rnobleeddy

Thanks all. There was a hair on the sensor. I used the compressed air this time, but will get a blower for next time. Unexpectedly clear tonight so will see if it worked!

Thanks - is there any reason why I wouldn't see it with a lens? In fairness, it may just be that I can't see it on the camera screen. I will check the lens flats when stretched too. I happen to have some compressed air handy as I needed it for something complete different, so I'll do some more searching!

I have a 130PDS, fully modded Canon 450D, Bader MPCC and astronomik CLS CCD clip in filter. I've started to see the following pattern on my lights - highlighted in red below on a flat. Initially thought it be a hair or a streak of dried residue, but I'm struggling to locate it. At least some of is making it through to to the stacked image (albeit only visible when fully stretched). I take plenty of flats, generally using a laptop screen and white cloth. I'm dithering but maybe don't dither far enough, and I probably haven't had enough images to stack in recent attempts (usually 20x5min subs). I'm not using darks. I do not see any hint of this when I use the 450D (plus CLS CCD filter) with a lens, so I guess it must be related to the scope or coma corrector. The coma corrector glass, primary and secondary look pretty clean except for what I think is a usual amount of dust dust. It's always in the same position on the image regardless of camera rotation. Hoping that someone with more experience could let me know what this might be - the size and the fact it's invariant to rotation would (in my opinion) rule out the optical train of the telescope, but then I don't understand why I don't see it with a lens?

Assuming you didn't scale either image, then I'd guess that the ISO 200 shot, because that has been proven to produce the best results. The bottom image looks better because its brighter but presumably as a lower signal to noise ratio. Or to know for sure, run a test!

Rather than starting a new topic.... I have a 450D, fully astromodded, bought from a member of here. I've only really just got everything up and running and the camera does seem noisy, so was wondering: - I read that the 18MP version (say 550D or numerous other models) is less noisy, but is there any indication of how much? Would it be a worthwhile upgrade? - Am I correct in my guess that a modded 450D will generally be better for DSOs than an unmodded camera with a slightly better sensor (clearly, that's somewhat DSO dependent) - There's no dedicated cameras available for <£500 that would provide a massive improvement AND offer a comparable sensor size? I should probably just use what I've got but the mind always wanders on to what's next! I'm happy to have a go at modding myself, although that becomes more favorable the cheaper the camera body is. I'd almost certainly go second hand from eBay. The other option is to wait a year and see if I'm still imaging, and then consider a dedicated cooled camera.

Thanks for all the advice here - I got dithering working, got my EQ6 up and running for longer exposures, and spent a little more time learning processing (in startools, which I realize is at the easier end of the spectrum) and got a much better result. I realize this is still far from perfect - a few stars look odd, there's too much noise at the bottom of the image and M31 appears to be too big for a single image from my OTA, but I'm pleased with the extra detail! startools_output_new_levels.TIF

I'm using a skywatcher 9x50 finder scope with a zwo120mm camera. The full kit is less than £200 new (finder, camera and adapter to connect them) or the finder and camera come up for sale here or on astro buy/sell reasonably often.

Thanks! I'll give that a go next time. I tried again last night with linear and whilst it seemed to run fine, it started so far away from focus that it was measuring the wrong part of the star, so ended up more out of focus! Edit - is there a good reason to suspend guiding? I've just found this means the star that was chosen quickly moves out of frame, but I guess I've missed something!

Funny thing is I did the same last night. I only got 2 hours but that didn't end up looking a lot better than my earlier attempts. I've resolved to have a better attempt at processing tonight!

Did you ever make any progress with this? Right now I'm focusing this manually, but almost defeats the point of having got it.

Thanks. Should have pointed out I'm imaging so ideally want to sit inside and control things, or even better, set off a sequence and watch TV! So I really want something that works in the steady state, especially as I'm actually looking forward to it getting darker as we go in to winter this year! I'll make a dew shield and see how that goes. Totally agree that everything FLO sell has been excellent - just wanted to check what else was on offer before dropping ~£130 on stuff I might not need!

I picked up a second hand older EQ6 that I got running with EQMOD. Guided for about 2 hours tonight (before clouds) with RMS error of around 0.8". Assuming that holds over more sessions, I'm wondering if I ought to bother with the Rowan belt mod or just leave it as is? Just wondering if anyone with experience of the upgrade? It's also worth pointing out that tonight's guiding had an RMS error of ~0.15 pixels with my current guide scope and guide camera. Is that likely to be a limiting factor? I'm happy to fit the upgrade, so the only negative is the cost.

After an imaging session last night I noticed that I was probably close to having enough dew on the main mirror to start to cause issues with images. I presume it's only going to get worse as we get into winter. I assumed I would need some heater straps so picked up a 2nd hand dew heater controller a couple of months back, but don't have any heaters yet. I've also seen dew shields that I presume I can make myself, but not sure what combination I'm likely to need. Anyone got experience with a similar scope? Assuming I need heaters, am I going to find anything cheaper than those sold by FLO? My controller can handle 2 heaters. I also have some spare powered USB ports that I can use if the USB heaters work well.

That's exactly what I'm doing. I didn't anticipate any problems with dew inside the box, but I only started this in spring. As long as you have an outdoor extension and an RCD in the house I don't think you'll go too far wrong.

Are you sure that the movement left is backlash and not just that you're moving the internals of the motor? How good is your PA? It probably depends what you're imaging, but with good PA I'd be surprised if that many subs were lost due to trailing at that exposure length. But either way you'll do better with shorter subs and less wasted. I did some research to see if I could find a way or making my EQ5 work better, but I came to the conclusion that it's probably better to save up for a better mount.

