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I use the starfield on the celestron avx, everyone that has looked through it and used it are very impressed. As in woooowwww

Please be patient with me as I have never looked through a telescope and everything I have written is only supported by what I think I understand after reading a lot of information online. My understanding could be incorrect, the information I have read may be inaccurate or both!! Guidance is very welcome. I have just bought a Rowan modified HEQ5-Pro mount and I would now like to buy a 3-4 inch refractor to go with it in a few weeks time. I hope that  a 3-4 inch refractor would allow me to do some casual observing from time to time with friends and family but really I am more interested in dipping my toe into astrophotography and then developing that hobby over the months and years ahead. I wondered if anybody had an opinion on the telescopes I am considering at different prices. A cheaper scope would allow me to buy a better camera to start with although I would expect, if I enjoy good success with the challenges posed by imaging, to be able to upgrade a cheap camera before the end of the year. Here is my shortlist which I have arrived at with the stipulation that the scope must be about 5-6Kg or under (for imaging on the HEQ5-Pro which has a limit of about 8-10Kg for astrophotography) and contain FPL53 glass to help with CA. William Optics Zenithstar 81 with the 0.8x field flattener/reducer. The aperture is 81mm and the focal length is 559mm allowing hopefully decent solar system observation with up to 160x magnification. WO has a decent reputation and the scope has been well regarded for quite some time. This is the cheapest option and it would allow me to spend about £400-£500 on a starter astro camera for planetary work and a good range of DSO. I would be able to buy a few decent Vixen SLV eyepieces and a Tele Vue barlow to get me going so this would be a decent starter setup but with the cheapest scope. Starfield 102 ED with the 0.8x field flattener/reducer: The aperture is 102mm and the focal length is 714mm offering slightly better (and more flexible) observation because of the larger aperture. I have sometimes read that apertures less than this do not give satisfactory viewing but opinions vary. This scope is just a little bigger and heavier than the ZS81 but negligibly so I suspect in practice. The extra cost really means a little extra aperture I think as I expect the optics and build quality to be the same as the ZS81 but I could be wrong. The budget for an astro camera may be similar to the budget for the ZS81 but I would need to rethink the eyepieces and/or barlow to do that. Matching a camera to the Starfield may be a little harder as the focal length is longer and I believe that some cameras paired with the Starfield/reducer may result in oversampling (according to online calculators anyway). This may be not an issue in practice of course! William Optics GT-81 IV with the 0.8x field flattener/reducer. The only triplet and so presumably the best optically and certainly the most expensive. This scope has been around for a long time and seems to be consistently well regarded. It has the shortest focal length at 478mm and is commensurately the 'fastest' scope at f/4.72 with the reducer. It would seem that this is the best suited to astrophotography with less time needed for exposures although I feel the other two would be very capable. I would really only be able to start with something like an ASI224mc astro camera (which seems odd given the cost of the mount and scope) allowing me to literally learn astrophotography technique but on a very limited range of targets. Astrobin does have some examples of good work with the ASI224mc so it may not be a truly terrible option if it means a better scope. I would be able to at least get going though and would seek to upgrade the camera as soon as funds allow; at least I would have a mount and scope that would not need to be upgraded for some time. I would only be able to buy one eyepiece and barlow to begin with but that would change over time. I have already budgeted for a WO dielectric diagonal and a dew heater and I am aware that some software such as PixInsight can be expensive but there is a lot of very well regarded free software available which is brilliant! The other potential extras much further down the line certainly can add up such as an electronic focuser, electronic polar alignment, a guide scope and camera and well, it is a long list! So, I have three well regarded scopes at different price points. Am I misunderstanding or underestimating anything? Which of the three options would you take and why?  

I average about 40 mins tracking on my platform. It actually lasts longer because I have it switched off while I am star hopping to my target and only switch it on when I am in the acquisition region.   I have not had balance issues and the recessed feet in the platform gives additional stability. On the basis that most commercial 10 inch Dobs are mechanically fairly similar, I think that it should work. BTW Peter found a great app which cheaply does away with the star hopping bit and turns the Dob into a GoTo scope. John    

I got a 300mm f2.8 lens from eBay, but it turns out the mount has a worn locking pin so it can rotate a bit when my astromechanics adapter is fitted, and the adapter is slightly too thin on the mount face leading to wobble (checked with genuine ef camera, rotation is the lens' fault, wobble is the adapters fault) I was able to use electrical tape around the flange face to provide enough packing (2 layers) to make it a snug fit with no wobble and resistance to rotation... However upon doing so the adapter no longer makes proper electrical connection with the lens! And it cannot control the aperture or focus. Which is very important as this lens cannot be focused manually. I'm hoping people here might have a good idea or two for me to try, as I really want to try and make this work, and the image I got from it last night (between clouds) showed it is a very sharp lens wide open at aps-c sensor size despite its age and the tilt introduced by the sloppy mount connection. Thanks for any ideas!

You're all welcome, hope it helps 🙂 There's always more than one way to do these things, but I found this most effective. I came across the Subtract method on CN a while back, so I tried it and adapted it to fit into a workflow with Siril. It sometimes gives issues if you have large halo's on very bright stars across a nebulous region, in that the blending might be a bit off and look artificial, but some masking and local tweaking can always be applied.  I never had an issue with noise, mostly just the checkerboard and transparency problem, and I suspected it might be related to varying FWHM values between subs 🤷‍♂️ I'm now on PI and trialing that, and I get the same issue with Starnet2 and the DSLR, so it must be Starnet related. No issue though with StarXT, which is also on trial, but it does cost £70 to purchase (on top of PI) and that doesn't include any of the other XT tools....