Vroobel

Dream Team

Finally my heavy ATM fork mount in action. All, excluding the 10" Bresser OTA, made from scratch at home/garden. A big harmonic drive is a heart of the mount. 70+ kg load capacity. 😁 The OnStep firmware @ FYSETC S6 board and the Astroberry @ Raspberry Pi 4 8GB do the job for me. It's not easy, but now I have 0.1 arcsec precision. Yesterday I checked its 1270mm focal length with the M57 and L-eXtreme, tonight I'm going to beat it with 2x Barlow ED. Canon 6D, Baader MPCC III and IDAS LPS-D2. Fingers crossed... 🤞

Hi The controller is finished now and I can share some facts and pictures. As you can see, that's a form of hat for a small 12V 30Ah rechargeable battery, like half the size of one for a petrol car. All design is made in a FreeCAD, I like this program, it's free and not too hard. This construction allows easy disconnection for charging. Once fully charged battery allows at least 3 nights of fun. It should be very cold and wet at night and I should use 4 heaters fully driven to significantly limit the time. The goal of reasonable mobility (using car) is obtained. Power switch, 4x20 chars LCD, encoder with micro switch and digital voltmeter including buzzer informing about drop of the voltage below individually set level. The 12V voltage provides excess over the need, as the Arduino drives 4 MOSFET transistors using pulse width modulation (PWM), so 9V or even 7V should be enough to drive the heaters. I don't know yet the efficiency of the set, when the voltage drops so much. The encoder is a great thing, rotation with explicit jumps allows to precisely increase or decrease the setting of deltaT over the dew point. The minimum reasonable setting is +6°C, but I let it change up to +20°C. Pressing the axis of the encoder I change an active channel, so I can set a different temperature for each heater. One picture below shows the selected channel by asterisk (*), while the value of deltaT is also displayed for the exact heater. The picture shows 3 heaters at work with settings 1:+10°C, 2:+15°C, 3:+20°C. The fourth channel is not occupied now. Why did I decide to be able to set different temperatures? Recently I checked it in practice, the lens of my Vixen A80M was fine with +6°C over the dew point, while BST eyepieces in the binoviewer were getting foggy because of extra humidity from my eyes! I had to increase the deltaT significantly (I don't remember, 15-20°C) to remove the dew, but in the meantime I heated up the air over the lens. Two USB sockets provide 5.1V power for the purpose of the RA drive in my EQ5 mount. Two aviation GX sockets are there for remote control and stepper motor of home made moto-focuser (another story, but the same Arduino and the same battery work for it). I like the GX connectors for their variety and stability. There is also an Adafruit BME280 weather sensor in front (instead the DHT22 mentioned in previous post, I changed mind) and a USB extension for the Arduino, so I don't need to open the box to improve my code. The code supports possibly every variant and order of connection and disconnection of the heaters and NTC sensors. This is against accidental tearing the cables out or if I forget to connect something and decide to do it later. The sensors are placed inside of heating bands. It's good to know that the NTC thermistors, which I used, has reversed characteristics, so if the circuit is open, the PID algorithm takes it as very high resistance that means low temperature and it strives to heat the heater up (https://www.sensortips.com/featured/what-is-the-difference-between-an-ntc-and-a-ptc-thermistor/#:~:text=Both negative temperature coefficient (NTC,allows current to pass through). The PID_v2 library is quite universal, but I didn't have more time to dig in it. I'd like to mention that the case is designed in a way to run the dew down, so it's safe. What can it do? - readout of an ambient temperature, relative humidity (and pressure of the air, if needed), - calculation of the dew point, - driving independently 4 channels using PID and PWM, - allowing of independent setting of temperature for each channel between 6 and 20 °C, - measurement of the battery voltage with informing (buzzer) about dangerous drop of the voltage, - providing 2 x USB power, - steering of moto-focuser based on LV8729 driver (or any in Pololu standard) and Nema 14 stepper with 5:1 planetary gearbox. The gadget was recently tested in its initial version during my first hunt for the planets, but I added some features, so I cannot wait for a clear sky now. BTW, regarding the additional drop of voltage on wires of the NTC, I took it into account and I think that the total resistance of the NTC and its wires is measured in the readout. I think I shouldn't care too much as the PID watches the process and heaters do the job. Let's check ASAP!

Hi, Tonight I began my first hunting for the planets with Vixen A80M. 😊 Saturn and Jupiter sorted, I still wait for Mars.

