8SE Imaging (again)
Posted 05 March 2010 - 09:46 PM
NexStar 8SE with f/6.3 FLR, Canon 450D, Hutech IDAS LPS filter, 1600ISO
In previous installations of DSO imaging with 8SE I have tried to go for very long exposure times (60s+). Careful balancing, alignment and some tricks with picking appropriate time for imaging were pretty rewarding.
This time I decided to go for short exposures but lots of them. I did initial run with 100 shots and I liked what I saw. Weather cooperated two nights in a row and I took 300 last night. The result is above.
Tonight, the weather cooperated once again. I am trying to capture 1000x 10 second images. That should be fun
Edit: comparison of old (2009) and new (2010) method:
Posted 05 March 2010 - 11:09 PM
Posted 05 March 2010 - 11:46 PM
Posted 06 March 2010 - 12:09 AM
I would say a cautious yes. What is needed is a mosaic, nothing extravagant, just a 2x2 matrix, a couple of hundred samples per cell.
Posted 06 March 2010 - 03:20 AM
Unless it's a closely guarded secret, I think you ought to publish details of this unique talent you have for coaxing such great images from the alt./az mounted 8SE, (if not just to bring tears to my eyes for investing in a sophisticated and expensive GEM for the purpose) ! :bangbangbang:
Posted 06 March 2010 - 05:10 AM
Posted 06 March 2010 - 08:23 AM
Careful balancing, alignment and some tricks with picking appropriate time for imaging were pretty rewarding.
Do you credit careful balancing and alignment as components of your success because the tracking was thereby improved?
Also, could you say a little about your sky conditions, i.e., how much light pollution you have?
You are truly an inspiration to those of us who think trying AP with an 8SE isn't worth the effort. Great work!
I concur with Tel's suggestion that you publish details of your work, either here or as a Cloudy Nights article.
Posted 06 March 2010 - 08:29 AM
I still say you CHEAT....You have to be, I know you are... LOL
Please do not take up drag racing with your family car....you could be running 8's if you get the kind of results you do out of the 8se for imaging...
Posted 06 March 2010 - 10:26 AM
Picture below was taken at midnight facing (south) away from red zone at ISO1600 2 seconds, half moon was rising to the left (east). Orange glow at the horizon is from another red zone south of my home location.
M42 images were taken between 19:00 and 23:00 local time. First images were taken with M42 being about 42 degrees above horizon and last images about 14 degrees above horizon.
I did not make it to 1000 images last night. I finished at 780 with camera battery flashing low. 582 were selected by DSS for final stacking. I am currently on image 201 for stacking The processing has been running on my laptop since 10 hours ago. I would say another 4-6 hours and I'll have results from last night.
As far as alignment and balancing for this latest run - no, I am taking opposite approach: disregarding both.
My reasoning for this experiment was that 10 sec shots should produce very little motion even if tracking is less than perfect. When I document my process you will see that (and how) I spend about 2 minutes for alignment.
In my previous attempts I would spend up to two hours carefully setting up balance and alignment and then go with 60-90 second exposures to minimize tracking errors. An hour or two of the setup was eating into my data collection time, which is precious given poor weather conditions at my location.
Posted 06 March 2010 - 12:57 PM
One question, is your 450D modified? If not, the reds came out pretty well in your finished image.
OK, I lied, one more question. Did you do any post processing in PS (or something else)?
Thanks for the excellent image.
Posted 06 March 2010 - 01:35 PM
I personally like "picture guides" and will do the same here.
First image is my initial state. That's how I store my 8SE so that it's ready for DSO imaging. Note, that all heating wires, power cables, and USB cable are already attached. This really helps when you are outside and it's cold and dark. I finally gave up on nice mounting options for just about all attachments - Velcro is my friend. I wrapped 4cm wide velcro pieces around all three tripod legs, so that I can throw any thing I am holding and they would not fall/dangle in the air.
You may also notice a counter weight that I made out of steel washers attached to the sliding rail. I did not really use it in this experiment, since balancing of the scope was not important. I slid all the way to the back side so that it did not get in the way when I attach dew shield. The reason I decided to keep it was that I thought it would not hurt since scope is back heavy and some counter balancing would be a plus. No deep science here.
Two heating strips also attached. One to the main scope and one to the green laser pointer (GLP). My GLP is really cheap and does not work well when it's cold. Heating strip gives me a few more minutes before it stops working. GLP is attached to the finder scope also with velcro: it allows very fast steering to alignment stars within 2 or so degrees.
Posted 06 March 2010 - 01:48 PM
Posted 06 March 2010 - 02:13 PM
Here are the steps:
Connect DSLR to computer with USB cable. Start application for remote control. Go into Live view.
Posted 06 March 2010 - 02:22 PM
When I see the star on the screen I push enter and start finer alignment, per standard 8SE procedure. In this case I was even ignoring Up-and-right rule for final approach. I caught myself doing in involuntarily anyway, thanks to a year long training that I picked up right here on CN forum
Posted 06 March 2010 - 02:38 PM
Once I had second star aligned, I hit final Align and scope starts tracking. I am ready for focusing.
Focusing is exceptionally simple with Live view.
First I switch in the Zoom view and then grab my Motofocus controller to adjust focus. Focusing takes about 30 seconds.
Posted 06 March 2010 - 02:47 PM
Simply hit M on the controller and enter "042", Enter. M42 comes into view. On the Live view screen it looks like a three star pattern, which I used to do "framing" of the nebula: I placed the star pattern in the upper left corner of the center white box every time when I was doing re-alignment.
Posted 06 March 2010 - 02:54 PM
Posted 06 March 2010 - 02:57 PM
I would come back every 30-40 minutes to make sure that the three star pattern did not drift too far away. I would actually push 8SE Move buttons while pictures were taken to get three-star pattern roughly in the original position. One image would get thrown away by later automated process. So what? Any attempt to "save" an image would lead to even more time wasted.
In 4-5 hours, I have around 800 images taken. I put the front cover on and take additional 20 dark frames. Dark frames need to be taken at the same temperature as normal (light) frames. I will take flat images later, since I can move the scope without disturbing light path (my home site).
At this time, I take my laptop inside the house and start with pre-processing of the images. I will add step by step instruction what exactly I do with (free) DSS.
Posted 06 March 2010 - 03:19 PM
DSS generates FITS files among other formats. I am pretty neutral on this whole FITS path, but it seems to be convenient for me. I used to process files with built-in DSS functions with little complaints. FITS Liberator plug-in for Photoshop saves me time, on average.
Liberating FITS is as simple as opening FTS files in Photoshop. I am presented with the interface that allows me to choose planes (color planes that is), setup intensity normalization function, and finally save single color (R,G, or B) into a TIFF file.
The idea here is very simple: use your human computer (brain) to evaluate what function is the best for intensity normalization (Log and Arcsin used most often) and then adjust little Level triangles at the bottom of the histogram. The goal here is to see as much details as possible while keeping Blue (black clipping) and green (white clipping) as minimum.
I immediately switch to Green channel (plane 2) to get rough estimate on parameters. And then tweak Red and Blue based on initial Green setting.
Note that each color is stored SEPARATELY in a gray 16-bit monochrome file
Posted 06 March 2010 - 03:21 PM
This is very timely, as the weather here is breaking and
I have a mostly unused 1000D waiting to catch some photons!!
Great work man!!
Posted 06 March 2010 - 03:33 PM
Posted 06 March 2010 - 03:45 PM
Posted 06 March 2010 - 03:50 PM