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Found 8 results

  1. We are running a session at my local society on transits and occultations. One station will focus on exoplanet transits, and we'd like to build a very simple model to demonstrate this. We have a star (light source) and an orbiting "planet" but I need to work out how to detect the changes in light intensity and display this on a laptop, like a classical transit photometry trace below (taken from https://heasarc.gsfc.nasa.gov/docs/tess/primary-science.html). Is there a way to take a feed from a DSLR through the USB output to do this, else I could get an adapter for my ZWO and put an EOS lens on the front of that. I really do want a light intensity vs time trace in real time on the laptop. This model will be run in a darkened room. Thanks for any comments. James
  2. Hi all: I've been looking to try some variable star photometry (hence deciding to post in this section) and was wondering if someone could offer some advice, as I seem to have hit a brick wall before I have even started. I recently upgraded my camera from a Nikon D3300 to a ZWO ASI1600MM, which I finally got the chance to try last night on M57 (imaging with a 130P-DS), mainly with the idea of experimenting with creating an LRGB image. When I was processing in AstroArt (including flats and darks) I decided to try some photometry, picking stars in a range with decent SNR but not saturated (I think, though I've not ruled that out). When I looked at the results (on LRGB, luminance and green images) they were all over the place, with errors ranging from about 0.1 to 0.6 magnitudes. I appreciate that I'm using a CMOS camera, not a CCD and that I wasn't using a V filter, but the AAVSO manual estimates a margin of error for DSLR photometry can be as good as 0.01 magnitudes, and these results were miles out compared to that. I've attached the output text file below, which shows the magnitude estimates and the residuals (E_mag) for the reference stars (the stars with an error of "1.0" are the ones I measured afterwards and have similar or worse errors). The jpg shows the stars I selected. For anyone who fancies taking a look, the fit file itself is at: http://nova.astrometry.net/user_images/1719235#original I'd appreciate any advice anyone has to offer, as I don't want to give up but don't see where to go with this. Thoughts that come to mind are: 1) The stars are saturated (seems unlikely as all have relatively low ADU for the camera, maybe about 10-20% of full well). 2) SNR is not high enough (AA advises >100, which they all pass easily). 3) Under / over sampling 4) For some reason the camera is not suitable (though my Nikon had the same issues) 5) Without a V band filter this level of error is normal (though seems to contradict AAVSO) 6) Something wrong with my flat (attached) 7) Something wrong with my annulus (ooh err). Was set at 3.5 / 1 / 5; messing about with it does not seem to make a huge difference. 8) Something wrong with the catalogue (GSC) that I am using. For some reason, AstroArt displays star magnitudes with an error, typically as high as +- 0.4 for stars of this magnitude in this part of the image. Am I using an inappropriate catalogue, or choosing bad reference stars? 9) I'm doing something else wrong that I don't yet know about. If any kind photometrists out there are feeling in a charitable mood I'd be glad for any pearls of wisdom you might cast in my direction. Cheers, Billy. starsoutput.txt
  3. Guest

