Very Amateur Astronomy

I think I’m running out of objects to image in Cygnus now! This one is the Crescent nebula, a bright emission nebula standing out from a region full of faint nebulosity. It is a target and indeed a region that would benefit from a modified camera, something I really must get done. However I am pleased with the result from what is essentially quite a short total exposure, if I get another night this week I may have to grab another couple of hours to bring out the fainter background structure.

It would be nice to try this area with the 250mm reflector to, higher resolution should bring out the very faint bubble nebula which is also in this field, but invisible at this scale and resolution.

I’m running out of ideas for widefield nebula to image at this time of year, any suggestions gladly welcomed, perhaps a field trip for a go at the Rho Ophiuchus Nebula.

Imaging Equipment

• William Optics ZS66SD
• William Optics MkII 0.8 Field Flattener
• Canon EOS 1000D (unmodified)
• Astronomic CLS CCD Filter

Guiding and Mount

• Vixen A70LF Refractor
• Modified Philips SPC900NC Webcam
• IR/UV Cut Filter
• 0.6x Focal Reducer
• Celestron CGEM Mount

Exposures

• 32 x 5 minutes (160 minutes total)
• 29 x bias
• 29 x dark
• 31 x flat

The images were calibrated and debayered in Iris then aligned, stacked and processed in Pixinsight.

This is part the Cygnus Loop (The Veil Nebula), a vast supernova remnant, taken on the evening of the 16th of June from the roll off roof shed. The loop comprises several well known objects, one of which, the Western Veil (NGC6960) I have previously imaged with the 250mm reflector. Also included in this widefield image are the Eastern Veil (NGC6992) on the left and Pickering’s(Fleming’s) Triangular Wisp (NGC 6979) in the centre right.

This area was another target for my summer widefield nebula mission, and is located not far from my previous target the Eagle nebula. Unfortunately it’s just a bit to big to fit in the area corrected by the William Optics field flattener on the ZS66, I’d like to try the new Skywatcher flattener with it at some point to see if that does a better job.

Imaging Equipment

• William Optics ZS66SD
• William Optics MkII 0.8 Field Flattener
• Canon EOS 1000D (unmodified)
• Astronomic CLS CCD Filter

Guiding and Mount

• Vixen A70LF Refractor
• Modified Philips SPC900NC Webcam
• IR/UV Cut Filter
• 0.6x Focal Reducer
• Celestron CGEM Mount

Exposures

• 40 x 5 minutes (200 minutes total)
• 31 x bias
• 31 x dark
• 31 x flat

The images were calibrated and debayered in Iris then aligned, stacked and processed in Pixinsight.

Taken on the evenings of the 21st and 22nd of May this is the north american nebula, a large emission nebula in the constellation of Cygnus.

Imaging Equipment

• William Optics ZS66SD
• William Optics MkII 0.8 Field Flattener
• Canon EOS 1000D (unmodified)
• Astronomic CLS CCD Filter

Guiding and Mount

• Vixen A70LF Refractor
• Modified Philips SPC900NC Webcam
• IR/UV Cut Filter
• 0.6x Focal Reducer
• Celestron CGEM Mount

Exposures

• 57 x 5 minutes (285 minutes total)
• 21 x bias per night
• 15 x dark per night
• 21 x flat per night

The images were calibrated and debayered in Iris then aligned, stacked and processed in Pixinsight.

We have had the joy of a few nights of clear skies over the last week, and I took the opputunity to get in some imaging. I wanted to try my hand at a nebula, but finding something of both reasonable size to make use of my field of view (42.3 x 63.4 arcmin) is proving a little difficult.

After a bit of hunting around I saw that the Veil would be coming up over the house from about 1am onwards which would give a decent 3 hour window for imaging before the skies brightened up to much and below is the result

In the end of course I actually ended up getting about an hour and a half of data, of which about an hour was really good, the lesson being to stop mucking about with software and just stick to what works. However, this is a good start and something to be moving on with, the image itself shows some issues with colour correction, the reds are to brown for instance. However I was happy with the result on this nebula from an unmodified DSLR.

