DFOSC: Available Grisms and Slits

The Danish 1.54-m Telescope

Available Grisms and Slits

DFOSC: Available Grisms and Slits

Grism	(nm)	Blaze (nm)	Grooves (per mm)	Dispersion (nm/mm)	Resolving Product	(nm)	Range (nm)
3	390	430	400	17	690	0.55	330-640
4	480	580	300	22	700	0.83	350-700
5	650	700	300	22	870	0.75	520-1020
6	390	400	600	11	990	0.39	320-550
7	530	525	600	11	1300	0.41	380-680
8	650	700	600	8.8	2200	0.30	580-830
9a 9b	...	...	79	2.6	4300	0.12	330-1100
10	380	390	150	46	230	1.7	330-640
11	520	500	200	34	390	1.3	390-760
12	730	700	75	91	200	3.7	520-1020
13	510	525	316	3.6	4200	0.12	480-580
14	463	428	600	9.5	-	0.54	327-612
15	586	527	300	21	-	1.2	323-912
16	700	728	300	20	-	1.2	398-1030

Notes:

The resolving power is computed for a 1" slit.
Grisms #9 and #13 are echelle grisms.
The given range for Grism 13 is achieved by using a special order sorter filter.
Grism #16 covers the whole visible spectral range in two orders, with wavelengths bluer than 323nm in the second order. It can be used with grisms #10, #11 or #12 as cross disperser.

Slits for DFOSC

A new set of slit was made available in January 1996. The following sizes are available: 1.0", 1.5", 2.0", 2.5", 5.0", and 10.0". These slits are longer than the DFOSC field size. The 1.0" slit is not very smooth showing flux variations of (+/-) 5% along the slit. Due to the flexure and limited offset accuracy of the telescope the use of a 1.0" slit is difficult. Furthermore it is often not very efficient considering that the seeing is often worse than 1.0". Thus, the narrow slit is only recommendable when the highest possible resolution is required and some loss in efficiency can be tolerated.

For use in echelle mode a special set of slits is available with widths of 1.0", 1.5", and 5.0", and lengths of 12.5", 11.0" and 12.0" respectively.

The Danish 1.54-m Telescope Available Grisms and Slits