rotatux

Yes I guess it would do. You may try prime focus on your existing 130p though as told by DorsetBlue, but it's focuser is not great and depending on your camera and adapters you may have difficulty to reach focus (which would be too close to the tube for the focuser). Given the cost of a "short" focuser and the burden of replacement on your OTA, the 130PDS is a good option and already has a quite good focuser from the start. As to what is doable with a synscan az + short newton or frac, check what's possible on the thread named "noeq dso challenge". Especially search for Nigel G's posts as I seem to remember he has the same setup as yours, and did modifications for prime focus.

I know I know but it's only for image processing right ? But then since I'm quite satisfied with Fotoxx for now and it's free, I'm inclined to keep it like this. Will reconsider the day I will manipulate more-than-16-bits images of course. Or maybe Gimp 2.9+ will do the trick (I may build it to check -- needs free time).

From what I read here: https://en.wikipedia.org/wiki/Orion_Nebula#Coloration The center should be blue-violet because of the hot trapezium, and only some highly ionized O++ rich dust around ("high vacuum" regions) should show green. I also believe the green should come combined with other colors and come as yellow (with H) or cyan (with S), as no region should be pure oxygen ! Nice image Nige, very artistic and enhances many features !

Agreed. Even the second one at 5mn total time is better. The lack of color may also be caused be me (I don't recall for sure now) using gamma-based stretching on that one rather than my now usual brightness stretching. That former tends to burn colors and make all grey/white or the dominant color, so I rarely use it now. Ok I must remember about explicitly adding "0 flats" in my info then next time But I see no gradients; I see a decreasing noise zone around the general shape of the cluster, but I believe it to be dust as Ian pointed out. Anyway I didn't stretch it too much / nor shaved the background to keep the noise at a pleasing level (I like this grainy look of amateur astro images). In fact each time I have tried flats they have ruined the result, introducing awful gradients rather than removing them. But the flats I made on that occasions allowed me to check I have less than 0.5% variation in corners relative to center; So I don't bother with them anymore, I rather use darks which are necessary and efficient for my setup. Remember I have a 4/3 sensor so 80% smaller than Canon APS-C, that may be why. Right. However better do alt-az imaging when like me you're unable to PA an EQ correctly and get more than 30s subs from it, at least alt-az gets the subject centered... Thanks Ian, I have already read it as an sidestep from this thread when I saw your previous mention of it (also mentionned in the 130pds thread). Already see this, however I prefer a PDF cited somewhere in this this thread -- search for "Field Rotation V3.pdf", because it gives graphs per observing latitude, is based on absolute pixel displacement limit (though for APS-C), and gives the formulas to compute everything if not satisfied.

Hi again, here's my progress on M45. First image is for reference a session from this year in august, 50km from Paris, but with my EQ mount (sorry, just to show difference with others). Info: Capture = 19 lights x 30s x 2500iso, 8 darks, Olympus E-PM1 with Skywatcher 130PDS (no CC) on Omegon EQ-300 tracking RA only, no filters; Processing = Regim, Fotoxx, Gimp Second image is Alt-Az from late november 2016 from Paris suburbs. Having read the story about dynamic range and sensorgen.info I wanted to experiment with lower ISO. Not conclusive since 1/ my cam only has 12-bits depth, 2/ a simple contrast filter is not enough to dig faint signal like this from huge light pollution and 3/ the mount wasn't reliable at 30s so not many subs. Info: Capture = 10 good of 44 lights x 30s x 800iso, 17 NG darks, Olympus E-PM1 with Skywatcher 130PDS and CC on Celestron SLT mount, TS contrast filter; Processing = Regim, Fotoxx Third and my best image so far is Alt-Az from last 2016 evening at my deep country dark spot. Still not much structure, but anyway amazed that I can get far better images than with an EQ though high number of subs helps a lot with both noise reduction and signal depth. Info: Capture = 72 good of 98 lights x 20s x 2500iso, 38 NG darks, Olympus E-PM1 with Skywatcher 130PDS and CC on Celestron SLT mount, TS contrast filter; Processing = Regim, Fotoxx PS: Ken I know m45 goes high in the night but this was taken early (local 18h30-19h00) about 50-60° alt because sky was already very dark and also somewhat dry and cold (had to keep outside by -5°C). BTW I found that sensorgen.info must be taken with care: the measures are for a single average shot so especially noise and digital range may not be directly applicable to astro-imaging (because of subs stacking). The noise level should be a guide on how many subs you need to sort it out; IMO Real good info are the saturation level, as guide to sub length depending on subject, and quantum efficiency (I now lurk towards E-PL5 or E-PM7 :-P).

