Affiliation
American Association of Variable Star Observers (AAVSO)
Mon, 07/29/2024 - 19:20
Anyone on the forum who is using Shelyak's Demetra v. 7.3.8.0?
The reason: I cannot get past the calibration phase. The only "documentation" I can find is an older You Tube video where I cannot see the screen clearly enough to follow what is going on and, besides, the widow format seems completely different. Add to that, there is no detailed user guide.
Frustrated in TX,
Ed Wiley
Tagging along on this…
Ed,
Tagging along on this one. I spent many days trying to get calibration going, at least with the built-in sources (Ne, Ar, etc.) and there seemed to be some critical item/assumptions or steps missing from the video instructions, so I could never get past that. The acquisition automation was interesting, if a bit quirky to setup (have the UVEX with automation motors) and I also made it through the flat/dark/bias adjustments, but that is as far as I got. Hopefully someone can point to something new. It really seems to my very inexperienced eye to have potential.
-Mike
Hi Ed,
I am using a slightly older version 7.3.3 for my LISA, but I had similar problems getting past calibration. Also frustrated with poor videos - have serious hearing loss, so could not understand audio either.
At first had to manually select calibration lines, which was tedious
The Demetra example observations worked well, but my observations did not. Do the examples work for you?
Finally corrected a tilted camera lens in LISA and automatic calibration started working; the tilted lens caused serious coma which was visible in calibration images.
Calibration is still touchy and have errors that increase at blue end. *Calibration is the most difficult task in Demetra.*
Also changed calibration Neon-Argon lamp - original one turned black.
Automatic calibration works most of the time. Changing polynomial degree from 4 to 3 sometimes gives better results (also a larger RMS)
Am using Alpha CrB and PlotSpectra 1.6.1 to check calibration
What spectroscopy system are you using?
Joe Hobart
Flagstaff, AZ
Ed,
Critically compare your calibration images with those that came with the Demetra example objects. The example calibration images are very good quality; yours should look nearly that good with reasonably sharp - or at least reasonably symmetrical - line edges at high magnification. As soon as I improved my calibration images by reducing coma, my lines looked better, and automatic calibration started working. Right now I am reducing Alpha CrB, T CrB, and M57 from last night.
Before you Run Demetra be sure to select the automatic button in the calibration step for your object and response images.
Joe
The example file uses Vega for calibration. I tried to use the calibration lamp image (same parameters as the lights). Anyone tried that? After all, what is the lamp for anyway.
Ed
PS, figuring out the emission lines on the lanp is no easy task, I am still struggling.
Ed,
Vega is an A0V star with a very well known intensity profile used correct the *intensity* response of your observing system and the atmosphere. Vega is so bright it needs only a very short exposure. The Ne-Ar lamp is used to calibrate the wavelength of all your observations - including Vega.
I use Alpha CrB (a second magnitude A0V star) to both correct my system intensity response and to check the accuracy of the wavelength calibration system that uses the Ne-Ar lamp. I need a 60 second exposure to get a good image of my Ne-Ar lamp. This gives an image with perhaps 50 visible vertical lines.
The Ne-Ar calibration lamp images in the Demetra demonstration files are labeled: Name-of-object_NeAr-1.fit and Name-of-object_NeAr-2.fit. I found them in
C:\Users\Public\Documents\Demetra\Demo_LISA
Joe
Hello Ed,
I with John Blackwell who uses an older version. He has a video here:
https://youtu.be/EeQuJTwXxr4?si=ejz23gODcAsQxC7e
I don't know if it will be helpful or something you already looked at, but it is the best I have been able to find.
Thanks,
Bert Pablo
Staff Astronomer, AAVSO