Aramcheck

Thanks @MarkAR - In the end I had to resort to Photoshop to stamp out the blown-out nebula & overlay it.... See here. Cheers Ivor

49 x 3min exposures (2hr 27min) with SW200dps + EQ6 + Cannon 600d (astromodified) & IDAS D2 light pollution filter. Bortle 6 skies. In order to bring out both the detail in M57 and retain as many of the faint fuzzies as I could, I had to apply a different stretch to the target nebula and background & then combine them at the end. I really didn't want to lose IC1296 (a small barred spiral galaxy which Simbad indicates is 243 million light years away), but in order to retain that 'low surface brightness' galaxy, the area surrounding M57 was very blown-out. Similarly, when stretching to maximise the detail in M57, the fainter stars / background was lost. Combining the images was a bit of a nightmare - in the end I had to resort to using the stamp tool in Photoshop to remove the blown out nebula from the background & overlay it with the separate M57 stretch. Cheers Ivor

A black elasticated shower-cap is good for preventing light entering from the primary mirror end, if that is the source of the problem.

I took 2hr27min of M57 last night with our SW200dps & Canon600d. I'm trying to process it, but M57 is very bright compared to the rest of the objects in the sky. If I stretch the image to bring out the nebula I lose the faint detail such as the barred spiral galaxy IC1296, but if I apply a 'normal' ScreenTransferFunction stretch, the nebula is completely washed out. What's the best way to proceed? Should I process both & recombine with PixelMath, or Mask M57 & apply different stretches to the nebula & background? I'm early on in the workflow, having just done background removal, BN & PCC (so no noise reduction yet). Screen Grab shows the 'normal' STF & a MaskedStretch applied to a preview. Any help much appreciated! Cheers Ivor

From a couple of nights/early mornings in the back garden, about a week ago. SW200dps + EQ6, IDAS D2 light pollution filter & Canon 600d (astromodified). 9x50 finder/guidescope and Bortle 6 skies. Still having problems with random sporadic RA movement (40-75 arc mins!) - could it be gusts of wind? If so, why wouldn't DEC also be affected? M56 - 19x3min subs NGC6823 - 49x3min subs (the SH2-86 emission nebula is very faint). Intrigued to read that the central cluster has stars which are only 2 million years old & the dark dust pillar is caused by stellar wind eroding the dust. NGC6992 - 19x3min subs (Top) + 5x3min subs (Bottom). This was just an experiment to see what would come out in RGB & to attempt a mosaic. Camera battery died on the 2nd night after only 5 shots & barely had enough juice to take 13 flats. (& I couldn't find my spare batteries...) I've subsequently learnt how to generate a Mosaic plan using Cart du Ciel, which can be imported into APT as a Custom set of objects. Cheers Ivor

So far, I haven't managed to get Deconvolution to produce decent results & on this image Starnet++ also didn't do a great job. I did tone down the stars to some extent using a star mask & Morphological Transformation in Pixinsight, but I think I need to spend more time playing with Deconvolution! Cheers Ivor

I'd suggest getting a much longer total imaging time & to stick with one duration exposure, rather than a mix. If you can get away with 3 min subs then stick with that & get a total exposure of at least 1 hour (& preferably a lot longer). For Darks and Biases you can take more (about 50 bias + at least 25 darks), but you only have to do that once to generate Master Bias / Master Dark images, which you can then reuse. Flats, of course, have to be done each night, or each time the imaging train is changed. M31 is also a big image for the 130pds. I've only had one go at it & it took me 6 attempts at processing to bring out as much detail as I could in the outer edges, which are much fainter than the core. The red colour cast in the top image will be eliminated during the processing (colour calibration). Also worth looking at http://dslr-astrophotography.com/iso-values-canon-cameras/ which indicates that ISO 400 or 800 is optimum for the 450D. I'm also not sure how suited the Astronomik CLS CCD is suited for galaxies? Cheers Ivor

