Heart to accompany the Soul

It's a beautiful thing. This is 16x10min subs. 60 Flat frames and 40 bias frames. I took the Flat frames with 0s exposures in Neb2 and so used the bias frames as flat darks as well. I think the flats are coming out nice, as evident in the lack of a central halo.



But this image just has too many stars in it!! I don't know how to reduce them. Also I wonder how can I do a better job of data acquisition for this. Should I go longer on each exposure?? or do shorter, more numerous subs? Light pollution is definitely screwing me over to some degree. But there is a glimmer of hope.

ReSoul

After some feedback from Sander about there being enough data, and to just add processing, I decided to take another stab at this. With the same data as the previous post. And here's the result:



I used the Red Channel as a luminosity channel and some iterations of Histograms, Curves and Noel Carboni's "Enhance DSO" script. All in all very happy with it. Thanks for the suggestion about processing Sander.

Soul

After cleaning the corrector, remounting it etc. I decided to check if everything was ok yesterday night. Tried to image Soul Nebula (IC1848). Here's what I achieved:
My flats have gotten much better as can be witnessed in this image. I also too Flat Darks this time around. So here's the skinny on this: 17x10min light frames, 60x0.1s Flats, 40x0.1s Flat Darks and 40 Bias frames. All in all a pretty decent image assuring me that things have not gone horribly wrong. The collimation looks pretty good as well. Although this image probably needs much longer exposures time on each sub frame. Will have to come back to this target.

Fiasco

Yesterday, in an attempt to bring the sweet spot back to the center (as noted in the previous post about flats etc.), I tried recollimating the Hyperstar. After an hour or so of frustration, and lost collimation etc. I realized that the threads of the hyperstar had stuck to Hyperstar conversion kit in the corrector plate. I guess this was because of my attempts to get a better angle for the collimation screws on the Hyperstar. The collimation screws on the Hyperstar really need to be more accessible. They are hard to reach, especially when using a camera such as the QHY8 which has a profile which covers the screws from the top. Anyways, this whole thing meant that I now had to remove the whole corrector plate and rescrew the baffle tube to the conversion kit ring. What a hassle! But the silver lining is that since I had the corrector out anyways, I ended up cleaning it pretty good. One other thing that was stuck was the nose piece of the QHY8. I guess I lost whatever seal it was providing to the CCD. Now I will have to see if frosting problems will rear their ugly head. Finally as of tonight, I am back to my old IDAS-LPS-P2. And the Hyperstar seems collimated and I think I have the corrector centered properly. So the sweet spot should be back in the center. To collimate I started with the hyperstar completely flat and I need very little effort to bring it to collimation. One other thing that I ended up fixing in the process is the way the Robofocus was attached to the scope. I was using 3M mounting tape, which was rated for 2 pounds. I went to Home Depot and got Scotch mounting tape rated at 5 pounds and the robofocus seems to be a lot more stable now.

As I type this I imaging IC1848 (Soul Nebula). Hopefully it will turn out good enough to post. We will see...

Steep light paths and narrowband Light Pollution filters...

Recently I bought the Astronomik UHC filter to try and mitigate some of the light pollution problems I had been having. I have not posted a single image that was taken after obtaining this filter although I did do many runs of data acquisition. The problem being that in even data acquisition, after stacking them, I notice these diffraction color bands. At first I thought it was because of the flats, which I corrected as indicated in my last post. And even after that I notice the bands:

After some discussion on the QHYCCD yahoo forum, turns out that this is because of the steep light paths the the f/2 hyperstar system entails, combined with the large CCD chip used to image. The data is there as can be seen from the red channel:

The other channels show severe banding. Green:

And Blue:

As can be seen, the flat looks ok but is just not able to correct for these diffraction bands:

And the bands make it very hard to correct for it and bring out the details. People indicated that the Baader 35nm Halpha filter migt do a better job. The reason being that the steep light path basically shifts the wavelength by about 6nm and this leads to diffraction patters resulting in the color bands. The Baader 35nm, being pretty wide for a Halpha filter still captures the Halpha even though the shift happens and hence should preserve the data while cutting out all the light pollution. I tried stacking them without flats as well, to rule out the flats and the same problem exists. But oh well!! After 200$ for the Astronomik UHC, I think I am back to using the IDAS-LPS-P2

One thing that can be noticed here is that the chip seems to be offcenter. This was indicated by Sander after seeing my flats. I think the collimation effort pushed it a bit off-center. I can try and recollimate to bring it back to the center, but for now I think I am going to continue with this setup and the LPS to see what kind of results I get.

Analyzing the flats...

After getting the Astronomik UHC, I spent some time training foxusmax for the new optical train, with dismal results. I realized at this point that the screws on the Hyperstar were a little loose and my collimation was way off. Spent about half hour day before yesterday collimating it with good results eventually. But then noticed with the data I captured of IC1805 that my flats might not be optimal and might be contributing to the destruction of my images: 

The values are clipped and the flat is way too bright. The exposures were already 0.02seconds each so, going low on the exposures was not a reliable option. So I got milky acrylic sheets instead to dim the EL Sheet I was using in my lightbox. Subsequent to this the flats look a lot more well behaved:

Using the Flat ADU calculator on Starizona, I need to have around 26000 ADU for my flats. And in this image you can see that it is very close to that. The exposure now is 1.6 seconds and lot more reliable with headroom to experiment a bit.

More learnings...

By default Neb2 debayers the fits before saving it. This makes the fits files 3 times bigger. This is definitely a problem. I do not know how this affects the calibration, alignment and stacking in DSS!! Anyways, I gave another go at grabbing the data of NGC2237 (Rosette nebula) with Neb2 saving the data as raw files instead. And here's the result:


Overall I am very happy. But a few things I need to correct next time around. This data acquisition was originally 48 frames of 4 minutes each. But I could only use 35 frames since the focus shifted pretty severely during the run. and beyond the 35th frame it was completely out of focus. I need to setup focusmax optimally and try and use the temp. compensation feature. Calibration frames were 60 Flats and a master bias breated out of 60 Bias frames. Also, although the IDAS LPS is helping a lot, there is still a lot of light pollution gradients in my image and I have an Astronomik UHC on order. Hopefully that will help. We will see in a few days...

Horsehead and Flame

After a couple of more attempts I realized that there might be a problem with the way I was grabbing the data, so I bought Nebulosity 2.0 and tried grabbing the frames with it and I think it came out well. This is 25x2m light frames with 60 flat frames and 60 bias frames.



One more thing I realized is that I definitely needed longer exposures for most objects. I was doing 20s and 30s exposures but longer would definitely help. I stacked with DeepSkyStacer using AHD for debayering, sigma clip for calibration frames and auto adaptive weighted average for the light frames. I am pleased with the results. Obviously there is a lot of improvement to be had, but this is a great start. The optical train is Celestron C8 + Hyperstar + IDAS LPS-P2 + QHY8.

Horsehead Nebula is a dark nebula and the Flame Nebula is an emission nebula. Both very beautiful targets.