Exposure Templates

Exposure Templates provide the ability to set several exposure-related properties that are commonly used for the associated filter and the rig described by the applicable profile. Configurable properties include gain, offset, binning, and camera readout mode. You can also set the level of twilight and the moon avoidance parameters appropriate for the filter.

Each Exposure Plan references a single Exposure Template. With this approach, most of the reusable exposure properties are decoupled from Exposure Plans and easily reused.

Each Exposure Template explicitly references a single filter configured on your filter wheel by name. If you later change the filter name in the filter wheel configuration, you will need to update any Exposure Templates that reference that filter.

Basic Operations

Exposure Template Creation

New templates are added by selecting the applicable profile in the Exposure Templates navigation tree and then clicking the Add icon. The new template is saved, added to the navigation tree, and selected. Click the Edit icon to make changes. Note that you will have to set the filter to one of the filters defined in the filter wheel for this profile.

When you select a profile in the Exposure Templates navigation tree, the right panel shows a table of all templates for that profile. From there, you can jump to the view/edit panel for the template or copy it to the clipboard. After copying a template, you can paste it under this profile or select a different profile in the tree and paste it there.

Exposure Template Editing

Click the Edit icon to begin editing the template. The property value fields become active and you can make changes. Note that you typically have to tab out after editing to enable the Save icon.

When done, click the Save icon to save your changes or the Cancel icon to cancel.

Exposure Template Properties

Moon Avoidance

Exposure Templates provide multiple options for controlling when exposures are permitted given the moon age (phase), separation from the target, and altitude.

Classic Moon Avoidance

The Classic Moon Avoidance formula (“Moon-Avoidance Lorentzian”) was formulated by the Berkeley Automated Imaging Telescope (BAIT) team. The formulation used here is from ACP.

The formula takes two fixed parameters: separation (aka distance, in degrees) and width (days). From ACP: At full Moon the avoidance will be distance, and width days before (or after) the avoidance will be one half distance.

If the angular distance from your target to the moon is less than the calculated avoidance separation, the exposure plan will be rejected. The separation is calculated at ‘now’ plus 1/2 of the project’s Minimum Time setting. As the separation increases or decreases throughout a night, the avoidance determination may change as the planner is called again.

Relaxing Classic Moon Avoidance

Since the impact of the moon on sky quality diminishes as the moon gets near or below the horizon, it may be desirable to relax the impact of classic avoidance when this occurs. If the Relaxation / Scale property is not ‘Off’, then relaxation applies:

• The scale value adjusts the impact by reducing the separation parameter, in effect shifting the entire avoidance curve down and permitting closer separations independent of moon age.
• The Minimum and Maximum Altitude values define the range over which relaxation occurs:
  • If the moon altitude is below the minimum, then avoidance is off altogether and the exposure will not be rejected (at least not for moon avoidance).
  • If the altitude is above the maximum, then classic, unrelaxed avoidance applies.

Otherwise, both the separation and width properties are scaled by the altitude to reduce the impact of avoidance:

• Separation = Separation + RelaxScale * (altitude - MaxAltitude)
• Width = Width * ((altitude - MinimumAltitude) / (MaximumAltitude - MinimumAltitude))

The moon altitude used for relaxation is determined at ‘now’ plus 1/2 of the project’s Minimum Time setting. If you have Smart Plan Window enabled in Profile Preferences, then a target plan may extend for many hours - way beyond the minimum time setting. The moon altitude will only be evaluated at the start of the plan but it may change dramatically by the end. If this is a problem, set Smart Plan Window to off.

Setting Classic Parameters

When enabled, set Separation to the minimum acceptable separation at full moon. Then use Width to control how quickly the curve drops from the distance value. Some charts make this clear: X = moon age in days, Y = calculated distance.

Distance=120 and width=14

Distance=120 and width=4, showing much faster falloff from the peak distance value

The values used on the ACP site are very conservative. For narrowband imaging you could get away with distance=60 and width=7 which would need 60° separation at full moon but only 30° at first or last quarter.

Setting Relaxation Parameters

By default, relaxation will be off. If avoidance is enabled, you can enable relaxation by setting a scale factor of 1-8. The range defaults to -15° - 5°. To adjust:

• More conservative (closer to classic): decrease the scale, increase the min-max range, and/or shift the range to lower altitudes.
• More aggressive: increase the scale, decrease the min-max range, and/or shift the range to higher altitudes.

The attached Excel spreadsheet lets you experiment with different avoidance and relaxation settings and see the impact. It can be used for both classic and relaxed avoidance.

Color Cameras

If you’re using Target Scheduler with a color camera and either don’t use a filter wheel or use a single filter (e.g. for light pollution) in a filter tray for long periods of time, you can still configure Exposure Templates to work for your setup:

• Set up a dummy filter for your Filter Wheel. Go to NINA Options > Equipment > Filter Wheel and add a new filter. You need to provide a name, for example ‘LP’ or ‘dummy’.
• In Target Scheduler plugin > Target Management, add a new Exposure Template as described above. Set the Filter dropdown value to the filter you just created and name the Exposure Template appropriately (e.g. ‘LP’ or ‘dummy’).
• Set the other properties (exposure time, gain, offset, etc) as needed for your camera.

You can now reference this Exposure Template from your Exposure Plans as usual. In your NINA sequence, don’t connect a filter wheel and any instruction to switch filters will simply be ignored.

You can implement a similar setup if using Target Scheduler with synchronization.

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