Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.



  • Content Count

  • Joined

  • Last visited

Community Reputation

286 Excellent


About jimao22

  • Rank
    Star Forming

Contact Methods

  • Website URL
  • Skype

Profile Information

  • Gender
  • Interests
    Astronomy and astrophotography (solar and deep sky for the moment), ATM, DIY observatories
  • Location
    Ploiesti, Romania
  1. These days I was at some star-party into the mountains and I finally made the tests with the ATIK 460EX. The field is the bigger I can obtain with what I have and due to this fact, I made some exposures to Amdromeda and Pleiades. Andromeda is 27x60s+30*x20s+30x5s. M45 is 47x60s. All procesed in PI without calibration, no filters at all and a Moon at 35%.
  2. Finally I had some decent weather and I made some exposures with my new rig: the home-made mount, the Omegon 66/400 and the ASI 174 camera. All images have the roundness less than 0.1 (measured in MaximDL) and I found that is no need for long exposures to have very good results. The final result is a balance between the shortest exposure you can do it with a good enough SNR (1) and the longest exposure you can afford with a good roundness (2). (1) depends on the local light polution, the contrast between the deep-sky object and the sky background (2) depends on the mount accuracy On my site I found that I need exposures between 30 and 60 sec for the best results with this set-up. Next tests - with the ATIK 460EX CCD camera. Much bigger... M92 - 9 x 40sec M101 - 20 x 60sec M51 102 x 40 sec M51 - detail
  3. Due to the very bad weather this spring time, it was very hard to find a good night for testing properly the new mount. But somehow I find a proper night being with one of my astro buddies in my observatory. I made a lot of exposures with Sharpcap but the darks and flats made with MaximDL didn't work to calibrate these images. I suppose is some kind of incompatibility in acquiring the data. Even if I tried to make new darks and flats few day later using the same Sharpcap, I didn't obtain better results. The best results I obtained when acquisitions were made with MaximDL - lights / darks / flats and biases. But I had only 5 exposures like this, 90 sec each (lights). The result is great in my opinion, roundness of the stars is 0.084 and I am sure I can increase the exposure time somewhere between 2 and 3 minutes without problems - unguided subs with same great figures. The most important thing to obtain these results is the proper polar alignment. I think a PoleMaster it will be the best improvement ever for this nice mount I have.
  4. You cannot see it because is on the back side of the mount, where the motor is. Is not rocket science, is just a screw that make a lever to push the motor axis on the sector. Is not big deal.
  5. The friction drive can be adjusted with a screw. You cannot preload by pushing the shaft other than using some kind of lever operated by a screw. So is adjustable.
  6. An update to this project. After few runs for testing the pros and cons for this mount, I made some technical adjustments. 1. I had some problems to polar align the mount, due to the fact the polar scope was not illuminated. So I bought a device for this purpose, a part of the modular system of Star Adventurer mount. Problem solved. 2. I had problems to obtain a good focus for the stars. So I made a Bahtinov mask who fit perfect to my Omegon 66 telescope. The Bahtinov mask is a wired one - a mask with some good advantages over a regular one due to the fact an increased quantity of light is getting inside the camera sensor. As a result, you can focus with very short exposures (1), or on dim stars (2) or with narrowband filters (3). 3. I made a huge mistake thinking that the finder is installed on the right position on the horizontal bar (see the pictures from previous posts). The finder is aligned with the main telescope only on RA, but not on DEC. So, to resolve this problem I put a shoe on the main scope and use a lighter finder scope - in this case a green laser or a red dot finder. 4. I encountered some problems when went on the field at night and tried to power the mount from my car battery. The battery had around 13 V when the mount wasn't working but the voltage droped down to 10 V when mount worked. As a result, the mount was blocked after few seconds. So I made a 12 V voltage stabilizer. This device is inserted between the power supply and the control module of the mount and the tension never drop under 11 V no matter what. So now the mount is working in the field too. To be continued with pictures of deep sky objects... When weather will allow.
  7. Hi, As you can see in the pictures with the star shape analysis, the mount is working great, so the concept is very good. Moreover, I am sure the results will be better than usual commercial mounts same class because the friction drive is very stiff an robust and allow greater weights to be worn. The bearing is a radial SKF one and is mounted with a press, like the ones used in the car maintenance. And the machining was very precise being done on a CNC machine wit a high accuracy.
  8. We have an update from the astronomer Pablo Santos Sanz from IAA Granada, the coordinator of this project. He sent us some preliminary data and a map with the observers of this event. Is truly a rare event, as he said in the mail received. " I have generated a preliminary elliptical fit to the shape of Huya that I am attaching (North is up, East to the left). In my attached fit I have removed the scale in kilometers and the observers legend. Data are still under analysis and we cannot provide numbers in order to "protect" the future scientific publication currently in preparation. The additional information you could need: the occultation was observed from 50 sites (involving more than 50 people, including professional -from professional observatories- and amateur astronomers). From this 50 sites 21 recorded a positive occultation. Occultations by TNOs are really rare, and involving an occulted star so bright (about 10 mag) are even more rare. Usually we catch occultations by TNOs in the range 16-18 mag for the occulted stars, for this events we can predict now about 5-10 per month, but we catch positive around only 1 per month (in the best cases). This is the first stellar occultation by Huya, and a record in terms of the number of positive detections! The first stellar occultation by a TNO was detected in 2009 (2002TX300) and up to date we have detected 70 stellar occultations by TNOs/Centaurs (43 by 24 TNOs, and 27 by 5 Centaurs), and we have participated in more than 90% of them! The work to predict one of this occultations is really hard, and can last for years in some cases, due to the high uncertainties in the orbits of the TNOs and the small angular size of these bodies in the plane of the sky (GAIA DR2 is helping a lot, with a very accurate position of the stars). " The graphs down bellow is the photometry analysis for the Romanian astronomers involved in this (only two are a professional but one o them made the acquisitions from his private backyard observatory). I can tell you only that I'm number 7 in that list.
