Friday, February 2, 2018

PFS Upgrade Series, Day 9: I Love to Hate IRAF

This is part of a series of posts about upgrading an instrument at Las Campanas Observatory. If you want to start at the beginning, it's here.

Oh what a day what a day. It's almost midnight and I've been up since 5:30 am, so this will be short. After vanquishing the slit mechanism in the past few days, today was Jeff and my Battle With IRAF. We were pumped (bah-dum-chish) to start the focus test for the CCD, to find right combination of shims that go right in front of the dewar to optimize the focus of the instrument. To do this, we placed different thickness shims in front of the dewar, took five or six images at different focus values using the pinhole slit and with the thorium argon (ThAr) lamp on. 

Picture from a day or two ago, but annotated so you know what I'm talking about. I'll try to get a photo of the shims tomorrow, but it looks like this.
 Then we had/have to analyze all these images to figure out the best shim thickness and focus value. To put a long story short, we fought with IRAF (Image Reduction and Analysis Facility, an old, sort of black-box but very useful piece of software) all day on various computers to get this process working. We are finally finishing up now, but I've had a headache all day from all my negative IRAF thoughts. Unfortunately we didn't know if any better software to do these measurements, and Jeff already had some scripts from the last time he and Steve carried out this process, so we didn't want to make a big change and have it take even longer.

Finally we got IRAF working on my computer, as well as Jeff's, although mine doesn't quite do what I want it to do (run with Jeff's scripts). I could create this set of regions to define apertures around the lines we wanted to measure, though. We estimate a Gaussian fit in both the x- and y-directions for each line, in 30 images, totally 360 lines to measure. That's what I just spent a couple of hours doing. 
With the measurements completed, I've handed them off to Jeff, who will produce diagnostic plots so we can have our final answer and set the focus and put in a best-estimate shim tomorrow. Really we'll have to find the optimal shim thickness, and have the Carnegie Observatories machine shop make one for us when we get back. Then Jeff will install it during our next run in March (wow, not so far away!).

The other update is that Jeff took the slit mechanism side panel over to the LCO machine shop this evening and we'll have our final part tomorrow morning. I think we're going to just leave in the cable the Steve created to connect the slit mechanism to its power supply, rather than try to figure out that mess (see Day 8). It works, so why waste time fixing it? 

We were hopeful about moving the instrument back to the telescope tomorrow, and haven't lost that hope, but need to be careful and take our time. Even if we moved on Sunday, which I think is very realistic, that would still keep us on schedule. 

Also, quick update on the 51 Peg fellowship: The Heising-Simons Foundation posted a statement saying they'd "fallen short" with respect to gender diversity. I'll let you read it and form your own opinions, but I will say I completely agree that they need to carefully examine their process, and that they can do better. Remember, intention \ne impact. 

Oh, and I almost forgot, I had quite a fright this afternoon:

Tarantula in the conference room! I know it will not eat me, but just in case, I left and worked somewhere else. That was after making a very silly sound, as Jeff can attest to.

No comments:

Post a Comment