Magnum

Yes I think you are spot on here Olly, im using an OAG on the main scope, and the situation you described was also going through my head.

https://www.forbes.com/sites/startswithabang/2019/12/11/elon-musk-spacex-unveil-latest-starlink-plans-creating-an-astronomical-emergency/?fbclid=IwAR21FB450AbIGgojWWjfu69CWvzApwSKEaB3o4eNSrmoGT4hfY2ya7mJ2i0#21b0a134287e spaceX replies are so arrogant,

https://www.skyandtelescope.com/astronomy-news/starlink-satellites-astronomy/?fbclid=IwAR36gDC-IpwHfftlbz29_suH2O17RtKfW67Wgnc5ol0qre4wWXrSfYLonpU This article has some video simulations showing how they will look on average with 12,000. however space x have now applied for extra 30,000 bringing total to 42,000 if approved. If Amazon and others follow with as many each, I really do think we will get to a critical point where nearly every sub could have a trail. But thats the final orbits, unfortunately for us they will be launching them at a much faster pace than the orbits take to raise and spread out, so for several years we will be dealing with them at their worst. Ive been reading every article I can find on the subject. one interesting youtube video was interviewing the CEO of one of the more established satellite companies that will soon be launching new geostationary satellites, and from what he said Geostationary is a better technology than LEO. much higher bandwidth and a much smaller constellation required, much less wasteful. And for Astronomers much much less impact on the sky. He actually said he thinks SpaceX may find they have taken the wrong path altogether. Lee

Not had a chance to check my flexure issue since my last alteration, but it seems I only get the issue when imaging in the east. The following images were taken just after meridian flip, and only I tiny bit of elongation on the slave scope. both are 3 x 10 mins. As you can see my fields of view are totally different so have zoomed out the 460 until it was roughly the same scale. im not really sure what my plan is going forward, at the moment im just using them as 2 different sets of data so I can at least get to grips with my 2 new cameras at the same time, and it gives me twice as much to play with in the British winter. if I removed the reducer from the 383/102 combo then they would be more similar but I think the 383 really needs the extra speed of f5.5 vs f7. Or I could could swap the cams around in which case the scales would almost match, but then im not getting the benefit of the large chip on the 383 LOL. As you can see my alignment is pretty good with no adjustment devices.

Update, I determined that the Altair astro vixen bar was the weakest point as it is a lightweight design which has quite a lot of material removed for the recessed slots. so spent the afternoon repurposing one of my old homemade Dovetail bars, its 3/4" solid Aluminium vs the 1/2" Altair bar. Cut it in half so now have 2 🙂 but half way through I really wish I had bought a new hacksaw blade 😛 All back together and rebalanced, Quick wiggle test and seems to have made a difference. Lee

Yes its quite awful looking isn't it, Ivy is trying to reclaim my whole garden, everytime I try to tackle it its like loosing battle.

Yes ive been trying the demo version of that, but its limited to 60 sec exposures, and being short on cash at the moment I dint fancy spending out £50 until ive got the flexure issue solved, but then a couple of weeks ago I found the method I mentioned above of just finding out what delay I need on the 2nd scope to keep in sync with the main scope, Ive used it about 6 nights now and as long as I press start on both maxims at same second they stay in sync perfectly all night long. I found the 383 needs to wait an extra 9 seconds longer than the 460 due to the dither and download time etc. I always use a 30 sec dither delay between exposure so the 2nd cam needs 39 secs. im so happy with how this has worked. Going out to the Obs now to work on the flexure issue 😞

have you tried make the green channel a blend of Ha & Oiii rather than straight Oiii. I normally use a blend ratio of about 75%Oiii & 25% Ha.

The plate is actually a really solid and heavy Losmandy plate, unfortunately my old EQ6 only has a vixen saddle so for now ( until I find a replacement Losmandy puck going cheap :-p) so ive had to bolt the blue vixen bar to the underside, but surprisingly that connection is really rock solid, the only flex I can find is between the 102 scope and the plate, and a little on both focusers. so tomorrow im going to replace the clamp that holds the 102 for a bigger one with dual locking bolts, I dont think the holes match up so will have to modify it, thats probably why I didn't fit it before. I will try what you said about winding the focuser in and use extensions instead.

Carole is you issue vignetting or dust bunnies, or both?

Im also in the process of trying to get my (miss matched) dual rig working properly, and my biggest issue is also differential flexure, For the last few weeks I thought it was focuser sag as im guiding on the 127 Meade with an OAG and that rig always has pin point stars, but the 102 has slight trails, found a loose tension pad inside the focuser of the 102 but still getting the same issue. Theoretically the Altair should have amore rigid focuser than the Meade and thats confirmed by some aggressive flexing tests. But then when I think about it it could still be the focuser on the Meade thats casting it ,as that could be flexing yet still give round stars one its camera as its guided by the OAG. However im starting to think its the single bolt dovetail clamp on the smaller scope, if I grab both scopes and move up and down there seems to be slightly more movement on smaller scope. Does any of that make sense? Also last night the images taken on the east side of the meridian had trails but on the west side they were almost perfect. Thing I haven't had a problem with funny enough is alignment, all I did was use the pre drilled holes on the plate and clamps, and made sure the edges were square with each other before tightening, Can centre star in one and its always centred in the other one. Not much point to my post as ive kind of answered my own questions, but thought I would share anyway. With regards to capture itself and dithering, ive worked out a really simple method of having the exposures of both scopes synced to the dither. Guiding in Maxim I enable dithering with my normal 30 second delay between exposures using the ATik460. Then on a separate computer I have another Maxim running connected to just the 383, obviously this one knows nothing about the guiding so I found if I set the delay on this cam to 39 seconds and make sure I press start on both machines at the same moment, then it stays in perfect sync all night. Lee

