TG Basics

Hi Ken,

Thanks for the reply.

I did originally try all of your suggestions with no success. So after your reply I tried it again. This time it worked just fine. I THINK my error was asking for EN Cnc, not EV Cnc. This time I got the table and everything needed. And I was able to use Photomcap to get the data into AIP.  So that part is now all good.

I do still have a question or two about AIP. I did try creating my own file in AIP and I did a run using the Instrumental Mag, 1 star/line option. Apparently I did it almost correctly because the log came in the format out just like the file. But there are 2 items that are different.

First, I notice that the first item in the TG M67 file is M67 itself complete with all the info. My first item is EV Cnc. This was the Variable that is the first star I select in AIP. This, of course, is meaningless since we want only the stars C1, C2, C3, etc. So how did you get M67 as the first item in the TG file. Was this just any star that was used as a “dummy” to get to the C stars that are the actual targets?

Second, the IDs in my log are the AUID numbers. The IDs in the TG file are 1,2,3,etc.It would be easier for me to use 1,2,3, because I will number those stars accordingly on my chart in the order I click on them.  So how do I get the labels to read 1,2,3, etc.

Thanks,

Keith

Keith,

You don't need all the magnitude information on the M67 stars.  TG automatically retrieves it from the AAVSO web site's VSP tool.

What you do need is a comp list with the 64 ids (1-64) so you can select those stars in AIP4WIN and get the right Boulder identifier.  (The TG Users guide V 5.6  has a new appendix A that shows an image of the M67 field with the 1-64 star ids).

To help get the right comp star ids I created an AIP4WIN "STAR" file that contains all 64 M67 standard stars.  It is attached to this post.  (NOTE: When you download it, remove the _.txt at the end of the file name.  I had to add _.txt to be able to post the file on this blog.  AIP4WIN is looking for the file to end in .STAR".)  Copy this M67_Henden_Field_Comps.STAR file into the AIP4WIN/Data directory (usually C:\Program Files (x86)\AIP4Win\Data). 

Now start MMT. On the MMT Images tab load all your M67 images for all the filters.   Select one image to locate the comps (I ususally select one of the V filter images).  Go to the MMT Stars tab and click "Recall..." to load that M67 file containig all the comps. 

Select any star as the M67 target (i.e. AIP4WIN's "V" star - which again, is not used). Now select the comp stars - you'll see the comp number matches the boulder id. Once all the comps are selected, go to the AIP4WIN Report tab and select the options shown in the TG Users Guide section 4.4.1.5.  Then go to the AIP4WIN Execute tab, pick a good guide star and "Run Photometry". Because you have different filter images, AIP4WIN will usually ask you reconfirm the guide star between images.

AIP4WIN will find all the stars in each image.  Sometimes stars in one band won't have adequate SNR for AIP4WIN, but that's OK. AIP4WIN indicates the error in the output report file and TG handles it.

The AIP Instrument Magnitudes file created this wasy can be directly loaded into TG.

FYI, TG goes to the AAVSO web site to retrieve the current standard star magnitudes from VSP, so don't worry about the magnitudes in the STAR file.

One other suggestion - if you want to ease the star selection burden and only identify the first 30 standard stars, edit the STAR file (in Notepad) by deleting all stars above 30.)  Pragmatically I find the results are very good.

Another point - when you run TG you will get an error message that some of the Boulder id do not have an AUID counterpart.  That's true - some of the original stars are no longer in the standards field.  Don't worry, TG will generate the transforms based on the other stars.

Again, think about using VPHOT to identify the stars - it saves a lot of work

We - and other Python users - have found a problem with the terminal emulator on the latest Mac OS X V.10.10 release.  TG will not run.  Some conflict between Python and the new OS X.  We'll let you know once we find a workaround.

Keith,

Good idea.  I'll add it to the user's guide.

Gordon

Hello Keith

Good to hear from you.  I, similar to you, have always used another software for reduction (Maxim).  I used VPHOT only sparingly, and cannot say I am knowledgeable about its use.  

However, for TG, VPHOT rocks.  It does all the work for you.  You just load your stacked BVRI images to VPHOT.  Select "Standard Stars from Catalog" and it places all the apertures, etc.  Then just select the SNR, etc you want, and write the output, and you are done.  I think I could do it all in less that 1 minute per color.  Its worth the effort to learn VPHOT for transformations.

Gary