Sien

Thanks for your advice, will take it on board next time I have my rig stripped down.

What Stevie said. I'd wager a few of us are just unlucky in the QC department or the handling of the scope in its travels to your door. I checked mine again today and it was a fair bit out of whack checking with a cheshire, there's almost no room to maneuver between the focuser and the objective lens which leads me to believe the focuser assembly attached to the scope isn't entirely level (I think it might actually need a shim or grinding down the surface to tilt it the way it needs to be). Get what you pay for I suppose? I got it as close as I could but it took a LOT of back and forth, had to hold the front objective lens firmly in one corner and tighten it up while also trying to adjust the grub screws around the focuser. It's difficult to keep the lens where it needs to be because there's a rubber spacer between the outer ring and it just wants to grab the lens and spin as you are trying to tighten it. When you get it where it needs to be, I'd say it wouldn't hurt to apply some thread locker so it doesn't move with future bumps and such. Afaik, you'd use a laser to square your focuser, and a cheshire to collimate the lens from there. I've had fun with this scope but, think I'll be upgrading in the near future. This was my first refractor, but I spose I learned a lot, whether I wanted to or not I would have returned the scope but as a beginner I knew none of this until I was out of warranty.

That sucks, hopefully you can figure it out eventually. I think I'll pick up one of those tilt adjusters you linked just to have handy. Mainly what was laid out in this post (adjusting focuser via cheshire, adjusting the objective lens..the lens has a rubber ring around the outer diameter between the front placeholder that needed a bit of fiddling to get right) but I'm planning on going through the routines I came across in this topic here, it's a bit involved but hey, what isn't in this hobby! I'd already started collecting some data on the veil nebula and didn't want to disturb the image train until that's complete. Honestly I'd probably be happy leaving it well enough alone at this point as the problem is mainly in one corner but I would like to do some mosaics in the future so... Either way, I guess at some point you have to throw in the towel and just try and enjoy what clear skies you have, plenty of rainy nights to bang your head over the rest

Hi @WolfieGlos, wondering how you've gotten on since? While my issues have improved substantially I'm still fighting with some eggyness in the corners, I'll probably try bumping my backspacing to the 60mm mark and see how things are looking from there.

@WolfieGlos Are you using a field flattener? because without one your stars will appear "eggy" around the edges of the frame regardless of what you do. Field rotation due to polar alignment error, focuser slop from the weight of attachments and tracking accuracy can all add fuel to the fire. I'd suggest taking some short exposures of stars and checking individual subs. Periodic errors in your mount will introduce minute star trailing that will affect the end result once you stack (and wind, orientation of the scope in the sky, weight of cables etc can all contribute). Apologies if I'm preaching to the choir I found the cheshire quiet helpful to eyeball things as I went along and made my adjustments. As I mentioned previously, in my case I had to reset the orientation of the objective lens to get things right. I'll still be tinkering away long after this post! While software is useful for analysing what's going on, you should trust your own better judgement too, how happy are you with the pictures, can I get away with cropping 5% or more of the frame etc.

Sorry Wolfie was away on holiday and just came across these posts, I had a 1,25 adapter handy from my 10" dob so just slotted into that. The glue on your tube looks a bit suspect alright, have you measured from every side from the silver ring to the end of the tube? It's possible they applied the glue and then moved and set it after, perhaps leaving some residual that makes it look like it's offset? In my case I could not for the life of me collimate or get the focuser set correctly until I opened the ring on the front of the scope and moved the lens objective itself. I relied solely on the cheshire for my adjustments, I felt that was enough and am a lot happier with resulting images from where I started but I'll tinker a bit more with spacing. I had to set the lens and fiddle and twist the retaining ring until I was happy with what I could see through the cheshire. PS, plenty of people collimate their refractors with cheshires and lasers, I watched a vid where it was done professionally and they literally suggested it was better to learn how to do it yourself because they can fix your scope but unless they hand it to you, they can't guarantee it'll still be in shape after shipping.

Thank you, I had set these previously when installing the electronic focuser but it seems things had worked themselves loose, things feel nice and solid again after re-adjusting. I also have an EFWx8 hanging off there, probably asking a lot of this little focuser!

Don't we all I took some pics tonight in variable weather, had gusts of wind up to +20kts but the sky was clear so I figured no time like the present. Stacked less than an hour of L data, tracking fluctuated between 0.5 and 1.5 arc". Stars look pretty damn good to me after collimating with the chesire. I recently installed a zwo eaf and it's driving me bonkers with the 72ed. Worked fine for a while but now i have slop and sometimes the tube slips altogether...if i happen to bump it while moving things it doesnt know where it is etc. Story for another day! https://i.imgur.com/SmjZCRZ.jpg elephants trunk last night with slightly more favourable conditions https://i.imgur.com/Eun72Kr.jpg

I would say 800 possibly lowest for long exposures but for short subs that won't collect enough data, imo anyway

@Lee yep, I put a smidge of superlube on all my adapters now, been down that road one two many times now and it's not fun! Appreciate the diagram fozzy, I wonder why so many are having more success at 57-60mm, I realise a mm or two either side is to be expected but 5 seems a bit excessive.

