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Everything posted by coatesg

  1. Though, it cannot exactly repeat - entropy always increases (laws of thermodynamics) and so at any point in the future, there is a different universal state.
  2. I have for sale my William Optics FLT110. TMB designed triplet APO, 110mm aperture at f7. Has a 3.5" focuser assembly with slow motion, and is supplied with tube rings for mounting onto a dovetail. The telescope is in great condition - the optics are in excellent condition, and the telescope is in very good mechanical shape. Comes in the WO storage/transport case. Also included are: * 2" WO Dura-Bright Dielectric diagonal (in carbon fibre finish) * WO 50mm illuminated finderscope (erect image) - this has a slight tear on the eyecup rubber, but doesn't affect it's use. The finder mounts onto the dedicated adaptor on the scope. * Aluminium plate and McLennan gearbox - mounts onto the focuser shaft and allows mounting of a suitable motor onto the scope for focusing. * William Optics Flat IV 0.8x adjustable reducer which brings the focal length down to ~530mm - allows variation of the back focal distance to allow fine tuning to get optimal stars across the field. I also have a custom made threaded adaptor to connect this to the back of the focuser, thus avoiding flex from a 2" nosepiece. £1700 - I'd prefer to sell as a single lot, but will consider splitting if it goes unsold (I do have a couple of expressions of interest in splitting already). Buyer would need to collect due to weight - please don't hesitate to ask any questions. Please see the attached photos. Images taken through this scope can be found here: https://www.chromosphere.co.uk/tag/flt110
  3. It does depend, but of the tests I've run with this, especially for lower SNR data, WSC comes out better than the others. For larger data sets, the differences are marginal, and may go to other way. The good thing about PI, is that it offers the tools to try it out and measure/compare the results and use the most suitable one. Of course, the rejection parameters also make a difference!
  4. If you have >15 images, I'd def use Windsorized Sigma clip - should result in a lower noise in the final integration.
  5. The PSF from a star does not cut off at any point (in theory) - it fades such that it eventually can't really be detected, unless you stretch the thing to death. Eg I have images of a variable where I can see diffraction spikes from Alcor despite it being over a degree off field! This isn't a PSF/diffraction however, and I don't think it's necessary for - might be a reflection - in which case it could reflect almost anywhere really. Do you have a lens shield, and do you have it flocked? Is there flocking/baffling in the drawtube? All places to look for culprits...
  6. I think this is something to do with Alkaid (at mag 1.84) which is exactly in that direction, about 2 degrees away. It sort of looks like some kind of reflection possibly off a circular shaped surface?
  7. Had a productive evening last night - a good set of data on GSC 4163-0984 in UMa (a HADS star with 1.9something hour period) despite the wind earlier in the day!! Tried then to do a run on AC Boo (W UMa eclipsing binary) but got plagued by scudding clouds and gave up about 40 min shy of the minimum). Ho hum! Still, interesting curve - the contact binaries essentially go straight from one eclipse directly into the other so no plateau...
  8. This sounds like a homework question... As above, there's not really enough information to solve accurately as O type main sequence stars have a range of absolute magnitudes (range ~ 2 mags). Photogav's answer is the way you'd do it though, for this type of question, at least for non-cosmological distances.
  9. Yes - of course that works - though I'm thinking about the ability to schedule/work remotely without having to physically go and stick the lens cap on. My initial thoughts were whether something like an Alnitak flip flat would offer enough "light tightness" to work in this regard? I'm not sure a filter wheel would offer enough protection against light leaks around the outside of the filters (and not enough spaces in the wheel!)
  10. Bit of kit thinking here - CMOS cameras don't tend to have shutters in the way that many CCD based cameras do. Has anyone ever seen an external shutter that can be placed in the imaging train? (I'm thinking about ease of dark frame capture here - something with some kind of large thread like an M68 or whatever to screw in place in front of the filter wheel? Cheers
  11. Yes. The Northumberland at Cambridge is very much in use (12" something like f20...) - the University AS and CAA use it. When I studied there I used it a bit, but always preferred the rather good 8" f14 Cooke refractor (The Thorrowgood) next door... (Had a feeling the 28" at Greenwich is still used though)
  12. Has the OIII output always looked like this? I'm wondering if it's inherent to the sensor (polishing marks from the silicon on sensor). I'd always be applying flats fwiw. The lights and flats both show the same pattern, and so may well reduce out. My ST2000 shows quite marked diagonal lines from bond wire glints. Looks horrible on flats and lights with brighter backgrounds; reduces out well though.