Hi all, Recently I bought a quite nice Vixen A80M, and now equipped with driven EQ5, quality diagonal, OVL bino and some pairs of EPs I would say I'm ready to watch the Moon, planets, doubles, etc. But I cannot... I'm not sure a rest of the UK, but Liverpool is very moody in terms of weather. Since the New Year I had literally 6-7 good nights. But even if the weather seems good, the dew kills the fun. So I decided to build a 4-channel Arduino based smart dew heaters controller with DHT22 and NTC thermistors. Additionally I'm going to join a feature of the dew heaters controller with a moto-focuser controller, which is already working (as prototype). I use the Arduino Nano, so I have limited number of IOs. I have a plan to use a higher capacity rechargeable battery, because I want to make the refractor totally portable. A case for the multi-function controller will be 3D printed. My idea is to keep constant difference between a temperature of the heaters and an ambient temperature and I can easily do it using a PID_v2 library and some NTC theory. That works very well and I can control the difference of temperatures by potentiometer in range 0-20*C. I have two questions at this moment: 1. Is it really reasonable to base the algorithm on a dew point instead of my current solution? Or maybe I can switch the controller between the two options if/when needed? I know, how to calculate the dew point, but how the controller should work based on that? 2. How big the difference between temperatures of heaters and ambient should be? As I wrote, I can set it between 0 and 20*C now, but I can expect that too small difference is not sufficient while too big difference causes heating air over lenses affecting seeing. What is your experience in this matter? I found that some people don't need to use heaters with EPs, but in Liverpool I experienced the dew on EPs many times. BTW, today I found this project: Accidentally we had similar ideas, but my controller won't be so high-end. Despite this, if someone is interested in copying my simpler ideas I'll share them. Thanks for any support Tomasz

Wow, I know that sky! My friends lived in Thomastown, in a half way between Cork and Dublin. I was so hugely impressed how many stars I could see... ✨ ⭐ 😍 Now they moved elsewhere and didn't take the sky with them... 😒 Tomasz

It is, indeed! I'm gonna equip it with a bino, then the impression will increase.

Thanks 910mm, it's F/11.4.

Hi, I'm pleased to show another Vixen in action: A80M Japan. Unfortunately not at night, it's during observing the Sun. I've bought it from our fellow on SGL recently.

Very clever laptop stand OK, I like your pier as well

I will do it as soon as I am ready to go, but not yet. Thanks again.

Thank you, I appretiate it as well. Is the permission given to all astronomers amateurs, or personally to you?

Oh, thank you! 😊

I know the second one. In the first one I typed my post code and got... my post code as result. Thanks anyway.

Thanks for that. Unfortunately, both sites are not close from Liverpool. I try to experience with filters while I improve my ATM mount and learn the Astroberry, but in the meantime I am looking for a semi-rural land open for public. I already know about the Formby area, which is 30-40 minutes driving from my home. Do you know another one in 1h driving area?

Hi, Could you tell us, where is that place? Thanks.

Wow, you had the same idea as my one! I have working Atari 65XE with California Access 2001 floppy drive and cassette recorder turned into an "SIO2SD" that means there is SD reader/converter with 2GB of all games and demos ever released. I have an idea to buy 5:4 17" LCD and place everything in an Alu case as a old school 8-bit laptop. The result should be similar to your one! Regarding your one, it looks impressive, my daughter also likes it! 😁👍

I have read that the UV/IR cut filter may help, as the IR generates a halo around the star, so I ordered SvBONY 1.25" filter. Should be soon.

I mean the tip on the attached picture (screenshot of the "PHD2 Best Practice page" ) How to focus the guidecam better? I used a Bahtinov mask. Thanks again. I believe the mount didn't show its best yet! 🙂

Hi, The night 7-8th September was great, I waited for so good weather! As you advised, I began the guide with a 2 sec exposure. The misalignment wasn't too big, only 1', but I wanted to check how it behaves with different misalignment. Next time I will try 5' and 10' to be able to choose the best setting. I found guiding settings giving me spread of +/- 1", which is almost perfect in comparison to the previous results. As the chart is not a goal itself, I can present two single pics of M13 and M57, 60s and ISO400, taken by my Sony Nex-6. I forgot to attach my IDAS LPS-D2 filter, so the black is light gray. Taking into account that my mount drives a 10" Newtonian telescope with 1270mm focal length and the guiding isn't yet set up perfectly, I must say that the stars are very point. Not everywhere in the field of course, I should buy a coma corrector in future. Apart from "improving" the misalignment next time I'll try to use a Barlow lens (2x 2" ED) and swap settings of the camera with 4:3 ratio. Let's see what the future holds. Thanks again for your support!

Thank you, guys. I will try it all as soon as possible. Thanks Michael for the PHD2 basics!

Thank you for your answer. Could you please explain what exactly should I calibrate? Thanks.

