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How do I Plate Solve?

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JMLA's picture
How do I Plate Solve?


I've just gotten some images in my VPHOT account and none of them are plate solved so I really can't determine what star I should be looking at. I did a Ctrl + F in the PDF and looked at every mention of WCS and Plate that is in the VPHOT Users Guide and didn't find any instructions.



MZK's picture
Plate Solve

Hi Morgan:

Most users choose to plate solve their images on their own computers with PinPoint or It is efficient in terms of queue speed. (BTW, did these images come from an online scope like iTelescope? That would change my answer.)

VPhot does also plate solve if needed. However, you would need a telescope setup under "admin". See if you can figure out how to do that from trying or reading the manual.  ;-)

Keep asking questions as needed.

Ken (MZK)



spp's picture
More on Plate Solve

I'll just expand a bit on Ken's answer.

If your FITS header contains the RA and DEC information for the (approximate) center of your field of view and your VPhot>Admin>Telescope Setup contains the correct image scale, VPhot may be able to plate solve your image.   

It's generally better for everyone involved, you and other users of VPhot, to plate solve yourself before uploading your image.  (If your FITS header information is incorrect, or if VPhot can't plate solve for some other reason, the processing of all the images in the queue is slowed down.) 

If you don't have software to plate solve on you own computer you can use  In this case you'll still need to have the RA and DEC information, and also the image scale, in the FITS header.  In my experience rarely fails.

Even if the plate scale in your header is wrong, will probably still be able to plate solve your image, but it will just take longer.  In this case, be sure to check the plate scale that measured so that you can correct the information in your VPhot telescope setup.

Phil    (SPP)    


HQA's picture
plate solve

These images were taken with BSM HQ, and unfortunately on that night (160626), it looks like we were having mount problems.  Therefore, ACP didn't plate-solve the images.  It would be interesting to run one of these through and see where the telescope was actually pointed!  Hopefully later data on Morgan's star will be correctly pointed.


HQA's picture
plate solving done

Hi Morgan,

I uploaded the images from BSM_HQ on 160626 to and plate solved them.  Their center is RA 15:58:37.61, DEC +44:52:57.3.  A second set, from BSM_S on 160627, were also uploaded, and plate-solved to 17:01:25.56 +22:28:38.6.  The coordinates for the star in question (SY Her) are 17:01:29.25 +22:28:38.7.

From this, you can see that the BSM_S set of images are properly centered and should be useful in VPHOT.  The BSM_HQ images are far from the correct field, due to mount problems.  The target star is pretty faint and will require stacking of the B/V sets in order to get decent signal/noise on this mira near minimum.

Usually for images from AAVSOnet, the image acquisition program, ACP, plate-solves each image as it is collected, and VPHOT uses that plate solution rather than duplicating effort.  In the BSM_HQ case, since the mount was confused, ACP failed to plate solve, and since VPHOT uses the same plate-solving software, it also failed to plate solve.  The algorithm used in is more robust and was able to find the right solution.  So for most cases, you don't need to worry about this step, and if you do have to worry about that step, then most likely the images are miscentered and not useful anyway.  Unfortunately, it was the first set of images acquired for your program, and so you were rightfully confused!

There is quite a bit of additional data for SY Her from BSM_Hamren in Hawaii, but we are waiting for those images to get uploaded to HQ.


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