  13. Well, the biggest might have been the INT, before that departed to La Palma. The 36" at Cambridge (https://www.ast.cam.ac.uk/about/36-inch.telescope) is optical, and still in use for research on double stars IIRC - Edinburgh looks also to have a 0.9m Cassegrain (36") but (according to the wikipedia page) is no longer in use. (?) The 36" Yapp at Herstmonceaux also ties I think, but the 38" Congo at Herstmonceaux beats them all (though don't believe it is in use, and never had been, as the optics were rubbish...) I would guess Lord Ross' Levaithan at Parsonstown is probably the largest in the British Isles (but not the UK as it's in the Republic of Ireland) - 72"/1.8m!
  14. If I've been short of comparison stars, for a quick analysis I've looked at using the stars in the AAVSO APASS catalogue (you can access the data really easily by using Simbad). When I've requested an "official" sequence via the AAVSO process, they've used the same data. Though, I did manage to request a set of comparison stars recently, where there was nothing usable above 14th magnitude in the FOV (I had a shade under 30' like Dave) - the errors in the brighter comparison stars were up to 20% of the range of the variable itself - exception made to use them as the data can be adjusted later if the comparison stars are improved by a subsequent survey. (It makes no difference for timing studies, but for getting absolute magnitudes it does somewhat!).
  15. Good work Dave Lots of other things got in the way for me last week - hopefully be able to get back to it soon...!
  16. Just beware of going too high on the 120 - at very high gains it (for me at least!) introduces some significant fixed pattern noise. On related notes, dithering is definitely recommended.
  17. Chart: Updated - better chart with brighter comps.
  18. From BAA VSS group - see image below as just taken: TCP J06373299-0935420 (UG:) Discovery details: R.A. 06h37m32.99s, Decl. -09°35'42.0" (J2000.0) 2019 Feb. 21.4516 UT, 10.4 mag (CCD, unfiltered) Discoverer: Shizuo Kaneko (Kakegawa, Shizuoka-ken, Japan) 2019 02 21.452 UT Discovered by S. Kaneko, Kakegawa, Shizuoka-ken, Japan, with on 10-s exposure on eight frames using Canon 6D digital camera + 200-mm f/2.8 lens under the limiting mag = 14.5, who writes that nothing is visible at this location on a frame taken on 2019 Feb. 20.447 UT with limit mag.= 14.7. 2019 02 21.65 UT A (blue) progenitor candidate from Gaia DR2 is 0.3" away at R.A. 06h37m33.004s, Decl. -09°35'42.15" (equinox J2000.0, epoch 2015.5; Gmag. 19.21, parallax 2.7192 ± 0.4374 mas, distance ~0.38 kpc). Other designations are USNO-A2.0 0750-02439919 (Bmag. 18.6, Rmag. 18.9), USNO-B1.0 0804-0087491, GSC2.3 S3BJ014199 (Fmag. 18.9, Bjmag. 19.4), WISE J063733.02-093541.9, PSO J063733.002-093542.127 (gmag. 19.47, rmag. 19.32). Observations by the ASAS-SN Sky Patrol (Shappee et al. 2014ApJ...788...48S and Kochanek et al. 2017PASP.. 129j4502K) of the current brightening: 2019 Feb. 13.291 UT, gmag. fainter than 16.45; 21.156, gmag. 12.56. No previous eruptions or outbursts were recorded since 2012 Jan. 29; complete light curve at https://asas-sn.osu.edu/light_curves/aef18120-7c35-4b28-9a31-2e083608bf8f --- Patrick Schmeer (Saarbrücken-Bischmisheim, Germany) http://www.cbat.eps.harvard.edu/unconf/followups/J06373299-0935420.html Multiband and time-resolved photometry, spectroscopy, and precise astrometry are urgently required.
  19. Yes - target selection would be easier if you could select, but the beauty of SGP is that you can setup the sequences well in advance and just load/schedule them. I'll often do this using Simbad and a suitable FoV file (this would also give the rotation if using a rotator). Alternatively, copying in the RA Dec by hand is one option. The other is to use to mount to do the goto, manually frame in real-time, platesolve using the local solver and then use the results as the coordinates for the current target in the plate solve results box.
  20. In light polluted skies, for broadband (ie not narrowband!) pictures, ISO400 would be fine. 200 may also suffice - the likelihood is that sky background will greatly overwhelm read noise, as long as the exposures aren't too short. The subs may look rather weak, but stacking and stretching will reveal the target while not saturating bright stars to the same extent as for a higher ISO with smaller dynamic range.
  21. XP 32bit only supports MBR partitioning and not GPT which you need to use to support > 2TB discs. I presume you may have partitioned it using GPT on Win 10? Solution is either to get a drive with 3rd party software to work round it, go to XP 64bit, or goto an OS that supports GPT (Vista/7/10/Server 2008+ ). Win 10 preferable really given support etc
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