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mftoet

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mftoet last won the day on April 4 2014

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  1. A friend of mine owns a 180EDT. An instrument that dates from the time before Astro-Physics became a renowned brand. On the public observatory in Rijswijk (Netherlands), where I’m a volunteer, we have a Starfire 130EDT that’s excellent for visual observing the Moon and planets. I consider myself lucky to own a Mach1 mount. Acquired directly from Astro-Physics in 2009. In 12 years of use this mount never let my down. I’m on the waiting list for a Starfire 130GTX since 2016, but don’t know if I’ll order one if I get a notification. You can order one directly at several retailers in Europe (Baader, Optique et Vision, Unitron Italian), but the price is high: about 10k Euros.
  2. Thank you for your nice comments.
  3. Since about 6 months now, I've finally got the pleasure of a back garden observatory. In the area of the Netherlands where I live, sky conditions are terrible for regular, broad band deep sky photography (the SQM-value varies about 18 magn./arcsec). That why I like to visit dark sites like @ollypenrice's Les Granges every once in while. One of the great benefits of a personal observatory is that you don't have to setup and brake down your equipment for every imaging or observing session. To be able to do deep sky imaging from my back garden with narrowband filters, I decided to go down the ZWO route with an ASI294MM Pro (mono) CMOS camera and their ASIAIR device to operate the equipment and sequence an imaging session from a mobile phone or tablet. Apart from some inconsistencies and unpredictable behaviour in the guiding interface, I'm impressed what the ASIAIR is capable of. Especially autofocusing works like a charm. Because of the low f-ratio of the Epsilon-180ED (f/2.8), I use Baader Highspeed narrowband which are specially designed to use with fast optics. The OIII filter produces halos around bright stars. Apart from that, I'm very content with the performance of the filters. The last two weeks we had a surprisingly large amount of clear skies in The Netherlands. I decided to go narrowband all the way on the Rosette nebula, and captured data though Ha, OIII and SII filters. Processing a multi-colour narrowband image is quite different from a regular RGB/one shot colour image. My mind wants to make a natural looking image, but that's nonsense when your actually creating a false colour image. Pure SHO colour mapping didn't give satisfying results, so I ended up mixing the colours over the three channels which resulted in this pastel-shaded Rosette. Total integration time is 14.5 hours: 18x 600s SII, 46x 600s Ha, 23x 600s OIII. Ha only was used for luminance. Hope you like it. Higher resolution of the full field of view can be seen on my website.
  4. Thank you, Pieter. The observatory is great. The weather in current and recent winters is awful though.
  5. My first serious tricolour image in Hubble Palette (SHO) with a recently acquired ZWO ASI294MM Pro astro camera. Captured from my back garden observatory in the Netherlands. Exposure time: 3 hours (6x 600s Hα, 3x 600s OIII & 3x 600s SII) Optics: Takahashi Epsilon-180ED f/2.8 Filters: Baader-Planetarium Highspeed Mount: Astro-Physics Mach1 GTO Date: January 8, 2021 https://www.mauricetoet.nl/DeepSky/i-8j5wxHd/A
  6. I have a lot of images showing brown(ish) dark nebula. I don’t specifically try to bring out this colour or hue, it’s simply there. I always try to white balance my images on a the background sky (which can be hard to find when there’s lots of nebulosity in the frame. Furthermore I often increase the vibrance of the colours in my images by 20 to 30 in the Photoshop RAW converter. The last example is a rather interesting one: apart from what might be a gradient in the lower left corner, different hues can be distinguished in the molecular clouds: ‘50 shades of ...’?
  7. In the end: brown is dark orange. It’s also called a ‘context colour’. Here’s a YouTube video about brown not being an actual colour.
  8. That are excellent looking images! Nice to see Takahashi filled the gap between the 130 and 180 with this new edition of the Epsilon 160. The dedicated extender that’s in development also makes the 160 more versatile than its brothers. I noticed there are now lock nuts on the collimation bolts of the secondary. The adjustment/suspension of the primary mirror also differs from that of the 180. Good to see there’s an aperture mask on the (oversized) primary mirror. The 130 lacks one and therefore artefacts around bright stars (caused by the mirror clips) can occur.
  9. The colour gradients in your stack are also common with the D810a I use. There's always some green to purple hue. I think this is sensor related. The gradients can be corrected with the light pollution removal tool in AstroPixelProcessor, but sometimes needs several runs and careful placement of the calculation boxes. The issue with the bolts on the secondary mirror also sounds familiar. I think I've just finally managed to get the secondary mirror in the correct rotation opposed to the focuser (and also centred under the focuser). In my case, the dot on secondary has always been just slightly off center causing even worse star images in the corners than on your example image. Yesterday I've imaged with an ASI1600 4/3 format sensor and I no longer detect collimation error. I have to verify with the full frame D810a though. I collimate the primary mirror with the tube pointed straight upwards (to the zenith) and only use the cheshire eyepiece (not the tube with cross hairs). As Mark pointed out, you can screw the 1.25" adapter directly on the ED-corrector. That will make it easier to judge if all circles are perfectly concentric.
  10. That turned out excellent and very deep, just as you wanted.
  11. When I acquired the Epsilon-180ED, the RASA systems weren't released by Celestron. In the late analogue / early digital age, a friend of mine used an Epsilon-160. I fell in love with the crisp stars that telescope produced and promised myself I would acquire one some day. About 10 years later I ordered an Epsilon-180ED including the ridiculous expensive tube rings, base plate en 7x50 finder scope (which in the end I only use for star alignment after switching on the mount). Another thing that I like about the Epsilons (and other fast Newtonians for that matter), are the diffraction spikes. I know, you either like them or you don't. Would I consider acquiring a RASA instead of a fast Newtonian? Maybe, but probably not. A thing that would bother me is that the camera (and cables) must be placed in front of the corrector plate. I can imagine taking proper flats can be challenge with a RASA. So respect for those who manage to produce excellent images with these astrographs!
  12. Yes, you can, Richard. I suppose a 3D-printer can do the job.
  13. Thanks! The primary mirror of the Epsilon-180 has a diameter of 190 mm and has a mask / edge support with an aperture of 180 mm. A simple but clever solution to avoid undesired diffraction patterns like spikes caused by a turned down edge. (Please don't get upset by the dust on the mirror: this picture was taken just before cleaning...)
  14. Thank you Craig, Olly, Mark and Göran. @gorann: no the browns have nothing to do with light scattering in Earth’s atmosphere. It are genuine colours in these molecular clouds. You can also see the yellows and browns in dust lanes of other galaxies. I don’t know the exact (physical) reason for the colour, but probably a combination of absorption, reflection and ionisation in relation to the ratio between CO and H2 in these regions.
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