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The Warthog

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Everything posted by The Warthog

  1. The difference is in the width of the field of view. For a plossl lens, you get the full FOV at up to a 24mm eyepiece, but above that you need a 2" eyepiece. At 32mm, your FOV is restricted to about 48º, no matter how great the FOV of the eyepiece may be. This makes a great difference in the Widefield eyepieces with FOVs of 60 to 100º.
  2. If you have lost, or never had, a case for an eyepiece, you can get a free replacement from your local pharmacist. If you have a good relationship with him/her, you can just ask if they have a pill container that would fit your ep, or could they put your latest prescription in a pill container that would suit you. I go through a lot of pill containers, so I have used a number of them as ep cases to replace missing ones. I also have a good enough relationship with my pharmacist that I could just ask for a pill container if he wasn't busy. Some of your relatives or friends may be able to supply
  3. I put a right angle finder with correct view on my Newtonian. Although its view is right side up and correct left to right, it is easier to use than a refractor-type correction with the inverted view of the Newtonian, and helps me avoid neck strain. I use a red-dot finder to get close to the object and use the optical finder to close right in on the object. Adrian's description of using an inverted finder is probably the best description I have ever seen. If the crick in your neck doesn't bother you, you will have less need for the red-dot, as you will be looking along the axis of the scope w
  4. To me, that looks as close as dammit. Sixela is correct in his analysis of your previous pic, but you seem to have taken care of his suggestions. I always keep the French proverb in mind, "Le mieux est souvent l'ennemi du bien" or "you can drive yourself crazy striving for perfection in areas where the incremental benefit is less than the work required to achieve it." French is such a compact language.
  5. Why do you feel you need to replace the existing screws? My C6N has a push-me pull-me system for collimating the the primary; I.e. two different size screws at each adjustment point, one which moves the mirror up the tube, and one which pulls it down the tube. It was invented by a sadistic ****. Still, if I needed to replace them, I would take out one of each, take them to a hardware store, and pick up screws the same size.
  6. Oh, you can google tables that will tell you what the offsset should be. Such as: Secondary Mirror Offset Calculator . However, you will also start worrying yourself to death needlessly because they specify a centre dot offset.
  7. The required offset is very small, a matter of millimetres or fractions of millimetres. If you ignore it entirely it will have very little effect on your scope's imaging. The reason for the offset is that the edge of the cone of light coming from your mirror is slightly closer to the focuser at the top of the secondary than it is at the bottom. So, the secondary should be offset away from the focuser. You can achieve this by tightening the screw on the spider away from the focuser, and loosening the one toward the focuser. It is the least of your worries in collimation.
  8. There are a good number of amateur telescope making sites under that name. If you can build a box, you should be able to make a working Dobsonian telescope.
  9. I am not suer what the axial tilt of the moon to the sun is, but if it is more than a degree or two, your city at the north pole would be in darkness for half the year, just as the north pole of the earth is. I just looked it up; the axial tilt of the moon is 1.5º, which leaves some high peaks in sunlight all year 'round, but at ground level there would be darkness for half the year. Some trigonometry should tell you whether that would be a great problem. The upper reaches of your dome may be high enough to catch sunlight, and the upper parts of your rotating solar cell array may be able to re
  10. I have two that i use, a book by Ian Ridpath that contains about 20 pages of line drawings and photographs of the moon in sufficient detail for most small to medium scopes, and a folding Rukl atlas sold by Sky and Telescope that gives a 2' x2' map in great detail. I got the map in refractor semi-inverted but I use it with my reflector with a little mental gymnastics. Ialso use VMA for planning my viewing and reviewing what I saw afterward. I'm afraid you may not be able to get teh Ridpath book in the UK (A Pocket Guide to Astronomy) as it seems to have been a special printing for Chapter's, bu
  11. Well, how bad is that 10mm ep? You have an f/8 scope, so an ep would have to be pretty bad to give you significant distortion. I would get a decent 6mm ep, and replace the 10 and 25mm later. Might even replace the 10 with a 16 or 17 if your main interest is DSOs.
