dazzystar

No problem. I thought they'd be some technical calculator for the belt length?

Thanks @fozzybear for the images. It's the belt lengths which I can't figure out how to calculate. I have (according to George Cushing) the following pulleys:- Dec 12T motor, 48T worm, 4:1 ratio. RA 20T motor 48T worm, 2.4 ratio.

So the approx distance between centres is 42mm. The bore diameters of both pulleys is 5mm so would the belt length be 84mm + (5 + 5 /2) = 89mm? Or as close as I can to that? I do have a little play in adjustment. Here's an image of the DEC axis (I hope I've got that right and it's not the RA axis!) motor which has a centre to centre distance also of 42mm but the bores are 6mm and 5mm so (6 + 5 /2) so 89.5mm belt length?

@yuklop thanks. Would love to see some of your OnStep builds. Going to measure and order the GT2 belts today or tomorrow. The attached image shows a tight fit for the belt and no idea how I'm going to get a measure in there!!!!

Hi @yuklop Mine's going very slow. I've built the MaxPCB version and it works surprisingly, I've had a lot of help from George Cushing in getting the firmware right (I think). I've printed a couple of stepper mounts and attached them to the EQ3. I now need to work out how long the belts need to be. I'm awaiting an email from George on the correct way of measuring for this. Where did you get your belts from by the way? Once I've got them fitted I can then test it all out before going to work on redesigning the stepper mounts to neaten everything up. Cheers Daz

Hi All, I'm in the final stages of trying to fit an OnStep goto system to my EQ3 Synscan mount, doing away with the stock control box and motors. Has anyone done something similar? Cheers Daz

Thanks @Stu but not sticking. Putting it down to the fact I have covid...

I should have added guys (and thanks for the replies by the way) that I know what RA & DEC mean I just can't remember what axis they're on!

Hi All, I've got one of those mental blockages where for whatever reason I'm unable to remember which is which with reference to RA & DEC. Is there some tips / rhyme or something that can help me remember? Cheers Daz

Thanks. Any pics?

Stunning!

Ah...thanks...just checking!

Thanks but this is what has got me thinking. How can the motors move the scope freely if the clutches are engaged?

Hi All, This may be a really stupid question but I was thinking last night that if I have to engage the clutch to stop the mount from moving when not in use, do I need to disengage them when it is in use? In other words, if the motors are fighting the clutch when it's engaged that can't be a good thing! Cheers Daz

Perfect. Thank you!

Thanks. Is there a UK wide list of astro clubs or do you know one near me in North London / Herts?

Hi All, I understand that bigger is often better but how much better is my question. For example, I currently have an ST102 with a 102mm diameter objective lens. Would something like a William Optics Zenithstar 73 III or RedCat 51 outperform it for astrophotography use and if so why? Cheers Daz

Great Pic @vlaiv

Yes, looking for a ZWO mini guide and an ASI120MM camera. Not sure how long the ST102 will be with me for as everyone has slated it as a scope for AP work so will probably look for something to change it to. Any ideas and a value on the ST102? The ASI183MC will stay for quite some time as I don't have the money to upgrade both!

That's right. It's a Startravel 102. I'm waiting to find a used guide scope and camera and will be using PHD2.

According to astronomy.tools CCD resolution calculator my resolution is 0.99" / pixel if that helps?

Thanks @Same old newbie alert for the reply too. How do I find out my image scale? I have a ZWO ASI183MC camera.

Yes, I commented on that thread but the OP hasn't posted any replies yet.

Do you know what the performance of my EQ3 goto mount is? I'm planning on upgrading it using the OnStep system shortly too.

Thanks guys for the reply. A lot of it went over my head to be totally honest but I need to learn more about this stuff.