From last night & early this morning... NGC6888 the Crescent nebula taken with the SW200dps & Canon 600d (astromodified), IDAS D2 light pollution filter & EQ6 mount + Bortle 6 sky. 44 x 3min subs. According to the inter-web, it's about 5000 light years away & is about 25 light years across. The bright star at it's centre is a Wolf-Rayet star which is shedding it's outer envelope in strong stellar wind (ejecting the equivalent of the Sun's mass every 10,000 years). The Stellar wind is colliding with material previously ejected from the star, when it was in its Red Giant phase, with two shock waves moving inward & outward. The inward bound shock wave is said to be heating the stellar wind to x-ray emitting temperatures (million kelvin to hundreds of millions kelvin?). Removing the light pollution gradient was a bit tricky due to the extent of the Ha in the region & I consequently lost some of it. Also had to drop 12 subs due to random movement in the RA, which I've yet to account for. I checked no cables were snagging & paused the image run to switched the initial guide star. Towards the end of the night I also had to change battery in the DLSR & tried running PHD2 calibration assistant (without success, though the RA seemed to better behaved afterwards). Attached guide log, in case anyone can suggest anything I can improve on the dithering time-outs & the odd RA pulses. Cheers, Ivor PHD2_GuideLog_2020-09-09_215940.txt

It is an amazing feeling being able to capture these DSO images. Couldn't resist having a quick (and rather inebriated) play with your data. Looks like you have a bit of coma, but good stuff! Cheers Ivor (PS: I mangled the star colours somewhat - not sure what happened there!)

It's caused by a combination of:- direct emission of light into the atmosphere, scattering of light by atoms & molecules in the air (Rayleigh scattering) + scattering of dust/water droplets (Mie scattering) reflection of light from the ground & other surfaces Scattering of light emitted at or close to the horizontal is a major factor in skyglow which is seen many miles from the source. The US Dept of Energy did some interesting modelling of skyglow from different light sources:- https://www.energy.gov/sites/prod/files/2017/05/f34/2017_led-impact-sky-glow.pdf https://www.energy.gov/eere/ssl/potential-impacts-led-street-lighting-sky-glow https://www.energy.gov/sites/prod/files/2017/08/f35/Sky-Glow-Webinar_7-27-17.pdf The only paper I've seen where measurements have been taken of a city before & after LED lighting was installed is in Tucson:- https://arxiv.org/abs/1802.03474 (If memory serves this showed approx 7% reduction, but isn't conclusive as they had equipment changes between the before & after measurements) Cheers Ivor

@westmarch - That's good to hear - how did you phrase the request, i.e. was it because of light trespass into windows, or did you just say about light in the garden? Cheers Ivor

Just heard that the closing date for submissions to the APPG Dark Skies / light pollution consultation is 27th September. https://appgdarkskies.co.uk/dark-skies-consultation Cheers Ivor

Thanks for sharing the data - had a quick play with it in Pixinsight. Cheers Ivor

In general you'll want to take a set of Bias + Darks & Flat frames in addition to the actual pictures of the nebula (usually called the 'Light' frames). You can get away with re-using Bias + Darks, but Flats must be taken at the same time as the lights in order to accurately capture the vignetting, which will vary with camera position & focus. Bias frames consist of a set of pictures taken with the shortest possible exposure & with the camera lens cap on. These are combined to produce a Master Bias image which will be subtracted from the Lights. The bias is a small pre-charge which is applied to each camera pixel and varies from pixel to pixel. Dark frames consist of a set of exposures with the lens cap on, taken at the same ISO & exposure duration as your Light frames. These are combined to produce a Master dark, which gives an image of the thermal noise & hot + cold pixels, which again is subtracted from the Lights. (Some will say you don't need these but doing so halves my noise level on my 600D). Flat frames consist of a set of exposures taken with the telescope & camera in situ & are taken with a flat light source. Some people use a diffuse white light source (eg white LED panel & white acrylic sheet, laptop screens & T shirts... or the clear sky & white T shirts). The Flats are combined to give you a Master Flat image. This is best described as a portrait of your optical system, which will generally be darker at the edges than the centre & will include any optical 'dust-bunny' effects caused by dust. When processing the Lights will be divided by the data in the Master Flat data to even out the pictures. A good book to get started with Astro Photography is "Making Every Photon Count" by Steve Ricahrds. Cheers Ivor