« Perhaps you have balance issue that is effecting your exposure length sucess or maybe it was a bit windy. » That's what I suspect. (the balance, not the wind I had zero) I attached a 500g weight to the front to test, assuming the OTA would be pulled by the mount gears (rather than the reverse) when tracking east. That's how my last M42 and my next M45 were taken, then 20s didn't work on M42 at ~35-40° alt (<33% good) but was fine 2 nights later on M45 at ~50-55° alt. So I'm quite confused currently about this. Maybe I will try balancing the reverse way (put the weight at the back) and see what comes.

« Welcome to the dark side » Thanks ken. « So keep pushing that mount harder! » Err, for now my mount is quite reluctant to this :-/ : trying 30s gave a reject rate of about 85%, so I must be careful. I am working on M45 image where I pushed to 20s with only 26% rejects, so I try improving until I can find the root cause for this mis-behaviour. « You also seem to be managing your light pollution very well. You will be surprised how well software can remove light pollution gradients » Indeed I tried the background removal of Regim on the 2nd image, it's powerful but I find it not very precise, and I dont' like the cushion-like bumps it leaves on the background. So I've opted for another technique... « Have you considered using DeepSkyStacker to stack your images? » Yes but I forgot to say I'm exclusively on Linux so my options are more limited than yours (and don't speak of Wine plz ) On the negative side, Regim only outputs 16-bit and no more, though it stacks on 32; And is probably slower than DSS. On some positive side, Regim has B-V color calibration, which gives me hassle-free color-correct images, while I read many here seem to struggle with the color module of ST. « Nothing wrong with that image, and you should be pleased with that. » Thanks Ian « good to see that you've resolved the Trapezium too » yes it is burnt in the 15s subs so I tried my first HDR with just a few lower exposure subs and it worked just like I expected. « Hi rotatux, welcome to The No eq dso challenge and SGL » Thanks Nige « look forward to seeing more of your DSOs » will post a few more in coming days, I don't want to crush the thread with my messages :-P Edit: Quote seems to not work at all for me so I opted for this manually quoted form. Also I need to find where to set a signature... (not found in profile)

Hello, I'm new to SGL but having patiently read this thread from start to end over several weeks I decided to sign in and post some of my results to encourage others (if still needed :-) ). FWIW I'm the proud owner of a SW130PDS so I've also read the entire "imaging with the 130pds" thread (over several months). (sorry if I'm a bit long for this first post) My first images were about 3 years ago on Nexstar SLT mount. Here the kind of thing I got: Infos: Capture = 3 lights x 20s x 800iso, 2 darks, Olympus E-PM1 with Celestron MAK127 on Celestron SLT mount, dydimium filter; Processing = ImageJ + Gimp Then I mostly turned to wide-field with old lens on self-made barn-door-tracker, had some nice images but always from only a few subs, due to my software pipeline of that time. Then 1.5 year ago I bought a RA-motorized EQ3/4-class mount, in the hope to do unguided longer subs. I found it's good enough but is cumbersome to take to my pet dark spot (16kg+optics to take 50km and 45mn from home). I did some imaging with it and it's average, allowing good 30s subs but 60s is harder and depends on good polar alignment (which is too long for me and wastes rare good nights time). So after reading this thread I thought "why not give my SLT a try again". In the meantime I have discovered Regim and it has changed my astro-imaging life ! Though it's not good at everything, it now allows me to properly align and stack many more subs. So stacking a quite high number of subs from an Alt-Az mount doesn't frighten my any more. Here's one I did 2 months ago: Infos: Capture = 103 lights x 8s x 1600iso, 21 darks, Olympus E-PM1 with Skywatcher 130PDS and CC on Celestron SLT mount, TS contrast filter; Processing = Regim, Fotoxx, Gimp I am quite pleased with it since it's from Paris suburbs with huge light pollution, as this shows: This shows possibilities are limited in such conditions without a good LP filter... so I had another try a few days ago on holidays from deep country and quite very dark spot: Info: Capture = 86 good of 101 lights x 15s x 2500iso and 48 NG darks + 11 x 10s x 1250iso and scaled master dark, Olympus E-PM1 with Skywatcher 130PDS and CC on Celestron SLT mount, TS contrast filter; Processing = Regim, Fotoxx My current masterpiece