Are you sure this is correct? In the instructions for mine (which admittedly doesn't work for other reasons) that's only mentioned when using the noise reduction setting. If yours is the qumox then I've been able to do 1s intervals between longer exposures, but for some reason mine only works when the two cables are pushed halfway together.

I had a similar issue with my EQ5 which I've tried to resolve as well. I got one good session out of it but I'll wait for another before I declare success. First question is probably what are you aiming for? I've had good quality 5 min exposures but I'll probably end up trying to make 3 minutes my standard. There's always going to be backlash, so focus on the imaging outcome you want rather than the backlash itself. Generally my best guiding has been attained by having very accurate PA, whilst I've struggled if have poor PA and a lot of guiding is needed. To try to make it better I have - used sharpcap to get good PA. Best £10 you can spend imho! - followed the worm gear tuning guide linked to above. Ensure the work gear shaft is tight against the bearings as well as the gear meshing - the motor cogs can be adjusted by undoing the 3(?) Allen bolts. My RA motor had the two gears miles apart initially, but was easily adjusted - follow the usual approach of intentionally unbalancing in one direction and/or aiming for a small PA offset and guiding in one direction only

Thanks - I'm aware of dithering but couldn't seem to find that option in EKOS when I looked. It definitely exists though. I can probably do the research myself, but is it dithering or dark frames, or would both still be worthwhile? I've skimped on darks because it's usually been quite late before I've moved on to them - this should be less of an issue with the nights getting longer.

Mine was actually loose to start with and needed tightening. I've since followed a few of the steps in the video below, including swapping the worm shaft bearings. It's hard to know what helped, but RA now guides at less than 1" which I'll take for this mount. I've only had two proper sessions but DEC was fine the first time with good PA. The second time, I accidentally moved the alt bolt after I'd started imagine, and PHD2 later reported a 1 degree PA offset, so I'll probably let the mount off in that case!

Thanks - this was exactly what I was hoping was the case. I guess the correct way of thinking about it is that I'm lucky to have got a decent image of M27 given the moonlight, rather than worry why M31 wasn't as good. Once I've had a few more good runs I'll work out the best exposure length is and work on a dark library.

Sorry for the confusion - the Reddit post was someone else's work I stumbled upon when I was waiting for DSS to stack my attempt, and I couldn't understand how far less data resulted in better results! For my subs, the EQ5 is guided. The mount has terrible DEC performance and so if I get good PA I tend to be able get up to 5 minute subs. The 1 minute subs in this example were because I accidentally moved the PA, so I'd get 3-4 minutes of solid guiding (less than 1" RMS) and then the DEC axis would jump by 10" and ruin the sub. Bizarrely, rather than fix the PA I decided to go with 1 minute subs and throw away every 4th one.

Thanks, The exposure length change was down to botched polar alignment on the second night. My mount guides poorly in DEC and probably needs a little more work on the DEC backlash. Assuming I get good PA it seems that 5 minute subs are fine, although I'm still working out the sweet spot for balancing exposure time and reject rate. I also have an EQ6 mount that I'm working on tuning, which will hopefully just be better. I was at ISO800. I was hoping that I could just leave the CLS CCD in my camera for everything - are there different filter requirements for galaxies vs nebula (assuming I'm sticking with OSC)?

Thanks - I'll have another go when the right combination of moon/weather/spare time allows!

Those were probably linear. I'm still new to post processing (even unsure which tool to buy!) but I followed a tutorial using GIMP this morning and teased out a little more detail, at the expense of more noise.

Very new to this, but after a frustrating summer with clouds and getting used to equipment, I finally got everything working last week. I've captured short amounts of data on M13, M27 and M38 that aren't going to win any awards, but they look OK and reassure me that everything is working reasonably well and I'm stacking correctly. Then there's M31! Across 2 nights I have about 1hr20m of data spread across 48 subs consisting of some 4 min and 3 min subs and a lot of 1 min subs, with corresponding darks, flats and bias frames for each night and exposure length. I stacked these as 3 groups in DSS, but I've also tried individual sets of data and leaving out flats/darks/bias in various combinations to rule out issues with any individual aspect. I've taken out the obviously bad subs but a few with star trails appear to have made it to the final image below, and there's probably also a soft focus on at least one night. However, none of this would appear to explain the problem - which is there's almost no data on the outer part of the galaxy. Night 1 (about 1/3) of the data had a bright and almost full moon close to M31. Last night was about 60% moon but it wasn't very close at the time I was imaging. Kit is a 130PDS, EQ5, modded Canon 450D with bader cc, and Astronomik CLS CCD. Bortle 5 skies. A couple of the stacks are below and one of the best individual shots. Whilst some of the stacks with all the data seem to skew towards red, none of the attempts I've made have any real detail in them, presumably because it isn't there. I then see posts on Reddit like this and wonder what I'm doing wrong! So wondering if anyone with more experience could advise: - is this what you'd expect to see given my equipment or is something awry? - if this is expected, what would have the biggest impact on making the image better? Clearly more subs at longer exposure can't hurt. - Does the moonlight effectively kill the image? Or light pollution? I can drive a relatively short distance to a darker site but I'd rather work from my garden if at all possible, because that's possible most clear nights, whereas moving the kit is time consuming - I tend to skimp on dark frames a little (I have 10x for the 1 minute subs, and maybe 4 each for the 3 minute and 4 minute subs) - is this an issue? - are there any other tips/tricks to pull any more structure out? The images below are auto-scaled with the ASI fits viewer. Stacked using a subset of the data with flats/bias/darks All data stacked, just lights One of the 3 minute lights