T A WOW Posted October 23, 2012 Share Posted October 23, 2012 Hello everyone. A quick question. What is better for just looking at the stars,DSO's and planets. Would I be better off with a short or long f ratio. I don't really have any plans for astrophotography in the near future. Also I'm not sure if my next scope would be a refractor or reflector of some description (although I'm keen on a achromatic refractor.) it depends on what's available for a good price, and what I can mod/upgrade the most. Thanks T A WOW Link to comment Share on other sites More sharing options...
Perkil8r Posted October 23, 2012 Share Posted October 23, 2012 Long F ratio for planets, lunar and solar, faster for faint stuff. My personal opinion is frac for round bright things, reflector of F5 or 6 for fuzzies. Link to comment Share on other sites More sharing options...
Doc Posted October 23, 2012 Share Posted October 23, 2012 I agree with Mike. A F10 refractor for Stars and Planets and a F5 reflector or dob for DSO's and star clusters. Link to comment Share on other sites More sharing options...
Guest Madatter Posted October 23, 2012 Share Posted October 23, 2012 Yet Ive been looking at the C8-SGT for dso's and thats f10, so are they exceptions, or am I reading this wrong? Link to comment Share on other sites More sharing options...
Brantuk Posted October 23, 2012 Share Posted October 23, 2012 The faster the f-ratio (i.e. lower) the quicker they gather light for imaging - big plus. But conversely fast f-ratio scopes are less forgiving of lower quality eyepieces for observing and more fussy about collimation - could find yourself spending silly money on lenses to get the best views after spending hours getting the mirrors lined up perfectly. Generally circa f-10+ for solar system, f-5 or less for imaging dso's. Midrange f-7'ish for dual purpose. Achros are nice for solar system, splitting doubles, and resolving globulars in my experience. I'm sure others will offer more suggestions Link to comment Share on other sites More sharing options...
Doc Posted October 23, 2012 Share Posted October 23, 2012 With a F10 cat you can simply bang in a 6.3 reducer and you have a F6.3 scope. They even have a 3.3 reducder to give you F3.3 but it's not great for visual, but OK for photography. Link to comment Share on other sites More sharing options...
Guest Madatter Posted October 23, 2012 Share Posted October 23, 2012 With a F10 cat you can simply bang in a 6.3 reducer and you have a F6.3 scope. They even have a 3.3 reducder to give you F3.3 but it's not great for visual, but OK for photography. This is what makes forums so great, I didnt know you could do that! Link to comment Share on other sites More sharing options...
Perkil8r Posted October 23, 2012 Share Posted October 23, 2012 The main reason I say short reflectors for faint fuzzies is that you need appature, and appature costs £££'s especially with fracs, but with reflectors you can generally get a lot more bucket for your £. Smaller appature fracs re great for bright shiny things though so say a 80 or 102 frac at f10 or so would be great and still be relatively cheap. To get faint stuff IMO you need at least 200mm if not more hence my reflector suggestion. My 200p is great for fuzzies, but a 250 or 300 would be my choice if I could get away with buying one. Link to comment Share on other sites More sharing options...
philjay Posted October 23, 2012 Share Posted October 23, 2012 phwah, f10 is for sissies Seriously, if your after good performance on stars, planets and lunar go long, f10 plus. I personally prefer refractors for double stars and planetary because the unobstructed optics give high contrast views. However Scts or Maksutovs at f10 -12 give superb views as well but require longer aclimatising for temperature, eg cool down, typically my old 5" mak required an hour to aclimate before it could be used for serious detailed observations whereas my 5" triplet refractor takes half that. Its all down to personal preference really, some folks prefer the convenient size of an sct or mak wheras an f12-15 refractor can be quite long. Its a case of try before you buy and see which you prefer. I regularly bring long fl refractors to meets yur welcome to have a gleg through one phil Link to comment Share on other sites More sharing options...
BAZ Posted October 23, 2012 Share Posted October 23, 2012 Phil, it looks like you have typed in black text, can't see the post! Link to comment Share on other sites More sharing options...
Perkil8r Posted October 23, 2012 Share Posted October 23, 2012 I had to highlight it to read it Link to comment Share on other sites More sharing options...
Brantuk Posted October 23, 2012 Share Posted October 23, 2012 I've coloured it in for you Phil lol Link to comment Share on other sites More sharing options...
T A WOW Posted October 23, 2012 Author Share Posted October 23, 2012 Some very good advice then. I need a long f ratio for stars and planets and a short one for fuzzies. Dual OTA then. Speaking of which, does anyone know much about the Meade lx80 mount. Looks quite tasty for the £££ Link to comment Share on other sites More sharing options...
Brantuk Posted October 23, 2012 Share Posted October 23, 2012 I've heard good things about Meade optics - on a par or just slightly better than Celestrons - the one I looked through was pretty impressive. Trouble is I've heard loads of poor to bad stuff about the longevity of their electronics. Plenty have gone wrong within waranty and aledgedly they are dreadful at after sales service in the UK. So it's a tough one to call. Link to comment Share on other sites More sharing options...
philjay Posted October 24, 2012 Share Posted October 24, 2012 I've coloured it in for you Phil lol This tablet im using has a mind of its own does this show? I would hang fire with the lx80 till meade sort any teething troubles out. Link to comment Share on other sites More sharing options...
Guest Tweedledum Posted October 24, 2012 Share Posted October 24, 2012 I am with Kim, the LX80 mount has not yet been proven, and I would not buy anyway until there was some on the used market that had some depreciation kicked out of them. I loved my 10" LX200 (sold), found the electronics very reliable, my spare handset, bought in anticipation of failure is now in an observatory in Sweden. As for focal ratio, you will not notice the difference until you start imaging. For visual all depends on the exit pupil on the brightness of the object being viewed. Field of view and magnification come into play with higher focal lengths as you rarely need to introduce barlows, 30mm in the f10 Meade used to yield 85x, in Micks bresser that yields 25x. Higher focal lengths are more forgiving of eyepieces too. Having a central obstruction also reduces contrast, so back to personal choice and what your budget is!! There is an excellent long vs short focal length discussion here : -- http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/forum/longvsshortf-ratios.html Cheers Link to comment Share on other sites More sharing options...
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