Vroobel

ngc3031, thats very clever! I just checked, the Mars show's little difference in comparison to the Stellarium, but the Jupiter is nearly exactly same! I'm impressed! I can use it instead of typing hundreds line of code based on the "Astronomical Algorithms". After a check of all planets I think is more accurate for the gas giants then other planets, but I gonna play with it! Even with the tiny inaccurates I can use a wider eyepiece to find the planet and then use another one. Let's try the ISS...

Hi old_eyes, The Google Maps does it. Simply type the address and press longer red drowing pin. I used my phone now, but PC version gives you more. Tomasz

Something for Python lovers: https://rhodesmill.org/skyfield/earth-satellites.html I have to install this package and try.

Thanks, Dave. Could you please share some details with us? I'm interested in and technically ready tor the accuracy of seconds. Tomasz

I think the Stellarium is accurate enough within 30 days since update of TLE. Wht is the TLE? https://en.wikipedia.org/wiki/Orbital_elements#Two-line_elements You can get it from the https://www.n2yo.com site after registering. Every time I get it I have same numbers, because possibly it's valid for some time or forever - I don't know yet. I saved a file with the data and will check it for every several days. I read on Wiki that it becomes inaccurate after 30 days. I found similar need of the Ra and Dec coordinates here: https://www.physicsforums.com/threads/satellite-right-acension-and-declination-calculations.220399/ then jumped to mentioned subject: https://en.wikipedia.org/wiki/Orbital_elements and found the description of the TLE. After then I found the pdf file: spacetrk.pdf - it's there: https://www.celestrak.com/NORAD/documentation/spacetrk.pdf And here my headache began... I know that the TLE includes coded orbit of the ISS, but is here any matematician / physicist / astrophyisicist able to pass through the equations and receive the Ra and Dec? But I found also this: https://github.com/brandon-rhodes/python-sgp4 - "Python implementation of most recent version of the SGP4 satellite tracking algorithm". So will try to sort it out. Tomasz

BTW, a video linked below shows how it should work. There is Starlink recorded, but the idea is exactly same. I expect a little bit longer delay between the slew and the tracking related with my software, but can't be sure. You can hear single "beeps" with decreasing intervals, so I think the mount reaim an OTA several times, then the proper tracking starts. Unfortunately palm-trees are disturbing. A most interesting part begins after 16.00 minutes. Tomasz

At a second look it seems to be not so easy. First of all you have to provide coordinates of your location. It can be your home or some other places, more then one, but you have to choose one as default. Every time you request for data from the server sending dedicated license key you do it for the selected location. I just checked: added my home coordinates taken from GPS in my telescope and also another location outside the city taken from Google Maps - the most recent location is always the selected one, but you can change the selection. Thus you have to be prepared and location has to be provided and selected if you want to track the ISS outside your home. Every request for positions of the ISS is limited to 300 sets of data, every position is for one second, thus you have set of data for following 5 minutes. It not too much. You can ask for the data maximum 1000 times within 1 hour. My Az drive allow to revolve the telescop 360 degrees within 5 minutes (I know, it's not fast...), I shoud reach an opposite (faretst) position within 2.5 minutes. I should figure out how to aim the telescope in position, where the ISS will be after maximum 2.5 minutes, then the tracking shoud do its job within remaining 2.5 minute. It's long enough to make quite nice video. Not bad, but it's still not set of desired equations... I'll try to play with that a little bit, but will still seek another way. How the Stellarium is doing that? It use TLE data as well, but I launched it with no internet conection, so it couldn't get data from the serwer, but it is working despite no link with serwer. Interesting...

I agree with you, James. If I understand it properly we can get a kind of set of positions for next 300 seconds. It's not too much. I think the API gives data about now + 300 seconds, but I'd like to have data about 10 mins later + next 300 second. Without some attempts I can't say anything. As I read earlier in the linked sites, the software for equatorial mounts use the TLE data as well. Tomasz

Thanks artem. The software is for equatorial mounts: "Satellite Chaser is a software made for tracking and guiding on satellites using ASCOM compatible equatorial mounts." I pasted link for it earlier, so maybe James or other owners of equatorial mounts will be interested. I have motorised my Dobsonian mount, which is quite unique, so I have to find another way.

