Helix nebula mixed results

[xiongz (Zonghou Xiong)]

After months of fixing my CEM60 mount, I finally got it run normally at desired accuracies and managed to snap a few hours of good data. As it is approaching late seasons for Helix, I thought it might be best to mix these few hours of data with fairly amount of earlier shots I got when the mount was faulty. Back in May I was experiencing irregular RA spikes and went on changing, one by one, tripod to a pier one, RA worm, and RA ring gear. As problems still persisted and were getting even worse, I couldn't think of anything else being wrong except for the motor or bearings. As I took apart RA worm again it was obvious the two bearings were faulty/worn. Quick change of the bearings immediately gave me around RMS 0.3 arcsec of guiding accuracy both in RA and DEC, which was huge relief for me as I was considering upgrading to a higher capacity one.

With the mount fixed I was only able to get two clear nights of imaging, with some 25x 10min subs of Ha and 13 sub of Oiii, ASI2600mm cooled to -15 degrees, 3nm Antlia filter, with a rebuilt Skywatcher 300F4 scope, OAG guiding. However, there were tens of hours of data when I was testing and fixing the mount as guiding errors for RA were about 1 while DEC was between 0.2-0.3. I removed or reduced stars of old images and used good stars from good Ha and Oiii of the past two week to get mixed results, which seemed to be quite ok. Here is HOSO image of about 46 hours in total, 170xHa, 43xOiii, and 64xSii. With HOSO I meant the blue channel was 50% Sii and 50% Oiii. I preferred this mixed colour as it would otherwise be either too blueish (HOO) or too yellowish (HOS) at the centre. I also used Ha as luminance to enhance overall details. Image was cropped and downsized by about 50% so it could be uploaded here.

Clear skies,
John

[CaptainCook (Gary)]

How did you get the purple and red to be different..where is the Sulphur in relation to H and O? The reason I ask is I found a paper on the structure of the Helix and it showed the SII was stronger than the other two but I have only imaged it in HO..(mine is here) and wondered what else you can get/add with SII.

[xiongz (Zonghou Xiong)]

Hi Gary,

It was Sii. Sii was very week but spread out just like Ha. I had to do excessive stretching to bump up Sii signals. As I was using Ha as luminace, overstretching of Sii would not affect noises and star sizes.

John

Originally Posted by CaptainCook

How did you get the purple and red to be different..where is the Sulphur in relation to H and O? The reason I ask is I found a paper on the structure of the Helix and it showed the SII was stronger than the other two but I have only imaged it in HO..(mine is here) and wondered what else you can get/add with SII.

[xiongz (Zonghou Xiong)]

I reworked a bit on the image, noticing that there were excessive noises in outer regions. It turned out to be over weighting of new Ha with only so many subs (25) when fixing stars. I also added a bit Oiii in centre region in luminace bringing out a bit of radiants of Oiii. Earlier mount errors would also have affected overall details but it isn't possible this year now to repeat such massive hours when the weather was so good a couple of months ago.