GraemeH

If you're likely to want to print some of your images, then I'd say you should also consider some kind of calibration device (something like a Datacolor Spyder, or a Colormunki Display - other calibration devices are available). This allows you to ensure that what you see on your screen is an accurate representation of the data in your image, and it helps enormously in producing prints that look like what you see on screen.

I can't remember if the frame count in the middle bar is for all loaded frames or only for the checked ones. Are your darks and flats checked in the file list?

I set up with the intention of getting more data on M42 despite the proximity of the moon (I know it was a silly idea, but it's been ages since I saw a clear sky). It soon became obvious that I was wasting my time, but I didn't feel like switching my gear to shoot with my Edge HD8 so I just decided to grab some shots of the moon with my ED72 for some fun. This is a stack of the best 150 from 500 frames (1/250 s @ ISO100), prepared in PIPP then stacked in AS!3, gentle wavelet sharpening in Registax then final adjustments in PS CC.

Spent a little more time reprocessing this one with a particular focus on trying to improve the colour balance. Managed to deal with the dark lines emanating from bright stars a bit more effectively in this version too I think.

Thank you Martin - I think I agree with you about the colour. I just used Star Colour Calibration in APP and didn't make any other colour adjustments for now because it really needs more data to do it justice.

I don't have enough data on this yet, but was just delighted to be able to get imaging again after almost 6 weeks of solid cloud cover. I guess it's pretty much compulsory to point at M42 every winter. This is just over 2 hours of 60" subs split roughly equally over 2 nights. Scope: Evostar 72ED Mount: Nexstar Evolution on wedge Camera: Canon 1100D (unmodified) Guiding: QHY5Lii-c and 9x50 finderguider Flattener: OVL non-reducing flattener Software: APT, PHD2, CPWI, APP, Photoshop Frames: 127 x 60" @ ISO1600, 25 Flats, 100 Bias Feedback and CC very welcome - thanks for looking. Graeme

Others have already given perfect explanations of why Polaris isn't suitable for aligning an equatorial mount, but it is perfectly good for alignment of a Goto Alt-Az mount. The same arguments can be used to explain why a star near the zenith is bad for Alt-Az alignment (Alt=90°, Az=anything you like), but perfectly good for equatorial alignment.

There are currently quite a few 6D mk I bodies available from https://www.mpb.com/en-uk/ for around the £500 mark.

My QHY cameras are only used for guiding - all of my imaging is by DSLR only right now.

As far as I can find out, the Celestron 6.3 reducer has a backfocus design distance of 105mm. This means that you are correct that it isn't compatible with the Celestron OAG if you are using a DSLR or other long backfocus camera. If however you have a different type of camera with a shorter backfocus then the Celestron OAG would be an option. From the kit that comes with the Celestron OAG, the SCT adapter has an optical length of 25.3mm, the OAG body is 29mm and the male M42 and M48 adapters are 12.5mm, leaving you a total of 38.2mm for the camera and any M42 or M48 spacers.

I prefer the first one - the second image has a little bit of a painted look, but I have to qualify that comment by saying that if I could produce something a quarter as good as either version I'd be delighted.

I could be completely on the wrong track here, but I remember something similar when I used to have the JNOW option active in APT - there was always an offset between my solved coordinates and the framed view in Stellarium. I set everything (APT, EQMOD, PS2, ASPS, although I can't remember if all of them had an option) to use J2000 coordinates and then everything lined up perfectly.

WIth my recently posted M31 mosaic, I had frames with wildly different background brightnesses due to having some subs ranging from either side of a full moon, through until just after new moon. For me, APP did a great job of normalising, using 1st order LNC with 5 iterations, but I think the thing that made the biggest difference to the background smoothness was setting MBB to 50%. Spending a long time in building a model for light pollution removal in APP made a big difference too, trying to follow the guidance from one of Mabula's videos on LP removal. I'm too new to APP to know how well these settings would apply to a different integration, but I guess it couldn't hurt to try. Graeme

New revision of this image - as usual I was too keen to share what I had before I was really happy with it.

I can confirm that HLVG definitely works with later versions - I have it installed in Photoshop CC 2020 and it works well.

I'm now ready to call my project to image M31 complete, having reached a total of 17 hours 40 minutes on this. I've posted an earlier work-in-progress version of this previously in the Getting Started Imaging section, and I'm now ready to ask for some constructive criticism from the SGL experts. Equipment Details: Scope: Evostar ED72 Flattener: OVL non-reducing flattener Mount: Nexstar Evolution on wedge Camera: Canon 1100D (unmodified) Guiding: QHY5Lii-c with Skywatcher 9x50 finder Acquisition Details: 620 x 60", 28 x 120", 128 x 180" all at ISO 1600, captured with APT and CPWI Ascom driver with PHD2 guiding, in a 2x2 mosaic 100 Flats, 100 Bias, No darks Processing: Calibration, Registration, Normalisation and Integration in APP Light Pollution Removal, Star Colour Calibration and initial stretching in APP Final adjustments and cropping to give 16:9 ratio (to fit my screen as a wallpaper) in Photoshop CC Thanks for looking. Graeme

This won't be the whole story for your problems, but I noticed from the PHD2 log file that you have the focal length set at 299mm and said that your guidescope is 200mm fl.

