Aramcheck

Why bother with AP? - For me it's a way to see stuff that I wouldn't otherwise have a chance of finding in our light polluted skies. It's also a challenge to get the best data you can & to learn how to process it.

Just finding & verifying this stuff is real is a buzz!

I also find it fascinating to plate-solve & annotate the processed image to identify very distant galaxies & then calculate their distance by looking up the redshift/radial velocity on Simbad. Finding a few pixels that represent light from a galaxy that has taken 1-2 billion years to reach the camera is mind-boggling.

It's also nice to sit outside whilst the scope/camera/computer is doing its stuff. I've seen some spectacular shooting stars... and (with the light pollution) I can see the bats and the occasional flock of migrating birds. It's peaceful just watching the few stars we can see stars revolve... Also using a pair of bins & my pocket Sky & Telescope atlas to identify & learn where things are is neat.

Cheers
Ivor

Thanks folks! I'm not entirely convinced that it's a stray diffraction spike, given the distance but I think I'll have to wait & see... It's nearly a month now since we had any suitable clear skies! I still suspect that it was something to do with the camera orientation, so will have to have a play around if the problem occurs again. BTW I have flocked the OTA, but haven't painted the outer focus tube black yet.

@ollypenrice - Thanks - I find trying to get the colours look right is always a bit problematic. I use Pixinsight's 'Photometric Colour Calibration' but still have to adjust the R-G-B histograms if I use the ArcSin stretch (my preferred option now on the RGB as I tend to extract & process Luminance separately).

Thanks again everybody.
Cheers
Ivor

This was 117 mins in Bortle 6 with a SW 130dps & a Canon 600d (astromodified):-
https://stargazerslounge.com/topic/369470-m33-130dps-odd-light-artifact/

It would have been longer but clouds stopped play (again) & at the here at the moment clear skies are few and far between.

IMHO Bias / Flats & Darks are a must. (You'll have to check processing with & without darks - I find it's better to use darks). Vertical lines on the 2nd image looks (to me) like bias.

If APP does deconvolution then try that to reduce star bloat... It took me a while to get settings right in Pixinsight...

Noise is inherent with a DLSR, unless cooled. You can eliminate it to some extent in processing.

Cheers
Ivor

Thanks very much for sharing the stacked data! If you use APT to control your camera, have a look at the Framing Mask feature (see:-https://www.astrophotography.app/usersguide/framing_masks.htm#) which is supposed to help framing between different sessions. (I've had no experience with it yet - clear nights here have been few & far between!)

Anyway here's my quick process of the data - I couldn't get rid of the line at the bottom left...

Cheers
Ivor

44 minutes ago, wimvb said:

It could be a diffraction streak. Any straight line or edge in front of the scope can cause this. Even a washing line for example.

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

1 hour ago, matt_baker said:

Do you dither?

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

5 hours ago, PeterW said:

If you only want to view in perfect skies then foreign travel is your only option.

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

6 hours ago, Daf1983 said:

With regards to processing, what do you mean by 'blurring out background noise'?

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.

On 18/11/2020 at 21:29, ScouseSpaceCadet said:

My dad loves nature. Sitting on a canal bank fishing is his idea of heaven. His garden is a love affair. The small lawn is like a perfect green carpet. There are lovely flowers, plants and a hedgerow teaming with birds. Happy gnomes are everywhere, as are a multitude of multi coloured solar lights illuminating the space like a grotto.

 

@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

1 hour ago, david_taurus83 said:

Apparently, a study in Arizona measured street lighting to only contribute around  20% of actual light pollution. I'm struggling to believe that though. It would have been interesting to see the result if they had shut off all lighting for a minute or so and captured it from space.

https://skyandtelescope.org/astronomy-news/street-light-pollution/

 

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

6 hours ago, andrew s said:

For modern man night holds few fears (at least for us on SGL) but for our ancestors night was to be feared as they were pray to a number of night hunters. The desire to have a safe haven with fire and light was probably encoded in our behaviour then which persists to this day.

Personally,  I enjoy a dark night and wish others did too. Maybe the desire for light at night is a deep connection with an ancient nature not a modern disconnect.

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

On 11/11/2020 at 10:49, cloudsweeper said:

The only explanation I can come up with is that these people are utterly disconnected from Nature.

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.