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Maxim Usatov

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  1. Tried the TS flattener at various spacings, didn't do much good for this particular scope. It's fine, really. I can tolerate that for the views I'm getting and the correct orientation with the prism.
  2. Yeah, through the filter this 6" is really an apo! I wish the field was flat, but I think I'm fine with that instrument. Honestly, I haven't tried 3 nm in the city. I've tried 7 nm on Rosette with the 90 mm refractor and it was disappointing, and M42 was OK'ish, but the whole experience still a far cry from Gavin's pictures. Rural sky was a completely different story.
  3. I've been an amateur astronomer for fifteen years, but I think only the last few nights I was priviledged to observe Milky Way's hydrogen regions in all their glory - thanks to NV. The setup was: 6" TS f/5.9 Achromat on TS alt-azimuth mount PVS-14 with Harder 2100 FOM tube 67 mm TeleVue Plossl, giving 13X magnification and 3-degree field of view H-alpha filters: Baader 7 nm and Antlia 3 nm APM Amici prism for right angle correct orientation view Interstellarum Deep Sky Atlas Bortle class 4 site at Wembury Point, England (SQM showed 20.60). Transparency 6/7. Initially started with the summer classics - M57, M13, etc, but once I tried the 3 nm filter on the Gamma Cygni region, I literally couldn't pull myself from roaming around this region surrounding Sadr all the three nights. It was mind-blowing. IC1318 and Crescent both photographic in appearance. Glowing, cury, textured emission in high contrast to dark patches and filaments. The dark triangle near LDN889 not only apparent in form, but exhibiting detailed structure. The eyepiece view was quite similar to this picture, if you squint your eye a little: https://bit.ly/3hJ4Ws4 The Crescent showed doubling front in the north and Y-shape in the center, mottled body, almost "electric," I guess, due to the scintillation. Visually was very similar to this picture: https://www.astrobac...-6888-Large.jpg Numerous DWB emission clouds and the Sh2-101 Tulip in Cygnus were bright - the whole region all appeared as pierced and surrounded by faint hydrogen emission, which was also easily apparent in the eyepiece. The extent of the nebula seen far exceeded what was shown in the Interstellarum atlas. NGC 7000 North America's Gulf was very detailed and at high contrast, with bright knots in Mexico and in the north. The IC5067 Pelican was bright, showing three protruding "fingers" and irregular shape. IC 5068, the Cygnus Arc, was bright and apparent, split into multiple irregular regions. IC5146 Cocoon was pretty bright, without much fine detail inside, and apparent central star. Looking at the Interstellarum Deep Sky Guide, I now see that on those emission nebulae I saw about similar level of detail to what Uwe Glahn saw in his 27" reflector. The wide field of the 6" showed the whole western portion of the Veil in its field, with irregular bright "claw" of IC1340. NGC 6974/9 with Pickering's Triangle, shown as visible from 12" aperture in the atlas, was pretty bright in the eyepiece. The eastern part had less detail, but its overall irregular shape easily seen. Ventured to IC1396 in Cepheus, it appeared very extended and pretty faint, I couldn't see much dark detail, although central round dark region was apparent. Sh2-132, Sh2-157 (bright), NGC7635 and NGC7538 all exhibited some degree of detail, but I am not too familiar with these objects, and left them for another occasion. I don't think I could see the bubble itself with certainty, but it's on a to-do list now. Going south, M27 was bright and pretty compact, compared to vast hydrogen clouds of Cygnus. I won't mention myriads of well-known and obscure star clusters along the way. I think I could see into great "depth" and could observe less well-known NGC clusters well. (Dolidze-Dzimselejsvili 11 is a really peculiar alignment of stars!) Roaming along the Galactic equator, I have never seen so many stars in the eyepeice in my life. I own mostly Cassegrain designs, but f/5.6 reduced to f/2.3 is something else. Carpets, laces of stars! I tried switching to "normal eyepiece", but literally couldn't see much, compared to the NV mode. The eye wasn't properly dark-adapted, and, to be honest, after the level of detail seen in NV it felt a little futile. I tried 7 nm H-alpha filter, but it showed significantly less detail than the 3 nm Antlia. From dark nebulae, Barnard's E (B142) in Aquila was apparent without filtering. Some dark nebulae, if overlaid on HII emission, were better seen with the hydrogen filter on. The last night before returning home I explored Sagittarius, literally bumping into M22 very low on the horizon while scanning manually, and it was a sight to behold! Definitely a top globular in my book now, replacing M13, along with Sadr surroundings being visually more engaging and richer than even the great Orion Nebula! And then... M8 Lagoon was almost a live photograph - silky-smooth whirlpool, bright and detailed flower-like center with stars, dark patches - it's difficult to describe! Looking at monochrome photographs of the Lagoon, I think visually what 6" showed that night comes quite close. I could spend the whole night on that object alone (or the Sadr!) but that was my first overview "mission" so I had to move on. The M20 Trifid was very bright, almost laser-etched on the sky background with irregular patches dividing it easily seen as pitch-black filaments. This photograph is similar to what was seen in the eyepiece (although yes, there was noise in the tube, and it wasn't that deep, so squint to get an idea): https://bit.ly/2TesrQo In that area further, M17, Omega, was very bright and high-contrast as well - I could see the Omega shape in it, so now I finally get why it's called that, and the center emission region was extremely bright and knotty. M16 Eagle appeared as an eagle with wings open, and although there was lots of texture, I couldn't see Pillars of Creation that night, but definitely worth a try at a higher elevation and with a barlow. Suddenly, my visual astronomy life is enriched with so many objects, exhibiting so many details. Comparing what I've seen with Uwe Glahn's and Ronald Stoyan's sketches in the Interstellarum Deep Sky Guide, on extended emission nebulae a 6" aperture with FOM 2100 NV under Bortle 4 sky shows more detail than unaided 27" reflector under very dark sky, and definitely exceeds 14". Could it get any better? On the way home, I had the opportunity to visit the Stonehenge! Max
