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Ricochet

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Everything posted by Ricochet

  1. I think you have to double the light gathering capability of the binoculars to account for the fact that you have two sets of lenses and eyes so that the light gathering capability of a 70mm telescope is equivalent to a pair of 50mm binoculars and a 100mm telescope is 2X. Unless of course there is some loss factor required to account for the way that the brain processes the images from each eye.
  2. Well if the scope fell over clearly the tripod is also defective! I think this makes quite a good excuse to invest in a nice new dob.
  3. The Omnis are a common 4 element eyepiece design known as a Plossl that gives a 50 degree apparent field of view but at short focal lengths can become uncomfortable to use as the eye relief becomes very short. In years gone by a Plossl would have been a prized possession. The X-Cell LXs are a newer 6 element design giving a larger 60 degree apparent field of view and much improved eye relief. They are commonly recommended as a step up for anyone looking to upgrade from the eyepieces normally supplied with a telescope or from Plossls. A similar performing eyepiece is the BST Starguider/Explorer which is available from http://www.skysthelimit.org.uk/ for £50.
  4. Is it me or do the eps supplied with the national geographic look like 0.965" bin jobs? Best to avoid that scope.
  5. I'm going to make it 6/6 votes for the XT8. I haven't regretted buying my 8" dob in any way, but with any of your other options I think I would have been looking to upgrade.
  6. I would suggest that you only consider visual and buy the biggest reflector on a dobsonian base that your budget allows. Reflectors on equatorial bases are not nice to use for visual observations compared to a dobsonian mount. You should put imaging on the back burner as it will require a much bigger budget and separate scopes.
  7. Another +1 for a chair. Luckily I just happened to have an old drummer's stool and so far I've found it has enough vertical adjustment for use with my dob at any angle. As for keeping warm, multiple layers definitely help. Good quality shoes with chunky soles to insulate you from the ground, two pairs of socks seem to help in the event that the inside of the shoes get a little damp with the boundary between the two somehow preventing water being absorbed by the inner pair. Tracksuit bottoms under jeans work quite well on the legs and there's a good chance that you'll have both of those if you dig far enough into your wardrobe. The torso I haven't cracked yet for extended sessions even with clothing that I would be fine with during a winter day. Good quality hat, gloves and scarf are of course needed (although I use a snood type thing in place of a traditional scarf as it can be pulled up over nose and mouth and to join with the hat.)
  8. The "8.8" is the focal length. For your needs a focal length of 8.8 is quite short (short fl = high magnification, long fl = low magnification). Magnification is found by dividing the focal length of the telescope by the focal length of the eyepiece. For any given apparent field of view (the "82") a longer focal length gives a wider field of view (True FoV = Apparent FoV / magnification) so you want a long focal length, i.e 24-30mm to widen the view. However, it looks like that scope only has a 1.25" diagonal so a 24mm 68 degree eyepiece or 32mm Plossl will give the widest view you can get without upgrading to a 2" diagonal (assuming that is possible on that scope). Given that you don't have any telescope yet there is not much point in worrying about eyepieces. Buy the scope that you want and try it with the eyepieces supplied. Only then will you know if you want more magnification or a wider field of view or whatever. The only accessory you should buy at the same time as the scope is the dew shield.
  9. Given that it's a road trip, how big is your car and how much space is left for a telescope once you've put suitcases with three week's worth of belonging in it?
  10. A 7mm ep will get you to 178.6X so I would probably get one of those. Celestron do a 7mm in their X-cell LX range which is considered a good quality step up from those supplied with your scope. However, you should be able to get some good use with just the eyepieces supplied with your scope so there is no need to buy more eyepieces straight away. After a few sessions using it you will have a better idea of what you actually want. A moon filter you probably don't really need. If it's too bright try using a pair of ordinary sunglasses. Anything with a lens at the front really needs some sort of dew prevention: dew shields, dew heaters or both (heaters also need a controller and power source). I don't know anything about power banks but I believe some people use car jump start kits as a power source. I'll leave it to others to advise you on this though.
  11. Or rather how they look when you look through the focuser.
  12. The spider vanes aren't important when it comes to collimation so I wouldn't worry about it.
  13. I posted the technique I used for realigning a focuser in another thread. http://stargazerslounge.com/topic/258529-collimation-europa-200/?p=2827874 It was a similar idea except instead of marking a point on the secondary I removed the secondary and marked a point on the opposite side of the tube. However, I was repositioning the existing focuser so you might want to make some additional measurements to confirm that the distance to the centre of the new focuser is also a possible distance to the centre of the secondary. If you are able to reuse the old mounting holes for the new focuser I doubt it will be a problem. If you can fit the new focuser without removing the secondary then you might find that it fits perfectly anyway and a minor collimation tweak on the secondary is all that is needed.
  14. That's a shame, would have been interesting to hear it.
  15. To be fair there are some professional ebay sellers who provide an excellent service: replies to enquiries within an hour, free delivery, immediate dispatch of replacements for faulty items without having to send the original back first. My local shop sells that zoom for £90 so assuming the ebay ones are genuine effectively getting one for half price seems a good deal.
