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I am new in astronomy and got my SkyWatcher Star Discovery 150Pi WiFi AZ GoTo, however I am experiencing one big problem. When I try to align my telescope using SynScan Pro app on laptop or smartphone the telescope always points wrong direction. I do not have hand controller.
I set telescope north using compass, enter latitude and longitude, but when try to align 1 star or 2 stars, telescope spins way, way off. When the star is in the South East it shows north east, or sometimes points absolutely wrong direction. When it is set on the north and object is 98 degrees east it goes some 30 degrees. It also points lower or higher.
I am totally lost.
I use 8 AA batteries.
What I do wrong?
How to fix this?
Hi - I'm a relative newcomer to telescopes with goto - still trying to figure them out.
I have a problem with Goto on the 8SE.
Alignment usually works (Not always, but usually)
I believe my set up is correct - time and date, DST and UTC (It's currently BST in the UK)
I usually use 2-star alignment (Currently, most convenient for me are Sirius and Procyon)
Alignment usually succeeds, but goto just doesn't. The scope slews away, sometimes even to a completely different part of the sky from the selected object (I'm familiar enough with
the sky to be able to identify several bright stars without assistance)
Bizarrely, this happens even if the goto object is one of the alignment stars - how could it possibly not be able to find a star when you've explicitly told it where it is?
I've read that goto sometimes doesn't work well on battery power, so I've aquired a mains adapter. No change.
I haven't yet updated the handset firmware (I'm waiting for a serial-usb adapter.)
Any help would be appreciated.
For quite a while I've had an issue where the images I take have trails that show up when going higher then about 20 seconds exposure time. I do a rough polar alignment where you can still see the polaris in the scope as I live in the north of Sweden and the EQ3-2 mount doesn't allow for accurate adjustment above 64 degrees.
I'm 100% sure that the locatation, time zone and time is correct, I've also parked the scope to the position with the scope facing polaris and the weights downwards. I did a 3 star alignment and after a 1 min exposure with my Olympus 420 the result was as the first image I attached. For 20 second exposures I get the second image attached but once in a while without having touched the scope (yes I am 100% sure of this, I stood perfectly still a good distance away from the scope and triggered the shutter with a remote control) I get results such as the third image.
My guess is that the cogwheels are slipping somehow but I'm gonna ask here to be sure.
I'm looking to get a reasonably portable astrophotography set-up, using a 60-100mm refractor, with a suitable goto mount. I spotted the Explore Scientifice exos2-gt with pmc-eight goto system, which looks like quite an elegant solution, and wondered if anybody in the forum owns this mount, and what they think of it's performance & usability?
this is my first post at SGL, and it will be quite long. I am not native a English speaker, so please excuse any mistake.
I have quite some plan with my telescope mount and its goto control, and I am looking for some feedback and comments. If somebody else did a similar project, please let me know. And please feel free and encouraged to make suggestions, ideas, critics, etc.
The story in a few buzzwords: Raspberry Pi Zero → direct control of TMC2209 stepper drivers via the Pi's Uart serial interface to drive my telescope mount. I am writing a software (optionally: open source?) to control the mount. The language will NOT be C, as typically used for Microcontrollers (I know for instance OneStep)
I am using Kotlin, which is a more advanced JVM language.
I think this should be enough information to filter the readers who are interested in reading the rest of my post.
Now the long and detailed story:
My professional background: I am a physicist, and did a PhD in EE (Power Electronics). Later, I became software engineer. Besides being fascinated by Astronomy, I am a tinkerer (Reprap 3D printer, electronics, …). I did grind my first mirror (a 6'' Schiefspiegler) when I was 15 years old, and I built the cookbook CCD cameras in the 90's.
After many years without a telescope (study time, relationship, ... ), I settled down with my family, and I started to get back to Astronomy.
Recently, I did by a quite a massive second hand mount: the “Vixen New Atlux” from another other stargazer in Switzerland. My opinion is that the New Atlux' mechanical design is superb. It has (had...) internal wiring, the counterweight bar can be hidden in the mount for transport, good polar alignment screws, it has an excellent polar finder with a dimmable LED.
But on the other hand the electronics: two weak servo motors in combination with the incredible Starbook 5.... Seigh... the starbook...(!) it is, well... the mount is just superb, and no more comments about the starbook game boy, which shall rest in peace at the garbage dump.
I removed the servos and all electronics, and I put 2 stepper motors into the mount, which are coupled to the gear with a timed belt. My original plan was to put an Arduino into the mount in order to control the steppers. I have an old goto Celestron cg-5 with Starsense, and it would have been quite easy to mimic - with the Arduino as interface – the servos of the old cg-5 and translate the Starsense control signals to my New Atlux. I can write C, and there is even an open source project called OneStep, which uses a Microcontroller in a similar way as I do.
But I don't like to write C code anymore. In the 3D printer community, people need to use real time electronics to control the printer steppers. Due to the real time requirement, C with a real time microcontroler (Arduino & similar) are the only option for 3D printers.
Do we need real time for our telescope? No. We don't need to control a lot of Motor accelerations and high speed control. For the telescope, we need to set the Motors speed precisely, and we need to drive to any position in an accurate and controllable and slow way.