    Variable star

    Hi, I am doing an end of degree project on variable stars due next thursday and London's weather does not allow finish it. I was wondering if someone would do me the favour of observing the pulsating variable star V0460 Andromeda http://variablestars.net/stars/460/ in the Johnson R filter, for a period of 1 hour and 50 minutes? please? Thanks so much!
  4. Hi, after almost 2 months of clouds there was finally a clear night in sight. I made most of it, imaging until clouds rolled in about 4 in the morning. I shot these using two telescopes at Taurus Hill Observatory. Its fun to operate two at the same time, luckily its possible from indoors. Ill also attach here light curve of variable star V0416 UMa that I made during the same night with C14 and SBIG ST-8 on Paramount ME mark II. Other images are taken with 16" f/8 Meade SCT and SBIG STT8300M on Paramount ME mark I. Im expecially happy with Dembowska, I tried to get complete light curve twice in 2017 but clouds or fog always ruined my photometry. Milkyway was also beautiful as always, I spent some time outdoors just looking at it while telescopes clicked more subs. Worth every second in the cold, windy night!
  5. I would like to start photometry of variable stars and eventually would like to be able to contribute to the AAVSO . I am going to buy a CCD camera and need to match it to one of my two scopes. I understand that for photometry the FWHM of a star should cover 2-3 pixels. I’m not sure which scope is best for photometry. I have a Celestron 8 Edge HD and a Skywatcher 80 Equinox Pro. Which scope is likely to give a big enough field of view to pick up comparison stars yet also capture enough light to give scientifically useful data?
  6. Hello everyone, Our family owns a campsite located north east of Catalonia (Spain). I myself have been an amateur astronomer since I joined the undergraduate Astronomy club at Harvard. After coming back home I cultivated my passion to the point where I became confident I could teach introductory astronomy lessons to kids and families of the campsite. Little by little the interest has grown up and we get a lot of recurrent customers willing to learn more about this wonderful hobby (last observing sessions we were up to 300 people!. So I've convinced the director (my brother) to step up investment on astro equipment to setup a fully automatized dome with a telescope that could be used on observing sessions for families and could also be rented for remote observations (ex. exoplanet photometry) during the off season months. The campsite already has all what's required, a private owned land with good views of a sky that's pretty dark (average SQM 21.00), electricity and internet access through wifi. Our current requirements are as follows: 1-The observatory scope should carry a competent instrument for exoplanet photometry. 2-The observatory should be versatile enough to also be used for visual use on public viewing sessions of the sun, moon, planets and DSO. Public viewing sessions using a projector and camera are also contemplated. 3-The observatory must be fully automatized so that I can control it from home. 4-The observatory should be an attractive instrument to be rented online by other people through service like itelescope in the off season months when I'm not controlling it remotely to allow from some payback of the investment. 5-Although we have people living in the campsite almost every day of the year, the observatory should be designed like a remote observatory, so the instruments should be protected against accidental sun exposure, rain and theft. 6-The observatory will be located next to a river on a typically humid area, so robust, reliable electronics are a must. The plan is to use the following equipment (everything is up to debate, as long as other suggestions fulfill the requirements): Dome: Fully authomatized SopeDome 3M cupola (shutter with 100cm), the idea is to mount it on top of a 4m width x 4 lenght x 1m height concrete base (we're pretty cost efficient pouring concrete this days in my country). Mount: Software Bisque MEII Mount. OTA: I noticed that the Meade 16" F8 ACF OTA is priced the same as the GSO 20" f8 RC OTA when one adds up all the dew heaters and motor focusers required for remote operation. Both could be carried just fine by the planned Software Bisque MEII Mount at a max weight of 109Kg). I'm now assaulted by last minute doubts, in one hand, I love the spike free images that the Meade 16" would provide, both for visual and for AP. On the other hand, aperture rules for photometry and the GSO looks very tempting indeed, here's a list of pros and cons for each OTA: Meade 16" F8 ACF OTA (Weight 40kg approx) Smaller central obstruction 12.6% as a function of area Better for visual Easier cleaning/maintenance Smaller light gathering power GSO 20" f8 RC OTA (Weight 78Kg approx) Bigger central obstruction 47% aprox as a function of area (EDIT: I think this was listed as a function of diameter, my guess is that it's about 22% as a function of area). More light gathering power Better for differential photometry? Requires field flattener for larger CCD chips. I would greatly appreciate some advice regarding the OTA. Thank you very much in advance.
  7. I've been trying to do some photometry with my DSLR with a view to using it on variable stars as a quick "grab and go" solution when there is a gap in clouds etc. Rather than looking at variables I decided to start off with comparing some fixed stars to identify how well I can estimate magnitudes with my DSLR, and the table above shows the results. Using only two stacked frames (5s, ISO 800, F3.5 on my 5DMk2) with no darks, light polluted london sky, and just one comparison star I seem to be able to get to around 1% variance for the majority of the readings, with the worse being 2.54% out. Trying Chi Cas, against Upsilon1, Upsilon2 and omegaAnd comes up with M4.67 which is mag0.03 different (0.55%). I'll be honest I am surprised at the results as it is not all that far off the 0.01-0.02 mag range often quoted for looking at exoplanet transits for example. Has anyone else tried this exercise as i'm interested to know how these results stack up - good or bad. The only thing I know for sure is I couldn't get it that close visually using my eyes!
  8. Hi! This is from last night. Taken at Taurus Hill Observatory, Finland. Florence is still quite bright but relative speed to background stars has slowed down alot as the asteroid moves away from Earth. Perioid seems to be approx. 2,4 hours. In the second image I stacked 1 hour of 60s sub-exposures to show movement of the asteroid.
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