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I think that to answer the original question we need to know what direction the drift is in. Is it along the RA axis, the Dec, or some of both? Plate solving a single sub should provide this information, but a trailed one is a bit too difficult.

The code for PHD2 is open source and although I don't really understand a word of it, the guiding stats calculations are contained in almost 700 lines of C++ here: https://github.com/OpenPHDGuiding/phd2/blob/master/guiding_stats.cpp

Many thanks for the prompt reply, Patrick! I guess APT (which is usually warming the camera at this stage) may be the culprit. I'll experiment with making CduC the last item to close.

A small but irritating problem has been apparent with Cartes du Ciel. I use it to slew the mount to target. This works well and a single plate solve, sync and re-centre usually has the target spot on. Start guiding and away we go. At the end of the session we stop guiding, shut PHD2 down, park scope and then try to disconnect and then shut down CdC. Unfortunately, no matter how I go about it, the CdC 'connect' window remains active in the task bar. The only way to get rid of it (that I have found so far) is killing it via task manager. I feel this should not be necessary? Does anyone else suffer this, admittedly fairly trivial, problem, or know a way to get it to shut down properly and close its child window in the process?

Don't think it's coma so much as tilt. Here's what ASTAP measures (28%):

Not quite. The Bias should go in the main group as they don't change, but the flats may very well be different, particularly if any dust has moved around, so you should take flats for each session and group them with the lights. You don't say what camera you are using, is it cooled? Are all the darks at the same temperature and gain or ISO? If they are, then they shouldn't vary much between nights and many re-use a 'dark library' for several months at a time. If the camera is an uncooled DSLR howeever, you may find that the darks do more harm than good and may not be at the same temperature as your lights, although experiences and individuals vary quite a bit on this.

Wow, you've really caught the dust there, Alan. Nice work! It might be my screen (or imagination!) but there seem to be some darker artefacts on the left edge and I wonder if these are interfering slightly with the dynamic range. perhaps cropping them out and re-balancing would show a different result?

Think we got it this time. Dreadful seeing last night, but think the marked. blurred dot matches this image ?

Can't be sure but are the truss tubes fully extended? If not, that might account for lack of focus.

Possibly, Vlaiv. I last did M31 with a 200 mm Canon lens this time last year. Here's a quick 'n dirty reprocess just to show there might be something there. and a zoom in. With strong imagination there's possibly something there:

Thanks both! Really blown away by seeing stars in another galaxy - wanted it to be so but couldn't quite believe it, that's made my imaging month.

Been revisiting previous targets with my still-new-to-me ASI 2600 MC. Last night was M33's turn and the extra detail that is becoming apparent compared to images from 5 years ago is throwing up all sorts of questions. One I'd like some help with from fellow SGLrs is the detail in this heavily cropped, very quickly processed and probably over-sampled snippet. What are the blue dots in the spirals? Surely they can't be stars (at 3 million light years)? And their arrangement, closely following the galaxy's spiral arms, suggests they aren't foreground objects either. Don't think they're processing artefacts, although they might be. Can't find any details in my usual sources on-line and wonder if anyone can point me to a good reference?

It is possible to post process in DSS, but quite difficult to achieve worthwhile results. Dedicated post processing software ranges from free (the already mentioned Gimp is one example) through the moderately priced, StarTools, Affinity Photo, to the more expensive Pixinsight, Astro Pixel Processor or Astro Art, for example. You can also use non-astro software like Photoshop (if you don't mind the subscription model). Many of the paid for varieties have a free trial period, some have an unlimited trial but won't allow saving. If you look through previous Stargazine episodes, some of the already mentioned programs have episodes dedicated to their use. Might be worth a look to see if any appeal?

Not sure how well this will work but Uranus is mag 5.8 at the moment, so might be naked eye visible, certainly do-able with binoculars, and Neptune is 7.9 so possible in a scope. A 5 degree star field chart of each might mean you could get four planets (well five if you include earth) in one night, which would be a nice haul?

If you can't find a supplier of a ready made one, it might be worth using one of the on-line Bahtinov generator programs to produce a suitably sized one and then submit it to one of the laser cutting services? I did this some years ago for my 8" and used black acrylic but for 20" perhaps aluminium or even thin steel might be more appropriate. Might also be worth cutting one out of cardboard using the generated pattern to make sure it works OK before investing in the real thing?

Bob Here's an alternate rendering, this time in StarTools. Like Pixinsight, it has a trial version, but is significantly less expensive if you purchase a full licence. I think you need to take flats and am not sure that 5 darks are actually helping, maybe try stacking without darks and see if that makes a difference?

I'm just up the way in Stirchley. Not sure if it's going to clear tonight!

I put the Bahtinov on the lens hood of my 200mm Canon lens and it works fine like that.

Sorry for the ambiguity; it is Windows 10 pro.

Me too! 64 bit pro version. Think all OS versions of ST use the same algorithms? Happy to be corrected, if this is not so.

There are a couple of threads over on the StarTools forum that might help: https://forum.startools.org/viewtopic.php?f=8&t=1378#p6859 and https://forum.startools.org/viewtopic.php?f=8&t=1999 but if not, then posting your specific issues over on that forum should get Ivo's ( @jager945 on this forum) attention, he's usually pretty quick to respond.

Here you go, processed in StarTools 1.8.518. Not sure if it's what you were after, nor why there's no colour? But you have some detail in the dust lanes and some of the outlying nebulosity. The focus is possibly a bit soft, but nothing desperate. I did have to crop quite a bit, and you might want to revisit your calibration frames, particularly the flats, to see if they can be improved to help with vignetting, but that's way better than my early attempts at M31, so well done!

I had hoped to get a bit more data for this one, but that's beginning to look unlikely, so thought I would post what we have so far. 90 minutes with an L enhance filter and 40 minutes of RGB for the star colours ASI2600MC using the SW190 MN on an AZEQ6 GT. Very little of the Oiii showing so far. Comments welcome, as always.

Afraid not! Cold and cloudy UK, unfortunately. I just used the location function in Stellarium to show the view from the place shown in your post.

Non expert disclaimer here, but my reading of the specs for an EQ8 is that you have 10° of adjustment either side of the central position of the 'north pin' so while 'as-close-as-possible' would be nice, you can be a fair way off and would still be able to achieve polar alignment.