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Everything posted by DrRobin

  1. Well done Alexandra, just seen your photo on the BBC website. Robin
  2. Nice one Steve. All of my solar kit is still in hiding, Sept 2018 was the last outing in Crete, perhaps I will go and have a look to see if it is still there? Robin
  3. It seems to take several seconds (30s?) to transit the disc and is not massively out of focus so it must be a reasonably sized object some distance away. It's random nature, speed and size rule out an aircraft or satellite, if I had to guess I would suggest something at about 500~1000ft away, moving at around 10~30mph. It appears to change shape, so your guess that it is a sheet of something been blown along by the wind (tumbling) is consistent, but not as high as you suggest. It might be a drone, someone at 500ft and moving about 10mph, but been manually controlled and changing ang
  4. We have all been there, moving telescopes round the garden, chasing the narrow window in winter. Sadly my solar telescopes haven't made it back out of storage since sometime last year (or was it the year before?), I forget when, but looking at some of the other posts there has been a few spots to look at, so good luck. The other option is to drive out to a car park, you get some funny looks, but that is all.
  5. I saw a bright flash last night at 23:34 and initially thought it was lightning, but a check on lightningmaps.org confirmed it wasn't and anyway the colour was wrong. I assumed it was a meteor and the report below confirms this. https://www.bbc.co.uk/news/av/uk-england-derbyshire-51373851/exploding-meteor-caught-on-doorbell-camera-in-derby I live 10 miles west of Newcastle Upon Tyne and it was due east at 23:34, I guessed somewhere over the north sea. It must have been pretty big to be seen so well in Derby and due east of Newcastle Upon Tyne. My night sky camera caught it, in
  6. It's a simultaneous equation, x is the distance of the train from the bridge, y is the length in the bridge (in terms of time) x = y/3 and x+y = 2*(y/3) x therefore equals y and therefore the speed of the train is 3x. We did these in school.
  7. A focal reducer doesn't change the F ratio of the scope, it changes the size of the sensing element. Your 200mm RC is still F/8, but the pixel size has effectively doubled in size (4 x the area) and this makes it more sensitive at the cost of resolution.
  8. Binning doesn't help that much. If you use a 2x2 bin (4 times the area), but they way the signal is read it is more like 2x the signal. To get back to 4x signal you have to use 4x4 bin, roughly speaking. Smaller pixel sizes often have a lower light sensitive area to total area, due to the need for readout registers. It's so dfficult to compare different ccds. If you look at my post from 2013 you will see I differentiated between a DSO (the subject of this thread) and a star. This is important if you are considering point sources or a light spread out of an area.
  9. I was making the assumption that it would be the same camera on both. If you change the pixel size then everything changes, oh and you might as well change location to above the atmosphere where there is less loss. I doubt this is true either, both systems end up with the same amount of sky per pixel, if both cameras have the same sensitivity (difficult to achieve) then both will image in the same time as they both have the same number of photons to play with.
  10. How faint you can see depends on how many arc-seconds per pixel and the signal to noise ratio of the chip. Hubble is in space so has very low noise. The F-ratio, aperture and pixel size all then contribute to the number of photons in each pixel from any given light source. If you increase aperture and as a consequence increase F/ratio (focal length) then the number of photons per pixel might not change and you won't get any more signal. If you increase pixel size then you will see faint objects provided you don't increase noise as a result, but at the expense of resolution.
  11. Simply put..... F ratio determines how long you will image for (your exposure time); Aperture (and focal length) determine how much you will fit in. E.g. a 12" F/5 telescope will have the same exposure as a 6" F/5 telescope, its just that the 6" will cover a much wider field.
