| Info | Votes | Messages | More Stats |
 Up One Level
|
 | ||||
Subject: Re: vote by xxx.xxx.75.131 By: webmaster Date: 01/16/2002 03:40:49 pm PST > I would appreciate it if someone could tell me what I am doing wrong. I would like to think its because I live in a large suburban area where the seeing is not the best, and I am hopeful that a trip to a more remote sight will improve performance. > To verify the quality of your scope you should always do a star test and verify that the scope is at least well collimated. Read your users manual on instructions on how to collimate. There are times during shipping and transport when the optics can get knocked out of alignment. Some scopes (such as Maskutovs)aren't recommended for self-collimation. The star test also allows you to rate the optics you're using. Ah yes, that reminds me that there's sometimes other areas which may degrade observing performance like poor star diagonals/prisms, eyepieces, or barlows. Often times mass marketed scopes come with poor quality eyepieces. It doesn't sound like this is the case in this instance. Nevertheless, it might be something to play around with. Also, it's best to let your scope sit outside for some time so that it equqalizes with the ambient temperature. If you don't, you'll get air currents in the tube of the scope which will degrade performance. Of course, some times its not the scope/optics itself, but either bad seeing conditions (twinkling stars are signs of bad seeing) in which case you simply need to be patient and wait for another night, or overpolluted skies which will reduce contrast. In the later case, you need to find a new site away from urban light polluted areas. Here's a few links: Star Tests: http://voltaire.csun.edu/tmb/tmb4.html http://aberrator.astronomy.net/html/body_star-testing.html Collimation: http://www.weasner.com/etx/warnings/collimation-warning.html http://home.earthlink.net/~steve1998/ETX.html http://perso.club-internet.fr/legault/collim.html http://www.astronexus.com/gatfaq/collimate.html Seeing: http://perso.club-internet.fr/legault/seeing.html Subject: Focal Length By: Anonymous (xxx.xxx.23.162) Date: 03/13/2002 04:28:14 am PST To: Anonymous (xxx.xxx.61.72) Unless I'm missing something here, I don't see why you are saying there are two different eyepiece magnifications based on Sky&Telescopes 121mm aperture finding. Smaller aperture has nothing to with focal length. It does affect focal ratio (12.1 vs 12.7), which isn't used to calculate magnification. Since the primary mirror moves for focusing, it does affect focal length. So until someone actually measures and describes what is going on here, 1540 is the only known focal length to use for eyepiece magnification calculations. Subject: Re: Focal Length By: Anonymous (xxx.xxx.23.162) In Reply to: Anonymous (xxx.xxx.23.162) (Original Message) Date: 03/13/2002 04:56:00 am PST >To: Anonymous (xxx.xxx.61.72) > >Unless I'm missing something here, I don't see why you are saying there are two different eyepiece magnifications based on Sky&Telescopes 121mm aperture finding. I missed something here! Sorry! You mentioned that S&T measured the f/l at 100mm longer, which is actually a small 6 1/2% adjustment to advertised 1540mm f/l. So, where you say 240X using 1540mm f/l and 300X using 1640mm f/l, 300X should really be 255X. Not much different. I know this is nitpicking (sorry again), but just wanted to point out its not that big a deal. Let me add this, too. I've had two samples of this scope. One focused down below 20 ft. The other one wouldn't focus below 50 ft. My guess is that there is a wide range on actual focal length based on the sample you get. Subject: Re: Focal Length By: Anonymous (xxx.xxx.60.207) In Reply to: Anonymous (xxx.xxx.23.162) (Original Message) Date: 03/28/2002 04:47:02 am PST It's not just the smaller apperature, its the combination of the smaller apperature and the longer focal length. Orions spec: f/l = 1540mm & 127mm apperature If you divide 1540 by 127 you get a ratio of f/12.1 S&T Spec: f/l = 1630 & 120mm apperature If you divide that 1630 by 120 you get a ratio of f/13.5 Magnification: It may not seem like a lot but with high power eye pieces the diffeerence is significant. Take a 6.3mm eyepiece for examlpe. Orion: 1540mm / 6.3mm = 244X S&T: 1630mm / 6.3mm = 258X Throw in a barlow and the difference doubles. Of course that is an extreem. I hope this makes what I was trying to say more clear. No offense taken. Subject: Re: Focal Length By: Anonymous (xxx.xxx.60.207) In Reply to: Anonymous (xxx.xxx.23.162) (Original Message) Date: 03/28/2002 04:55:03 am PST I just read your second posting. Your right about my original message. I made a mistake on my math. I had my 1200mm Newt in the back of my mind when I wrote the magnification at 240X. The difference is not as extreme as that posting would have you beleive. Sorry for the confusion. Subject: Re: vote by xxx.xxx.175.30 By: Anonymous (xxx.xxx.96.200) Date: 07/28/2002 01:47:20 pm PST >Optics seem a little weak, but for the price its a good starter scope. These little beauties are punched out by the thousands in mainland China and you know labor doesnt get any cheaper. Star test show good but not great optics ( sub Intes or Meade). My thinking is if it gets you involved long enough to buy a real scope, its served its purpose. First this is a real scope. Second Meade sucks!! Subject: Re: vote by xxx.xxx.175.30 By: Anonymous (xxx.xxx.95.20) Date: 08/16/2002 06:57:40 pm PST >Optics seem a little weak, but for the price its a good starter scope. These little beauties are punched out by the thousands in mainland China and you know labor doesnt get any cheaper. Star test show good but not great optics ( sub Intes or Meade). My thinking is if it gets you involved long enough to buy a real scope, its served its purpose. Do I detect a hint of astro-snobbery? Do you really expect it to star test like a Tak, APM or AP for $400? I own one of these and think the optics are quite good. Maybe you got a hold of a bad unit. Subject: Re: vote by xxx.xxx.175.30 By: Anonymous (xxx.xxx.189.129) Date: 11/20/2002 05:19:30 pm PST I tried one and it is incredible. Try looking through the little lens instead of the 5 inch objective and give a comment on that. And dont forget to remove the cover. Subject: advise By: Anonymous (xxx.xxx.239.5) Date: 10/15/2003 05:44:39 am PST hi i live in pakistan and havent used any scope ever. i want to buy a scope that serves both the purpose of planetary view and deep space view. i have read some articles and gathered a bit of information as to which type of scopes are there in market but since i havent used any as telescopes are not available in pakistan , i would appreciate a bit of advice. actually i want some good scope that i could use for both planetary and deep space viewing. costing less than US$500-600. The environment here is dry and humid most of the year and there are certainly no service centres here. As you all are experienced, i definitely could use a good piece of advice. i have my eyes set on Orion Starmax 127 Mak/Cass. Page 1 of 1 | ||||||||
