SteveBz

Done. Seem to have got it down to about 1-2 secs. Ie less than half the original. I don't know what the worm still holds for me. It's harder to test. I'll try puting a marker on the OTA itself.

Bottom meaning the one with the blue cable tie. I'll do as you suggest.

It's a bit runny. I thought I had some motorbike chain lube but I can't find it.

You can see I've put a blue cable tie on the bottom spindle. When I change direction I can count to three and it has just started moving, so I'm thinking 2.5secs.

OK fantastic> Done it. I feel I've shaved about 1 sec off the top gear. But there is still 2-3 secs between the top and bottom gear. How do I do the bottom one? Can I have a belt-drive kit please? S.

Oh, wow. I'm a gonna do it now!!!!! I didn't see that. 😀

Yes, I've backed off from 5 mins to 3mins as well but I haven't really got the unbalancing/small PA error thing working well. Dithering hits everything. Every time I dither, it takes much of the following exposure to settle. Tx, Steve.

Hi Martin, So I did lift off the motor and give the worm gear a little tighten, but I didn't go the whole hog and take off the worm covering. I should do that tomorrow. But if you look at this photo, the top cog contributes a lot to the slack. If I run it back and forth, there is a real deal maybe of 3 or 4 secs. Even if I fix the worm gear, that still leaves almost too much to handle from that top cog. It seems to me that I need to get a belt-drive to overcome that alone - or use compensation. What do you think? Regards Steve.

Hi Budgie, Thanks for this. I don't really want to strip it right down, but it maybe a good idea to take the worm off and make sure it's fitting snuggly. Do you know how to set the phd2 backlash compensation? I'll try tomorrow. Looks like we're in for a week of fine weather. Tx Steve.

I thought I recalled that you were a Siril user. Is this the color photometry correction, or something else?

Wow, twice the price of an mpcciii for a smooth tube. So I take it removing the brass compression ring didn't work. Did you try an angle-grinder on the offending shoulder bit? A bit offensive, I know, but if the slope went the other way it would pull it in rather than push it out. Maybe a slow drill would be better. Steve.

GPU? Like a computer card? What does that mean? Steve.

Hi People, I have quite severe backlash, such that guiding assistant just gives up. It seems to be about 11 secs in total, the one time GA came back with anything, but it's about 3-4 secs if I measure it by hand. Here's some guiding. Actually, it's worse when I'm dithering. So, I tried measuring the backlash with by counting and it's about 3-4 secs. If I used PHD2 guiding assistant, mostly it fails, or it comes back with a very big number, like 11,350 msecs. I tried entering this: But then I got a see-saw mechanism, even when I dropped 8,000 to 3,000 it was the same. I've taken the motor off just now and looked at the grub/hex-screw mechanisms. One hex-screw was loose, so I tightened it to hand tight and let the grub-screw off an eighth of a turn. I'll look again this evening. I ran a three hour sequence of exposures on NGC6888 (with dither) and this is what I got on EVERY image. Amazingly, they stacked nicely. So last night I ran without dither and it was mostly OK. What I want is full dither, but to do that I need to deal with the backlash. Here's a photo of the motor and gears, most of the backlash seems to come from the top gear (ie the 12-tooth gear and its neighbour). I guess the rest comes from the worm-gear: Does anyone have any suggestions? There doesn't seem to be a belt-mod for the EQ5 as far as I can see. Maybe there are better Dec backlash compensation settings I could use. Thanks, Steve.

I did think about that. Have you done it? Are there any repercussions? Sometimes it just makes things worse! If I use a woodworking G-clamp (with rubber feet!), it does actually hold it in place. But then it doesn't look quite so lovely...plus the question of additional weight. S

Hi People, I measured the new spacer and it's about 3mm which would put me exactly on the 57.5 line. However, the ridging on the mpcciii plus the compression ring cause the whole camera to slip out by a further 0.75 of a mm or so, putting me just over. However it's a great improvement.

Hi Alacant, Thanks for that info. It clears up the problem. Actually I had 2 spacers to choose from. I'll remeasure in the light of this information. Maybe I can even improve it some more. I can certainly improve the focus a bit, and that might give me more stars when I'm pointing away from the milky way. I've used lockdown to make huge strides in my equipment and software. Next I really need to look at that dec backlash. It's becoming the highest priority by quite a margin. Regards, Steve.