Good evening, I decided to create a separate thread from the one about my ATM fork mount. The mount is ready enough to begin astrophotography. I have taken an opportunity of several clear nights to set up my guiding, but after a failure every time I have no choice and have to ask for help. My guider is based on the SW 8(9)x50 180mm finderscope and the ASI120MM mini camera attached to the finderscope with an adapter designed and printed by me. It's OK. Recently I used a dew heater designed by me for the Baader Zoom 8-24 Mark III - it matches perfectly. I decided to go towards the Astroberry and Kstars/Ekos. I tried to use the built-in guiding software, but finally I chose the PHD2. Both with the built-in guiding software and the PHD2 I have never obtained satisfaction. Look please on the charts from last night (on the bottom). First of all I don't know whether the problem is caused by my lack of knowledge about the guiding or by the unknown fault of the OnStep @ MKS Gen-L v2.1 cooperating with the Astroberry. I have some bad experiences with the OnStep or the Ekos, but I hope that is another issue. Let's assume that everything is OK with the hardware/firmware. The Astroberry works on the Raspberry Pi 4 8GB RAM. A base of the mount is leveled properly. A wedge and fork are aimed excellently, originally using the SharpCap Pro, but recently using the modern Polar Alignment Tool from the Ekos. Both ways give an accuracy about several arc seconds in total. I know that people obtain arcminutes and the guiding can do its job. The wedge is stiff and the less than 20kg OTA with accesories are nothing for the mount as I hanged on it with my 70kg with no bigger stress, siriusly. I didn't weld the fork yet, it's aluminium, so I have to order the proper service. But the only bent I expect is towards its sides (left or right), which can be important, when the fork is rotated more than 60* left or right, never when the OTA is aimed near the Zenith. I found out that the OnStep may have problems driving the stepper motors when their wires are longer, so I changed the relevant parameter and compiled. Additionally I reduced the accuracy from 0.5 arcsec to 1 arcsec. I was advised to also consider a cone error, but still with no good result. As you can see in the pictures, the guider escapes towards North West (Is that because I live in Merseyside? 😁) In the second picture is an amazing concentration of the marks in the top left quarter of the Target chart. What did I try? - leveling with two different spirit levels, - changing algorithms, - changing an aggression around defaults, - binning 1 and 2 with relevant values of the MiMos (I understand that if MiMo=0.2 for binning 1 than it's 0.1 for binning 2, but maybe I'm wrong), - focusing the guider with the Bahtinov mask, - attaching the Baader UHC-S 1.25" filter on the camera for eliminating an IR; I have no 1.25" UV/IR cut filter, - Guiding Assistant and its suggestions, - Drift Polar Alignment (I damaged the excellent alignment this way, so I had to fix it in the classic way), - a Dec backlash analysis and attempts of use its results, - guiding with and without a calibration, - guiding using one and more stars, - manual and automatic choice of star(s), - and of course the exposure time between 0.5s and 6s. The guiding floats are usually in range (-2",+2"), but sometimes reach much more, like 8". I found out that the guider should be screwed using a more stable bracket with two rings, but it's not heavy, it's not 80mm APO. The recent nights have been windless and I am surrounded by fences, shed, house and trees, so no wind is in my garden. Because of unexpected backlash in the Dec axis the OTA is not balanced, so it's bottom goes down itselfs. As I understand, the only problem with the backlash can be visible during the GoTo, not during the tracking when the Dec stepper motor shouldn't work apart the guiding. Is it possible that the dev heater around the guider cell affects the air over the guider? I can try to guide without the heater tomorrow. I can also try to connect the OnStep controller to my laptop instead of the RPi. Maybe the 180mm focal length is wrong? I have a plan to make a kind of shelf which I will hang on the fork instead of the OTA. I will screw a spare finderscope shoe to use the guider as the only OTA on the fork. My idea is to check if the over 17kg load generates the problem somehow. BTW, I will use the shelf for another, smaller OTA or simply for my DSLR with a Sigma Zoom lens. Is there anyone who experienced a similar problem and sorted it?

Hi, Since my last post I made some additional amendments, everything for the ease of assembly and mobility. The electronics found a home in the fork frame, so it must be powered and the Ra stepper motor must be connected in easy and safe way. I like multi-pin sockets and plugs like the one used for connecting a microphone to CB or other radio station, so I use them everywhere it's reasonable. The stepper motors and the drivers are powered with 24V using a pulse inverter and it's good at home. But I have a plan to go somewhere under darker sky in future so I had to change the idea to be ready to power them from the car battery, which I have at home. Therefore I replaced the 24V pulse inverter with a 12V one supported by a 12V/24V 10A DC/DC inverter. It's placed in the fork frame as well, because some equipment (a dew heaters driver, an intervalometer, a dummy battery and a main mirror fan) requires the 12V power as well. BTW, the weather won't improve till September, so I can do much more peacefully...

Hi. Unexpectedly, yesterday my telescope got its first light on the new mount. I am delighted by the precision of a polar alignment given by both leveling and the mechanics of the wedge and also the home made guider (the SW finderscope and the ASI 120 MM mini camera) did the job excellently. I'm not so happy in relation to its tracking. I still have some error and I don't know yet what does bring it. After first several hours of use I have some vision about its modularity, cables and the assembling and disassembling ergonomics.