Aramcheck

Thanks @wimvb - I guess that is a possibility, although I would then expect it to have moved over the course of the evening relative to the camera image. As far as I can tell it's in the same place on all the subs & only appears smeared on the stacked image, once the subs have been star aligned. I certainly have problems with low washing lines though & have walked into them in the past! Cheers Ivor

Yes - between each exposure, though it sometimes times out & on this occasion after the meridian flip PHD stopped guiding in Dec. (It was also the first time out with the guide-scope on the 130dps) Cheers Ivor

On 20th Dec we finally had a bit of clear skies. Because it was pretty windy I set up the SW 130dps & set about taking subs of M33. It wasn't the target I had in mind, so during set-up I had the DLSR (Canon 600d astromodified) rotated almost 90 deg to my normal orientation... (and so the Galaxy wasn't framed well). On initial stack of the data, I noticed each of the light frames had a line which looks like some light leakage or reflection, which I haven't seen before. Any ideas what this might be? I had a black shower cap on the primary mirror end of the scope (which blew off half way through the session) & I keep a cover over the camera viewfinder. The artifact is in the same position on all of the images, and thus appears smeared in the stacked composite. (Guiding also wasn't working properly as I failed to redo the calibration after needing to do a meridian flip after the first 3 subs). I've managed to remove the artifact in processing using StarNet, but I'd still like to know what the problem was. Cheers Ivor

In Pixinsight, when you open an XISF the relevant RGGB order is displayed in the Process Console. You should use that order when debayering the images. @geeklee beat me to it answering the STF bit! Cheers Ivor

The APPG also have an Adjournment debate on the proposals penciled in for Monday afternoon in the commons. Cheers Ivor

Best dark skies I've seen (so far) have been about 5 miles north of Dolgellau. It's always depressing coming home... You've gotta love Wales Cheers Ivor

Have you tried it in the daytime on a distant object? Cheers Ivor

A heads up on tomorrow's APPG policy recommendations... Cheers Ivor Ten Dark Sky policies for government - Overview.pdf Ten Dark Sky policies for the government - APPG for Dark Skies.pdf

It depends on the software you're using, but the idea is to mask off areas of high signal & to blur the background. In Pixinsight I use the MultiscaleLinearTransform (MLT) tool on the linear image & ACDNR once the image has been stretched & is non-linear. At the end of processing I sometimes then use a PixelMath expression to try to reduce any remaining DLSR mottling. The screen grab shows a before & after image of the MLT process on a small area of background. Cheers Ivor

Pictures from my 600d also have a lot of noise & ISO 800 is said to be optimum for that model (http://dslr-astrophotography.com/iso-values-canon-cameras/) Increasing the total exposure time will help, as will more careful processing when stretching the image & also when effectively blurring out the background noise. More dark & bias frames might be an idea too - these can be reused for the same camera settings, so it's worth making a master dark & master bias. You may also find that processing without darks is better (although I've found darks do help with the 600d). It's also worth covering up the viewfinder, to prevent any light leakage. Some folks also advocate leaving the flip screen open to help cool the camera, and to minimise the use of the liveview screen. Cheers Ivor

During WWII my grandad sent rabbits in the post from out in the country, to my mother in London, with just an address tag & stamp tied around the hind legs. I wonder what would happen if you tried that now... Best packaging we've had recently included some wool insulating material in a delivery from the German deli. Amazon consistently deliver stuff in ridiculously over-size boxes, but I'm glad the use reusable/recyclable paper padding. Cheers Ivor

Have a look at this thread:- It'll depend on what software you're using - in Pixinsight HDRComposition will do the trick. Cheers Ivor

I got an email from the APPG group with details of the launch of their policy paper, following on from their recent Dark Skies consultation:- ************** "Following our widespread public consultation on Dark Skies which reached over 170 respondents, as well as inputs from amongst our own membership, I’m pleased to invite you to the launch of our policy paper ‘Ten Dark Sky Policies for the Government’ on Wednesday 9th December at 15:00. The paper was produced in consultation with representatives from CPRE, the Commission for Dark Skies, the International Dark-Sky Association, the Institution of Lighting Professionals, the Royal Astronomical Society, the Federation of Astronomical Societies, South Downs National Park Authority and University College London. For the event, we will be joined by our parliamentary membership, as well as: Emma Marrington, dark skies expert and Rural Communities Enhancement Lead at CPRE, the countryside charity. Dan Oakley, Lead Ranger and Dark Skies Officer at the South Downs National Park, Coordinator of the UK Dark Skies Group and current Chair of the IDA Dark Sky Places Committee. Attendees will be sent Zoom meeting details after registering for our event via the following link: https://www.eventbrite.co.uk/e/policy-paper-launch-ten-dark-sky-policies-for-the-government-tickets-130410255585 The event will take place just after a webinar on preventing obtrusive light by our partner organisation the ILP, which attendees may also be interested in." ********** Cheers Ivor PS: Mod's please move or delete if need be.

