Affiliation
American Association of Variable Star Observers (AAVSO)
Mon, 05/09/2022 - 17:47

Hi All,

 

Is there a place I can get sample calibrated FITS file to practice photometry?  Im just getting started and broke my arm last week.  But want to proactive the software and doing photometry?  

 

SN: What is a simple, affordable, photometry software that is suggested? 

If you're an AAVSO member,…

If you're an AAVSO member, send me your observer's code and I'll copy a few calibrated images I have in VPhot to you.

BTW: You'll need to make a VPhot account.

Peter

BPEC

 

 

Affiliation
American Association of Variable Star Observers (AAVSO)
Software for photometry beginners

Alfredo,

I agree that VPhot is a good option for you, especially if you are already a member of the AAVSO.   Once you set up a VPhot account it is very easy for other VPhot users to share images with you.  There are written and video tutorials to help you get started and an AAVSO on-line forum where you can ask questions.

If you eventually want to use your own equipment to take images for photometry you will need another program to calibrate the images (remove unwanted signals from optical artifacts and camera electronics).  VPhot does not do image calibration.

Astronomical Image Processing for Windows  (AIP4Win) is another option .  It is now a free download and is supported by an i.o group forum.   AIP4Win does image calibration and many other things, including photometry.  Some people have trouble installing this on Win10 computers, but help is available in the i.o. group.  I have been told that there are few, if any, problems installing this on Win11 systems.  I use older versions of AIP4Win on WinXP and Win7 computers without problems.  I would say the learning curve for AIP4Win is a bit steeper than for VPhot, but it has many useful tools not available in VPhot which are very helpful if you are making your own images. 

AstroimageJ is also free.  It does photometry and image calibration.  It was designed primarily for exoplanet transit observers, but it is becoming popular with variable star photometry observers as well.

Phil

 

Affiliation
Variable Stars South (VSS)
Alfredo,

Since you are…

Alfredo,

Since you are working with FITS files, I would recommend you look at AstroimageJ. In my opinion, it has advantages for ease of working, particularly if you are performing time series photometry on short period variables or eclipsing binaries requiring dozens or hundreds of exposures per night.

First, browsing all images in a folder is very efficient, like running a video in slow motion (at least with the binned images I take). Even with hundreds of images you can find those rendered useless by cloud quite quickly. Second, zooming in (to check such things as contaminating stars, appropriate aperture radius) is facilitated with a double click on the star, which zooms closely in but keeps the star in the field of view. Third, setting up callibration files (e.g., master darks, master flats and the callibration process itself), aligning images (if needed) and finally running the photometry are all quick.

AstroimageJ can output a large amount of data (many columns across the data file) but I cope with this by automating the most laborious tasks in spreadsheet templates. It routinely ouputs the times of mid exposure in JD_UTC, HJD_UTC and BJD_TDB. Airmass is routinely output for the target star, even without astrometry to capture WCS (World Coordinate System) data, as long as the ID of the target is entered. AIJ then instantaneously captures the target data from SIMBAD.

A nice feature is that a light curve of the target star develops and displays in real time as the photometry of each image is done.

And as Phil notes, all of this is free.

Roy

Affiliation
American Association of Variable Star Observers (AAVSO)
Comp Sequence and AAVSO Report format

Roy et al:

Two issues that I find problematic with some photometry software is whether it easily generates a suitable comp star sequence and if it creates a valid standard AAVSO Extended File Format (AEFF) report.

AFAIK, AIJ does not automatically provide a standard sequence or this report. There is a BAA spreadsheet template that can help create such a report but the process requires some manual effort.

Have you been able to resolve either of these issues in an efficient manner?

Ken

PS: Personal opinion: Most observers are willing to expend considerable money to purchase hardware (scope, mount, camera) BUT most appear to be unwilling to do the same for software, even if it greatly simplifies their photometric analysis. I find this a bit short-sighted!

Affiliation
Variable Stars South (VSS)
Comp Sequences and AAVSO Report

Ken is correct that AIJ does not provide automatic sequence selection or an AAVSO report.

I have never used software that selects comp star sequences and therefore do not know if the selected sequences are editable. In particular, I mean the facility to reject individual comp stars. Because without that facility I could not use selected sequences. I have only ever used 14 bit and 12 bit cameras for photometry. They do not have the well depth for me to cope with the wide magnitude ranges often present in AAVSO sequences. The other issue is that my targets are well to the south and some have no AAVSO sequences. I know sequences can be requested, but the first mentioned problem is still there.

I just use spreadsheet templates to generate AAVSO reports.

With respect to puchasing software: I have tried to be economical with my equipment purchases and have never used expensive, high-end setups. Components in my current setup for bright star photometry cost hundreds, not thousands of dollars. And that's Australian dollars. Likewise for software. I regard that as a personal choice, not short-sightedness.

Roy

 

Affiliation
Variable Stars South (VSS)
AIJ will repeat a sequence automatically

I should have added: although the placement of apertures is done manually (with automatic centering) in AIJ, the following is useful.

If the same field is captured through two or more filters, then the 2nd, 3rd, etc. times the field is measured, an option to place the same sequence automatically can be user selected.

Roy

 

 

Affiliation
American Association of Variable Star Observers (AAVSO)
RADEC Sequence List

Roy:

In fact, if your images are plate-solved, you can create/use a RADEC sequence list with the target position and your desired comps, with their position and magnitudes. Do this once and you can use it again as needed.

So AIJ can do normal AAVSO differential photometry if one is willing to put in the extra effort to create a sequence and a spreadsheet to generate an AAVSO (or BAA) Report. 

I choose to use VPhot (free with AAVSO membership but in the cloud) or LesvePhotometry (free but needs PinPoint ($)) for my photometric analyses.

Ken

Affiliation
Variable Stars South (VSS)
Problems with platesolving

Ken,

Yes, I'm aware of the RADEC list feature. However, I've not been able to implement plate solving with AIJ. I am presumably using an incorrect setup, but it doesn't bother me as it's not essential for me.

I should do a VPhot CHOICE course.

Roy