zenith.
This model is limited in scope, and if longer time exposures are needed or imaging with long focal lengths, we have a very
extensive method using APCC-Pro with APPM that can take variable refraction into account as well as other factors.
Error Codes
●
DEC Line Full: All 8 points of the constant-DEC line have already been mapped.
●
No DEC Lines Avail: All constant-DEC lines are already populated.
●
Not Tracking: Mount is not in tracking mode and cannot map.
●
Sequence Error: Already in mapping mode.
●
Time Too Short: Didn’t track long enough to get good data (currently at least 10 seconds is required).
●
Excessive Drift: Amount of measured drift is way too large, i.e. did a large slew in the middle of the drift measurement.
●
Model Disabled: Modeling unavailable in this unit.
