Seelive

I suppose it depends on your definition of level 😕

You could try removing the stars then applying different stretches before recombining in the final image?

Yes, unfortunately it appears you can only install / run 1 version of DSS at a time but as most (if not all?) previous versions of DSS are available on GITHUB you can easily back-track if you need to.

The last release of DSS used the latest version of LibRaw which for some cameras results in images of slightly different sizes to those created using the previous version of LibRaw, so any existing calibration images became incompatible requiring new calibration images to be created (the same thing happened when DSS changed from DCRaw to LibRaw). (I believe DCRaw was dropped because it was no longer being updated to support newer cameras.)

I thought all existing PAE data were erased if you performed a new star alignment?

How many lights are you stacking? Idealy for Kappa-Sigma to work properly you need at least double figures. If most of your images have a similar overall intensity you could try reducing the Sigma value (from the default value of 3 to something less, say 2) but only just enough to remove the trail.

If you are polar aligning prior to switching on the handset/controller, where are you getting the 'time' value that you set Polaris to on the polar scope graticule 'clock'? From a seperate app?

Pleased to hear you've found a probable cause - sometimes calibration frames can cause more problems than they solve 😕

What are you using to stack the data? I've once seen similar artifacts from one of my DSS stacks, changing the alignment method (from the default automatic) removed them.

On an image like that, the RGB histogram peaks will be the 'sky' background. As a basic starting point, just try setting the peak of each channels histogram to the same value using your processing software (by just offsetting each channel's data and not by changing the RGB ratios as that may cause more issues).

That last image looks like you have selected the 'No alignment' option. Can you upload a few lights to a file sharing site? I'm sure there are plenty of people who will be able to analyse the cause and/or suggest a fix to your problem. Have you tried the DSS forum?

... and found some gap between the object and the centre when I turned around the shaft 180 degrees... Do you mean it didn't remain on the graticle circle when you rotated the RA axis or it moved off the circle centre? The adjustments required are quite fine, just a quarter turn on the grub screws makes a big difference. My mount had cone point grub screws which tended to 'dig' into the graticule mount making fine adjustments difficult. I replaced them with cup point which made accurate alignment much easier.

At 120s exposure and without a NB filter I would suspect that the photon (?) noise of a Bortle 8 sky would overwhelm any camera noise (from my Bortle 6 sky it certainly overwhelms my DSLR noise at 180s) so I guess you're just fighting the noise created by the light pollution.

Welcome. I had a similar gap and in the day remember trying many times (unsuccessfully) to hypersensitive TP2415 to reduce the effects of reciprocity failure. And all those hours spent at the eyepiece trying to keep the guide star centred on the OAG cross-hairs for just a single exposure! Just a couple of years ago I first used a DSLR plus stacking/processing for a wide field astro image and my jaw literally dropped at the result. I always used to look at and was impressed with the images in my astronomy books of the day (eg Burnhams Celestial Handbooks, which were always my favorite books for selecting a nights target) but these days .... lets just say opportunity has moved on in leaps and bounds.

I would expect it to be metric so try measuring the diameter. The thread at the bottom (securing the eyepiece tray/spreader to the legs) is M12 so I guess the top thread will be the same (I can't measure it without dismantling it)

I haven't found a weather site yet where I can look on the site for the current hour and then look outside and confirm it to be 100% accurate every time. However, I can look at satellite images and if it looks like there's cloud above me I can almost guarantee it will be cloudy if I look outside. So I tend to look at the images to see which way the clouds are moving and how fast. That way I can only blame myself if I get it wrong 😊

It's obviously not a RAW image as it has colour so is it actually the JPEG image from the camera? If so I would suggest first stacking all your true RAW images and then apply colour balancing to the resulting image before deciding if you need a filter.

At f2, may it also be worth including an unfiltered image?

I assume an identical stacking method was used in both programs? Is the apparent difference significant for all equivalent stacking methods?

Only when the day ends in y

If you park the mount at the end of a session and it remains un-moved between sessions you shouldn't need to re-do the mount star alignment as any existing alignment 'parameters' will still be valid, but if you do move the mount between sessions then any 'saved' mount alignment data will become invalid so it will need to be 'recalibrated'.

According to the light pollution map I'm in a Bortle 5/6 area but the local town (south) and an equally close very large industrial estate (south east) means that anything below the celestial equator between SE and S are heavily light polluted. All street lighting in this part of the county is now LED and I suspect the industrial estate lighting is either still HP sodium or has been changed to LED. Early last year I imaged Orion with a 50mm lens on my unmodified APS-C camera and having to deal with removing severe LP gradients during processing, I decided to purchase an IDAS D2 clip-in filter and tried again. Although the light pollution background was slightly less (but certainly not significantly less), the bright star abberations introduced into the image together with a reduced colour spectrum meant that the original image was infact far better. The abberations were probably due to the low focal ratio I was imaging at (f2.8) so at normal telescope focal ratios it may not be such a problem, but as the filter removes mainly the 550nm to 650nm region of the spectrum (yellow to orange) I could not fully replicate the colour range of the unfiltered image.

I select the 2 (or 3) stars in advance of a night-time session. I power up the mount (polar alignment is irrelevant) and set the time and date to the time when I expect the mount will actually be aligned. Then I select the first alignment star from the provided list that I know will be visible at the expected set-up time, let the mount slew to where it thinks it is and just except it (as thought the star was perfectly centred in the eyepiece). Then I choose the 2nd star from new list provided that I also know will be visible. If I can't find a second visible star from those offered, I just restart the alignment process choosing a different visible 1st star until I get 2 (or 3) stars that I know will all be visible. If the visible sky is extremely limited it can take several (hence time consuming) iterations but at least it is done during the day and when you set-up for your night-time session, you already know which stars to select.

Their is the Pointing Accuracy Enhancement feature (see under tne Advanced functions of the instruction manual) but I suspect it might not be quite what you are looking for - the enhanced accuracy is generally only applicable to sky zones where it as been applied (85 zones for the whole sky) and all data is lost upon re-doing star alignment.

The direction of a unipolar motor is quite simply changed by changing the phase of the drive signals, there's no voltage reversal involved.