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Dave Sexton

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About Dave Sexton

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    Nebula

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    http://www.astrophoto.homecall.co.uk/index.html
  1. I am an infrequent imager, I know, but I like to post what I capture. I set the scope up on the patio on Saturday evening only to have the clouds roll in an threaten to put a stop to my planned imaging session. Fortunately, I held my nerve and did not break my setup down and the sky cleared later in the evening. Not a perfect sky, but good enough for an imaging session. My location in the suburbs of Worthing is far form ideal as an imaging venue, however, with a suitable light pollution suppression filter (I use the Hutech IDAS filter), it is possible to get quite satisfactory results. Indeed, I was happy with this shot of IC1318 (the Gama-Cygnus Nebula). The capture is a stack of 40, 180s exposures taken with a QHY8 at prime focus of a 200mm GSO f/4 Newtonian with a Baader MPCC. I used Nebulosity v2 for camera control and PHD v 1.10 in conjunction with a QHY5 for guiding my EQ6Pro; guiding was in ASCOM mode, not ST4 (I find that ASCOMN gives better results). The images were calibrated and debeyered in Nebulosity and average stacked using AIP4WIN v2.3.0. Following an initial scaling operation, final processing was performed using Photoshop CS2. Other than user of Gradient Exterminator to eliminate vignetting (the lazy way, I know!), nothing other than standard Photoshop features was used for the processing. Even at 180s, I have still managed to saturate the centre of some of eth brighter stars. It si taking some getting used to working with a faster ‘scope. This is a revisit of a previous post for me as I had been less happy with the result last time. I ma now content that I am on the right track with this ‘scope (collimation, focus, focuser stability etc. have all provided me with challenges that I am now on top of). Regards, Dave
  2. Although conditions were far from perfect, it was a nice surprise to see a clear sky on Sunday night into Monday morning, especially as I wanted to test another focuser modification. I was able to collect just 10 360s subs of NGC 6888 before it became too cloudy to continue. Of the 10 subs I collected, AIP4WIN rejected two during stacking (because their tracking had fallen below standard). I rejected a couple more myself as it was clear that the sky had started to mist over a little. The result below is, therefore, a stack of just 6 subs of 360s. That's not enough for this target. A reasonably pleasing image, nonetheless, despite the noise. I will try and augment this capture with some Ha data at some point in the near future; this might bring out the fine detail that I know is in there. Regards, Dave
  3. There's soem nice detail in this shot. Seems to be one of those objects that responds well to narrow band imaging.
  4. Martin, It was the standard focuser. While I recognise that a Baader Steel Track would improve the situation, a much cheaper (and entirely satisfactory) option was to use the GST standard profile focuser. If I am going to spend any additional cash on focus, it is going to be spent on motorisation and introducing the ability to focus remotely and not on the basic focuser mechanism. The standard GSO focuser (not the low profile one) will work well with a load of up to 2.5kg. It is certainly smooth as silk with the QHY8 loaded on it. The big issue with the GSO at f/4 is hitting the very tight critical focus point. A motor will be of more use to me here than anything else as it will make controlling fine focuser movements a lot easier. Regards, Dave
  5. Steve, I meant to look at your post yesterday and never got around to it. This has come out rather nicely, though its almost a shame there are so many stars as they somewhat mask the beautiful areas of nebulosity. Nonetheless a nice image. Regards, Dave
  6. The issue was really the focuser itself. My QHY8 weighs in at 625g and the low profile focuser was not able to support thw weight without sagging. The only way to prevent the sagging was to tighten the tension screw on the Crayford so tight it rendered the focuser effectively unusable. I was able to improve matters a little, but gave it up as a bad job in the end. Sadly, the Crayford I lifted from my 6" does not have the 10:1 mechanism. However, I have decided to motorise the focuser that I fitted as acheiving focus by hand on the fast (f/4) Newtonian is a bit too hit and miss. Besides it annoys me that focus is not the only thing I cannot do from the comfort (and warmth) of my living room ;-) Regards, Dave
