MOCAdb Spectral Typing

Spectrum

Comparison spectrum

No spectrum selected

Standards

Standards source Only consider field, solar-metallicity objects Spectral grid Standard

Display

Symbol size100%

Processing

Normalization preset Bins per micron Normalization regions Minimum mean log-wavelength overlap 80% Apply dereddening (slow) Apply brown dwarf slope correction All standards shown in red Show L/T/Y chemical features (0.4–50 μm) Show OH airglow lines (strength-weighted) Show Paschen + Brackett H lines Deactivate low-resolution display mode

Loading best-fit comparison

Loading χ² map

Using URL Parameters

The MOCAdb spectral typing page can be opened with predefined state by appending query-string parameters to the URL.

Common examples

?specid=450&grid=field&bins=200
?specid=450&grid=field&grid_index=4&norm=0.860-1.350,1.445-1.800,2.010-2.400
?specid=450&deredden=1&fix_rv=3.1
?specids=450,451 to stitch and type spectra from the same object.
?specid=450&cloud=1
?specid=450&standards_source=pickles&grid=III%20weak%20M%2FH
?mock=1&specid=450 for a network-free local sample dataset.

Spectral typing parameters

Parameter	Values	Effect
`specid`, `moca_specid`	Numeric MOCAdb spectrum ID	Preselects and computes the comparison spectrum. Defaults to `450`.
`specids`	Comma-separated MOCAdb spectrum IDs	Stitches spectra from one object through their overlaps, merges overlapping bins, and types the resulting composite.
`grid`	Spectral grid ID, such as `field`	Selects the standards grid. If omitted, the page starts from the grid with the best finite chi2 value after a comparison is computed.
`grid_index`	Non-negative integer	Selects the starting standard within the chosen grid. If omitted, the best chi2 standard in the selected grid is shown.
`bins`	Integer from 1 to 2000	Sets the number of bins per micron used when processing spectra. Default is `200`.
`norm`	Comma-separated wavelength windows in microns	Sets the normalization regions. Separators like `0.860-1.350,1.445-1.800` are accepted; the preset selector fills this value.
`min_overlap`	Percentage from `0` to `100`	Requires templates to cover at least this percentage of the comparison spectrum in log-wavelength space before they are included in the chi-squared map. Default is `80`.
`deredden`	`1`, `true`, or `yes`	Fits and applies dereddening to the standards before computing the final displayed match. This is slower.
`fix_rv`	Positive number, or `free`	When dereddening is active, holds `R(V)` fixed and optimizes only `A(V)`. Use `fix_rv=free` or leave the field blank to fit `R(V)`.
`cloud`, `cloud_correction`	`1`, `true`, or `yes`	Fits a one-parameter brown-dwarf slope correction. This cannot be combined with `deredden`.
`cloud_alpha`, `cloud_alpha_fixed`	Positive number; `cloud_alpha_fixed=0` or `cloud_alpha=free` to fit	Controls the slope-correction wavelength exponent. In the page controls, entering a value fixes alpha; clearing the field fits alpha.
`standards_source`	`moca` or `pickles`	Selects either the MOCA UCD template grids or Pickles luminosity and metallicity grids.
`only_field`	`1`, `true`, or `yes`	Limits MOCA UCD templates to the `field` grid, or Pickles templates to `V solar M/H`.
`showoh`	`1`, `true`, or `yes`	Overlays vacuum OH airglow lines with opacity scaled by their catalogue strength.
`showhydrogen`	`1`, `true`, or `yes`	Overlays the vacuum Paschen and Brackett hydrogen series, including Brγ at 2.1661 μm.

Cache

This page keeps the standards grid, downloaded spectra, and computed comparison payloads in server memory for a short period. Clearing the cache forces the next interaction to redownload and recompute.