Rosette Nebula 01/02/13

Tzetze

It was off to a dark site to test out the new powertank and guidescope. Had also done some more fine tuning on the mount and wanted to see how the guiding would perform.

First target of the night was the Rosette Nebula. I had no trouble finding a guidestar with the new ST80 and had high SNR in PHD. The wind gave some trouble however and with it hitting the scopes side-on gave a little rocking back and forth in the RA axis even with a slight imbalance on the East side to keep the gears fully loaded. The Dec axis looked very smooth in PHD graph and stayed close to the origin. A huge improvement over it's previous performance. I managed to get 6x 600s subs off before the wind began to catch in the front of the dewshield and cause too much instability for further imaging.

Here's a screengrab of the PHD graph. Mmmmhh buttery smooth Dec! :pac:
The gap between one horizontal dashed line and the next corresponds to 1 pixel on the guidecam. The image scale being 4.4 arcseconds per pixel.


I did some extended processing on this image. Created a greyscale luminosity layer where the sharpening and stretching was done. Also an RGB layer which was heavily blurred before saturating the colours. I boosted the red nebulosity in the final flattened image as my camera is unmodded and doesn't pick up the red spectrum thanks to it's IR cut filter.

6x600s subs
45x darks
25x flats
50x bias
450D, SW ED80, CG5-GT, PHD-Guided
Stacked in DSS, Tweaked in PS


Rosette Nebula 010213 by .Tzetze., on Flickr

The powertank performed very well, btw. I stayed at the dark site until the dawn so I could take flats through a white t-shirt at the sky. Slept in the car while subs rolled off on target #2 (safely behind a locked gate with dog for company). So, the whole setup was powered for a good 12 hours. Checked it's charge when I got home and there was enough in reserve for another 10 or 12 hours. Looks like 2-night sessions under darkest Irish skies are definitely on the cards!

DubOnHoliday

That is a superb image, well done.

ZeRoY

Great work TzeTze, glad to see all the setup is working for you! That pic is amazing, I hope I can get to this level at some point this year

ThatDrGuy

Thats beautiful Tzetze. The mobile set up seems great, sleeping in the car is really sacrificing for your art. Im not sure what the results of my custom 11 OTA set up will be but bright orange seems likely. Would need a lorry to move it at this stage : fingers crossed for clear night plus blackout. A really clear night in Nov I saw the pacman nebula looking amazing visually, want to capture it but I can't tweak my set up with all the clouds.

Tzetze

ZeRoY wrote: »

Great work TzeTze, glad to see all the setup is working for you! That pic is amazing, I hope I can get to this level at some point this year

Cheers Zeroy. It won't take that many sessions to find yourself up to speed. It's just that the sessions tend to be very much spaced apart.

ThatDrGuy wrote: »

Thats beautiful Tzetze. The mobile set up seems great, sleeping in the car is really sacrificing for your art. Im not sure what the results of my custom 11 OTA set up will be but bright orange seems likely. Would need a lorry to move it at this stage : fingers crossed for clear night plus blackout. A really clear night in Nov I saw the pacman nebula looking amazing visually, want to capture it but I can't tweak my set up with all the clouds.

Thanks Doc. It wasn't the most comfortable of nights in fairness, but well worth it in the end.
There are plenty of examples of fine work from light polluted cities, if you can get a clear enough signal above the sky signal, then a lot can be done for the image in processing.
Pacman nebula looks a nice target. I've not seen it visually, but at 35', it would frame nicely with my setup...

Nerro

that's a nice picture and a great report to read!
what fine tuning did you done on the mount?Maybe you have the logs of before and after?
would love to compare yours and mine but unfortunately my auto guider is stand alone one, so didn't took any logs.Never the less when i was imaging IC 434 over the week end the hand controller showed minor adjustments which were expected as that was my first time I used drift allign because the mount don't have polar scope...to be honest I expected worse...
On the next session going to connect everything to the laptop and have a look as still can't get over the down grade from NEQ6.

Tzetze

Nerro wrote: »

that's a nice picture and a great report to read!
what fine tuning did you done on the mount?Maybe you have the logs of before and after?
would love to compare yours and mine but unfortunately my auto guider is stand alone one, so didn't took any logs.Never the less when i was imaging IC 434 over the week end the hand controller showed minor adjustments which were expected as that was my first time I used drift allign because the mount don't have polar scope...to be honest I expected worse...
On the next session going to connect everything to the laptop and have a look as still can't get over the down grade from NEQ6.

