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DrRobin

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DrRobin last won the day on July 29 2016

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About DrRobin

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    Wish I was somewhere sunny!

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    http://www.drrobin.co.uk

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  • Gender
    Male
  • Interests
    Astronomy, obvious really.
    Sailing
  • Location
    Newcastle Upon Tyne, UK
  1. 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 less (at the edge of the aperture) and increases the f/stop, so might actually help the Etalon work better. If you use a different f/number then you will need to experiment to find the best place to put the Etalon. Remember that the Etalon has a fixed aperture so it is likely that it will need to move backwards in the tube towards the eyepiece. Using a Etalon on a lower f/stop scope will probably lead to a smaller field of view over which the Etalon will work (smaller sweetspot) which would be counter-productive. Peter [Drew] will know more about this than the rest of us put together, interesting that he uses a 6" f/10 lens. It is the same with a Quark, Daystar recommend a F/4 to F/8 scope although the Quark has a 4.2 x barlow installed, which sets the f/stop to f/16 to f/20 which is the range they decided on.
  2. 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 pretty good and flats take care of the field. You can have similar problems with a [double stack] Lunt, I have to have my second Etalon in just the right place and right state of tune for it to work well. I found a focuser rotator which was just the right size so my second Etalon is permanently fixed to the front of my Lunt. All that said, I would still go for the Quark, it lets you use your expensive scope for something else. If buying second hand just confirm with the seller what the views/images are like and that it achieves lock for all of the settings. With a bit of luck they will have used it for imaging and can send you some images.
  3. 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
  4. 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 reasonable amount of memory for the operating system you are going to use, 8GB for Win 10 is enough.
  5. 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 slightly easier to get on with. However, in 2019 with falling solar activity I would choose the Quark, it is cheaper than a Lunt and you can use the scope for something else. In the last two years I have used my Lunt once or maybe twice, I have used my Quark a lot more, but only when there is something to look at.
  6. 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 the primary or perhaps a heater element next to the fans. I would make it switchable of course. The real problem is my location, the mist forms on the river down the hill (mile and a bit away) and slowly creeps up the hill. Probably for about 1 - 2 hours before it obscures the stars my primary mists up, so a heater gains me that extra hour or so. Usually by Midnight it is a waste of time, too much mist. Have you got a 10" truss tube or is it a solid tube? Robin
  7. 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 to 20 minutes before I spot it and this spoils the images, even though it is still relatively clear. I have seen very few dew heaters for a primary and wisdom seems to suggest that they are avoided, the scope has primary cooling fans. Does anyone know if you use a heater tape or similar to prevent primary dew? Ta
  8. 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
  9. 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), 31/01/19 by Robin DrRobin, on Flickr Robin
  10. 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.
  11. 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?
  12. 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
  13. A new AR this morning (no number yet) but looks quite active in Ha. Good enough for me to have one last session before packing up my kit for the trip home. Calcium-K The Sun in Calcium-K, a new active region, from Crete, 11/09/18 by Robin DrRobin, on Flickr Hydrogen Alpha The Sun in Hydrogen Alpha, a new active region, from Crete, 11/09/18 by Robin DrRobin, on Flickr And the out-going 2721, now officially gone The Sun in Hydrogen Alpha, old sunspot 2721, from Crete, 11/09/18 by Robin DrRobin, on Flickr Hope you get a view of the new spot as it develops.
  14. Nice shot John. Ah the benefits of going east. I am currently on holiday in Crete, so much further east and south than usual, it makes a huge difference and the 'almost no cloud ever' helps.
  15. Not much to see Charl, so you made the best of it, nice prom photo. I have been in Crete for two weeks, wall to wall sunshine and can tell you you haven't missed much.
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