Imaging with GingerGeek for another exoplanet. This one starts its pre-transit at 23:55 and should just about be on the point at the meridian where we can perform a meridian flip and then image all night.
We like to make sure we have the right star field so actually having a photo from the exoclock website helps. Tonights candidate is the dimmer star to the left of this pair.
The star is a magnitude 10 star in Lacerta. Unfortunately despite the forecast it has just clouded over, here is what we would have been imaging.
So the evening started well, I had logged into IMT3, got the dome ready, TheSkyX/SGPro software was up and running, CMOS camera was cooled and I was already syncing on a bright star even though it was still twilight.
Dave and I had chatted the previous night and had settled on HAT-P-32b in the constellation of Andromeda. The reason was due to the target position in the sky, the time of rising and setting was before the rise of the sun so we could get a full ingress and egress and no meridian flip was required.
Then the gremlins started to play havoc with our efforts and I was having major issue with guiding to the point that I was going to give up as the issues were eating into the desired 1 hour egress monitoring time period. Dave joined the session to help resolve the issue and we managed to start imaging about 10 minutes before the start of the transit.
Dave had to go to bed due to work commitments but I was determined to get the full set of observation and run it through the HOPS analysis software. It was an uneventful night interspaced with music, movies and hot cups of tea.
Once I had transferred the data over the internet to my server, performed the analysis and sent the result to Dave it was 5:30am so I crawled into bed around 6am.
@ 19:00 Opened dome in order to cool the dome and scope down.
@ 21:00 GingerGeek arrives, wine is poured and we took 5 x darks, flats and bias for both the last run and tonight. The flats (red) were 3 seconds exposure to get 2/3 well depth required for this.
@ 21:44 Slewed to WASP-93b before we set about focusing on a nearby magnitude 5 star using the Red filter. Starting focus position was 58841@19.42℃.
@ 22:06 After failing to focus using the Red filter we resorted to using the Luminance filter to auto focus and achieved a excellent fit (focus position 61630, HFR 4.95 @20.83℃).
When we swapped back to the Red filter, SGPro then moved the filter offset to focuser position 60630. We slewed back to WASP-93b (GSC:3261:1703) and found a guide star just off centre of the star field with the exoplanet target.
Started to take exposures to find the brightest value of the centre pixel of the star and make sure it was 2/3 full well depth and thus 33,000 ADU (even though it is a 12-bit camera SGPro is set to 16-bit for ease of use. Eventually this was achieved at around 200 second exposure.
@ 22:51 Started imaging, 18.21℃ was measured at the focuser.
Frame and focus of starfieldTarget star for Exoplanet measurements Local conditions200s exposure of starfield
Started around 21:15, Guiding by 22:02, Capture started 22:22, Finished at 03:31.
Dave and I are part of the amateur exoplanet monitoring effort for the ESA Ariel mission. We decided that we would allocate some time to try and provide observing data towards the project whenever we could.
Part of this requires some forward planning such as looking at the upcoming transit visible and their associated time. This is due to the altitude of the object, the ingress and the egress times of the projected transit.
Prior to this we had discussed in advance which object to target for the chosen evening. All the hard work of choosing objects is done by the Exospies project website as they list the candidates they need data for via a schedule. So it’s a simple task for use to go through the list and work out what fits best for us.
Unfortunately whilst opening the dome to cool down I decided to review the schedule but I was hit with a server 500 error from the website. In a panic that I might miss the start of the event I scoured the internet for alternate exoplanet transit time websites and found the excellent Exoplanet Transit Database of the Czech Astronomical Society.
I had issues with focus drift all night due to the temperature fluctuations but at a recent Zoom session it was discussed that images can be out of focus with no detrimental effect on the measurements :
SGPro Image History
I was unable to auto focus successfully maybe due to the low altitude and seeing. I also discovered that temperature compensation was enabled so we probably need to remeasure the temperature compensation coefficients so the focus deltas are better between the par focal filters.
The object was at a relative low altitude, the outside temperature was warm and although the skies appeared clear our AAG CloudWatcher sensors via the Grafana dashboard told a different story. For us a truly clear sky is anything equal or lower than -18℃.
Sky Temperature – it was clear but it wasn’t !
Sky Temperature – T’was warm !
After performing a meridian flip, resumed the guiding I started to feel tired so I set my alarm for 3am and went to bed. Unfortunately there appeared to be a guiding issue at some point shortly I went to bed.
Guiding issues shortly after meridian flip
This was investigated using the phdLogViewer and shown to be a loss of guide star and didn’t recover for around 18 minutes.
The guiding issue also caused the image to shift so the target and reference stars moved. We need this in frame in order to run the frames through the provided HOPs data analysis program which hopefully won’t have a problem in reading them. That’s an exercise for this weekend and hopefully we will have enough data to yield a decent light curve that we can submit.
I managed to get only 45 minutes worth of data the other night to test if I could both acquire data and then process it. It took some time to get the downloaded HOPS software from the ExoClock mission working on my Mac, but with the help of Angelos from the project. So I opened the 46 images, I did not capture darks or flats and of course no bias due to it being a CMOS camera. I added information about the observatory and then ran the reduction and alignment code.
Completion of details and opening of 46 images
So the initial chart looked promising, I had taken the first set of frames almost on time for the transit even though you are supposed to start 1 hour before. This was because it took me so long to setup. So the data looks like it shows a decrease in brightness over the 45mins, however I have asked Angelos for his opinion and await a response.
Output from clicking Run Reduction
I then selected the target star, KELT-18 with the red circle below, along with 5 comparison stars. I may have selected stars incorrectly here as they are probably suppose to be not variable.
Alignment and comparison star window
The resulting table appeared with the size of the box for each star and its position.
Resulting target and comparison stars
I then ran the photometry code and the following chart was created which to me showed I had done something wrong given the scatter.
Graph output with actual photometric values and PSF in red
I then for fun ran the fitting code from this screen.
Information for Fitting
The fitting showed and increase in brightness which was clearly incorrect. So I have learned a few things with this, first is to read up on using the software for analysis, second is to gain more data and calibration frames.
Resulting output clearly showing problems with data