Thanks Carol. First the sensor is smaller than the fully illuminated image circle of the scope, so any vignetting would be outside of this frame. Then regarding dust bunnies I meticulously clean the filters before I put them in the filter wheel, then attach to scope and camera immediately so they are completely sealed in, whenever I have to remove the camera ( which is very seldom ) I always blow the filters with a Rocket blower before re fitting. sounds like hard work but literally only takes a couple of minutes. Narrowband is much more forgiving for vignetting than LRGB, Ive sometimes had a little bit of slightly darker corners with the bigger sensor of my 383 doing LRGB but then I just perform a flatten background process in Maxim to each channel prior to combining them, its like DBE in pix insight. Ive noticed most pix insight tutorials online people combine their channels first then spend ages trying to correct horrendous colour gradients and noise etc. But if you flatten each channel first then there is nothing to correct later. I like to do processing in a logical progression and none of the tutorials ive seen do it this. Lee

Here is another image I took on Monday night, IC410 The Tadpole Nebula. This is 14 X 15 mins in Ha with my Atik460 CCD and Meade127mm F7.5 Triplet refractor. As usual guided, captured, stacked & stretched in MaximDL, processed in Photoshop. No Darks or Flats

Thats worked pretty well Olly, ive found there are various different colour schemes I can get out of Bicolour. Here is my image, definitely not as good resolution or as deep as yours, but I was pretty happy with the colour I got out of it, I should have stretched the area around the tail more. Happy New year Lee

Nice one Olly, yes I picked up the tail recently too, though not as deep as you have. what sub length are you doing on this? Why dont you make a Bi Colour version with the data you already have. im not sure LRGB would really add anything compared to narrowband on this target. Lee

After my main target last night I had a quick go on the core of M42, this is 15 x 30 secs in Ha plus 15 x 30 secs in Oiii so only 15 mins total capture time. Captured with my Atik460 CCD and Meade 127mm F7.5 Triplet. I used much shorter subs than I normally do as the Trapezium stars are extremely bright so I didn't want to overexpose them. After that I then set a sequence of 10 min subs to get the faint stuff in the background, but it clouded over after only 6 subs so that will have to wait now. As im running a dual rig I also have another set to process now from the wide field scope. guided, captured, stacked and stretched in MaximDL, processed in Photoshop. Cropped quite bit to show the detail in the Trapezium

Ok was just a thought, though while we are talking about voltage 14V is a bit on the high side, Atik told me that 13.8V is the absolute maximum I should use with my camera. My Maplin 5amp bench supply puts out exactly 13.8V so I decided to edge on the side of caution and use my other power supply that is 13V.

Im no expert at all on this, but may as well offer My first thought that it could be Voltage instability, I have done experiments with my Kaf8300 camera and voltage definitely has an effect on the amount of noise, my cam is significantly cleaner at 13V than at 12V. Maybe the examples you have been playing with were taken with a non regulated power supply, or supply that is failing? Anyway just a thought Lee

its generally a nice image, nice and smoothe and I like the colours of the bright parts, but for me the grey point is not correct as the background is very red. hope you dont mind, but Ive opened it in photoshop and confirmed with the histogram that the red channel as a long way to the right of the green and blue channels. a simple click on the mid grey eye dropper tool then click on a point in the background that I think should be close to neutral grey. hope its ok to post 2 examples just to demonstrate what im saying ? Lee

If its a known good battery then that should be putting out around 12.5V anyway and be fine, just keep an eye on the voltage every few months.

Not sure how they can call it a snow storm, the Sony sensors ive used show maybe a dozen, Kodak chips on the other hand could be described as a snow storm.

Its precisely for the reason that the dark current is so low, that I dont use darks. As both Atik and Starlight Express state, using dark with these Sony chips can actually introduce noise into the image. I think Craig Stark also came to this conclusion when he first tested the 314: quote "The dark current is so low, however, that you may-well be better off simply taking a large stack of bias frames once to use for bias correction and use a simple bad pixel map for hot pixel removal". I think this is the method Olly choses to implement, Ive tried that then tried dithering and both gave me similar results except dithering also has other advantages, I guess I could do both but im probably the laziest imager there is. 🙂 Sorry if I went off the original topic slightly, my answer to that is I find -10C fine with Sony sensors, though he mentions running off batteries which I wouldn't recommend, you want to be above 12V as low voltage can increase noise, though thats more of an issue with the Kodak chips. With my new Atik 383 it is noticeably cleaner at 13V than at 12V. Lee

Maybe I don't see that as my skies are much brighter than yours Olly? sky glow is probably swamping any read noise in mine. though I haven't noticed that with my narrowband subs either. I just looked at a 15 min Ha sub with mostly empty sky and the darkest pixels are 350 ADU with the average around 400ADu. so thats massively brighter than your background. Dithering should smooth out any noise in the image though, wether its read noise or shot noise or dark current, as all of those things will be effectively moved against the true signal, so the algorithm should through away everything else . I find I need at least 12 subs to make SDmask work at its best with at least 5 dithers, though I just dither every sub so I know it will work reliably. Lee