Use a program like Astro Photography Tool (APT) to control the mount. (Stellarium / Cartes du Ciel can also be used) I like using APT https://www.astrophotography.app/ as I can control my camera, plate-solve images etc. Plate-solving means there is no need to star align, although when going to an initial bright star to focus effectively does the same thing, as you sync the mount to the software once you've got the star used for focusing centred in the APT live view. For polar alignment, you'd use the polar scope - though for this I've opted to fit an iPolar, which makes that a lot simpler. Nowadays I only use the Handset control for visual use & don't bother guiding then! Cheers Ivor

It's in the 'Bonus Content' image gallery. The web address is on page 5 of the magazine near the top right of the page. Nice image BTW. Cheers Ivor

Both UK and abroad. Although the consultation is aimed at the UK, I think it's fair game to count travel abroad to dark sites. Thanks Ivor

I'm putting together a response to the UK Government's new Dark Sky consultation from out local Astronomy Soc in Leeds. https://appgdarkskies.co.uk/dark-skies-consultation Thought it might be an idea to try to find out how many of us plan holidays around dark skies? (Since my wife & i have taken up astronomy, I'm always checking the light pollution map & moon phase & looking for suitable accommodation) Any responses gratefully received! Thanks Ivor

Having a play around with the free Siril software & I'm using the latest version 0.9.12 for Windows 64 bit. I've seen from tutorials that you should be able to resize the sample box that is used during Background Extraction, but there doesn't appear to be an option to do this in my version. Any ideas on how to do this? Cheers Ivor

I've submitted a response & sent to members of our society. Found it very hard to limit myself to 1,000 words though. Thanks for mentioning the survey @clarkpm4242 , I wonder though whether more folks would respond to it, if it was in a separate Topic thread. Cheers Ivor

NGC7129 - a reflection nebula in Cepheus. At 3,300 light years away it lives up to it's 'Small' monicker. The open cluster (NGC 7142) was a bonus surprise, as was the edge on faint fuzzy PGC97261. The latter, if I've remembered the calc correctly, is approx 398 million light years away. SW200dps + EQ6. Canon 600D (astromodified) + 21x180 subs + Bortle 6 sky. Roughly processed in PI. Haven't managed to get out since June. due to clouds & only got an hour's worth of data last night, due to clouds rolling in at about 1:30am. Looks like the scope modification I did to reduce the flaring around bright stars has worked (i.e. covering the primary mirror clips with a ring of black plastic). Lately I've been wondering whether I should try using a 2" Barlow with the DLSR when attempting the smaller DSO's - would that work better? Cheers, Ivor

The EQ-2 mount also isn't good enough for general Astrophotography use, though you may be ok for Lunar images. To photograph deep sky objects you need a good solid mount which can be polar aligned accurately & which had very good tracking, so you can take long exposures without star trailing. When we started out with an EQ-2 130M, I made a wooden adapter so I could replace the scope with a camera and a findershoe attached to a piece of wood. You might find something similar would be ok for widefield shots, using your DLSR, though exposure times will still be limited. Cheers, Ivor

I had great difficulty using the polarscope on our EQ6 mount & wasted lots of potential viewing time with it. I tried fitting a webcam & then using a DLSR right angle viewer, but neither worked very well. I then got an iPolar (£199) which has been a great help... It means I can do the polar alignment at dusk & it only takes a few minutes. https://youtu.be/4MXjN34Om_g Cheers Ivor

@Jamgood beat me to it... I agree - it could likely be that the laser alignment itself is out. I find basic collimation easier just using an alignment cap & the procedure given here:- http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/ That said, the three SW OTA's we've had from FLO didn't really need any adjustment for a long time after purchase... Cheers Ivor

No. It only helps with the Polar Alignment as it sits in the exit aperture of the mount's polarscope, i.e. you're aligning the mount to celestial north, whereas Cone error is caused by misalignment of the telescope axis relative to the mount. Best check that it would work in Southern hemisphere too! Cheers Ivor