Vroobel

Hi, After some attempts with the Arduino Mega 2560 and AstroEQ firmware I had to leave it. I asked its author for access to higher number of micro steps, but they didn't response. 32 micro steps mode gives me 2 arcsec accuracy in Ra axis and 2.5 in Dec one. It's not acceptable for me. I focused then on the OnStep @ MKS Gen-L v2.1. As I use Nema 23 stepper motors, I chose the Trinamic TMC5160 drivers, because they have external MOSFETs onboard and can give really high current with small amount of heat. As an author of the OnStep firmware warned, I had to cut a CLK pin. I am possibly a second person who had to solder it to GND (in GoTo slew randomly Ra or Dec didn't work, now is OK)... It doesn't work with the EQMOD, because it's compatible with Meade standard. Instead of that I used the APT app and of course the ASCOM Platform. I am amazed... 😳 It's so silent! I recorded a Sirius-Polaris-Sirius slew as sample, just to share it on the YouTube. You can hear the mouse click louder than the stepper motors. Special thanks for my friend Sebastian from our Polish astro forum. He shared his knowledge and experience with me and patiently answers all my questions.

Hi, I have to rest a bit from the manufacturing, so it's good time to think about hardware and software. In the beginning I had a plan to rebuild my own software written for my previous mount, motorised Dobsonian one. But my friend, another astronomer amateur and DIY enthusiast encouraged me to look at the AstroEQ or the OnStep software which together with the EQMOD or EKOS can work perfectly in my setup. Thus lest start with the Arduino Mega 2560 with the AstroEQ. I'll try to work on the EQMOD on Windows 7 laptop (I have spare one) - just to be familiar with that. I know that the Arduino Mega is the worst solution as it is not accurate, so I ordered the MKS Gen-L v2.1 which will work with the OnStep. It's the best mobo for the mount and works wireless. Finally I'm gonna install the Astroberry and EKOS on my Raspberry Pi 4 8GB.

It's very impressive! Today we have laptops, Raspberry PIs, Arduino, but I see you had to make your own controller. The construction must be very accurate. Are you still using it? Amazing job!

😁 As I wrote earlier, the jack is not my idea. If it can hold a weight of a half average car lifted, why not to use it for around 40kg load? The item in pics is a chamfer tool for any round rod, including threaded ones. I have made 48 x M6 rods that means 96 round edges to chamfer. This tool does it quickly and smoothly.

Thanks for that, I'll consider it when (if) my ones will do same. But it seems to be aimed in fixed position. Edit: I have got a clever advice from another ATM creator: two steel flat bars with long hole along, one end screwed at the bottom of the wedge, second end screwed in position given by the angle. That should fix the wedge in the position enough.

Another actively spent afternoon:

