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images look strange

SNH01
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Joined: 2011-01-29

I just uploaded a few pictures and noticed, that they look kinda strange.

What I did:

I use an SBIG ST-7 CCD-Cam (9µm pixel-size). My telescope (10" Newton) has a focal length of 1500mm.
Therefore I should have 1.23"/pixel. The help page of VPhot told me, that the ST-7 should have a gain of 2.3 e/ADU.
This ist what I wrote in the telescope-setup-page.

The tracking of our telescope is not very good yet, so that most of my stars look more like ovals than circles. We will work on this issue.

When I then view my images, they look strange. Also the histogram looks strange.  To even see my stars, I have to change the values in the image display tool to like 100 and 500. When I view my stars with the pixel/ADU mode, there are a view pixels inside this star which contain nothing, the value says "0". I attached both, the histogram and a star-picture to show what I mean.

Also, the values shown for the content of the other pixels are strange. When I view my images with other program like Astroart, they show me values
of a view hundred, not over 30000 like in VPhot. Astroart also does not show me "holes" inside my star image.

Despite those viewing problems, the photometry seems to work. But the FWHM-value for each star differs very much from the value I get out of Astroart. There, I get usually about the same value for each star.


I hope somebody can give me a hint, what is going wrong here.

greetings

Katy

problem found
SNH01
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Joined: 2011-01-29

Thanks to a friend, we finally found the problem here.

I use astroart to record and reduce my data. This program writes the data as unsigned 16bit integers in the fits-file. Every Software I use (Astrometrica, IRAF, CCDOps, ImageJ) has no problem with this, only VPhot.

Now, I will reduce my data with another program and upload this data to VPhot. I guess, I can live with this.

Does anyone else use astroart? Have you had any problems?

greetings

Katy

cannot delete images
SNH01
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Joined: 2011-01-29

I have the above problem again.

So I wanted to delete my image from the server but I only get an error:

 

Server Error in '/app' Application. Runtime Error...


What's wrong here?

greetings

Katy

cannot delete images
kge
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Joined: 2010-07-19

For some reason the processing software did not close its connection to your images properly, so VPHOT was not allowed to delete them. I have to look into why that happened.

I restarted the software, so you should be able to delete your images now.

Geir

thanks
SNH01
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Joined: 2011-01-29

Thank you, now it worked :-)


Maybe it happened because I broke up the upload after I found out, that there were problems with my images.

16 bit unsigned FITS images may work fine
rmu
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Joined: 2010-07-23

Many of us are saving images in 16 bit unsigned FITS format, me I'm using maximdl, but astroart images may work fine. VPhot shows images aplying equalized histogram, so they are not pretty. Sometimes I have an strong background, so my images not always looks fine in vphot.

Can you paste an screen capture to letting us see how your images looks like in VPhot?

I've had many guiding problems, my stars were not ellipses, they were straight lines ;-) You can try autoguiding.

 

Regards

Miguel

strange images
SNH01
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Joined: 2011-01-29

Hello,


Sorry for answering so late.

I tried a few things and it seems that astroart sometimes does strange things while reducing
the images. I still didn't figure out what exactly, but when I repeat the reduction, it seems to work
then. Maybe astroart has problems reducing a few hundret images at once.

In this case it has nothing to do with guiding problems. ;-)


Anyway, I attached two images of how the strange images look like. the first one ist the image shown in VPhot, the second one is one of these stars in pixel/adu-mode. the white pixels actually have a count of 0.


greetings
Katy

 

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