Vroobel

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.

Good to know.

Hi, Usually I make my astro-toys, then make a video and show them on YouTube and astronomy forums. This time I will struggle with a subject whitch I am not familiar with, thus I have to ask You for help. Especially someone living not to far from Liverpool or Manchester. I gonna make a bigger EQ fork mount for my 10" Bresser Messier (ES) reflector. I wouldn't even try to think about that without some very important and remarkably expensive part which I have bought as it is no longer able to be used at original environment. I mean a harmonic gear. My one is a little bit broken in area of one of many screw holes, but it is nothing as the fork mount is doing incomparable slower movements and operates with much lighter load. The gear has 100:1 ratio and around 4.5 kg of weight. Here is link to the gear in action: The fork will be made using aluminium plate and profiles while the base has to be made of steel. An idea of the base is shown in the bottom. I hope I can design everything on my own, but the only thing that I can not perform is welding. Therefore I would like to ask mates living in Merseyside or Greater Manchester and familiar with welding for help. Its not urgent, but I would like to know if I can obtain the help or should I try other ways. I believe that the common passion gathers people having different experience. Please don't hesitate to ask if anyone would like to know more details of my idea.

Hi, I have the Sony Nex-6 camera, that doesn't support wired intervalometers, so I had to do something to solve a problem of longer exposures. Please watch my another video presenting my own IR intervalometer based on the Arduino.

Hi, As I used a theory described in article of The Royal Astronomical Society of Canada as a base for my derotator acting, I decided to inform them about my project. An effect of the correspondence exceeded my vision: the author placed an information about my derotator in the article. 😲 http://calgary.rasc.ca/field_rotation.htm

Thank you for the information. Inside my derotator is simple universal board with only LV8729 driver and set of jumpers for micro steps set up. I can think about it and add a feature of the rotator when I make step towards the ASCOM compatibility.

That is right. But that doesn't change the problem of positioning the rotator before every session. This feature requires the ASCOM as well. Moreover, I know that some indicator of "zero" position should be implemented there.

🤔 I cannot say that I didn't think about it. But how will you connect it to your exact stuff? The derotator needs 12V, that is easy. Beside that it gets Direction and Step signals from the Raspberry Pi. And GND of course. I made it this way to adapt it to ASCOM in future, but the future isn't now yet. I don't have mount compatible with ASCOM, so cannot test it anyway. Edit: The LV8729 stepper motor driver can work with 6-36V, so the 12V is there only because i operate with this voltage in my system.

Look, the derotator is a kind of proof that it is possible to make it at home. It was like a bet with some people from the community. Since I finished this quite nice project I gonna prepare to performing of a big fork mount able to drive my 10" OTA. Today I made a deal and I nearly have strong harmonic gear box. That should be strong like the EQ8. I don't expect any problem with astro-photography at all, maybe only the light pollution...

I wrote my system completely on my own. I calculate both Az and Alt and put them into equation shown in video. My Latitude is taken from GPS. Everything else is a calculation based on complicated algorithm developed on my own as well. Finally every picture presents objects with the same angle.