I've got it! 😊 https://www.n2yo.com/api/#positions I gonna play with that tonight.

For you, as an owner of better EQ mount, it can be quite easy using dedicated software working with the mount in EQMODE (I'm sorry for mistake if happened - I don't have this kind of mount): https://github.com/AstronomyLiveYt/SatTraker I just seen the video about tracking the Starlink, looks good. https://www.cloudynights.com/topic/644609-presenting-satellite-chaser-a-free-software-made-for-tracking-and-guiding-on-satellites-using-ascom-compatible-equatorial-mounts/ or I'm not so clever in EQ area, the links are given me by users of Polish astro-forum in similar topic which I created earlier. I have both easier and more difficult task. I don't need to use any MoveAxis mode/command to follow the object, just need to calculate its position and delays between subsequent steps. But how to get the sky model, as you wrote? Right, let's continue when we get something. Thanks James Tomasz

Great! I'd like to ask an author or the site for his method of calculation the Ra and Dec. We have different mounts, so our ways will be different as well. I have the Raspberry Pi onboard and software written in Python completely by me, thus I can do whatever I want with my drives. But what are you gonna do to encourage your mount to find and track the ISS? Tomasz

I realised it was improper question. What kind of mount do you have? And what is your idea for the ISS tracking? I think it's too fast to simply use any GoTo feature to catch it and follow, so my idea is to calculate its position for 5-10 minutes later, to aim the OTA there and to wait, then to start the tracking in exact time. Look please at this site: https://www.n2yo.com/?s=25544 They evidently use some equations for achieving Ra and Dec of the ISS. I need them only for the job. Another question is its radial speed. Now look please at this video: https://youtu.be/qROmsXf8-fg I understand that the ISS pass about 0.5 degree within about 1 second, so my stepper motors will work really fast and the tracking will be similar to a slew... BTW, I have 10" Newtonian scope on a Dobsonian mount. Tomasz

Just a coincidence I will be happy to do it together with others. What kind of telescope do you have?

Hi, As my GoTo is successfully finished (some cosmetic issues remain) I shoud focus my attention on planets' positions. I have proper source of information: fantastic book "Astronomical Algorithms" by Jean Meeus, thus I will sort the planets soon. But planets are not a challenge for me at this moment, they are just something obvious to do in my list. I have another idea and ambitious plan for next project within the year: locating and tracking the ISS to be able to make a video of its fly, not only transition. Similarly to other objects, I need some equations. I'm pretty sure they are available somewhere, because plenty websites or apps offer showing current position of the ISS. I will use this topic for sharing a progress ot the project.

Hi, It looks like end of my troubles with GoTo. The reason of "random" deviation in the slew wasn't related with software, even it wasn't related with mechanical construction. It was insufficiently leveled base of my Dobsonian mount. I trusted too much earlier the level of my troley and mount without OTA, but this night I got the glare and checked spirit levels of all set and its full load. One of the spirit levels showed that it needs some improvement and 3 turns of one M10 screw (3x 1.5mm = 4.5mm!) was enough to do it. Finały I had a pleasure to jump randomly between M31, M13, M92 and M15 and also plenty multiple systems visible from my garden. I started with 38mm eyepiece (33x), then swapped it with 25mm (50x) and every time the objects landed in middle area of its field, but most often almost exactly in middle! I could check it with my laser. So I risked and added a Barlow lens x2 and again, randomly chosen objects could be found in middle of the field even with 100x magnification. I am proud of that, as the construction is my own at all. Another video on YouTube will show my GoTo and its accuracy soon.

I still try to solve the problem. My system doesn't have encoders as feedback, so I think stepper motors can loose some steps during striving to bigger speed of the slew. Any other ideas?

