Table of Contents
APO lab testing
September 2025 - fiber tests
Testing with fiber from FTO, two spools, each with 3 legs. Spool1=241587, Spool2=241586. Each spool has 3 legs. Also tested with short 50 micron fiber. Tests going through FPU calibration channel. Did several sequences. Images are 50s flat (quartz+LED) and 120s ThAr; if sequence has 3 images, the first is a guider image.
| Input | seq 1 | seq2, UT250925 | seq3, UT250925 | seq4, UT251001 |
| short | UT250923, 84-85 | 3-4 | 23-25 | |
| spool1,1 | UT250923, 86-87 | |||
| spool1,2 | UT250923, 88-89 | |||
| spool1,3 | UT250924, 3-4 | |||
| spool2,1 | UT250924, 15-16 | 5-6 | 20-22 | 1-3 |
| spool2,2 | UT250924, 9-10 | 7-8 | 17-19 | 4-6,16-18 |
| spool2,3 | UT250924, 11-12 | 11-13 | 14-16 | 7-9,10-12 |
Relative throughput inspected both through simple crossection and through integrated fiber. Former would be affectd by differences in focus; rough focusing was done for all setups. In all cases, it appears that the image quality through the long fiber is a bit worse than through the short fiber; it is possible/plausible, however, that that might be expected due to the fact that the long fiber includes an ocatagonal segment and also provides output in a 53 micron fiber (as opposed to the 50 micron short fiber). Hence the differences between short and long fiber links is more pronounced in the peak crossection than it is in the integrated fiber.
Three different sequences were taken. Only the first included Spool1. Between the sequences, it seems there is more variation in the throughput through the short fiber than through the long fiber, although there is some variation in the latter as well.
Sequence 1:
In the first sequence, Spool 2 legs 2 and 3 appear best, with leg 1 a bit worse. Leg 3 on spool 1 is about the same as leg 1 on spool 2, followed by leg 2, with poorest being leg 1 on Spool 1. This roughly matches the expectations from the FTO test report (pages 9 and 12).
Sequence 2:
In the second sequence, the flux through the short fiber was significantly lower. Leg 2 (Spool2) was the best, but leg 3 was now closer to leg 1 in throughput.
Sequence 3:
In the third sequence, the flux through the short fiber was intermediate between the first two sequences. The relative throughput of the legs of Spool 2 was similar to that of sequence 2. This sequence included images from the guider for each fiber; no strong changes in location of the fiber in the illumination spot were noticed.
Sequence 4:
Tests after pulling fiber through conduit. After first set of fibers 1-3, we refocussed spectrograph for a set with fiber 3, then rerouted fibers and refocussed with Zaber for a set with fiber 2.
May 2025
Re-assembled spectrograph in APO room. Solar light from long eShel fiber outside.
Solar and solar+iodine:
Resolution:
Spectrograph imaging focus run, 10 micro fiber:
Upper assembly manual focus sequence:
Image log