Edit: This is now 11.3hrs total integration time, my longest yet. Larger version available on Astrobin.
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This is 30x480s subs. I was hoping to get another hour or two last night, but the clouds came in early. Can't complain too much though, we've had a good run up here over the last week.
Anyway, I found something interesting doing this one. My dodgy pier doesn't hold alignment very well, and all of last nights (10 used here) subs I thought were throw-aways due to field rotation. I should have checked my alignment, but I didn't.
After stacking these less than great subs with the other 20 from the previous night, the eccentricity was still only 0.44 (as opposed to mid 0.5s to high 0.6s). I just integrated them to see what would happen, but I think in future I'll be using more of my "bad" subs. Honestly I wouldn't even know if I didn't know ;-)
This is a pretty dodgy processing job (I even used USM instead of decon), I'll do a better job when I get more data. Pretty happy with it so far considering there's only 4hrs of data here.
Last edited by codemonkey; 17-10-2015 at 04:17 PM.
Coming along marvellously! A great result and fantastic for the circumstances.
There's no sign of field rotation there. Stars look great. If the polar alignment is off along the same hour angle as where you are photographing, then you not only get nasty field rotation, your guiding can get lost in the dec backlash. Conversely, if by good luck your polar axis is off along an hour angle that is at 90 degrees to where you are photographing, then at least for an hour or so you get no field rotation and consistent guiding. Perhaps the pier moved in a direction that was harmless or even helpful given where you were photographing. (With our fork mount, we intentionally put the polar axis 0.04 deg west of the SCP. That gives excellent behaviour when photographing say 60 deg either side of the meridian. And 2.5 tonnes of steel reinforced concrete in solid rock makes it stay put!)
Coming along marvellously! A great result and fantastic for the circumstances.
There's no sign of field rotation there. Stars look great. If the polar alignment is off along the same hour angle as where you are photographing, then you not only get nasty field rotation, your guiding can get lost in the dec backlash. Conversely, if by good luck your polar axis is off along an hour angle that is at 90 degrees to where you are photographing, then at least for an hour or so you get no field rotation and consistent guiding. Perhaps the pier moved in a direction that was harmless or even helpful given where you were photographing. (With our fork mount, we intentionally put the polar axis 0.04 deg west of the SCP. That gives excellent behaviour when photographing say 60 deg either side of the meridian. And 2.5 tonnes of steel reinforced concrete in solid rock makes it stay put!)
Best,
Mike
Thanks Mike! :-)
There's definitely some movement in the subs from last night, which I believe to be rotation. PHDLab estimates a misalignment of over 29' and there's visible elongation in the subs, either NE or SW. PI reported quite high eccentricity; two which didn't even make it into this were 0.7+. All's I know is that when stacking the 10 "bad" frames with 20 "good" frames, the elongation disappeared and I was left with pretty round stars. Happy days!
I think I'm going to have to do some more work on the pier. In trying to save myself some money I've got a clearly inferior solution. I think it's the mounting to the pier that's the problem; I'll be looking into buying a proper pier top plate to hopefully sort this out. I've seen alignment change as much as 70' in a week; whereas parking the tripod on the same footing I'd end up about 15' after several weeks.
My footing is okayish, it's mostly just the dodgy DIY pier. Pier footing is 110x110x60cm (only 60 deep). It's in clay mixed with granite, but to get below that point in our soil would require the footing to go down over 3m. It moves a little but it's not too bad, certainly not 70' in a week bad.
I also intentionally misalign to improve guiding; I've got 2884ms (thanks PHD2!) of backlash in DEC so I try and keep corrections to one side. I'm going to be trying PHD's new backlash compensation feature to see if I can use that to correct in both directions whilst dialling in better alignment.
Quote:
Originally Posted by gregbradley
Awesome Lee. You must be happy with that. Lovely round stars too.
Greg.
