Xmas Pics - Horse Head, Tarantula, Eta & JB

[Big Dave]

4 Pics from xmas eve in a dark sky location. I was fairly happy with all of them.

Horse Head = 4x10Min LRGB
Eta, Tarantula = 3x5Min LRGB
Jewel Box = 3x1Min LRGB

All taken with WO FLT132+FF with STL11k Camera.

Had some issues with dewing on the guide scope which effected tracking a little.

[jase]

Nice work Dave. While its nice to be able to capture as many objects as possible in one night, I would suggest you sit on a single target and collect as much data as you can. Your image quality will certainly improve. Be careful of clipping the highlights when processing. Stars and some key features are rather saturated in the HH and Tarantual nebs. Make the STL work for you - don't be afraid to go 15 or 20min subs for luminance data. Overall, a good panel of images. Thanks for sharing.

[AlexN]

color in Eta Car. looks a little off to me, but detail is very nice, as is the horse head.

As jase mentioned, the Horse head pic shows a bit of clipping in the highlights, but overall a pleasing set of images.

Can I ask why you were using a separate guidecam/scope? Doesnt the STL11K self guide???

[Ric]

A fine selection Dave, some great captures in that lot.

Cheers

[Big Dave]

I seem to get better guiding using a seperate OTA and CCD than the self guiding. I think it has to do with the SBIG output to the Vixen Mount being not as controlled as PHD. The Vixen mount has some funny things going on inside of it!

Eta, well I was playing with it tring to maximise nebulosity without washing out the black in a photo editor (ACDsee).

Clipping, I am unsure what you mean?

Please note: I think my shrinking program seems to take the sharpness out of the image. They look heeps better full screen bitmap, but that is 20Meg +. I will have to play with the JPEG conversion and shrinking process.

[Big Dave]

I should have said each channel was 4x10 minutes stacked (40 minutes in each LRGB).
The Tarantula has me buggered; I just can't seem to get centre definition without killing the rest of the image. I really don't want to process them seperatly (Centre and everything else) and merge the two images together.
I am unsure how to fix this to date, more reading I think. I still are not using flats yet, they seem to make the final image worse.

[AlexN]

clipping is where the natural curve of the histogram is cut off or "clipped".

An image can be black clipped, usually done to reduce sky background noise or gradients.. sometimes done to create an inky black background... which-ever reason, its not the way to go..

Just as it can be black clipped, an image can be white clipped also, this is what has happened in your images, where instead of Alnitak appearing as a star in your image, its a stark white spot.. This can be caused by over-exposure, or over stretching the data to try to reveal more nebulosity.

Jase can likely correct my terminology here, as im fairly new to the game myself.. but generally speaking, Clipping the histogram is bad, for any reason.. There is almost always another way around it, whether it be taking some shorter subs and masking them in, creating masks and adjusting levels/curves for certain problem areas or other, more technical ways which again, Jase can describe better than I can..

All that being said, like I mentioned earlier, thats a great set of images for one night... I'd be very pleased...

Ps.. I want your camera!! GIMME GIMME GIMME GIMMME GIMMMMEEE!!! :D :D

Alex.

[jjjnettie]

I love your capture of the Flame and Horsie.

[jase]

Alex is on the money... in simple terms, clipping is the loss of valuable data.
White clipping = loss of details in the highlights - i.e. stellar profiles and/or bright features.
Black clipping = loss of details in the shadows - i.e. faint/dim nebulosity.

What are you using to stretch the data? Linear stretches i.e. levels is limiting as when you start to bright the image to show the faint details, it is also increasing the highlights at the same proportion/scale. You need to get comfortable with non-linear stretches i.e. curves. This will allow you to maintain the bright areas while enhancing the contrast of the faint/dim. I wouldn't recommend processing objects differently and relayering them unless you're experienced with photoshop tools. It can be difficult to get the right brightness/contrast so they integrate seemlessly. I've done it on a few images. Feathering and masking can greatly assist.

Strange you're having problems with self-guiding. Bin the guide chip 2x2 so you boost its sensitivity. Finding a guide star with the FLT132's focal length would be easy - especially with the field flattener. Make sure you calibrate regularily.

[AlexN]

mmm I would have thought that the STL11K's self guiding would be impeccable.. I've heard of people guiding some pretty serious gear using them.. 24" F/8 RCOS scopes and the like.. Your FLT132's focal length is MUCH more forgiving than the 24" RCOS... Mind you, this is coming from someone who's never used a self guiding camera... so my thoughts on them are completely speculatory..

[Big Dave]

Good Information from both of you. I will read up on these topics during the week, I still have the RAW files so I can try to process them again using the non-linier curves; you are right I used a crude linier scaling. The raw data should be ok so I have to get more familiar with Photoshop. I did most of my colour mixing in CCDSoft and used ACDsee to play with the levels.

The guiding issue is more an issue with the mount itself. More often than not the calibration from ccdsoft's autoguide using the STL's internal guider was failing. I had to turn the mounts gain to autoguider to 200% (20) (max) and calibrate for about 10 seconds. Sometimes it works, other times not. Just watching the Guide stars movement between calibration frames was not resulting in 4 clear directions.

Even when it works it does not seem as good as the DSI2, Piggybacked Megrez88, GP-USB and Phd results.

- Dave.

[AlexN]

mm I do hope its a vixen mount problem, Otherwise, WHEN I win lotto, I dont know what camera I would buy! :D


(Oh how I want an STL11K :D)

[h0ughy]

great shots to brighten ones christmas break. i enjoyed viewing them as the others have indicated it is better to get as much data on one subject as you can. nice work!

[Hagar]

A good collection of images Dave. Try some longer exposures and more of them and you will find the processing a lot easier. The flame nebula is a bit on the red side. Again longer exposures will give you a lot more data to work with and you wont have to splash colour into the frame .

Keep at it Dave.