I've been working on astrophotography for around the last month or two now, and I'm loving it and having a blast. However I'm feeling like my images are frequently too soft and lacking in detail - Horsehead Nebula being one that is really doing my head in but I'm feeling the same about Carina Nebula too at this point.
I'm trying to work out whether this is caused by lack of focus, too short integration time, lack of quality data, bad tracking, unrealistic expectations, or what is going on. My inclination is to BUY MORE STUFF to get more detail, but cruising astrobin and checking out what other people are doing with 102mm refractors on the same targets and they are getting the kind of results I'd like to achieve. And yes I'm aware that learning astrophotography is a process that takes a long time to master and I shouldn't really aim to knock off hubble for image quality from my backyard any time soon ... but I still want to!
Anyway, here's my setup:
SkyRover 102mm ED APO Triplet Refractor
HEQ5 Pro
ASI120MM Mini / Orion Deluxe 50mm Guide Scope (RMS error ~ 2.5")
Canon 6D Stock / ASI533MC-Pro
Any advice / suggestions on how to get more detail would be great. Thanks folks!
As marc says some flexure or drift causing star elongation, but the underlying data looks pretty good and may be more a case of working on your processing. Frankly that's what makes all the difference and it takes a long time to be proficient. So what software are you using and how are you going about processing?
Your focus doesn't look bad at all, but hard to tell at small web sizes. Not that focus seems to be a big issue for you going by the image but if you are uncertain about focus, and if you don't have an EAF, make sure you are using a Bahtinov mask which will make focusing very easy, even manually. Focus can shift as the temperature drops particularly if your OTA was not equalised with the ambient temp when you focused it so check your focus periodically in the night particularly after a big temperature drop.
The underlying data quality looks pretty good, as others mentioned once you fix your star elongation issues, you will be able to get some good data and can then work on your processing.
In answer to your original question though, more detail comes with more integration! And a big part is processing/stretching too, coaxing the detail out of your integrations is also important.
I would likely need some subs to know exactly whats going on, but you have bits of the image with up to 20% tilt error, however the focus is pretty good, (Software is maxpilote by the way, free just weird to use, no I don't know why the images are undersized )
The star trails should be what you attack first, as you where guiding and its consistent, could it be something like you where only guiding on RA? with a poor polar alignment, the graph in PHD should give some indication here,
for that mount I would assume better than 2.5" RMS, you might want to check the backlash is adjusted, and there are no sticky points, when properly adjusted the rock should be as small as possible without the worm gear ever binding when turned by hand (remove the belt to check) https://youtu.be/x79akiJO3pU
Next would be figuring out why some of your subs have a pretty nasty tilt, where cables getting dragged? or was that area imaged at a different time to the rest, e.g. battery change.
OK I've confirmed backlash in both axis doing the "rock test" so that probably accounts for the shoddy RMS error - or at least contributes to it.
Guide scope is mounted via finderscope bracket so there's lots of room there for movement there. I'll need to look at a proper piggy back setup for that I'm guessing.
Tilt error - ok now I'm back to school as I hadn't even heard of this til you mentioned it. There is definitely pre/post meridian flip data in here I think so hopefully that accounts for it. I won't stress about this until I've sorted out the backlash and got the RMS error down though, one thing at a time!
Thanks everyone for your input and suggestions thus far. I'm going to get to work improving my guiding, starting with fine tuning the backlash, and take it from there. Looks like I've got a couple of nights of ok weather coming up so long as I don't go buy that mono camera I'm thinking about, so hopefully I'll get some improvement in underlying quality over the next week or two.
All good, usually when I've started getting data for a night I will throw a sub or 2 into the software to try and catch stuff like tilt early, usually comes about from not enough tension on the focuser plate on my newt, or the camera adapter not being flat against the focus tube, however cables getting tugged makes it shoot up rapidly,
Glad to know you found your backlash, I would like to know what numbers you manage after getting it tuned in, its such simple maintenance on most mounts, but really improves how they behave.
As for belt tension, if you over tighten you will see it as a consistent error pattern every 16 seconds or so, this is the belt teeth, and its a sign to loosen it just a touch, you will re-introduce a hair more backlash by doing this, but the goal is to reduce the amplitude of that error so that the total error goes down.
did you capture and apply flats? looks like that would assist with processing and getting extra fine detail out of the image - that and a little drift which marc mentioned fixed would assist a lot.
First of all you are doing pretty good so remember that above all else.
My money is on poor tracking.
Often you can balance your scope in RA so it seems perfect but the mount likes a bias either to the West or most likey the East...so perfect balance may not be what will give you good tracking...you need to work out what the mount likes..unguided.
First thing to do is identify that RA drift is the problem so take say a 30 second exposure wait a minute or two take another and see which way the star is going...( You can use high iso or gain as you are just looking to see direction of drift)...East or West..adjust counter weights by moving say 15 mm...take two more photos to see how moving the counter weight has effected the drift.
It can take a long time...further do this without any guiding. ...also wait a while before you start as the mount may need to settle to its new position.
I have a HEQ 5 mount and I can get it to track for a minute by getting balance correct...
Of course before you do anything make sure polar align is as good as you can get it...
In any event take say 30 second, 60 second and 3 minute exposures and see if your trails get longer...I always adjust the length of my exposures on how long I can go before I notice trails...this means some nights may be 2 minutes others may be as short as 20 seconds...
Take heaps of subs and use only half of them as a general rule.
I have recently taken 750 one minute subs and used only 320 ... It is hard to throw out any sub but if it is not perfect get rid of it.
Further after you take a few..stop and examine all you have captured critically..blow up each sub and then inspect it...if you see trails or signs focus is out fix it early.
Anyways try to know your mount before you go to guiding...know its little quirks.
Flex should not be an issue.
Once you have polar and tracking worked out you can look at other issues..distance from flatner to sensor..tilt...internal reflections...flex..or how much money to throw at the problem..however your current image would be excellent if tracking was spot on I feel.
well after some adventures in tuning backlash, and playing with settings, I'm making progress on the quality of my tracking. Still got a ways to go but RMS error is dropping and I'm seeing more detail in my integrations. I'm having trouble uploading an image this morning but thanks to your suggestions and insight I'm definitely making improvements with my setup, and throwing out more dodgy subs / not chasing imaging in thick cloud etc!
Well I've done a lot of messing around and tweaking to try and eliminate the backlash. It's still not "good" so I'm going to get someone's help with it this weekend, but things are improving steadily and I'm starting to see the details in my captures that I'm seeing in other people's so I'm happy that I'm making progress.
Thanks for your input and suggestions - I still haven't tackled tilt yet (want to get the tracking sorted first) but I'm putting more attention on getting good calibration frames, and getting my guiding nice and tight.
)
