Page history

• 2/6/2019 : created
• 2/19/2019 : status update
• 3/25/2019 : status update
• 5/3/2019 : status update

Damage to FOCAS optics

During the telescope and instrument recovery works from the Hurricane Lane in August 2018, it was found FOCAS optics is severely contaminated by rain water, and the water penetrated into the inside of the lens unit.

Due to stains and condensations inside, the performance of FOCAS was found to be largely reduced.

8/30/2018	9/25/2018	10/18/2018
after water removal	after top-lens cleaning	at Cassegrain
	(The two pictures were taken with the same condition but different illumination)

Recovery Plan (2/6/2019)

In the week of 2/11/2019, we will work with engineers from Nikon and remove the lens-unit from FOCAS.

After the removal, the unit can be divided into two parts and we will inspect the lenses in more detail and clean the lenses as much as possible.

• If the lens unit can be fully cleaned, it will be reinstalled to FOCAS and we will prepare for the observations in March.
• If the lens unit needs to be disassembled further for the full cleaning, we have to send the lens-unit to Japan. In this case, it is expected to come back to Hawaii at the end of March.

Status Update (2/19/2019)

On 2/12, the collimator lens-unit was successfully removed from FOCAS. We cleaned the lenses and removed water inside as much as possible, but we found there's still stains inside of the lens system where we cannot access without further disassembly. Therefore, we have decided to send the lens-unit to Japan for the full recovery. It is expected to come back to Hawaii at the end of March.

Status Update (3/25/2019)

The collimator lens-unit has been disassembled, cleaned, and reassembled successfully at Nikon facility in Japan. It was shipped to Hawaii on 3/22 and is expected to arrive in the week of 4/1 (probably 4/4 or later). The schedule is very tight but we will do our best for the observations from 4/12.

Status Update (5/3/2019)

The collimator lens-unit has arrived at Hilo on 4/4 and was successfully installed into FOCAS on 4/5. After assembly works and operational tests, FOCAS was attached to the telescope on 4/10 and started observation from 4/12. Although we had to cancel the first three nights due to bad weather and an earth quake, the first observation after the recovery works was successfully done on 4/15. Since then, FOCAS has been working fine without major issue. We took some engineering data on 4/15 and 4/25, and results will be updated in this page.