  7. I have been having significant issues with "sagging" in the low profile focuser on my GSO 8” f/4 Newtonian. As a consequence, I have never had satisfactory results using this scope with my QHY8. Over the weekend, I transplanted a standard profile GSO Crayford form my 6” f/5 onto the 8”, having first estimated that it would provide sufficient “in-focus” to accommodate the QHY8 and the MPCC. The images below (M13 and the region around Sadir in Cygnus) were only intended to be focus/tracking test shots. However, despite artefacts cause by dust on nu QHY8 optical window, I was quite pleased with the result. It has certainly been so long since I had anything worth posting that I thought I would kick myself back into action with these. M13 is 10 x 300s subs, Sadir region is 15 x 300s subs. Both QHY8 using a Hutech IDAS LPS filter. Mount is an EQ6Pro guided using a QHY5 and PHD. At least this has restored my enthusiasm for imaging ;-)
  8. As you say, there is some nice detail in there. Of course, the 9.25" cat will do a nicer job still. I look forward to seeing it. Dave
  9. Disgusted once again with the weather, I had a play with processing some data taken last year in combination with some data from October this year. This is a combination of data shot using my QHY8 at prime focus of a 150mm f/5 Newtonian and my new 200mm f/4 GSO Photo Newtonian Astrograph. In both cases the mount was a Skywatcher EQ6 Pro, guided with PHD. The shot is a stack of 20 images of 300s on the 150mm 'scope and 25 images of 300s each on the 200mm (a total of 3h 45m of data). All frames were captured were captured and stacked with Nebulosity using a LPS filter. Adaptive stacking with rotation and scaling was used to accommodate the variance in image scale between the two 'scopes. Post processing using AIP4WIN, Photoshop and GradientXTerminator.. I didn't post the original 200mm data as it was a bit disappointing. However, when added with last year's data from the 150m, the result is pretty reasonable (if somewhat anaemic when it comes to colour). Just goes to show that you should never discard any raw data. Let's hop this cloud clears soon Dave (click to enlarge)
  10. Martin, Having had a fit in the middle of the night over my sensor frosting over, I was disparate to test the camera with a dew strip. So, I purchased an Astro Engineering Small Telescope Dew Removal System (AC369). It did the job, but I wish I had been more patient and purchased something more suitable as I also need to heat my guide scope. This is not a “glamorous” thing to spend cash on, so I am going to opt for something inexpensive like a Dew-Not two channel controller with heater strips. By the way, my sensor only frosted over when I removed the optical window. The space between the windows and the sensor is critical, adjust it and the sensor frosts. Dave
  11. Dave Sexton

    M39

    David, A nice image. I have not imaged may clusters myself and they never seem to image well when. This is a nicely composed image. Dave
  12. Rob, With or without the re-processing, a beautiful image! Dave
  13. Robin, Those IR filter modifications are certainly worth doing. The appeal of DSLRs is their simplicity, but the down side is the savage IR filters installed. My first Horse Head was attempted with an unmodified DSLR and is was not as nice as the image you have posted here. Dave
  14. That's a nice image. I confess that I am not very familiar with this object, but it is definitely one to have a pop at. It has to be said that our hobby is not so kind to laptops. I'm sure all that exposure to cold, damp air helps them on their way. Dave
  15. Martin, When I first got my QHY8, I had a very similar problem. Initially, the optical window was dewing up. To resolve this I removed the window, but then the sensor frosted. Eventually, I installed a dew heater around the the optical window (see photo below). Dewing is a particular problem on the QHY8 when used with Newtonian telescopes where the camera is often pointing towards the ground. When this happens, chilled air form around the cooled sensor falls onto the optical window which is in contact with ambient air on the other side. Dewing is inevitable. Anyway, glad the clean worked. Dave (click to enlarge)
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