Hi, Astro-amateurs trying to code their own astro-software can be intrested in a last update of the database described above. During a work on my own GoTo system I met a problem of calibration, so I had to properly define some stars for this purpose. Because of my location I chose 19 stars (including Polaris) which are visible on the sky over UK within the year. I used an application found on website of AstronomyNow magazine (https://astronomynow.com/uk-sky-chart/) for that. Similarly to other objects in the database, the stars have range of months of visibility on the sky. It is for avoiding of choice of invisible stars from the list for calibration. The website offers a choice of exact hour of observation, so I chose midnight. Some positions are multiple star, but they are here for calibration only, so I mean them just as single stars. You can find i.e. aparent magnitude for all the system. A difficulty level is of course 1. A stars' coordinates, their aparent magnitude and proper motion are taken from Wikipedia. Additionaly the coordinates have been merged to a values of hours/degrees in a decimal notation. SQL and CSV files for download: http://astro-art.pl/opracowania/TabelaWimmera_v3.2.3.csv.zip http://astro-art.pl/opracowania/TabelaWimmera_v3.2.3.sql.zip Pozdrawiam, Tomek

Hi all, Do you remember my huge worm gears and GoTo system built on Dobsonian mount and Raspberry Pi? https://youtu.be/u7_AuXA8eNs https://youtu.be/2W5UI7m4FnI It works very well mechanicaly - I can rate it looking on its tracking. Even a slew works well, but the correction is required. A problem appears exactly here. I can imagine how the original GoTo works with the Alt-Az mounts, but still know nothing about the correction of the slew. For beginning, I assumed that the first part of the slew moves the telescope to exact position of the object at the time of a choice of the object. But the object is moving at this time, so the second part of the slew moves the telescope slightly more. Of course, sometimes the telescope goes backwards then, depending of the direction. I'd like to explain my idea of the correction. After the first slew (its part 1 and part 2) I have to move the telescope a little bit towards the object both in Az and Alt axes. Every movement up and down, left and right is added or substracted (depending on the slew direction) to/from the primary numbers of steps and then a kind of factor is calculated, ie. Az=1.009912345 and Alt=0.999234567. That means numbers of next slew will be multiplied by the factors. I didn't know if the factor should be applied to the 1st part of the slew or to the 1st and 2nd ones together, so I developed a feature allowing to make a choice during the observation. I tried it yesterday and unfortunately it's not working properly. The results are random in my opinion, I can't find any pattern to sort out the problem. I assumed to add the factors to numbers of the steps, but maybe the correction is related with something else? I stuck now and have no idea what to do. Is someone here knowing the GoTo software and eager to give me a clue?

Thank you, also in behalf of Wimmer. I will inform about any changes and improvements.

