Adam J

I don't think its cables Olly as the fan tail is moving to a different rotation in different parts of the image always pointing outwards from the centre of the optical axis. So its more likely a optical problem, probably with the edge of the primary mirror.

I agree that halo is not normal and I think that something is wrong with the scope. Lots of people with similar issues recently. OP I would contact your supplier. Adam

Honestly, I would say that some of the stars are slightly bloated and that you need another 1mm or so additional back focus as you have not fully eliminated the field curvature looking at M31. However, those TS 72mm (and WO 73) doublets do tend to produce slightly larger stars anyway so it may be more the scope than it is the reducer. But I guess that is why people pay for triplets. Adam

How is the chromatic aberration with that x0.6 reducer? A common issue with cheap reducers below 0.8x? Adam

No its the Bayer matrix interfering with the sub pixel estimation of star position nothing to do with sensitivity. Adam

Oh its a huge difference in my opinion. It looks and performs like a mini HEQ5 pro.

The Star adventurer GTI is way ahead of a Eq3 pro in my experience, I get 0.5RMS guided from mine on some nights and thats at almost the full stated 5kg load. I am guessing that figure must be quite pessimistic. you will not do that with a Eq3. I would say that pushing it at far as 7Kg with a 70-80mm class scope would not be a problem at all. Now if we mean the AZGTI then I would agree with you more but still think its much more user friendly than the EQ3 pro, at least once its converted for EQ. To step up from either you really need to be looking at the EQ5 pro or the EQM-35. Adam

I think you will be waiting till next astro season if you wait for a SA GTI mount, they are ideal but just not available right now.

My reaction is that if you think you need a 5m usb cable for a guide camera, you are doing it all wrong. You need a usb hub on the scope.

DSLR have two filters that in the case of canon at least can be removed to allow full spectrum operation (350nm - 850nm) hence full spectrum = limited by only the sensor and not restricted by any filters. In terms of dedicated cameras some OSC will be full spectrum and some will come with a UV/IR or IR only Cut on their optical window, you need to read the fine print to know for sure. In the case of mono cameras they are almost universally full spectrum. Adam

I will advise you as best i can, like Olli above my first point is to push you well away from the ST120 OTA it is compleatly unsuited to the task of DSO imaging. CAMERA: Altair Hypercam 183C PRO TEC COOLED Colour 20mp Astronomy Imaging Camera (altairastro.com): £799 (Cheapest new cooled camera available, if you can spend £100 more the 533 version of the hypercam is much better) TELESCOPE: Sky-Watcher Evolux 62ED OTA | First Light Optics £329 (Do not worry about the small aperture and size of the scope it is all about being able to fit the large DSO targets on your small sensor, this scope is much better corrected too). FEILD FLATTENER: Sky-Watcher .9x Reducer/Flattener for Evolux 62ED | First Light Optics £229 (required to prevent optical aberrations in the corners of the field) MOUNT: Sky-Watcher EQM-35 PRO Go-To Modular Astronomy Mount | First Light Optics £659 (It is a tough call between this and the EQ5 pro but for me this is just slightly better, people say HEQ5 pro but it is out of budget and not required at this focal length also you should be able to lift a EQM35 in and out of the house without stripping it all down). TRACKING CAMERA: ZWO Mini Finder-Guider & ASI120MM-Mini Bundle | First Light Optics £222 (all you need for guiding). FILTER: Optolong Dual-Band L-eXtreme Filter | First Light Optics £239 (great for nebulas with a OSC camera) GUIDE SCOPE: It's packaged with the guide camera for you, see above link. CONNECTIVITY: Lynx Astro FTDI EQDIR USB Adapter for Sky-Watcher Mounts (see description for models) | First Light Optics £33 (2 m long model will allow PC control of the mount via eq mod). Total: £2510 (will be some delivery charges) All in all, that would be way way better than what I started out with and I did well. But a word of warning DSO imaging is difficult and so dedication will be required from you both to master all the above equipment and get the best out of it. Think of it as something that you need to build up to as opposed to jumping right in. For a beginner just getting a good alignment is a difficult task at first, then guiding, then image capture. Adam

Interesting as i have good clearance with my 1.25inch Astrodons, What I find is that its not the filter wheel that causes issues its some t2 extenders whos thread is too long and protrudes into the wheel when fully tight. As I generally need 1-2mm of spacers to adjust back focus for the 3mm thick astrodon filters I just place them on that thread and everything is fine. Adam

The 294 is a different beast to the 269. Adam

It is what it is. Give it a go.

The silver lining is that at least in this modern era you can slap a duel narrow band filter onto it, back in the day when these cameras first came out no such filter existed. So yeah duel narrow band like the L-extreme and 30min exposures.

What you really need to see is a dark frame from the camera, you dont say but is this an OSC or a Mono version? If its OSC I would stay clear as they never had a very good reputation unlike the mono version which certainly did. The OSC Bayer matrix seemed to hit the QE badly. All I see from the images is that as you say he is not using the camera to its best ability, these look like very short exposures. I have produced much better with a Canon 1000D even when I first got started. Adam

USB is much more reliable, i simply cant imagine using the WIFI connection myself not reliable enough for my taste and with no external antenna on the SA GTI the range is very limited. Adam

I would get a Mak if lunar is what you war looking for probably the Skymax 102 or 127. Both very easy to handle and will deliver better results than the EVO 72ED, the smaller of the two is reasonably quick to cool. Adam

No you can colimate refactors with a Cheshire too by shining a light source down the Cheshire reflector with the lens cap in place you will see reflections from each lens surface that should be concentric if colimated correctly. You do need a lens cell that has colimation screws though. Not all the cheaper refactors do. Reading further down this thread I see several procedures that I really do not recommend the OP undertake, moving the lens cell as a whole is one thing messing about with lens element alignment is a one way ticket to hell. Undoing the lens retaining ring.....really bad idea. De-centred lens elements on an APO leads to lateral chromatic aberration. I also see that the Cheshire method was explained. All in all this scope should have been returned and exchanged for a new scope. Adam

It won't be an issue have had mine out for years, no dew forms on it due to slight heating when running.

The flats are as expected but are they calibrating the lights correctly or do you still see the pattern in the calibrated stack? If not the it's ok.

Honestly I would be keen to split out the blue and green channels as the right image looks very red although I see better ha contrast in the right hand image I am worried that it appears to have less colour variations possibly indicating less OIII signal. Could be processing but a side by side oiii comparison will tell the story.

Honestly the red channel simply doent look focused. CA in the red perhapse?

As above what are you wanting to image and with what equiptment (telescope mount guiding). Adam

Patterns are present irrespective of gain if you have them. https://www.cloudynights.com/topic/779735-asi294mm-flats-lets-compare-notes/ Some images and other info in this thread. Adam