@ScouseSpaceCadet You should tell your Dad that slugs are one of the few creatures that benefit from illuminated gardens:- "The number of slugs, primarily Arionidae, increased strongly in the illuminated site but not on the dark site. There are several nonexclusive explanations for this effect, including reduced predation and increased food quality in the form of carcasses of insects attracted by the light. As slugs play an important role in ecosystems and are also important pest species, the increase of slugs under artificial illumination cannot only affect ecosystem functioning but also have important economic consequences." https://onlinelibrary.wiley.com/doi/abs/10.1002/jez.2170 Cheers Ivor

I found Dylan O'Donnell's youtube video useful in using the wizard to setup the guide scope. Just make sure you enter the guide scope focal length correctly! Cheers Ivor

I haven't read the original paper yet on this, but Tucson probably isn't a good comparison with UK cities. Tucson already dims street lights quite significantly, whereas the BS-EN13201 spec. for UK road lighting only allows for potential variation of lighting on major roads, not residential areas. I expect that dimming of street lights will become more common in the UK, when LoRaWAN networks are installed & lights can then be controlled through a central system. BTW the UK road lighting specification is also non-mandatory & only provides minimum lighting levels for different road classes, so there's no incentive (other than cost) for councils to minimise lighting levels. It also includes a section on lighting up the natural environment, which is completely opposite to what should be the case, if the natural environment/wildlife is to be considered. I'd be very interested to know if any major UK cities have a dimming regime. Cheers Ivor

There seems to be quite a strong evidence for lighting affecting people's perception of safety & fear of crime. eg:- http://library.college.police.uk/docs/hopolicers/fcpu29.pdf also - https://www.celfosc.org/biblio/seguridad/atkins.pdf But a pretty exhaustive study on the effects of lighting on crime which looked at data from 62 local authorities didn't find any overall correlation between lighting and actual crime or road sccident rates:- https://jech.bmj.com/content/69/11/1118 Also the Austrian government's guidelines for external lighting cites a study of 248,000 UK burglaries which found that 48% had outside lighting fitted, which suggests that security lighting isn't necessarily an effective deterent. Of course - there are many other factors to consider, such as light flux, spectrum & the amount of uplight (i.e. light shining above the horizontal). Nobody's suggesting that light isn't beneficial, but it should be adequate for purpose & only shine when & where it's needed. Cheers Ivor

I've also noticed a few front lawns in our neighbourhood being replaced with astro-turf, which is depressing, given that about 75% of the insect population in our city are found in folks gardens(*). I think there is also a diurnal bias & even folks who are interested in nature don't realise the damage artificial light does on nocturnal species. One of our neighbours, for instance, who does have a keen interest in wildlife, also likes their external 'insecurity' lights. Cheers Ivor (*) http://www.bristol.ac.uk/biology/research/ecological/community/pollinators/news/2018/nee-lay-summary.html PS: Another interesting doc from 2011: https://cdn.buglife.org.uk/2019/08/A-Review-of-the-Impact-of-Artificial-Light-on-Invertebrates-docx_0.pdf

There's also a good talk on the subject by Dr. Robin Glover https://youtu.be/3RH93UvP358?t=56 Cheers Ivor

When starting out I found Richard Bloch's youtube videos on Basic Processing and Stacking useful. Also Mitch's 12 video series. I've subsequently made more use of Warren A. Keller's "Inside Pixinsight" book, which I find indispensible. Light Vortex is good too - particularly like his bit on SubFrameSelection. Had a quick play with your M33 data - it looks to me like the focus was slightly off. Did you use the Bahtinov mask to focus? Cheers Ivor

Great to see this reported on BBC News 24 tonight, albeit in quite a short segment.

Couldn't get the 32bit TIFF to open in PI, so here's a quickish process of the 16bit version. Cheers Ivor

Hi Bill, Here's a couple of stretched jpgs from the tif file, which may make it easier for folks to comment. (Saves having to download & modify the tiff). I'm not an expert, but it looks to me that you have some coma issues, with the the distortion of the stars at the edges / corners of the image pointing towards the centre. Also - as there is some trailing at the centre, you probably should check the individual light frames, as some may have defcets due to movement of the scope during the exposure. This can be caused by gusts of wind, snagging cables, or mount issues. Also - the flats don't seem to have worked. There's vignetting around the edge, which the flats should have compensated for and a dust bunny is visible to the right (& up a bit) of 52 Cyg. It might also help to know what equipment you have used. Cheers Ivor PS: You can also try stacking in Pixinsight.

Thanks everybody - that's been a great help! Much appreciated. As per @happy-kat's suggestion I've loosened the bolt a bit, so the Alt-axis moves a bit more freely, but I'll be getting an AZ5 with Steel tripod ASAP. Cheers Ivor

Last Christmas we bought a SW Startravel 102, hoping to use it as a grab & go. I have however, found the mount to be rather disappointing, with the Alt-axis in particular being too stiff to position accurately (unless using the slow-mo control). I'm therefore thinking of upgrading to either the AZ4 or AZ5, but not sure which would be best option. The AZ4 doesn't look like it has any slow-mo controls, so how easy is it to locate & keep targets in the FOV? On the plus side, the AZ4 has a steel tripod, but for £30 more, the AZ5 has slow-mo controls... however, it comes with a lightweight aluminum tripod, which on the one hand would be good for moving around, but probably not so good if I wanted to mount our SW 130dps? Any advice from users of either mount would be much appreciated! Cheers Ivor