F25ND5 - NUV-MAMA

Description

The F25ND5 mode with the NUV-MAMA provides broad-band imaging with an attenuation of 5 × 10-6 with respect to similar broad-band imaging filters (e.g., 25MAMA, F25QTZ). The value of R80 and the central pixel flux are unmeasured but assumed to be approximately the same as produced by the F25QTZ filter.

Recommended Uses

This filter is recommended for broad-band NUV images that are too bright by a factor of 2 × 105 for the 25MAMA "clear" filter.

Special Considerations

The throughput of the ND5 filter and NUV-MAMA combination relative to the unfiltered NUV-MAMA varies strongly as a function of wavelength. At wavelengths between 3000 and 5000 Å the transmission factor is close to × 10-6. At shorter wavelengths the relative throughput can be a factor of ten or more smaller, while at longer wavelengths it is considerably larger, so special care should be taken for red sources. To make an accurate prediction of the expected count rate, observers should use a good approximation of the source spectrum as input for the STIS ETC.


Pivot λ (Å)

FWHM (Å)

AB mag zero point

Speak

Bλ

R80 (arcsec)

Flux in central pixel

2633.8

1514.7

9.185

5.01e+8

594.3

0.32

8%



Figure 14.31: F25ND5 NUV-MAMA Integrated System Throughput and Redleak




Table 14.13: Throughput and Sensitivity for F25ND5 NUV-MAMA

λ

Sensitivity

% Throughput

1200.

4.99E6

1.8e-7

1300.

1.32E7

4.5e-7

1400.

1.97E7

6.2e-7

1500.

2.66E7

7.8e-7

1600.

3.15E7

8.6e-7

1700.

3.35E7

8.7e-7

1800.

3.38E7

8.3e-7

1900.

3.04E7

7.0e-7

2000.

2.67E7

5.9e-7

2100.

2.67E7

5.6e-7

2200.

3.33E7

6.6e-7

2300.

4.72E7

9.0e-7

2400.

7.06E7

1.3e-6

2500.

1.14E8

2.0e-6

2600.

1.87E8

3.2e-6

2700.

2.85E8

4.6e-6

2800.

3.98E8

6.2e-6

2900.

4.50E8

6.8e-6

3000.

4.40E8

6.4e-6

3100.

2.54E8

3.6e-6



Figure 14.32: Point Source S/N vs. AB magnitude in the V-band for the F25ND5 NUV-MAMA mode. Top curves are for DARKTIME. Bottom curves are for average sky. Curves are labeled by required exposure time (sec.).




Figure 14.33: Extended Source S/N vs. AB magnitude in the V-band for the F25ND5 NUV-MAMA mode. Top curves are for an area of 0.2 arcsec2; bottom curves are for 1 arcsec2. Average sky assumed. Curves are labeled by required exposure time (seconds).