  12. Hi, My dad got me out of bed to watch Armstrong and Aldrin walk on the moon, I think it was delayed? but can't really remember, I was only 5. Fantastic achievement, this is what can be achieved when everyone pulls together. Robin
  13. Rear mounted Etalons are designed for a certain f/stop and need to be placed at the correct distance from the objective lens. It's all about the angle of the light passing through. I don't have the physics to hand but a PST is f/10, so really you want to keep the final scope at or near f/10 and the same relative distance from the objective as the PST. In front mounted Etalons the light [from the sun] is near enough parallel, in rear mounted Etalons, the light is converging, but not so much in a f/10 system. Restricting the aperture of a objective lens, results in light which converges
  14. I didn't say earlier (didn't want to put you off), I was one of the early adopters of a Quark, my first went back twice, it would reach lock and the contrast/detail was very poor. The one that replaced it was perfect, the contrast good a reasonably flat field. Unfortunately that one would reach lock (no green LED, either Red or flashing) either so I sent it back for re-adjustment. They decided to replace it. The replacement reaches lock, but the contrast isn't quite as good as Quark 2 and the field not quite as flat. Perhaps I should have stuck with Quark 2 but the one I have now is p
  15. I am still trying to improve in narrowband, but just had a go at the Tadpoles using a modified Hubble palette. I think it came out okay. 24x600s in each Sii, Oiii, Ha (12.5 hours in total) taken over 4 nights in Jan with a RC 250 and SX-35 IC410 The Tadpoles, 4 nights 13-28th Jan 2019, False colour narrowband 24x600s Sii, Oiii, Ha. 12,000 light years away, each tadpole is 10 light years long by Robin DrRobin, on Flickr
  16. There are a number of different i5 processors and the best site to compare on is www.cpubenchmark.net. Go for the fastest you can afford, it will last the longest. I would still get an SSD for the operating system and short term storage, whilst you work on files and then have another disk for larger storage or things you don't use all that often. An SSD will give you an instant speed increase, probably more than moving up on processor spec a bit. A 256GB is big enough for Windows, most programs and a few files, say a months worth. Get a 512GB if your budget stretches. Get a reaso
  17. I have a Lunt 60 Double stack and a Quark. I mostly image, so not sure if the balance swings for visual, but here goes. A Lunt (without double stack) is much easier and quicker to use than a Quark, the field is more even, well it is in mine. My Quark does give superior views. The warm up time is not really a problem, just plug it in whilst you set the scope up. Add a double stack to my Lunt and this improves the detail to almost the same as the a Quark, but the field flatness changes, well it does on mine. So a Lunt double stack gives similar views to a Quark and is probably slig
  18. Hi David, The fans on the back of the scope run all of the time the camera is on. I have an extractor fan in the obs to remove air through a duct as well as a desk fan to circulate the air in the obs, these are switchable, but mostly on when I am imaging, even when it is really cold. There is a small PC in the obs, but it is very low power/heat dissipation. I am not sure if the fans in the back of the scope blow or suck, I think they suck in air and across the back of the primary. The more I read the more I think it might be best to have a primary heater, either a tape round
  19. I have a 10" truss tube RC and unfortuanetly my location can get a bit humid and damp. It seems to be the primary that gets the dew. I have a small heater on the secondary (not often switched on) and another on the camera, but there is nothing on the primary. My scope is fitted with a canvas light shroud. The whole lot is mounted in an obs with several fans and is usually somewhere near ambient temperature. If I spot it happening during an imaging session then a bit of light heating of the primary with a hairdryer sorts it out for another hour, but I can have dew on the primary for up
  20. Thanks everyone. Just thought I would post a more typical picture of the view, taken this morning at about the same time. Look carefully and you can just about make out neither the Moon, Venus or Jupiter. Taken between snow showers. The view without the Moon, Venus or Jupiter, 01/02/19 by Robin DrRobin, on Flickr
  21. Hi, I have been watching this view develop for the last couple of mornings, waiting for the moon to be sandwiched between Venus and Jupiter. Well this morning it was perfect. Captured with a Canon 600D and 55mm lens. Despite been a lovely dawn it was very cold, about -6c. Fortunately this was the view from the bedroom window, stood next to the radiator and with no wind it was quite civil. Captured at 07:25 The Moon with Venus (left) and Jupiter (right), 31/01/19 by Robin DrRobin, on Flickr Captured at 07:35 The Moon with Venus (left) and Jupiter (right), 31/
  22. I think you are probably correct, the out of focus image suggests it is close. The only aircraft to come anywhere near during that frame was at 4,500 ft, so it was close enough to be out of focus on a F/8 system focussed several light years away. The only thing the aircraft's track didn't take near the field of view, but the recorded track might be wrong and it might have been closer to my location. Thanks.
  23. It might be, but then why didn't I get several in a line, that is usally what happens. In addition I didn't hear an aircraft during the frame. I checked FlightRadar24 for the time period, one aircraft did pass to the east of me, but looking at it's position and where my scope was pointing I doubt it was in the frame. Would a strobe light show up in Sii?
  24. Hi, I am imaging The Tadpoles (IC410) tonight in narrow band and one Sii frame showed a very bright spot, which does not appear on any other frames. The spot looks out of focus, but is strange as there is no trail. The exposure was 600 seconds, with a RC-250 and SX-35. Does anyone know what it might have been? Ta Robin
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