groberts

Thanks James, I will be doing some experimentation this afternoon using some of your suggestions; your reply to Olly on the subject is also interesting - always wondered what some of those terms in the menu meant! In view of this, by decreasing Kappa does this have any other impact on other aspects of the stacked image? Yes, we know Somerset well as our daughter lives in West Harptree by the Mendips + previousy in Ilminster. We'd move there in a flash were it not for another daughter and grandchildren in Brighton! Graham

Obviously this varies but usually at least say +5 hours of 3min or 5min = 60 to 100 subs; at the moment with good weather and time this has increased to +150. Kappa is set at 2.0 Graham

OK I've had a look at DSS and am struggling to see what's meant by the Sigma Stacking Options. I currently use Kappa-Sigma in the Lights stacking settings, which does not remove the plane tracks - do you mean this or something else? Graham

Thanks James, that sounds promising - will take a look. Graham

I live north of Gatwick Airport, though not actually under the flightpath and naturally have to deal with aircraft that still turn over our location. As if that isn't bad enough, we also get our fair share of planes from Heathrow + long-haul oveflights and low flying emergency service helicopters at all times of the night from Redhill aerodrome - I know, we need to move. Like others we're all noticing how much quieter the covid-19 world is + darker the skies, making astronomy in these otherwise weird times all the more pleasant. However, despite the signifcant reduction of flights in order to stop spreading the virus, it's ironic that I'm noticing more flights than ususal - most of which seem to find their way through my images! Not for the first time in recent weeks, when I've been imaging high in the sky around Ursa Major - last night being M63 - using 5-minute exposures no less than 30% of my subs were spoilt by high tracking aircraft between from 10.00pm until about midnight. i.e. almost certainly not orginating from Gatwick or Heathrow but maybe navigating via there. Thereafter things thankfully improved with only a couple of tracks over the next couple of hours. So, in this world in which flying has suposedly been severely restricted, what's happening? Freight perhaps but it still seems a lot of flights and certainly noticeably more than usual. I stack & calibrate using Deep Sky Stacker, usually after removing subs with the aforementioned plane tracks but was wondering if DSS can actually deal with such problems or is it best practice to remove them from stacking? Last year my wife and I went on an ammazing geological road trip of Wyoming-Montana-Utah-Colorado (we're both geologists) - you wouldn't have to be a geologist to enjoy it so here's my write-up if anyone's interested https://roundthebendpart1.wordpress.com/2019/10/17/dinosaurs-geysers-mountains-an-american-odyssey/. One of the highlights was the Dinosaur National Monument Park https://www.nps.gov/dino/index.htm which straddles Colorado and Utah and apart from having the most amazing rocks and literally scores of dinosaur finds, is a dark sky park. As a result one evening we went back into the park to enjoy it at night + get some pictures of the wonderful Milky Way sky. Mostly taking +/-20 second DSLR exposures, less than 1-in-10 of the resulting images were clear of aircraft tracks and this in an otherwise pristine night sky miles from anywhere = very sad! Graham

Thanks 👍

Indeed same here in Surrey, so hopefuly some more late nights coming up. As a matter of interest, which site / app is that you're using + is it any good / reliable? Graham

Wasn't imaging but we saw +15 of the SpaceX ones on Sunday evening about 9.55pm - I now know to be called Starlink https://www.starlink.com/ . At the time I didn't know what they were, they come along in a train one after another at realtively low altitude (550km), very strange + quite unlike 'normal' satellites that we're accusomed to. Amazing technology but if Mr Musk succeeds in putting +30,000 of these up, as planned, it's not going to be good for astronomy - I'm surpised there isn't better regulation of such activities? For future information, this link shows the day-by-day times and real time tracking map of each train: https://findstarlink.com/ They're working on darkening each satellite to make them less relfective to light, which are supposed to be most visually promiant at twilght and may help astrophotography? However, this will not be the case for radio astronomy! Graham

It's more than 2-years since putting my ZWO 1600MM-Cool to work and with time on my hands at the moment, I'm thinking it's a good time to have a spring clean. What is the best way to clean the filters and the sensor cover? Graham

Thanks guys. I now recall that is was binning and not dithering that apparently does not work with CMOS sensors - don't understand why? Notwithstanding, I'm pleased to hear that dithering does work and, furthermore, is worthwhile. Will give it a go. Graham

I just read another post on SGL which has got me confused. Shortly after I acquired my ZWO 1600MM-Cool at the end of 2017, I was told that dithering would not work with this or any other CMOS based camera (not sure why & probably wouldn't have understood it anyhow) but I now see others talking about just this. Can you dither with CMOS and especially the ZWO 1600MM-Cool? What setting works best with the 1600MM-Cool? Does it make much difference to the final image with the said camera + if so in what way? Thanks, Graham

Fabulous mosaic Adrian - just love these widefield images.