Hi William, I started off with a similar setup and hopefully can add a few pointers. After polar alignment, balance is of the utmost importance. I would not use the ball-head for anything other than wide-field imaging with a moderately light setup. Polar alignment and balance are much more critical the further that you zoom. This video includes a good setup routine and shows very clearly how to achieve correct balance in the the RA and DEC. You might need a longer dovetail/arca swiss plate or a lens with ring/dovetail combo to be able to achieve this but it won't hurt to try with what you already have at hand. Good balance will take most of the stress off the motor and in fact, some people even balance slightly east heavy so that the rig is already wanting to move in the direction of the sky while reducing the likely hood for backlash. According to this chart your cameras input read noise starts to level off between 1600 and 6400 iso. I'd probly start with 1600 or go with 3200 as a tradeoff between the two. Make sure any noise reduction functions on your camera are disabled if they exist. If you don't have an intervalometer I would suggest getting one, you could get by if your camera has the software built in but it's just another useful tool to have. Start with say 30s sub exposures at 1600, and try to keep your histogram at least 1/3 to 1/4 of the ways from the left, somewhere in that region means you will have sufficient data to stretch later. As you may already know doubling the ISO has an inverse effect on exposure time, so, the higher you crank it the less exposure time is needed, this invariably introduces noise but that's not too much of an issue as you will be stacking to increase the SNR anyway. It's good to grasp the basics either way. 30s should be enough time to diagnose any issues in your polar alignment or balance routine. Once you have that nailed, you can start to increase further to say 60s and see where you are then, are the stars still nice and round, are you still happy with the quality of the image? You may be able to push things a little further but without guiding at your max focal length that would be a stretch imo. Inspect your images and throw away any that don't look good, periodic errors in your gears, the wind and who knows what will occasionally throw up some doozies so just toss them as you go, there's no point stacking images that have bad data. You'll have much more success stacking 5-10 good quality images than 20 that introduce anomalies that will affect the quality of your final image. Once you have all that down, it's time to learn post-processing but I don't think ill jump into that rabbit hole with you! There are plenty of good youtubers out there now that focus on helping people new to astrophotography, nebula photos, kamil pekala, astrobackyard, cuiv the lazy greek, peter zelinka, all those should help you get started on your journey. Someone mentioned dithering above and you should definitely consider dithering at some point. If you have the wifi version of the starwatcher, it has a dithering function with the phone app so you won't be needing to do it manually. Kamil Pekala has a video describing autoguiding and dithering in the linked video. Worth mentioning that when you use the SA app it stores your last used settings into your sidereal (star mode) and needs to be cleared if you intend on using the mount manually in future. My 2 cents, or loose change might be better fitting, hope it helps you get on the road to taking pictures you'll be proud of. PS: A dew heater is a must as you've already well discovered. I'd also consider either making or ordering a bahtinov mask to achieve proper focus. If your lens is not too stiff it could easily move out of focus over the night due to temp variations, gravity etc so.. it might be worth checking you still have good focus every 30mins or so until you know the limits of your gear.

Cheers Lee, I will dive into that thread asap. I have been trying to unweld two of the zwo extenders to reach ~60mm but I think I'll just have to order more at this point, I've tried every variation and trick in the book without success and I value my wrists!

Thank you, that's what I was going for. I couldn't get to where I needed to be until I loosened up the main objective.

Hello, nope you are correct in saying that. I did some research and people certainly seem to use them and I had one handy so.. I put the lens cap on, shine a bright led through the side of the cheshire and it gives me a view of the concentric circles or doughnuts in view of the eyepiece. I got a bit further in my adventures here.. I was hesitant to mess with the optics but found another post where someone disassembled the 72ed and there are only 2 lenses held in place by the screw in front so figured it might not be too much of a problem to open it all up. Having removed the glue from the front screw and loosened the front element, it seems I can now get much closer to where I need to be (still fiddling away here!). I have a laser collimator as well but will need to make a proper mask to check the accuracy and alignment further. Difficult to capture an accurate picture through the eyepiece holding a phone but this is where I started. I imagine collimation got out of whack due to shipping.

Hello fine folks, first post here but long time lurker as I learn the foibles of this hobby. I've been struggling with curvature on this scope and so it eventually brought me to order a cheshire to check my scopes collimation and sure enough, things were a bit out of whack. I've been experimenting with an ovl reducer and an orion 0.8x reducer/flattener but was still getting some eggy stars towards my corners, my backspacing is currently ~57/58mm but I've read around here it could be anywhere up to 60mm. My question is to anyone who's been down this path and attempted to collimate the scope. When I look through the eyepiece, it's impossible to line up the "doughnuts" in any orientation without physically tilting the focuser. This leads me to believe that perhaps the silver housing on the scope that holds the focuser (and the 3 adjustment screws) might not be square with the focuser. Would I be correct in thinking that? If I tilt approx 2mm, with some finesse I can get the scope aligned but I imagine this is probably not ideal? There is a concave lip machined around the focus tube where the screws go and it's difficult to get anything tightened up and aligned correctly. I'm nearly certain I read someone post here that they had returned one of their scopes due to a similar issue? Any help or nods in the right direction appreciated, thanks.