Importing AIPS images into IRAF

Here is a question from reader donkeypuncher:

I'd like to use IRAF to do some analysis on images produced in AIPS. Alas, I am unable to open in IRAF the FITS files output by AIPS (task FITTP). I get this simple, non-informative message when I attempt to use the IRAF task display:

ERROR: Cannot open image (IMAGE.FITS)

I'm guessing it's a format issue, because I have no problem loading in ds9. Any ideas?

BTW, I like the site, thanks for your contributions!

My guess at an answer can be found if you click below..

I think that IRAF needs and expects the '.fits' suffix to be in all small letters. Try changing your image name to 'image.fits' and see if that helps.
Also-- something else I've noticed is that optical software often freaks out at the small pixel values in AIPS images (For example, are your pixel values on the order 10^-3 to 10^-6?). Once you get your image into IRAF, you might want to try multiplying your entire image by some large constant, say a million, using imarith. This could potentially save you headaches.

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Flux calibration scales at the VLA?

I've run into what looks like a systematic offset between flux scales of earlier observations and my observations. I'm using the 1999.2 coefficients to set my flux scale and it looks like the earlier observations are using the coefficients from Baars et al. (1977). Any ideas on what the differences are between these two systems? 5%? 10%? 20%? I've tried searching the VLA calibration documentation for the information, but didn't find anything useful (although maybe I missed something).

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Clearing AIPS Variables?

During my recent forays into AIPS scripting, I have often wanted to change how a variable is defined...say by changing an array from dimensions of 50 to 200. When I try to do this, AIPS tells me that the variable is 'ALREADY DF' (or defined, i'm guessing). Is there some way to clear a variable?

Well, I just thought to do a 'RESTORE 0', which seems to clear everything. So maybe that it is the best solution?

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MSGSRV Aesthetics

I've been wanting a scrollbar in my MSGSRV for as long as I can remember, and I finally got one! This is how I did it (on my Mac, running X11)...

I made a .Xdefaults file in my home directory with these lines:

AIPSmsg*scrollBar: True
AIPSmsg*saveLines: 500 

I quit out of AIPS and in the xterm where I was running aips, I typed:

xrdb -load ~/.Xdefaults

to make my computer register the .Xdefaults file.

When I started up AIPS again, I had a scroll bar! This page gave me this hint, plus tells you how to change other MSGSRV settings, like colors.

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Reading ASCII Tables into AIPS?

I'm trying to write a script where I repeat some steps on lots of different objects, and therefore I want to read a list of coordinates into AIPS. I currently have an ASCII list of x and y values. Can i read it into AIPS as two arrays so that my script can access them? Or do I have to do something hideous like manually fill the arrays within my script?

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AIPS system temperatures.. in miriad?

So we're trying to reduce our data in AIPS and then image in it miriad. Sounds familiar. Anyway, we want to use options=systemp when inverting the uv data. However, I've noticed that miriad doesn't appear to correctly import the system temperatuers from AIPS when using "fits" to read in the fits file that I wrote with AIPS using FITTP. In fact, it sets all the system temperatures to 60K, exactly.

There is an option in fits (varwt) to use the reciprocal of the noise variance on a visibility as its weight, but the system temperatures are still set to 60K.

Ideas?

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Mosaicing: AIPS/Miriad/whatever works!

Is anyone familiar with mosacing techniques in AIPS, Miriad, or both? I have 21cm VLA spectral line data, taken mosaic-style, and am having a heck of a time trying to stitch the pointings together. Here's what I have done so far:

Reduced in the standard manner with AIPS up until the 'SPLIT' step
Wrote out each pointing with FITTP
Loaded into Miriad
In Miriad, 'invert', 'mossdi', and 'restor', mostly with the defaults for parameters

The best way I can describe the results is like a bad patchwork quilt...does anyone know of a good cookbook or guide for putting together pointings into a mosaic? I know AIPS has some tasks for this (VTESS/UTESS/LTESS) but I haven't had success with them. Thanks!

Katie

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