Then, there are new stepper motor drivers available with as much as 256 microsteps. The TMC2209 stepper driver , which is very well know in the 3D printer community, is not vibrating at all. It runs just smoothly, also at very low speeds. I do drive my motor with 0.25 rpm (sideral speed). In case of a slew, I can accelerate to 1500x sideral speed, which also would allow me easily to track the ISS. Wonderful.
The current status of my project is:
The mount is equipped with the two new motors The TMC2209 drivers are connected to the Raspberry pi GPIO Interface, and I can control them via Software. Theoretically, I could attach up to 4 motors with a single Uart interface (1 wire protocol). For instance, a focuser or a filter wheel could be attached. I selected Kotlin as language. Java also would have been possible, but I think for a new project, Kotlin will lead to a much more readable code. The TMC drivers can be driven via a chip-internal clock signal. Different to what the 3D printer community is doing (they use the step / dir pins, and create every single microstep with the microcontoller), I can send a “speed” signal from the Raspi via UART to the 2209 chip, and it will execute this speed for me without any further action. The only time critical issue was that I need to precisely count the steps that the 2209 stepper drivers executed. This is done via a GPIO pin, receiving its index signal (a pulse for every 2209 fullstep). Here comes the pain with Linux (non real-time) and the Pi: For user programs, it is impossible to guarantee that every pulse from the stepper drivers will be registered. But I cannot afford to have a step count drift over time. The solution was that I wrote a Linux kernel module in C. I wrote that I don't want to write any C code. Well, a few lines for the kernel module were indeed necessary. I can live with that, having in mind that the rest will be written in Kotlin. The only task of the Kernel module is to count every registered step at the Pi's GPIO input pins. This kernel module output is then mapped to a character device file in /dev/ for every stepper. In Kernel space, it is possible to register and count interrupts without missing even any one of them. From a hardware point of view, this is indeed everything we I need. The project cost so far: 2x10€ for the stepper drivers, 2x10€ for the motors, 2x20€ for the tooth belts and pulley, 10€ Pi Zero plus some peripheral expenses: Micro SD card, USB charger, and 1200 € for the used Vixen new Atlux mount. And a lot of time.
I have so many ideas on how to extend the ecosystem of my software, but these ideas are for the longer term (maybe years from now on):
Multi-star alignment. The alignment should be able to be updated continuously during an observation night. With a set of stars, it should be possible to calculate the quality of the aligment points, and e.g. drop them if they are errorneous. PEC correction (should be easy on the Pi) End-Stop support The polar alignment routines of today's goto scopes are quite good. But what I would like to have is some audio-feedback when I move the alignment screws into the right direction. Possibility to pre-plan an observation night (e.g. the mount could tell you that the Jupiter moon shadow will be on Jupiter in a few minutes). Record the telescope movements during the night in order to be able to tag any picture. The TMC drivers have much more capability than what I am using currently. For instance, they could be current controlled for slews in order to set the stepper current exactly to the value that it needs without stalling. This saves a lot of energy. The TMC drivers have a feature called “Stall Guard”. This could be used instead of endstop switches (for 3D-printers, this is done frequently). Advanced options for tracking: siderial, solar, moon speed, ISS speed. Tracking in both axis (e.g. to compensate polar misalignments of atmospheric refraction) or just in right ascension. Commercial mounts do not allow much customization here. With slow slew speeds, 5V input via a USB-C cable is sufficient for the Pi + Motors. Usb-C and newer usb battery packs allow to output a higher voltage via USB. With an “USB-trigger”, the input voltage can be selected to my needs. Higher voltage allows higher slew speeds, but consumes more power. Autoguider support, or even better: simply connect a webcam via the Pi's USB connector and do the guiding on the Pi The Raspberry Pi touch screen could be used for telescope controlls Advanced German mount limits and meridian flip control (e.g. a warning about a necessary flip when driving to a specific goto target). An Android App, connected via WiFi to the Pi could be used as display alternative Language control (have a look at Mycroft, an open-source artificial intelligence). "Hey mount, please slew to the whirlpool galaxy!" Control the mount via SkySafari and Stellarium The Pi has a built in camera interface. How about an open source auto align? The Pi could look at the stars to align itself, which makes a lot of sense. I did already order a long focal length lens and monochrome camera from Arducam in order to do some experiments (the standard Pi camera has 3.5 mm focal length and is not really usable, although star imagining is possible). My first observation site is my balcony. And there, the real Starsense does not work at all. It always spin-loops on 2 alignment positions where the sky is covered by the roof – how silly is that?. This can be done better. Further, Starsense is doing only a initial alignment. It should update its position and accuracy over the time! I think I could do this better.
Besides all my ideas, the first and most important focus of the software will be:
Readability (therefore my choice of Kotlin), extensibility and open source. I like to have the Maths of the internal mount model clearly visible and understandable in the software. The calculations that are done within all our goto mounts are no rocket science. I admit, I am the nerd guy who wants to go the hard way and implement this from scratch.
I am looking for a good project name, do you have any suggestions? How about QuickStep? this is possibly too close to OneStep and would offend the creators of OneStep?
Does anyone of you have interest in joining my plan? Doing such a project in a small group would be more encouraging then just doing it for myself. And of course later on, I would appreciate if other stargazers would update their old mounts with my software.
Any comments on my project plan are welcome!