Craig a

I’m using asi533 mc pro, it’s not vignette, it’s very similar to this......... https://www.cloudynights.com/topic/557931-concentric-coloured-rings-caused-by-flats/

I forgot to add I’m using a led Tracing pad to take my flats, with a t shirt over the aperture

These rings arnt around stars or dust bunny’s these are big rings that emanate out from the center of the image gradually getting less further apart towards the outer part of the image, the scope is flocked and I’ve painted all screws and bolts with Matt black

Ok I’ve got a problem with the f4 skywatcher coma corrector particularly it’s length, when the cam is in focus the corrector protrudes into the tube by about 15mm with the ir/uv filter screwed into the end of it and it’s causing me big problems in my images, I’m getting some horrendous rings in my images, so my flats just dont work, it isn’t protruding far enough in to take chunks out the stars but I’m positive it’s giving me the rings problem, I’m sure the coma corrector is just too long, I have a moonlite focuser fitted to my Quattro 10cf, now is there anything I can do to combat this or is there a different coma corrector designed for f4 that isn’t 100mm long like the sw is? At the moment imaging just isn’t worth it with this issue, I deleted the last image session in a rage so I carnt show the rings I’m getting so I hope you can understand what I’m saying

Fantastic set of galaxys, sunflower looks awesome one of my favourites that galaxy is

More like an eq60 😂 but that is seriously cool

That’s a nice sparkling image, m36 is probably the nicest cluster in Auriga

Doesn’t sound right to me having to have the secondary screwed right up against the holder, to square the focuser properly on tube you need to take the secondary out and mark the point directly opposite the centre of the focuser hole which means taking the focuser off the tube aswell, there are vids on YouTube of how to do it, but I wouldn’t be happy with a secondary that’s butted up against its holder, doesn’t leave much room for adjusting the secondary does it, what Newtonian is it you’ve got?

I have an f4 Newtonian and honestly wouldn’t even touch a lazer for collimating the secondary I do use the barlowed lazer to do the primary,you should be able to get the secondary centred under the focuser, I used a concenter for the fist time last week and got the secondary perfectly centred and round under the focuser, I wouldn’t use the concenter to do the primary though as the movement of your head looking through it isn’t stable enough to to keep your eyes fixed looking at the centre circle hence the barlowed lazer is a better way of doing the primary, that’s my findings anyway hope it helps by the way using the concenter has got my secondary looking the best it’s ever been under the focuser

My concenter arrived last week and got straight onto collimating my Quattro 10 inch, have to say it’s a great bit of kit I don’t think my seconary has ever been looking so good it’s perfectly centred under the focuser and is perfectly round aswell, it’s expensive but so what we spend 100s if not 1000s on our scopes so what’s 70 quid to get probably the best collimation ive ever seen in my scope

Ok thanks all, I managed to focus the OAG on a distant roof I could see, I focused the main cam first then focused the OAG took abit of fiddling but may need a final tweak under the stars but so far it working just need these relentless clouds that have been here for over a month to disappear so I can try it out, but the weather for the foreseeable future is looking rather bleak

That’s a really interesting image and them set of stars forming a D shape inside the nebula is fascinating

That’s an absolute beauty

Yes the circle should remain stationary when it’s locked down

Thanks for that olly, I shall try to get focus as sharp as possible then, I’m really hoping I will be able to pick stars up in what’s going to be a really small fov on the OAG

Thanks I’ve done the measurements and think I’ve got it reasonably close, I’ve got to bring the rig inside this weekend to fit the rail kit to the neq6 but from my window I can see the Welsh hills about 15 miles away so I can finish the focusing in daytime on them

Received my zwo OAG and in the process of setting it up, my question is when measuring the distance from prism to guide cam sensor to get it the same as the main camera sensor, do I measure from the bottom of the prism or centre of the prism?

I’ve just bought one of these today and carnt wait for it to arrive to give it ago, expensive? Yes but in my opinion worth every penny if it helps my images look better in the long run , my f4 scope can give me a headache when it comes to collimating it if this cures it it’s better than buying a box of paracetamol once a week 😂

Ok thank you for clearing that up for me

Thank you for explaining this to me, off axis guiding is a new endeavour for me but I believe olly when he says every newt should be guided this way to prevent differential flexure, so that 30mm you speak of it this from prism to guide cam sensor? Or prism to be less than 30mm away from main imaging camera sensor? looking at zwo website it looks as if the prism holder is 31mm long? Would that mean if I’ve got less than that from prism to main cam sensor I’ve got no chance of reaching focus with the guide cam?

I was looking at the zwo OAG v2, it is 8mm prism https://www.firstlightoptics.com/zwo-accessories/zwo-off-axis-guider-oag-v2.html The camera came with all the spacers to get 55mm back focus I just thought I could swap the 16.5mm spacer and put the OAG in its place, both the same thickness like shown in the pictures on the link, didn’t realise that would change with a faster scope? but I spose I could swap the 21mm I have closest to the camera and put the OAG closest to cam and put the 21mm between the cc and OAG does that make sense?

Makes sense, abit off topic here sort of but the guide cam I’ve got is the Orion starshoot would that be sensitive enough to use on a off axis guider at f4? I’ve read elsewhere that it is no good on an off axis guider because it Carnt pick up faint stars

Ok thanks, super pixel mode? Do I use that when stacking or debayering? Or when capturing? Never used it so not sure how to use it?

Ok so is it possible? I have been imaging with my 533mc pro and 130pds although I like the wider fov I have also got my Quattro 10inch Newtonian and as I’m a galaxy and planetary nebula imaging fan would like to stick the 533 on that purely for the longer fl the Quattro gives me, I understand at 0.78 arcsec pp I’m oversampling and not gaining any resolution because of Uk seing normally being poor, also I understand guiding would need to be pretty good so I would be doing away with the guide scope and buying an off axis guider to help with that, would I be mad going for it as I love my Quattro to bits and have done a lot of work to it and Carnt bear seing it in the corner of the spare room gathering dust!

That’s my point if 316 can withstand sea water in my eyes that’s one of the best