Hello again, I'd like to share with you what I already performed. First of all I have made a plywood model of a wedge to avoid expensive mistakes. As another ATM maker from Poland suggested, I used a car jack for its elevation. It's strong enough to hold a one ton load. I have bought thick aluminium C-profiles and performed proper hinges for the jack. Four other high quality hinges (keeping dimensions) placed on edge will provide stability, so the wedge will not be wobbly. During performing the wedge I figured out that it will be better to weld the harmonic drive wall downwards instead of upwards, so the eyepiece - if I wish to observe - will be around 300mm lower. That is a significant difference. When some aluminium parts arrived I began working on the fork and fixing of the OTA. Several points of the mount at the same time. An aluminium base plate, 600x300x12mm with a big central hole and 16 small ones around for the harmonic drive, two round 600x30mm pillars in the middle of each side of the fork, two "tables" holding axes fixings. And here I have to explain my idea. I'm gonna use two high quality worm gears dedicated for CNC as axes holders. One of them - ratio 80:1 - will be driven by a Nema 23 stepper motor. I will remove the worm from another one with a 25:1 ratio, which I already had, so it will work as the axis holder only. I have designed and performed a kind of saddles holding my 10" OTA, which is 17kg load, without accessories. They will allow you to easily seat the OTA on the fork. I wrote it down very briefly, but it took me several months to get it done, mainly because of the waiting for the material. The sellers on eBay are now scammers and swindlers who use COVID and delays to sell goods they don't have in stock. I waited over one month for aluminium square and rectangular profiles and finally eBay gave me a refund for them. Now I wait again for the same stuff, but not from an eBay seller. I hope it will arrive on Monday, 7th June. In the meantime I have made some steel elements of the wedge. Supported by my friend I decided to fix the harmonic drive and its stepper motor to the fork permanently. This is because the fork base must be screwed to the harmonic drive using 16 bolts. It would be simply annoying to screw and unscrew it every time when I want to use the mount and finally the threads would be damaged. So the harmonic drive is attached to a 400x200x8mm steel plate. This plate will be put on the wedge top plate and screwed using eight welded M8 bolts. I expect that the steel wedge with the car jack will be heavy enough even without the harmonic drive, so the drive can be a part of quite light aluminium fork. The wedge top plate has a 90mm hole in the middle to let the stepper motor attached to the fork and the harmonic drive pass through. Using a 500x200x6mm steel plate I have made supporting triangles which will be welded on both sides of the wedge. It sounds complicated, but believe me, it will be very easy to assemble. All mount will be assembled using three parts: an "A" shape steel base, the wedge and the fork. I have 4m of 50x50x5mm steel square profiles for the "A" shape base. But this is the future... Regarding the mentioned earlier other OTAs, I'm gonna use a kind of shelf on the 300x30x30 aluminium bars (parts of the saddles) and screw it to them using M8 bolts. My idea is to install a rail in one of the existing standards to the shelf to be able to attach any OTA smaller and lighter thern my 10" Newtonian one. Tomasz

Exactly. In the meantime I found another cheap one from China including a 2" M48 barrel, so I ordered it. It will take longer time to finish my ATM EQ fork mount, so I will check its quality and accuracy without the cc. Its price causes that I have to collect the money. 😒

I checked it right now. My T2-E-mount adapter attached to the camera gives exactly 55mm space, so I think it's made as a standard. Unfortunately it's T2 thread, not the M48. I found 3 small headless screws and detached a T2 ring expecting the M48 one inside, but there is nothing useful. It will be difficult to find proper threated ring for this exact adapter. I think I have a choice between looking for another M48-E-mount adapter 36.5mm long and another same aplanatic 4-lens cc with the T2 thread. As the mentioned earlier Sky-Watcher one has also the M48 thread I tried to find the M48-E-mount adapter and found this one: William Optics M48 Wide T Mount For Sony Nex E Series. https://www.rothervalleyoptics.co.uk/william-optics-m48-wide-t-mount-for-sony-nex-e-series.html There is no information about its height on this website nor others, so I guess the height must be a standard. Thank you again Jamgood Tomasz

Oh, my friend, your informations are very helpful. Thank you so much for that. I used the camera and didn't realise that there is the marker, but it is there indeed! Should it be exactly 55mm? Thank you again, Tomasz

I use a Sony Nex-6 mirrorless camera. I have read that to use the cc with my 1270mm OTA (over 610mm) I need 55mm distance between the M48 thread and the sensor. I have to check how high is my T2-E mount (Sony) adapter and find a proper M48-T2 adapter. There are lot of them in the market, how did you know which adapter you had to buy? Thank you for your support Tomasz

Hi Jamgood, it's me again. I have read on the linked page that there is a camera connection through M48 thread in the cc. Does it mean that I have to buy T2 ring as it's not included? Was it ready to work after a purchase? Thanks. Tomasz.

That's unbelievable! How it's made, that two items giving similar effects work in different ways... 🤔 The cc suggested by you isn't cheap, but I seen pictures taken with it. It's designed for full frame sensor and even with that stars are sharp around at the edge. Is there any way to use it for visual observation as well? I have a quite nice 38mm Erfle eyepiece for wider and brighter DSOs, but it shows the comas perfectly too close of the centre.