  4. Sold. Many thanks to all interested. I wish I had more of these EPs to sell!
  5. For sale 40 mm Explore Scientific LER 62-degrees Eyepiece, 2-inch, almost new in box. £100 plus £3 shipping.
  6. Here is the recent light curve I have made of CG Draconis - an eclipsing dwarf nova star with a twist. The data was taken with 0.5 m CDK telescope in New Mexico during the night of May 16, following the call by J. Shears from the British Astronomical Association Variable Star Section. Being a dwarf nova, we are looking at a binary star system with the primary component being a white dwarf that accretes material from a main sequence secondary star: (illustration taken from NASA/CXC/M.Weiss.) As the mass falls onto the dwarf, it forms an accretion disk around it which is thermally unstable, producing periodic outbursts. The CG Dra system is very active. In addition to outbursts, CG Dra is an eclipsing binary. As the secondary component orbits the white dwarf and the extended accretion disk around it, it obscures them every period which results in an eclipse detectable with photometry (Shears et al. 2008). In brief, the CG Dra system can be characterized as following: - Outbursts approximately every 11 days. - Two types of outbursts: short and long. - Short outbursts endure for about 4 days, long for about 8 days. - Shallow eclipses every 4 hours or so, of about 0.16 magnitudes depth, 18 minutes duration. The system had only a few observations since 2008, so the goal was to check on the current behavior and see if there's anything new going on. I have observed the system remotely for three hours in the Johnson V filter, starting 06:02 and ending 09:04 UTC. The individual FITS frames were calibrated and processed with the MetroPSF photometry program I wrote. MetroPSF calibrates the images astrometrically, matches sources with AAVSO Photometric All Sky Survey (APASS) DR9 and VSX catalogs, identifies variables, conducts photometry and generates the reports and light curves pretty much automatically once all the settings are done correctly. In the light curve obtained we can see a ~ 0.2-magnitude dip beginning at about 59351.28 JD. This does not look like an actual eclipse. More likely it is just irregular modulations in the accretion disk - the 0.15 mag flickering this system is known of makes it a difficult target. Perhaps, the accretion disk is clumpy. The problems of CG Dra - why this dwarf nova is interesting: 1) Spectroscopic observations by Bruch et al. (1997) on a 3.5 m telescope at Calar Alto in Spain show that the secondary component is of K5 ± 2 spectral type. For main sequence stars there are known mass-type relationships that allow us to estimate the mass of a main sequence star if we know its type. If we know the mass we can estimate its period in a binary system. A type-mass relation taken from Schmidt-Kaler (1982) would imply a 6-hour period for CG Dra, inconsistent with 4-hour period observed by others. This can be explained by the secondary having higher density that a main sequence star, but this has never been observed in any dwarf nova before. 2) If CG Dra is a normal dwarf nova then the main sequence star of mass corresponding to the K5 ± 2 spectral type would not fit into its Roche lobe. The material begins to transfer when it overflows the Roche lobe, which appears to be impossible in this situation. Mass transfer and outbursts shouldn't be taking place! 3) Radial velocity measurements in the spectrum of the K5 V secondary are on the order of 30 times smaller than predicted for this system. It appears there is not enough wobble of the secondary in orbit due to the gravitational pull. Bruch et al. (1997) suggest the K5 spectrum may actually originate from a star that is not a part of CG Dra system. An optical coincidence? It would be interesting to capture an eclipse and follow this system. References: Bruch, A., Schimpke, T., Kochsiek, A. 1997, A&A, 325, 601 Schmidt-Kaler, T. 1982, in Landolt-Bornstein, 2b, ed. K. Schaifers, & H. H. Voig (Heidelberg: Springer) Shears, J., Boyd, D., Brady, S., Pickard, R. JBAA, 118, 6
  7. StellaLyra 3mm 1.25" LER Eyepiece, new in box, £40 + £3 shipping.
  8. Selling Takahashi TG-L Alt-Azimuth Mount with Tripod. Cosmetically and mechanically both are in very good condition. This is the beefier version of the TG mount on a tripod with a height-adjustable column. Perfect for a 60-90 mm grab'n'go telescope. I've seen people putting 100 mm f/7 apo refractors on it, but I think it is intended for a smaller and shorter telescope, as it's half a fork after all. With legs fully retracted the tripod height is about 50 cm. Fully unfolded the height is about 95 cm. The vertical column with the mount head combined further extends the height up to about 155 cm. Good zenith access. The mount, as I bought it, came lacking the knob to tighten the column, so there's a simple screw there instead now. Can be replaced with just any screw with a knob, shouldn't be difficult. The vertical column has a tendency to jam a little when going up but this is minor - cured by simply pressing a little forward on the column when erecting it. The head is in very good condition and is flawless mechanically. £542 plus shipping.
  9. New EP in box, used it just a few times. £125 + £3 shipping in the UK.
  10. For sale 24 mm TeleVue Panoptic, great condition, in box with manual. £229 + £3 shipping in the UK
  11. Galaxies from central London? Really puzzled. I could barely see NGC 2903 in Leo which is quite bright, but transparency was not very good that night. I would be very curious to compare views through different telescopes/NV devices. Probably need to try pump up the magnification. Bright globular clusters are looking extremely good in NV indeed!
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