The information below is presented in chronological order: most recent measurements are at the end of the document.
After HDI was returned to KPNO in late 2014, measurements indicate that the response to light may be non-linear above roughly 30,000 counts per pixel. See HDI Tech Note 8 for the details.
We recommend flatfield exposures with mean values less than 30,000 counts.
On Jan 21, 2014, RIT students Sravani Vaddi and Kayla Emerson experimented with the flatfield lamps to figure out the appropriate lamp settings and exposure times to yield a decent signal in each of the common filters. Their results are shown below; their goal was to find combinations which would yield around 25,000 counts in an image.
| Filter | Lamp setting | Exptime (sec) | Mean counts |
| U | High 100% | 13 | 24,000 |
| B | Low 100% | 25 | 25,000 |
| V | Low 100% | 12 | 25,000 |
| R | Low 100% | 8 | 26,000 |
| I | Low 100% | 8 | 27,000 |
| Hα (6580) | High 50% | 11 | 24,000 |
| Hα+40 (6620) | High 50% | 11 | 25,000 |
| Hα+80 (6660) | High 50% | 11 | 25,000 |
| Hα+120 (6700) | High 50% | 11 | 27,000 |
| Hα+160 (6700) | High 50% | 11 | 26,000 |
Con Deliyannis took dome flatfield exposures during Feb, 2015. His measurements are as follows; I suggest that you use them to compute an appropriate exposure time which yields somewhat lower count levels. I've subtracted a constant 3000 ADU from the values he reported to account for the bias, so please treat these as rough estimates.
A very rough summary of these results is that the U-band exposures appear to require MORE time than the Jan, 2014, images, while the BVRI exposures appear to require slightly LESS time. One might interpret them to mean that the high-intensity lamp is a bit less powerful than it was in 2014, but the low-intensity lamp is slighly more powerful.
| Filter | Lamp setting | Exptime (sec) | Mean counts |
| U | High 100% | 40 | 41,000 |
| B | Low 100% | 30 | 39,000 |
| V | Low 100% | 15 | 42,000 |
| R | Low 100% | 9 | 41,000 |
| I | Low 100% | 9 | 41,000 |
Con measured the following times for flatfields on Dec 8, 2015.
| Filter | Lamp setting | Exptime (sec) | Mean counts |
| U | High 100% | 18 | 27,000 |
| B | Low 100% | 18 | 26,000 |
| V | Low 100% | 9 | 27,000 |
| R | Low 100% | 5 | 26,000 |
| I | Low 100% | 5 | 25,000 |
Kaitlin Schmidt and Ekta Shah of RIT acquired dome flatfield exposures during Jan, 2016. Be careful to verify that the telescope is aligned properly with the dome-flat spot! The measurements are as follows.
| Filter | Lamp setting | Exptime (sec) | Mean counts |
| U | High 100% | 20 | 23,000 |
| B | Low 100% | 28 | 27,000 |
| V | Low 100% | 12 | 25,000 |
| R | Low 100% | 8 | 27,000 |
| I | Low 100% | 6 | 23,000 |
| 6580 | High 50% | 16 | 26,000 |
| 6740 | High 50% | 14 | 26,000 |
| Gunn Z | Low 100% | 15 | 25,000 |
Thanks to Douglas and Follette for the Gunn Z value, added 6/20/2016
In Oct, 2017, Allyn Smith checked the flatfield lamps. His measurements are shown below, but his executive summary was the low intensity lights do require more time now than previously, but the high intensity lights seem to be functioning at about the same level.
| Filter | Lamp setting | Exptime (sec) | Mean counts |
| Harris V | Low 80% | 12 | 13,000 |
| Harris R | Low 80% | 10 | 17,000 |
| Harris I | Low 80% | 10 | 20,000 |
| Wash M | Low 80% | 16 | 16,000 |
| Wash C | High 75% | 9 | 18,000 |
| Wash 51 = DDO 51 | High 75% | 5 | 20,000 |
| Hα (6580) | High 50% | 20 | 25,000 |
| OIII | High 90% | 12 | 24,000 |
| SDSS u | High 90% | 75 | 21,000 |
| SDSS g | Low 80% | 17 | 15,000 |
| SDSS r | Low 80% | 10 | 15,000 |
| SDSS i | Low 80% | 10 | 15,000 |
| SDSS z | Low 80% | 16 | 14,000 |
A set of measurements were made by RIT students Marko Ristic, Teresa Symons, Brent Neves, and Kain McCall in Jan, 2019.
| Filter | Lamp setting | Exptime (sec) | Mean counts |
| U | High 100% | 45 | 21,000 |
| B | High 70% | 8 | 22,000 |
| V | High 50% | 6 | 23,000 |
| R | High 30% | 8 | 22,000 |
| I | High 20% | 8 | 22,000 |
| 6580 | High 70% | 8 | 23,000 |
| 6620 | High 70% | 7 | 22,000 |
| 6660 | High 70% | 7 | 23,000 |
| Stromgren b | High 70% | 19 | 23,000 |
| Stromgren H-Beta wide | High 70% | 19 | 21,000 |