Where is your focus position with the cc in comparison to setup without the cc?

Thank you very much. Your cc is very similar to the Skywatcher f/4 Aplanatic Super Coma Corrector, its price is also similar (SW is slightly more expensive). Is it the same product?

Hi, I use the Bresser Messier Newtonian 10" F5 OTA and temporarily Sony Nex-6 camera to perform astrophotography. I wrote temporarily, because I will consider the A7 body in future, but cannot be sure. I will also consider a dedicated astro camera with full frame, if my plans succeed. I would like to ask you which coma corrector is the best for my set. I have read about: - the GSO/Revelation photo-visual cc (very cheap and quite good value for the money), - the Baader Mark-III MPCC (photographic) (still not bad price, doesn't change F), - the Explore Scientific HR cc (photo-visual, helical focuser, excellent correction). The last one is possibly the best among listed above. Moreover, ES = Bresser, so I would assume that this cc is designed for the ES/Bresser Newtonian telescopes like the Baader 2.25x Barlow lens is designed for the Baader 8-24 Zoom lens... But I found out that every cc causes troubles: some guys experienced issues with their focusers, others ones with back-focus distance of their cameras. And what about the asto camera? Do they cause any problems with the ccs? Is there any owner of ES/Bresser Messier Newtonian OTA (the best if it's 10" F5) and Sony mirrorless E-mount camera using one of the listed or another coma corrector? I'll appreciate every opinion. Tomasz

Hi, I just began building a heavier EQ fork mount for my 10" Bresser Messier. I own used 100:1 harmonic drive... ...which will be driven by Nema 23 stepper motor equipped with 25:1 worm gear (picture attached). Even without using micro steps mode I can obtain 500,000 steps per revolution. Simple use of 16 micro steps mode gives 8m steps in total, that is much more than needed for an astro-photo. Here is its live story: Tomasz. I'd like to add, that the harmonic drive should easily hold a static load 50+ kg as it worked in 5-axes milling machine similar to a robot's arm. So the advantages are: zero backlash, high precision and high load.

Thanks, Dave. Unfortunately I cannot trust the "similar" size. I have opportunity to make it universal, so I prefer to choose the bigger size and make a kind of adapter to the smaller size. The advice about place of focuser became significant. To be honest, how to observe (not astrophoto) objects close to the Polaris? 🤔

Hi guys, I just come back to the game. Presently I'm working on the EQ fork mount for my 10" Bresser Messier OTA, but if the project is successful I would consider moving towards something better, like the SCT 11. I'd like to ask owners of that stuff with the original fork mount, doesn't matter what kind of type , what is the distance between mounts of the fork? What is the distance between most far points of the OTA mounts? I'll appreciate your response. Tomasz

Probably you are right, as other people told me the same. They told also that cheap MIG welder is not good choice, but I don't have too much money to spend. I have to buy a good quality mitre saw (Evolution) and also high class bench drill press (Bosch). The welder is not only purchase related with welding. Years ago people didn't know MIG technology and used electrodes only and despite that they had not bad results. I think I could do it like many other, just have to be patient in learning.

I wrote "no so high accuracy", that means 1 arc sec / step or 0.5. It's not too bad I hope. 😁

BTW, I bought an arc welder last week together with everything necessary to weld. I have 2 weeks till end of the June to learn welding enough to perform solid and good looking joints. Later it will be difficult as I come back to work.

Thank you. You are right, I gonna use the small worm gear to drive the HD. Taking into account ratios of the HD and used worm gear, 200-400 stepper motor and its micro steps (LV8729) I can reach even 0.1 arc sec/step accuracy for the Ra axis. The Dec axis will have not so high accuracy, but sufficient enough. I want to use my earlier experience and make worm gear again, but this time I will use smaller fully aluminium blank. I have some sketches but excluding the fork I'm not sure if anything of my concept can be understood. It will be much easier to see that built step by step.