The way that the SharpCap polar alignment works is by finding the centre of rotation between 2 platesolved images in terms of RA/Dec coordinates after moving only the RA axis. In theory, there is no restriction on where the scope points - it's just that I believe SharpCap only has solving indexes for near the polar regions. There is definitely no requirement for your guide scope to be aligned either with the polar axis of the mount, or with the main scope.

Thank you Olly - I'm sure I can't be alone in finding that the more I improve in this hobby, the more critical I become of my own images, so it's nice to hear that whilst there are still some flaws, I'm doing OK.

A few more subs added to this one, and some of the original ones discarded after closer inspection. This is now a total of 466 x 60" with all the rest of the details the same. A little more time spent in processing to achieve a result I'm happy with.

I think this is exactly right - the sensor doesn't have a gamut by any definition I understand, but the sensor/filter combination might do.

I always enjoy reading your posts, but rarely feel like I have anything useful to contribute to the discussion. This time, I think I have a little knowledge from a previous career in chemical manufacturing of dyes that allows me to comment on some aspects of your post. My understanding of the term gamut (which could be wrong) is that it is always a subset of the full range of possible chromaticity and lightness combinations from an infinite variation of spectral curves. In this respect it is true to say that both human vison, and a camera sensor do not have a gamut as such. We can see every possible chromaticity and lightness combination (although the ability to perceive differences between 2 combinations is not uniform across the whole colour space). Every display medium (screen or print) is defined as having a gamut because there are some points in the whole colour space that cannot be accurately represented. The ability of human vision to differentiate between 'colours' comes from the fact that every wavelength within the visible spectrum triggers a non-zero response from at least 2 out of the 3 types of cone cells. Our perception of colour comes from the relative strength of the response from each type of cone cell. When it comes to a mono camera and RGB filters, the measurement doesn't follow the same pattern. The filters sample the incident light within 3 distinct bands with very little crossover. You correctly state that this means the camera with a red filter cannot differentiate between a source at 605nm and one at 615nm. Perhaps human vision could be more accurately simulated if it were possible to make pseudo-RGB filters with transmission curves like the primary colour functions of the CIE standard observer? I look forward to reading where your investigation goes from here. Graeme

I have recently purchased the EAF and fitted it to my Evostar 72ED. I'm very happy with the focusing performance, but I'm experiencing similar issues with the temperature reading. Last night the focuser was reading -8.5°C (definitely wasn't that cold) and I had a small digital thermometer outside at the same time which read 1.8°C. There was a thin coating of frost on some of my gear, so I don't think the 1.8°C reading was entirely accurate either - I'd guess maybe 1-2 degrees below zero. I happened to find this thread, and updated my firmware to see if it helped but it made no difference. Today I messaged ZWO via their facebook page to ask about it. Their response was that the actual temperature isn't really important and that I shouldn't worry about it - it should still be accurate for tracking changes in temperature. I don't disagree with the thinking, but it's still not really a satisfactory response in my opinion. I did ask if there could be a way to have an offset value applied in the ASCOM driver, and they said they'd pass my comments to the developers. Maybe a future firmware update will provide this option. Graeme

As the title says, this image represents a number of firsts for me. It is my first attempt at a mosaic image, which was impressively easily handled by my first use of AstroPixelProcessor, and it is also my first multi-night image. I know there are still some residual gradients visible as well as some uneven background across the mosaic panes especially at the top left, but I'm really posting this to express my delight as a new APP user. My individual subs were suffering from very variable gradients from an almost full moon, as well as some thin high cloud causing big shifts in background brightness even within a few minutes. APP handled them all very impressively. Technical details: Scope - Evostar 72ED with OVL non-reducing flattener Focus motor - ZWO EAF Mount - Nexstar Evolution on wedge Camera - Canon 1100D (unmodified) Guiding - Skywatcher 9x50 finder with QHY5Lii-c Software - CPWI, PHD2, APT, APP, Photoshop CC Subs - 408 x 60" spread over 4 quadrants and some of the centre of the image (dithered every 5 subs), 100 flats, 100 bias Feedback and CC welcome as always. Thanks for looking. Graeme

I made an autofocuser using exactly that stepper motor for my C8 Edge. I had already upgraded the stock focuser to a Feathertouch, and had a bracket made to put the stepper on the Feathertouch shaft. I'd be happy to send you a drawing of the bracket if it's of any use to you - you'd just have to change the length to make it fit the stock focuser shaft, and find a flexible coupler that can attach to it.