You should be well pleased with that - excellent.

Don't know anything about RPi4 but does that mean it's pulse guiding OK? Yes my ASI120MC was very temperamental - euphamism for wouldn't work with anythng at first - but with the correct driver and only using the USB2.0 port on my laptop it's been OK. Not surpirisingly it sounds like things have moved on since then. Graham

Thanks Avocette thats helpful. I bought this ZWO ASI120MC camera not long after they first appeared - about 2015 /16 I think - and had some problems getting it to work at all at first. Finally discovered it would ony work with a USB 2.0 port but not at all with USB 3.0 i.e. not back compatible. Notwithstanding, I successfuly used it a few times for planetary imaging using Firecapture which worked OK. However, I have never used it for guiding. My core softare is now VIA EQASCOM which works very well with EQMOD / CdC / PHD2 / APT but never know with ZWO stuff it can be fickle at times with other software. As a matter of interest are you using the ST4 guide connection direct to the mount or pulse guiding via a computer + any issues /advice? Graham

Thanks Billy.

Thanks but already successfully been using flats, darks & bias calibration for some years to remove such issues. I've now been back to look at the history of the problem which shows: No sign before 2018 Only evident in LRGB subs i.e. does not apear to be present in narrowband wavelengths At first I thought it was a stacking artifact but, of course, being present in the subs that can't be the case. If it's not in Ha OIII SII but it is in LRGB i.e. not the sensor which then would suggest the filters but it still has to be something common as it's the same pattern in each LRGB wavelength? Frankly I'm baffled!

Definitely not dew drops, the object lens was bone dry on Monday evening. As to position, I'm not sure, though it certainly has happended before. I'll try and go back and take a look at this.

For some unkown reason I seem to get fairy rings in some of my pictures, though not always, which are usually only apparent in the darker sky areas. Below is an example of a highly stretched L sub where the 'rings' show as a collection of slightly darker patches, not unlike mare on the Moon! In the subsequent part processed image the areas appear as the aformentioned Fairy Rings? Any ideas on what these are and how to get rid of them? Thanks. Graham

Still prevaricating over a guidescope to go with the AstroKraken Samyang 135 rig using a ZWO120MC camera. Was erring towards a smaller scope like the ZWO Mini Guide Scope oe smething similar. But (a) there's a lack of stock and (b) reviews are mixed. Wondering if something like the RVO equivalent version https://www.rothervalleyoptics.co.uk/rvo-32mm-f4-mini-guide-scope.html or the larger SW Evoguide 50ED might be a better choice? Any thoughts / personal experience of these please?

The new rig looks very nice Adrian + the quality of the resulting image speaks for itself - pity about your sight lines though, I know what you mean! I've decided to go with the off-the-shelf AstroKraken rig to get me going with a modded DSLR - if I can remember how it works still - it's been a while since using DSLR for AP. However, I'm still battling with what to do about a guidescope. Something small and light apeals for now but your experience with the ZWO mini guider is of some concern and I am now drawn towards a similar version by RVO which apprently has better / longer focus travel. Of course with all the current problems it's not in stock now. However, assuming all goes well my end game is to use this lens with my ZWO1600MM-C at which point a more comprehensive rig seems likely. If it's not inconvenient, would appreciate another picture to show how the equioment is now loaded from below / the front. Your experience with the ASIair etc is also very compelling + I see you're now using their autofocus too? Look forwards to seeing more from your new set-up. Graham

Great + thanks

I purchased my ZWO 120MC in 2014 - one of the first - and it is therefore only USB 2.0 compatible but should, I believe, still be OK for guiding? I obviously need to know the pixel size for PHD2 but being somewhat old not sure what this would be, as the various current 120MCs now comes with different pixel sizes. Anybody able to help please? Graham

Thanks Adrian, much appreciated. Still yet to decide the way forwards but I have the Samyang lens now, so will need to move forwards on the rest soon. I've long been thinking about which way to go next and in life and so astronomy, generally like to see and understand the big picture - the Samyang widefield images look just the job. Great thread, thanks to everyone's input which I've been reading avidly before pushing the button. Graham

Adrian, I am faced with establishing a similar rig and would be interested to know: What's the ring size on your rig? What's the autofocus equipment you're using? What's your experience with the ZWO Mini Guider like? What's the backfocus for the ZWO 1600MM with this lens? Thanks, Graham