  12. I actually used a Scotchbrite once. No, really, my daughter worked for 3M, and it was a new product designed to leave no scratches at all on anything. And it was my 4.5" mirror, and I only used it to wipe away my tears when..., er actually to wipe away the last drops of water. It did leave no scratches. You've done a nice job on that mirror. Now you can go back to your normal blood pressure dosage.
  13. I'd be happy to show that to my friends and family, if I did astrophotography. It looks pretty much like what I see through the ep. Good first effort!
  14. What really helps is to check here and make sure the GRS is near the meridian at the time you are viewing. A yellow or green filter will help a little.
  15. You can use this scope comfortably on a small table or stool about 12" - 20" high. Those walls around your garden may help cut down stray light from the street or your neighbours. You should find you have a very usable sky from your garden. You won't be able to see right down to the horizon unless you are in an exceptionally dark town.
  16. You can make these chairs quite high, although I would think that 4' would be a practical maximum. That should put you in a comfortable position to view through a Dob of that size. I find, though, that I am only in the chair if I am watching the Moon or a planet for a long time. On DSO`s I usually move from one to another fairly quickly, and am on my feet for that. BTW, I really like the hinged top on the illustrated chair. Here`s a couple of pics of my mark I chair.
  17. That makes you a little bit older than I, because I remember the $64,000 question from 50's TV. The items pictured, if they are what they claim to be, would have a minimum new value of about $360. That makes £80 a fair price, assuming reasonable condition. You should check for American used markets. I'm a Canadian, so I buy within Canada, although I have bought from members of SGL, and a few American observers whom I know well. I don't know where to shop used in the states.
  18. Hey, Lotusland! Welcome from St. Catharines, Ontario. You'll like it here.
  19. I made a satisfactory Denver observing chair. Once I had seen a picture and got the idea of how it was made, I made up the dimensions to suit myself. My only problem was that the friction fit that is supposed to hold the chair in place didn't really work, so I am going to run 3/8" half round channels across the back, and put a piece of 3/8 dowel in the back slider of the chair to engage the channels with more force than the friction fit give me. I have two cedar skeletons for the chairs in my shed that I am going to make into my mark II chair next year, if I have time. (My workshop is outside,
  20. Could I suggest that you save a ltttle longer and check the used market, too. I don't usually suggest making a serious start with a refractor of less that 90mm or a reflector of less than 5" (127mm) Scopes of this size usually have tripods and mounts that are a little better than the department store models, and better optics and eyepieces, too. Your finder scope should not be less than 6x30. With a refractor you should have a right angle diagonal eyepiece holder. A 70mm refractor will be no more satisfactory than the one you have now. You should get great looks at the Moon and larger nebulae
  21. ake the 130P with the motor, if that is definitely the scope you want. If you can wait awhile and come up with £20 more, the SkyWatcher 6" Dob is an excellent choice. A very advanced astronomer I know used one for years, and nothing else, until he finally bought a 12" scope. I had some very nice views of Jupiter through that 6" scope. At f/8, it is more forgiving of lower quality eps than an f/5 scope. Be that as it may, you won't be disappointed with the 130 either. I used a scope on a jiggly mount for a few years, and as long as you waited for the jiggle to stop, you could get some very nice
  22. A few years ago friends of mine were referring to it at the 'Great Beige Spot.' I only saw it for the first time, just barely, a few nights ago.
  23. Ive always enjoyed your presence here. Hope you get somewhere with less rain. European beer is very good, esp German and Czech, and they do have internet, although I'm not sure what Internet is in French. I think it may be 'Internet.' Have a great hereafter!
  24. I went to Toronto (100km away) on Wednesday to watch my daughter get her master's degree , leaving my scope covered in a tight fitting and fully waterproof plastic cover. I didn't secure the bottom of the cover however, so when I got home I discovered the 50km winds that happened earlier in the day had removed the cover, and my scope had been sitting in a moderate rain for about an hour. I glumly put the scope back in the shed, and retired for the night. The next two days I didn't have the nerve to look, although I know that any damage will be done earlier, rather than later. But today I went
  25. It could be age. Are you over 60? I'm 61, and I can't find things I had in my hand only a minute ago, and then I remember I pulled my zipper up.
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