OHP2017 - The day I (almost) discovered a new variable star !

During OHP 2017 spectroscopy workshop, I used my small Televue 85mm on the NEQ6 mount with a ST1603 CCD camera.

I tried to mount a guiding camera but it didn't work: I needed some spacer to be able to focus both camera and I have to admit the off axis guiding module is very thin and doesn't leave lot of space for the camera. I do not really like the use of it but maybe once I got the right spacers, it will be ok...

Anyway, I played with Prism v10 software and acquired some images of CY Aqr, a pulsating (delta Scuti type) variable star. The screenshot below shows the run during the night. The maximum ADU count was measured inside a small box and without (auto)guiding, the star moved out of this box so the count dropped for some time. I moved the star back inside later on (well... I slept some time during those acquisitions!).

Prism software has a photometry module which is fairly simple to use (once I changed the catalog from GSC to GSC-ACT which is the one installed with Prism!). This module extract all the stars, look for the best references and map all the stars on a graph with magnitude & RMS. The stars should all be on a "main sequence" except the one which are variable!

I quickly looked at CY Aqr and result shows a very nice light curve, which can be improved by better selecting the variable stars and enlarging a little bit the measurement area:

Anyway, I noticed a star whose magnitude varies in a nice shape:

YES! This is a variable star which isn't indicated on Prism and the GVSC (Global Variable Star Catalog)!!! The star is GSC0567-1919. So I took images during an other night at OHP and a third night from home with the same setup. I sent the measurements to Raoul Behrend (managing asteroid rotation curves in Europe and variable star light curves) and Romain Montaigut (from CALA local club). They made some check and (unfortunatly) the variable is already known as VSX122414:

The light curve is very nice and this shows how to look at your pictures to search for new variable stars!

OHP2017 - Mosaic with Prism v10

During OHP 2017, I used my small Televue 85mm refractor on a NEQ6 mount with a ST1603xme CCD camera.

In Prism v10, you can use the automatic observation to acquire multiple images to do a mosaic. In Observatory menu, select "objects to observe list" then create a list of targets around your object to acquire the mosaic.

In this exemple, I am targetting the Veil nebula so I used the coordinates of a star between the two nebulae.

After having created my observation list (3x3 images around Veil nebula), I used the automatic observation tool to acquire all the images, 15 exposures for each section. Here are the screenshots for M31 and M45 mosaics:

I reduced each section (actually, in Prism, you just process everything and each section is preprocessed independantly) and export them as JPG images using the same visualization levels.

I tried Prism tool to assemble the images but it didn't work (alignment were not very good) so I used ICE (Image Composite Editor), a free Windows 10 tool to do panorama. It worked very well on the Veil nebulae, less on M31. Here is the result on the Veils - a nice picture with a very large field of view:

OHP2017: Automatic observations with PRISM v10

Every year, a group of spectroscopists gather together at Observatory of Haute Provence. This year, more than 50 people joined this world class spectroscopy star party with around 30 telescopes in the field!

OHP 2017 group picture

I brought a NEQ6 mount for Steve Shore (a professional astronomer from Pisa university, who came to give us several astrophysics courses) students. They were very autonomous so I did setup my second NEQ6 mount with a small Televue 85mm refractor and a Zwo ASI178MC color CMOS camera.

Alessandra, Marco, Marco & Giovanni

The Zwo ASI 178MC is a low cost camera which works very well for astronomy with small exposures (less than 30sec typically). File size is fairly large as this is a ~3000x2000 pixel image with a Bayer color matrix. While well adapted for some visual assisted astronomy, it is not designed for science.

my own equipment at OHP

PRISM v10 includes a very powerful automatic observation tool. I played with it and basically loved it. It is very easy to use and I was able to acquire several objects in Sagittarius with very few clicks.

The process worked very well except that the TV85 defocused itself after some time and I have no motorized focuser.

Preprocessing, image alignment and addition took lot of time due to the large number of images and large file size. Result is still satisfactory, specially as the Zwo ASI178MC camera is fairly low cost:

 M22 (Trifid) nebula

M8 (Laguna) nebula

 M17 (the Swann) nebula

M16 nebula

 M22 globular cluster

M11 open cluster 

 M15 globular cluster

 M39 open cluster

M30 cluster

 M34 cluster

 NGC7331 galaxy in Pegasus