  9. I made some (poor) photometric analysis in MaximDL with my data. What I know is the shape of the light curve is correct. I don't know (yet) how to adjust the parameters inside the program to have right magnitude of the stars. I used 1 reference star and 1 check star. I made 2 graphs - first made from all my data (around 790 exposures) , to see if any other object intersect the path of star light and the second graph made from only 70 exposures centered around the occultation itself, to have a clearer idea about the shape of the curve. Is not to much, but it is fun - I can tell you.
  10. Is interesting that as we know till now, only 14 astronomers had took pictures to this occultation and 11 of them are from Romania. The one who did organize the whole event was Marcel Popescu, a Romanian astronomer from La Palma, so perhaps this is the reason why so many Romanians... Thanks for sharing the program. I will give him a try asap.
  11. A friend suggested using the tracking speeds used by ASCOM, so that I can no longer compute them (I only started calculating them and it was a beautiful exercise of theoretical astronomy). So I used the "Sidereal tracking rate" = 15.041 arcseconds / second and "Lunar tracking rate" = 14,685 arcseconds / second ( https://ascom-standards.org/Help/Platform/...eRates.htm). After two attempts to reduce the errors to lower values, the third one came out perfectly (or almost) so that the 35 degree circle sector of the mount was moved by the engine in 2 hours and 19 minutes vs. 2 hours, 19 minutes and 37.2 seconds as the theory was. Approximation was good enough, I said ... The last step was the star test. So, Sunday night - March 18, I pulled out the mount outside the observer, pole aligned not very accurate, and looked at a brighter star from the southwest sky that was at my fingertips (star turned out to be Procyon of the Canis Minoris). I made 30 'and 60' exposures, obviously unguided, with the ASI 174 mono camera, using FireCapture as an acquisition software. The .fits images I've uploaded to MaximDL to analyze them there. The results were more than my expectations. The roundness of the stars was between 0.162 and 0.25 (the latter eliminated by the software) for the 30 'and 0.170 and 0.252 exposures for the 60'. For unguided images, at first try, I think is amazing! I am so pleased!...
  12. Problem with the shaft was solved by grinding it (the fastest method). The remaining problem before goes under the stars with the mount and the telescope, was to adjust the sidereal and lunar tracking speed. This was not an easy task. The first time I had to figure out what is the current speed and precisely determine the major angles of the circle sector on which the engagement is made. That's why we used a special protractor. I found that for a full bow stroke we have 50.6 degrees and the angle between the arms of the arms is 35 degrees. This was the one I used for the following calculation.
  13. Sunday was a big day! I inaugurated the warm room (1), I made observation and shots to the trans-neptunian Huya asteroid occultation (visible from my observatory) and I made first test under the stars of my DIY Astrotrac type mount. It was a magic night, with clear sky, nice temperature and great results. Speaking of my observatory, I brought the furniture inside, I changed the sensors of my alarm system on new position, I brought the new wood-stove (which will be amazing on the next winter time) and pre-prepared the electrical installation. All is left to do is to connect everything on power, to install the window (I am waiting for my special glass - toughened double glazing anti-theft) and to move the desk and the computer in the new home. The old observatory room it will be only for my telescope and some tool boxes for DIY activities. The warm room is very nice and cosy and I can tell you is a great game changer, even if it won't look so. The meteor camera is back on-line as well.
  14. Thank you all ! Is just about now I am back on my computer. Some brief information about the set-up, the exposures and the target. So I took the shots from my backyard observatory, MPC code L15 (Saint George). I have a topic with the building process of my observatory here on this forum - is called "A Romanian observatory". The camera was the ATIK 460 EX mono, the telescope - MN190 and the mount - an EQ6 belt drive (a DIY old project). Because we need to obtain valuable data by having a very accurate light curve, the exposures should be as short as possible. This contradicts the need of good signal to noise ratio (about 10 minimum). On the other side, a CCD camera have a long delay of downloading all data, is the sensor is big. So I had to make exposures at binning 3x3 and to reduce the field at minimum, all for a fast download and high SNR. At bin3, my camera have around 916 x 730 pixels. I made a subframe of 200x200 pixels which is roughly 11'x11', enough to have 2 other stars near by our Star as references when photometry will be applied. With these settings I could made exposures of 3 sec with a delay for download of 0.74 sec (a ratio of 80% / 20% - which apparently is the best approach). The target - Huya - is a trans-neptunian (also called a plutino object). It was discovered in 2000 by an astronomer from Venezuela - Ignacio Ferin - and it have around 450 km diameter. Hubble found that Huya have a satellite with a diameter of 200 km, so is a binary system. The extended map of the occultation strip is bellow.
  15. Last night (Sunday to Monday), a rare event happens. A dim star (mag 10) was occultated by the trans-neptunian asteroid - Huya. The strip where this event was visible passed near by my observatory. So 2:53 local time I was outside to take pictures of this event. It was a very nice night, with clear sky and good temerature for this time of the year. My data obtained by me is already to the profesional astronomers in La Palma, where they will obtain new information about this remote celestial body. I was not alone in this enterprise - another 10 astronomers around the country being involved in the project. I used my data to make a short film of the event with the most important part - occultation itself. The strip where this event was visible:
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.