StuartT

and now after my Photoshop adjustments. I think the one with the calib frames looks a little over-processed. I think I prefer the subtler look of the one without any calib frames With calib frames Without calib frames

ok, so here is a direct comparison. a) is the one using previous session flats and has a pretty terrible gradient. b) is only stacking the light frames - no calibration frames at all. This is just as they both came out of APP so none of the usual post stack fiddling I normally do. I'd say that b) wins a) b)

ok, so would it be better to ; a) use flats from a previous sequence (with a slightly disturbed imaging train) b) use no flats at all

Thanks. Would you say it's ok to re-use all the calibration frames from a previous night? I did unscrew the camera, but everything else was left in place

Thanks Adam. I did eventually get it sorted out. It was in fact a mechanical problem. My fault for not tightening the screws enough. No app can fix that!

great! Thanks so much everyone 🙂

Backlash and step size both at 150

right. good point. I tend to do all my calib frames the next day anyway

In tonight's session, the clouds rolled in and ruined my last few images. I want to remove them before I stack everything in APP. But I can't view FITS files in anything. So is there an app that will let me scroll through them all and delete the bad ones? Or can I just submit them all to APP and it will just ignore the bad ones?

I wasn't really thinking about the calibration frames. I assume those are unaffected by a meridian flip. What I was asking was whether or not I have to rotate the images from the second night through 180 degrees so they match up with the images from the first night. But it sounds like Astro Pixel Processor is clever enough to do that on its own

Great! I shall try this. Thanks

oh really? so if I add the two sets of lights as two different sessions it will figure out one set is the 'wrong' way up? Cool!

Sometimes my scope is one one side of the pier when I shoot one sequence and then on the other side when I shoot a second night. This means that one set of images is rotated 180 degrees from the other. If I am combining the two nights in Astro Pixel Processor do I need to tell it that there is a difference between sets? Or is it possible to rotate one set of FITS by 180 before I start stacking? Thanks

Yes!! I can't tell you how pleased this makes me 🙂

here is the centre (save you a bit of searching around) RA 21h 0m 2s Dec +43d 41m 42s

Hey thanks! I am a newcomer too. This is only my 4th DSO. I have now added the info on acquisition details. In terms of finding the target, I use NINA's framing assistant which is great. I knew I wanted to be in the N America nebula somewhere (as there is lots of lovely stuff and it's too big for me to fit in all at once in this focal length). So I entered NGC7000 in the framing assistant and it steered the scope there. Then just I adjusted position a bit until I liked what I saw.

you know what? I now feel like a dummy. 🤦‍♂️ Just been out to check the rig and sure enough, there was quite a bit of play between the coupler/shaft when I turned the coarse knob! I was SURE I'd tightened that up! Anyway, I have now tightened both grub screws really tight and there is now no play (at least, no visible play). So if I get a clear night again tonight, I'll run another autofocus curve.

yes. I tried that last night. The graph looked even worse. Maybe the focuser motor is defective?

150mm Esprit (FL=808mm) Astronomik UHC filter ASI 2600MC Pro unguided 143 x 35sec subs gain=100 1h25m integration time

ok, take the point. But isn't a setting of 1000 going to take care of that?

Thanks. That's a nice illustration. Except that I don't think this is backlash, as even dialling the OUT backlash to 1000 doesn't fix it. So there must be something else going on. I think I probably need to dismantle it and try again. Maybe the grub screw isn't quite on the flat part of the shaft or something.

So this is the bit I don't understand. I was thinking the backlash meant the autofocus doesn't work? But maybe that is wrong? Do you mean that the flat part on the right doesn't mean the minimum is in the wrong place?

excellent! Thanks! I don't want to waste a clear night because I can't work my new focuser! 😉 Only problem is, it's very hard to judge what the best focus is on a laptop screen! It's going to be around there though, I guess. 20 or so either side prob isn't noticeable

Yes. That's what I meant. Sorry, I said lowest one, but I meant the x-value of the y minimum point, so 24600. Problem is, now I have attached a motor, I can't use a Bhatinov mask like I used to (because the motor seems to prevent you turning the focus knob). Unless I just take the motor off the scope.

so I assume the white points on the graph are actual measurements of focus (star width?). So if those are actual measurements, surely I can just read off the x-axis number of the lowest one and enter it into the focuser? Then it should be in focus, right? I assume 50 or so either side won't make a lot of odds