To be honest, I'm not an author of the original list. I think I should write a few words about it's origins. Over ten years ago one Polish enthusiast of astronomy came up with an idea to create a list of objects for observation, that should be easy to understand for absolute beginners, usually having simple and small scopes or binoculars. This way he created document of about hundred DSO, many asterisms and also multiple systems worthy of the observation. The Table contained the Messier's, NGC, some Mel and IC numbers, a range of months when you can observe the objects, constellations, a maginitude, Ra and Dec positions, pictograms represents: difficulty of the observation, size of the objects (whether you have to use small or bigger magnification), binocular (the object is attractive by the bino or not), sign of "must see it" and "must show it to others" and last one like "show it to larger group". That was really great job! Thousands people, beginners or not, downloaded it and had pleasure to use it. The masterpiece have got a name "The Wimmer's Table", as his nickname is Wimmer. Presently we can use the 3.2 version of the list. Unfortunately the masterpiece is written in Polish language, but hopefully will be translated. If you want to look at content of the Table, you can visit his website, where it's "electronic version" is located. There is language switch in a top right corner. http://picios.pl/wimmer/ OK, but I wrote something about database in the title... About one and half year ago, in summer 2017, as a DIY enthusiast I wondered about a future of my telescope. I knew something about GoTo, so considered a kind of database of objects. Any objects, even several stars for a beginning, which I could use for calibration purposes. I was absolutely surprised by "The Wimmer's Table" when I found it! That's it, I thought! Thus I created a MySQL database, but when I started entering data from the Table, I realised, that something else could be there as well. You can find a full list of fields of the database with descriptions below. nr | A number of the object in the list, as it is in the original "paper" version of the Table. After DSO, asterisms and multiple systems I placed a few stars needed (I think so) for a calibration of GoTo system, and a first of them is the Polaris. The stars have 4-digits numbers. Last group includes objects of Solar System (for my own system based on Raspberry Pi), but I wrote software for following the Sun and the Moon, planets have to wait. The US objects have numbers based on 5 digits. XXXXX and XXXXX_pl - different fields like for example a name of the object in English language and it's equivalent in Polish language, so: name / name_pl | A name of the object, that is obvious. messier | A number in the Messier's Catalogue. ngc | A number in the NGC Catalogue. others | A numbers taken from other catalogues, if found. That is optional, but I can improve it, if have list of the numbers. type and type_full / type_pl and type_full_pl | A category of the objects. As it is database, users can group a result of a query and use it finally to prepare a journey on the night sky in range of the selected category. Ast – asterism, Ga – galaxy, GC – globular cluster, MS – multiple system, N(D)+OC – nebula (diffuse n.) + open cluster, N(E) – nebula (emission n.), N(E)+OC – nebula (emission n.) + open cluster, N(E+R) – nebula (emission n. + reflection n.), N(P) – nebula (planetary n.), OC – open cluster, OC+N(E) – open cluster + nebula (emission n.), OC+N(E+R) – open cluster + nebula (emission n. + reflection n.), S – star, SS – Solar System, SC – stars cloud. (n. = nebula, an abbreviation because of limited space in my LCD 4×20) season_1 and season_2 | A range of months in which you can observe the object from our location. constellation / constellation_pl | Obviously, name of the constellation. w_magnitude | A value of an apparent magnitude. This is a real number with dot as an decimal point. The "w_" as a prefix here and below means that the value is taken from the Wikipedia, because I found some differences between "The Wimmer's Table" values and the Wikipedia. We agreed together, that a future show what is the truth. They are not big differences, often seconds only. w_ra | A right ascension expressed in a decimal value of hour angle. It is real number in format 11,9 that means 2 significant digits and 9 decimal places. w_dc | A declination expressed in a decimal value of angle. It is real number in format 11,9 that means 2 significant digits and 9 decimal places. w_ra_h, w_ra_m, w_ra_s | A right ascension expressed in hours, minutes and seconds of hour angle. w_dc_st, w_dc_m, w_dc_s | A declination expressed in degrees, minutes and seconds. ra_apm, dc_apm | A proper motion of some objects (if applicable), useful in calculation of proper position of the objects in relation to J2000.0. The ra_apm is expressed in seconds of hour angle. difficulty | A simple level of difficulties expressed in values "1", "2" and "3". The "1" means easy, the "3" - hard to observe. size | Another parameter easily describing an object's size expressed by two values: "L" - large, that means easy to find and observe using small magnification and "S" - small - bigger magnification is required. app_size_1, app_size_2 | An angular size of the object, such as galaxies, which can be inscribed in a rectangle. Units of the angular size are given by letters: "d" - degree, "m" - minute, "s" - second. binoculars | A parameter suggesting using of binoculars, if the object has big angular size and an only small magnification can be used in this case to see all the object in a field of view. It can have two values: "1" and "0" as "yes" and "no". have2see, have2show | This pair of parameters inform about "necessity" of seeing the object and showing that to bigger group, as the object is definitely worthy of that. As above, values are "1" and "0". details | Additional information taken from Wikipedia like separation of multiple stars or apparent magnitude of their components, etc. comments i comments_pl | Additional comments such as real number of multiple system's or cluster's components, exact place of the object on another object's background, etc. page | An original "paper" document contains maps of sky, sketches of objects and descriptions, so this value indicates their location. checked | This field can be used to mark objects already found and observed to avoid a repetition. map, sketch_1, sketch_2, picture_1, picture_2 | These field are dedicated for high-capacity binary file such as pictures of maps, sketches, etc. Presently they are empty, but will contain graphics soon. I have planned to develop two versions of database: with and without graphics, second one will be much smaller. description i description_pl | Descriptions written by Wimmer and taken from original document and also their translations. The values listed below w_ra = w_ra_h + w_ra_m/60 + w_ra_s/3600 and w_dc = w_dc_st + w_dc_m/60 + w_dc_s/3600 appeared a bit later to make calculations easier. A programmer had to do it himself in his script earlier. It is also important to know that as the value of the declination can be negative, it's all elements: w_dc_st, w_dc_m and w_dc_s are negative as well in that case. Please forgive me any misspellings or translation errors if happen and please, inform me if you find it. You can download the database in a native format of MySQL here: TabelaWimmera_v3.2.2.sql or/and it's equivalent in CSV format here: TabelaWimmera_v3.2.2.csv