Thanks Greg! :-) Pretty happy with the stars! You wouldn't think 1/3 were bad throw-aways eh? Could be a bit tighter like yours and and Mike/Trish's, but I'm still pretty happy.
Forecast says it'll clear up this evening so hopefully I can get some more data. If the forecast is right over the next few days I should be able to finish it up completely.
The scope really is delivering; though you wouldn't guess it from the review thread, I'm really happy with it. By far the sharpest images I've ever gotten.
Moonlite should be here for the scope in the next couple of days; it'll be interesting to see whether I have to keep refocusing with that. If not, I think my shaft couplers are at the post office and I'll start work on building automated focusing.
The better news, equipment wise, is I've found out my recent issues with RA and major, major backlash (and hopefully the high-frequency noise I was seeing): the pulley on the RA worm had come loose. Ripped it apart again yesterday and fixed that up.Looking forward to seeing how it guides again now. The other night I did some PE analysis and found a really smooth curve, so hopefully with this fixed up PEC will make a huge difference.
Got another ~3hrs of data last night, making this now the longest L integration I've done; 6hrs, 56min. Micro data for some of you, but a big effort for me :p
Pushed this pretty hard (see second attachment of original post)... might have overcooked it.
Hopefully the weather will hold and I'll get some RGB tonight.
Coming along really nicely Lee.. I agree it might be pushed a little hard however you're showing great detail in the arms and plenty of background galaxies... How did you go for clouds last night? I was imaging for a couple of hours until an abundance of wandering clouds sent me packing at about 10:30... Ironically, one of my kids woke up and kept me awake until nearly 4:30am, and from about 12 onwards every time I looked outside the sky was clear as a bell...
To say I was kicking myself was an understatement...
Yeah, after reviewing it I definitely pushed it too hard. So now I've redone it, pushing it hard in a different way lol. Happier with this one though. I've replaced the overdone one in the original post now.
Cloud cover last night was great; had a small patch come up just after it cleared (and I thought "yep, here we go, typical!") but then nothing until I packed up around 11:30pm.
Looks pretty sweet Lee, lovely contrast. Sometimes in images of NGC 300 it is had to tell what is noise and what is actual resolution of the galaxy and I think many processors like to kinda convince'emselves that some of the noise is stars, but I recon you have done a good job here Looking at your image I can see why it is such a popular target this time of year.
Looks pretty sweet Lee, lovely contrast. Sometimes in images of NGC 300 it is had to tell what is noise and what is actual resolution of the galaxy and I think many processors like to kinda convince'emselves that some of the noise is stars, but I recon you have done a good job here Looking at your image I can see why it is such a popular target this time of year.
Mike
Thanks Mike! It's definitely tricky to identify the noise from the detail in this one. I've probably still pushed it a bit hard, and when I do the RGB I'll likely dial it back a bit.
To be honest I just wish I had a smaller (FL) scope for this... bit too up close and personal for my tastes, but I only have the one scope now and no reducers, so it is what it is.
Quote:
Originally Posted by Paul Haese
The latest version looks pretty good Lee. I like the detail levels of the later version.
Thanks Paul!
Quote:
Originally Posted by gregbradley
Looking good Lee. I hadn't noticed those 2 dark areas in my subs. Are they processed or in the RAW data? They look like dust areas in the galaxy.
Greg.
Thanks Greg :-) They're definitely in the raw, but they have also been enhanced with local histogram equalisation which I used to bring out the arms a bit more.
I did get some RGB last night, but haven't had a chance to give it a real go. First impressions are that I may need more data... back to work now (just been on leave) so I'll have a play when I get home tonight.
My last annual leave was 5 days each side of new moon. 10 nights, I imaged for 7 of them. Hahaha
Niiiice. I had one week off and I think I imaged on 5 of the nights? Best run I've had in forever though, so it was most welcome. In fact, I actually welcomed the two cloudy nights so I could relax lol.
Looking at your image I can see why it is such a popular target this time of year.
