When I have transformed my DSLR observations I have used the spreadsheet method which can be time-consuming. I decided I would image a standard field and calculate my transformation coefficients. There was a post a few days about this topic. For my FOV for my telescope and DSLR, it is 153 x 102 arc-mins. If I select a std field M67 chart I can get about 30 stars avoiding the very center of the cluster to calculate my TCs. I would like to use VPhot to try to obtain my instrumental mags but have had some issues in the past with vphot for DSLR photometry because of difficulty plate-solving probably because of the larger FOV and the fact that the stars in the DSLR images are more defocused than a typical CCD image. My questions: can you obtain TCs from different standard fields and avg them together? Do you have to obtain TCs from different ISO settings that you use (I use ISO 400 and ISO 100, basically different gain settings)?
Barbara
It's a good exercise to get your hands on data and see it spread out on a spreadsheet. As you note, it is a time consuming process.
I invite you to then try the new VPhot workflow: https://www.aavso.org/new-vphot-workflow-simplify-prepping-data-tg
This workflow depends on having a sequence saved that has the labels replaced with AUID's. If you could share with me (SGEO) the sequence you use for DSLR/M67 , I'll take care of the relabeling and then post is as a commonly available sequence.
Then the only extra step would be if the images have the filters tagged as TB, TG, TR in the images. Then you would want to have mappings set in your telescope profile:TB->B, TG->V, TR->R. This is so VPhot will know which references to associate with the images.
I'm eager to see the comparison of methods.
Thanks,
George
If you load all 3 images as a time series then what do you use as a target? I have tried using EV Cnc as a target because that is what I use when obtaining a standard field chart for M67. When I put in EV Cnc for the time series, it says it can't be identified. If I load one image at a time and ask for a sequence it will give me a standard star sequence for that one image. So I don't know how to load the 3 color images at once
Barbara
Hi Barbara,
The common sequence named "com M67 AUID" is seeded with the target HW Cnc.
You were close!
George