I followed these guides, but don't yet have the bearing upgrades (hoping to get them in the near future).
http://astronomer.proboards.com/index.cgi?board=Equipment&action=display&thread=3079
http://www.astronomyboy.com/cg5/Astronomy_Boy_CG-5.pdf

Used 1200, 1500 and 2500 wet paper and a metal polish suitable for Aluminium. All from Halford's.

I used a thicker lithium lube than the recommended white lithium, but seems to work fine. Don't make the same mistake I did of using the aerosol based white lithium from Halford's. It's too thin and my mount seized when I put my 10" on it!. Had to resand and polish the parts and use a thicker lithium grease.

I don't have a logfile or graph from before the tuneup unfortunately. The dec axis was so stiff and sticky (stiction), when a correction had to be made for drift there would be no response for quite a while until the force would build up enough to overcome the stiction then the dec line would spike right off the graph, take an age to come back to the origin, overshoot and repeat the process. It took a couple stripdown/rebuilds to sort out.

Nerro

Just went thru the guides...jeez I don't think I have the guts for it.I have heard that you can tune up your mount but didn't expected that it involves striping it down completely.
I follow the "if it's not broken don't touch" rule.there is one too many examples where I have "improved" the item...
Never the less thanks for sharing!

ZeRoY

Nerro wrote: »

I follow the "if it's not broken don't touch" rule.

This is it. Best to see what results you get without tuning first then apply a fix if required. I have a LXD75 and there are also some hardcore tuning tutorials but Im staying away for now until i see how guiding goes.

Tzetze

Yep, see how it performs first for sure.
You can at least look into removing the backlash from the gears in both axes. It's easy to do.
http://www.webalice.it/michail.xintaris/cg5%20regulation%20eng.html

There's a fine line between no backlash and the gears binding too tightly, so it's worth giving that a check in case it's on the binding too tightly side of things, although it's more likely that you'll have quite a bit of backlash instead.

Iancar29

...Drool...

ThatDrGuy

Some progress on getting my mount working,

I finally got enough autoguiding to make a graph:



If your wondering where DEC went, well... my drift align is in beta stage and only works in lattitude and I didn't do it. Feeling
quite positive about the RA though, given how windy the night was. Got about 5 minutes guided before it vanished due to
DEC issues.

Tzetze

Guide to PHD Guiding
What to do When PHD Guiding isn't Push Here Dummy

Try easing up on the RA aggression Doc, around 90-70 maybe. I think the max RA could come down to 300ish, maybe less.
What guidescope and camera are you using again?

ThatDrGuy

Thanks Tzetze. Have read the guides, so much customisation needed they arn't very helpful. I use a Orion Starshoot autoguider and a ST-80. The orion starshoot drivers barely work with windows vista ( on my laptop) and PHD always crashes when I click on a star. To make it work, i have to connect camera, connect a simulated mount, then in loop mode switch it to shoe string usb gsb1 control. Then it only crashes 50% of the time. I will try it with the setting you recommend, hopefully get a smoother RA. I think the wind has quite some influence in the sine type pattern seen, the large ota with dew shield is like a sail. Next step I think is to build a lateral adjuster and get a really smooth polar align ( with a usable DEC) Ive heard the chunky mounts have a lot of DEC issues because of the gear sizes so polar align needs to be spot on to minimise DEC adjustments.

Tzetze

I'm not so sure that's entirely wind as I've seldom seen it's effects to be so periodic. Looks more like the software is overcorrecting. RA agression is the percentage of calculated correction to be applied. In your case above it's applying 113%. I would try halving that and give the graph a couple of minutes to settle.

Wailin

Brilliant image. What type of powertank is it? I have the skywatcher 117A which is decent but as soon as you add things like laptops etc it struggles.

Tzetze

Wailin wrote: »

Brilliant image. What type of powertank is it? I have the skywatcher 117A which is decent but as soon as you add things like laptops etc it struggles.

Thanks Wailin. I built my own powertank with a 110Ah battery and toolbox. Thread here.