This weekend we have four nights of clear skies forecast which I am hoping to make use of, and this time going back to my trusty William Optics ZS66SD to take a proper wide field image of this area.

As I recently identified and fixed a major issue with mirror slop in my reflector I decided to take some time out to have another run at capturing periodic error, as my previous results along with my guiding were badly effected. Here is the PEC recorded over 8 worm cycles :

The data shows a periodic error of +8.4/-5.7 uncorrected, much better than the +14.2/-13.0 I had previously recorded. I will get out on the next clear night to record the corrected results.

It’s been a while, and I apologise for not posting sooner as I’ve not been entirely inactive, just rather unproductive with processing. Most clear nights have been spent tuning and learning about the CGEM, and most spare days spend on modifying the scope. The result of this is that I now have reliable clean guiding, the main fix to achieve this was to put in locking bolts for the primary mirror.

Most photography time has been spend on a wide view of M106 and NGC4217, with several other galaxies also visible. I’ve had significant problems during image processing with noise, which I guess is a result of my new ability to expose for much longer periods, I need to investigate a suitable maximum exposure time for my light polluted skies, ten minutes may be to much.

I had 33 good ten minute exposures but the fainter areas of M106 were getting lost in the large amounts of noise, mostly red grain. In the end I decided to make use of all of my test images which included a stack of 5 minute exposures and some which were not flat fielded in order to improve the signal to noise ratio, so the total number of exposures used was 83, which works out at about 11 hours and 40 minutes of data. Some experimentation with my new found ability to guide will be needed to make the most out of exposures at this sort of length.

Here it is anyway,  not the best image but proof at least for me that more exposures equals good SNR.

I thought I’d publish my results from measuring and training PEC on my CGEM, other users may find the results useful as might potential buyers. I used PEMPro after researching the subject as it is generally thought to give the best results, though I had a bunch of issues getting it to work properly with then SPC900NC webcam, see my earlier post on that subject if you are having problems.

PEMPro offers full support for Celestron mounts as well which is handy, allows you to directly upload a PEC curve to the mount. Anyway, on to the results, the first screens show the uncorrected curve written after 5 worm cycles.

Individual worm cycles :

PEC Curve :

The reported periodic error is +14.2/-13.0, certainly enough to give me problems with extended stars on the RA axis at my image scale, though guiding corrected a reasonable amount of this it was not perfect by any means.

The PEC curve created from this data was then uploaded directly to the mount and I took another set of two worm cycles with PEC running to get an idea of the improvement.

Individual corrected worm cycles :

The data shows corrected periodic error of +5.5/-5.1, a great improvement and a 5 minute guided exposure afterwards showed much better stars, and also showed up how badly out of collimation the scope had become during the recent pier installation. There are probably better results to be had with more worm cycles of data, and I’ve not looked into smoothing the curve or adjusting the time shift, but I’ll report back when I do.

If you have been looking to get accurate periodic error correction then you have probably found your way to PemPro by now. If you have an SPC900NC webcam, like many of us do as it is the default model for long exposure modification, and you have found PemPro, then you have likely found out that the two of them together makes for rather a mess. Pempro crashes every time you try to set the exposure levels for the cam.

Here is a quick way round that, you will need some software that works with the webcam, I use the free version of K3CCD Tools and WcCtrl (web cam control) to manage the webcam settings.

1. Start K3CCD, centre a star and set the correct exposure and gain to get the image.
2. Start WcCtrl, connect it to the webcam so that it inherits the settings, I’ve found WcCtrl won’t let you switch to manual exposure by itself.
3. Stop K3CCD, leave WcCtrl open and start PemPro.

PemPro will now run with the webcam settings defined in WcCtrl, and you can now use the software to sort out your PEC.