  16. You are probably right there. I didn't want to preclude the idea that an eq mount might be ideal for a frac and could have put more emphasis on the specific issues when pairing a Newt with one.
  17. What you could do is to put the 2" ep holder in, wind it all the way down and then try holding your 1.25" eyepieces above it at the points at which they focus. If there is a decent gap between the top of the 2" holder and the tops of the ep barrels you will probably be fine using an adaptor. For reference my clickstop protrudes 9.5mm from the top of the 2" ep holder.
  18. Oops, deleted the wrong line from the first quote. Can a mod fix that?
  19. A dob is not "better" than a tripod, the advantage of a dob is that it is cheaper. For a few tens of pounds you get something that is very easy to set up and use and that is very stable and damps down vibrations very quickly. In fact with my 8" dob I don't remember ever having any sort of vibrational issue, ever. If I wanted to get the same stability and vibration damping from a tripod then I would need spend hundreds of pounds more. More portable than what? The mini dobs you were looking at before are a lot more portable, even though they have a bigger aperture. The Astromaster would be more portable than a full size dob, but at a huge loss of aperture. The bigger the aperture, the more light gathering capacity which allows you to see fainter objects, or see more detail in the brighter objects. For reasons stated below I would discount the 70mm Astromaster but the 90mm might suffice. An eq mount is not really too complex, especially if you're only using it visually and polar alignment doesn't have to be spot on. As long as it is roughly in the right area you can track an object across the sky using the RA slow motion control with only a small tweak on the dec control every now and then. The disadvantage an eq mount has is when you try to use a Newtonian on it and the eyepiece and finder rotate around the tube as it slews from one point to the other. In my experience a Newt is much better suited to a dob base than an eq one for visual work (photography needs an eq mount though). For viewing the planets what you are after is high magnification, something in the region of 150-200X (200 being a limit imposed by the UK atmosphere). Magnification is calculated by telescope focal length / eyepiece focal length so a telescope with a reasonable focal length is preferential here to get those high magnifications. In addition the limiting magnification of a telescope is roughly 2X the aperture in mm. For this reason I would suggest an absolute minimum of 90mm aperture (max mag of 180X), but more if possible. Also, something with a larger aperture will give better views of deep sky objects in the future. Based on that I would suggest one of: Celestron Astromaster/Skywatcher Evostar 90mm + Skywatcher Heritage mini Dob, but will need barlow lens for decent magnification A 6/8/10" dob as an all round scope.
  20. No, you would have to remove the Clicklock or any other adaptor in order to use the 2" eyepiece. However, if Stu is right about the 200p not being able to reach focus using the 2" EP holder plus an adaptor then unfortunately the whole idea is a non-starter really.
  21. http://www.firstlightoptics.com/adapters.html I assume that anything listed as a 2"-1.25" adaptor should work unless anyone knows of a reason why not for your specific scope. Personally I would recommend the Baader Clicklock as a great improvement over anything with a thumbscrew.
  22. I I agree with this. If it's within your budget it's always going to be worth spending more on aperture at the outset until you get to the point where weight/portability becomes an issue.
  23. I have not used the scope for photography but the secondary appeared off centre as per your description and there was not enough secondary adjustment available to "centre" it.
  24. I've actually just finished repositioning a focuser because of the exact same issue with the position of the secondary. However, rather than the focuser needing any up or down movement in the holes what was actually needed were a couple of washers to shim out the bottom edge of the focuser shoe in order to change the angle of the focuser so that it is now pointing through the centre of the tube. The method I used was: Position scope horizontally so that nothing can fall down the tube and hit the primary mirror. Remove secondary mirror/spider Take a thin piece of card and place it inside the tube using the tube edge to keep it square and always keeping it pressed against the circumference of the tube. Position the card so that one edge is butted up against the bottom of the focuser (or focuser hole) and the card runs around the bottom of the tube. Use the edge opposite the one butted up against the focuser to draw a line on the inside of the tube (or masking tape then draw the line on that). Repeat with the card butted up against the top side of the focuser to make a second line. Place the card in the tube so that it touches both lines and mark the position of the lines on the edge of the card. Take the card out of the tube and measure the distance between the two marks, Find the midpoint and mark that on the card. Place the card back in the tube so that the original marks on the card line up with the lines in the tube and use the midpoint marked on the card to now mark a new midpoint line in the tube. If you now look through the focuser you should see three horizontal lines on the opposite wall of the tube. Measure the distance from the end of the tube to the edge of the focuser closest to the edge of the tube and the edge furthest from the edge of the tube. The average of these two should be the distance to the centre of the focuser. Mark this distance on the central line you have drawn in the tube. If you look through the focuser you should now see a cross at the point exactly opposite the focuser. Put your cheshire into the focuser and compare the position of the crosshairs to the position of the cross you have marked on the far wall. If your focuser is correctly aligned the croshairs and cross will also be aligned. A small error of a few mm is probably fine but if it is significant adjust the focuser position as needed. Replace the secondary and follow your favourite collimation guide.
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