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HELP needed - file header

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moont's picture
HELP needed - file header

I am new to VPHOT. Tried uploading an image of NGC 3532 (using the upload Wizard) so as to check the new standard star values loaded into VSP. My image was taken using an Orion Starshoot G3 camera and processed using the Orion Studio software. Plan to do the online course when it is next available but would appreciate if anyone out there can suggest how best to view the header of the FITS file and correct it so it will load and display in VPHOT.

Attached is a screen shot of the error message I get in VPHOT.


File Upload: 
spp's picture
FITS header problems

Please see the next post.

spp's picture
FITS header problems


I think working to get the FITS header right is something that all new VPhot users have to go through.

I'm sure you'll get several recommendations about software to use to edit the FITS header.  (I use a program called fv on my Mac.)  If you edit the header by providing the value of the keyword EXPTIME and also add the keywords (and associated values) TELESCOP (necessary to match your image to your telescope setup in VPhot) and OBJCTRA and OBJCTDEC (necessary to plate solve the image) you may be able to get your images to work so that you get an idea of the power of VPhot.  I think there may be other acceptable header keywords that will work which provide the same information, and perhaps there are other required keywords of which I am not aware.

You will eventually also want to add keyword CALSTAT (with the value BDF) for VPhot to recognize this as a calibrated image, also FILTER with the value that corresponds to the filter you used.   These last two keywords may not be strictly necessary for the image to be displayed but would be necessary before actually doing the photometry measurements.

I think the more important question is how do your get your software to do this automatically.  I'm not familiar with the Orion Studio software.  Perhaps there are "preferences" or "setup" tables that need to be filled in so that the software can add this information to the header.   Perhaps you'll need to use a different software package altogether to get the header filled in properly.

I use CCDSoft5 to control my camera.  This fills in everything I need but CALSTAT, which I add myself with a FITS editor.




SGEO's picture
Starshoot Fits Header

Greetings Tex,

Hope all is well down-under!

Well, EXPOSURE / EXPTIME at 0 are not going to make VPhot happy.

I downloaded the Orion Camera Studio software and it doesn't offer a lot of options to control the camera output and FITS header fields. That may because I don't have the camera in hand; it does look like a nice camera, though. You may need to use some more complete software package as the camera is ASCOM compliant.

Send me the fits file and I'll see if I can find out what needs to be done.


mgw's picture
Free FITS header editor


Here's a free FITS header editor -


WGR's picture
FITS Header


Thanks Gordon for that tip.  I use Maxim, and it fills out the FITS header for all this, but every once in a while, I need to edit one in bulk.  I put it on my tool bar for future use.



wglogowski's picture
Hello Tex:

Hello Tex:

I had great difficulty with VPhot as a beginner.  I attached a spreadsheet of all the header info that is necessary.  The data in red is essential if you want VPhot to do a plate solve and give you a WCS that is "green", which means good.  If your camera does not automatically generate the data you can manual enter the info.  The toughest piece of data to get is the Airmass, I found that you can easily get this from your planetarium program. The only trick is that you need to manual write this down throughout the night as the declination changes.    If I can be of any help feel free to reach out.  


File upload: 
B.P.Vietje's picture
FITS Header Info

Hi Tex, You're on the verge of exploring one of the slickest pieces of photometry software available -- once you learn the secret handshake, it is simply amazing how fast & easy things can be in VPhot -- at least when the image upload lines are relatively small. It seems there are two issues here: 1) editing your FITS headers to get you in the door (the secret handshake), and you have already gotten excellent advice on that. Then 2) how to set up your imaging software so this is all automated in the future.

Let's look forward to the second one. Like Gary, I use MaxIm DL, so once these fields are set up in the program, I never have to go in and add/change/delete anything. I know nothing of Orion Camera Studio... Are you able to share any details about that software (users manual, perhaps) so we can help with that part? If that software is a little weak in the FITS header department, there may be other options that don't cost much to control your camera, and save you all the back-end editing.  Just one fella's opinion, but I would not want to calculate and then add my airmass in after a long night of observing, and I want Bill Gates or Steve Jobs to do that for me!

As you've already seen, there are a boatload of really nice people who will help you through this -- the core and great strength of AAVSO!

Clear skies,

Brad Vietje, VBPA

Newbury, VT

David Benn
David Benn's picture
Hi Tex

Hi Tex

I wrote a couple of scripts for this kind of thing, so if you don't mind the command-line, see my rather aspirationally named GitHub repository:

This one in particular modifies FITS files I generate from IRIS, which I recall you mentioning you use for processing.:

Nice if you want to bulk update files too.


BGW's picture
David Benn's script...

This won't be a solution for everyone, but I took David's script (link posted on an AAVSO forum some time back, as well as in this thread) and "enhanced it" to suit my needs.  Using other pieces from astropy (where the original script gets the fits handling code) my script now inserts target name and coordinates, and calculates HJD of mid-exposure, and airmass and inserts them too.  This cleans up my overall data processing flow, because now instead of computing those things when needed, they are all in the fits header.  But I know this kind of solution only works for you if you are comfortable hacking and running scripts...  Not as clean as, e.g., having your image acquisition program simply put everything in the header in the first place...



Given a FITS UTC time, is there a handy way of fixing botched FITS airmass calculations? (MaxIm and the mount got temprairly lost in the wrong hemisphere)




Traverse Peter
Traverse Peter's picture
Hello Tex

I use AstroImageJ to edit and change FITS Header

AstroImageJ / Open (FITS image)  then Edit / FITS Header.



moont's picture
Thank you

Thanks to all for the responses to my call for help.

Phil, I appreciated knowing that this is a common occurrence for newbies to VPHOT. George, Pierre, Brad, Walter, thanks for your suggestions.

I have downloaded F4W2HDU fits editor as suggested by Gordon and will use that as he has successfully edited my images of NGC 3532 with it.

This year I have swapped over to using a ZWO ASI174MM camera CMOS and SharpCap capture software so will see if images from it load into VPHOT. If not, now have a FITS editor to fix them. Will report outcome on this forum in case others wish to explore use of this camera. ( It is only 12-bit, minimum for photometry, but has global shuttering, no ABG and is linear up to its full-well depth.)

Main reason for jumping into using VPHOT before doing course was to help with checking magnitudes and colors of stars in NGC 3532 selected for standardizing photometry. This is one of 2 clusters recently added to VSP for southern hemisphere observers to use to work out transformation coefficients.

Again, thanks


ka5sma's picture
sharp capture


Does Sharp Capture software put the correct info on fits header?  for uploading to VPHOT ,  am thinking about purchasing a ZWO camera


Mike Miller

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