I nearly always buy my stuff off eBay. My C8-N a 200 mm diameter Newtonian with 1000 mm length cost 100 GB pounds including a frozen EQ5 mount. I tried to fix the mount but ultimately bought a goto EQ5 from a member of my local club for 300 pounds. Total 400 pounds. It still works beautifully. eBay is your friend. I just posted a Canon DSLR to Poland for 12.50 pounds postage and tracking. Also, local Astronomy clubs are very welcoming. When I joined they just adopted me and lent me equipment to try out. So that was great too. Good luck. Steve.

Hi Tommohawk, Thanks for replying. Yes, I think there must have been a slight tilt. I hope I've fixed that now, but the most important thing was I inserted the OAG m48-m48 spacer, which is about 2 mm between the OAG and the MPCCiii and amazingly it works fine. I have no idea how, but really it's beautiful. I have also inserted a 5mm CS-C connection spacer and the OAG focus is also much improved. I now have very round stars in the OAG and lots of them and the main image looks good. Looks like you are based near to me. Regards Steve.

You just have to 'stretch' the histogram more using your tool of choice. Asinh is the preferred stretch, available in a number of tools. If you haven't got your head round curves yet, there are plenty of vids on YouTube. Once you understand what it means you can easily fake asinh to produce the same effect. Steve.

Hi Stu, Yes, I've just bought a 450d as well and it's much noisier than the Nikon D5000 I was using before. At iso1600, the noise and banding really scream out. I used 800 last night and I really think I need to knock back to iso400. The fact that your noise is clustered shows you were not using dithering. It's a must for noisy cameras. I've had to convert to Canon because I've just bought an OAG that only has Canon connectors. Regards, Steve.

Great photo. Nice to see you using Siril.

I agree with Kevin. I would also add that now I've upgraded I'm no longer portable, so I use an EQ3-2 plus small newtonian for portable events and for testing. My eq5 plus C8-N remains permanently set up in an observing shed. Staying small and light is to remain mobile. Regards Steve.

Hi Astrid, Astrophotography is a journey not a destination and certainly an EQ3 will give you some photos. You won't be able to do long exposures without guiding, and an EQ5 might be better, but it's much heavier. I assume you are thinking of the 150P (P for photography). There are lots of other things you'll have to think about, like manual, vs driven, vs GOTO. Manual won't give you much in the way of photography, but drives or GOTO will both allow photos. Good luck and welcome to Stargarzersloungse. Regards, Steve.

I've just remeasured the distance from the sensor mark on the camera to the TOAG/MPCCIII junction as 54.5mm.

Hi Guys, I just decided to upgrade my guiding to OAG from guide-scope. I hope I've got the spacing and things right, but I seem to have a deal of coma that wasn't there before (and a bit of gradient). Here's a picture followed by a full description of the problem: I have a Newtonian C8-N with a low profile focuser so I bought a TOAG like the Orion TOAG. Because I had a Nikon camera, I had to switch to Canon to make the T-ring adaptor work, so in fact there's a steep learning curve with all this equipment: Canon 450D, TOAG, QHY5L-ii m. Plus existing Newtonian and MPCCiii with light polution filter. After a lot of faffing around in daytime looking at the local trees, I managed to get it to focus on both cameras and two nights ago took about 90 mins of NGC6888 (see above). I was quite pleased with the focus and guiding and it looked OK apart from the gradient and coma. This post is really about coma. The TOAG comes with a number of spacers/ adapters and the MPCCiii comes with a couple of small spacers and adapters. With the Nikon I had both adapters in place and it worked well. As I recalled these were for the Nikon only because of it's slightly different flange-depth. I thought the Canon didn't need then so I took them out. As you can see the Bottom right is especially coma filled, but to some extent all the way round. I imagine it's worse in one corner because maybe my collimation is a tad off, but the bigger issue is coma. My main optical train is Canon 450D DSLR->Canon DSLR thin profile T-ring adapter->TOAG->MPCCiii->LP filter. On the TOAG side, it's not yet quite right and gives strange shaped guide-stars, but that goes: QHY5L->c-t adapter-> TOAG (I have a 5 mm spacer on order). I hope if I can improve the coma in the main cam, that will improve the guide-cam too. Does anyone know anything about the relative spacing of the MPCC iii in a Canon/TOAG environment? Regards, Steve.