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250px or smaller. Again.


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For months I have been agonising over whether to get a 200p or 250px as my first, and probably only scope. During this time I have annoyed just about everyone I've spoken to about it due to the overwhelming weight of indecision that I've been able to draw upon, and I dare say I've been massively over-thinking it. So I'd be most grateful for any clarity that anyone can shed on my dilemma.

The scope will almost never leave home, so moderate light pollution and Mag 5 skies will be all it gets on the best of nights. Its primary use is for DSOs, so more and yet more aperture is the way to go on that one. However, I'm weighing this up against the convenience of the 8", which will show less, although I understand not so very much less than the 10", yet it's F/6 and so will hold collimation well and won't terrify the eyepieces. Depending on what day of the week I ask myself the "what scope" question, either one of these can win.

I am happy to pay the extra for the 10", and the weight doesn't bother me - it's a 15kg tube I believe, I'm quite at home moving 25kg bags of building sand around the place so I think I'll be fine with that. I'm happy to pay as much as the scope again to get some quality eyepieces - I don't think field of view is a big issue for me so I was thinking along the lines of TV plossls or Vixen SLVs. It could be done for cheaper I know, but I don't mind paying a reasonable premium for some top notch glass and being satisfied that I'm seeing everything that the skies and the scope are capable of showing.

So what it comes down to is how much of a pain is F/4.7 going to be? Will I need a coma corrector for 50° eyepieces? Also am I going to have to collimate it every time I want to use it, because I really don't like the sound of that. I get the impression you can collimate the 8" and only really need tweak it occasionally - grab and go in the truest sense. Can the same be done with the 10" to a lesser degree? It'll be the solid tube version if that makes any difference. If it's okay on these points I'll go with the 10" and enjoy the superior views. If it can't then I'll go with the 8" and use its convenience to swat aside those "what if" questions I'll be getting.

Thanks,

Mark

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Sounds like you have talked your self into the 250. I've got one.

Portability - Not An Issue - If you are used to lugging around building sand, you won't even bother taking it apart to move it. I've had mine for of a year and haven't removed the tube from the base yet.

Eyepieces - Not An Issue - Plenty of budget. Do it gradually. Find out what works for you. I would go wider than 50° for all but my high mag planetary / double eyepieces. 68° is a good cost/FOV balance. 82° is better but more expensive to get the same quality. Have a look at the selection on my signature. The only thing that I would change is the MV 28mm for an ES 82° 30mm. You can get a good starter eyepiece collection for £250 (eg. A mixture of MaxVision 68° and BST Starguiders).

Coma Corrector - Don't need one - Very few 250px owners use them. I have one but haven't used it yet as it needs an extension ring (and no clouds)

Collimation - Not An Issue - Takes <2 mins while you are waiting for your eyes to adjust.

Viewing - You will see more with the 10".

Hope that this is of use.

Paul

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You will only need a coma corrector if you decide you don't like coma and want pin sharp stars ot the edge of the field of view. People seem to be less bothered by coma than astigmatism, which is eyepiece produced.

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I don't think a 10" f4.7 will be a pain at all. I find my f4.8 very easy to collimate, it just needs a tweak occasionally. As for coma, I only noticed it to the point it was annoying with my 26mm Nagler which has an AFOV of 82°. I doubt you'll notice anything with 50° eyepieces.

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i had a 250PX myself and if it is really the only one scope you intend to by and the split is between 8" or 10",i would say go for the 10" 250PX. As you said,weight is not an issue and in real life this scope isnt really that heavy either. That 250px has a very good quality mirror and holds collimation superbly.AS usually with all factory manufactured scopes you will need to do some small "tuning" but that can be done gradually and nothing to worry about at the beginning.Suggest get a telrad as finder,you dont need coma corrector (i didnt need any) and eye piece wise you will be perfectly fine with medium range ones.Suggest get the scope first,try it and then go into next stage of eye pieces :)

Good luck.

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I'd go for the big one. I don't use a coma corrector with an F4.1 20 inch and no visual buff has ever complained while using the scope. I do use TV premium EPs though. Nagler, Ethos and Radian.

If it's more or less staying put you'll appreciate the aperture.

Olly

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Just echoing other comments - the 250px takes 2 mins to setup - grab and go - and is fantastic value. I love mine. I'd recommend acquiring quality eps overtime - and fov helps for manual dob, and you're investing money for a potential future scope upgrade. I see the Orion Nebula as distinctly green with my TV eps - grey with my cheap plossls (!). I dont use a paracorr either. 250px has 1.56x light grasp of 200p... go for it! ;) Best of luck -N

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Btw I find my 250px hardly ever needs collimation - I keep checking but rarely needs to be touched. This scops has shown me so much - great all rounder imho for planets, nebulae, comets, galaxies, globular clusters - even detail on the ISS ... amazing to see so much with your very own eyes with a mirror, some lenses and a simple no fuss setup :)

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I'd also say based upon your comments regarding using from home , weight no issue and your one and only purchase , get the 10". No reason not to . I've just aquired a 250px second hand . Now it come with a couple of fairly cheap eyepieces, so when I had a quick test with it the other night I was expecting whole flocks of seagulls

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Another happy 250PX owner here. It is tougher on eyepieces than an 8" f/6, I borrowed a Meade one for a few months before deciding which size to get. I'm glad I went for the 10" and built up a set of Pentax XW eyepieces over time.

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I would also like to echo what everyone else has stated, accounting for your reasoning, the 250 will be very satisfying. Concerning a coma corrector, consider as a low priority, something more as an option to factor in down the line perhaps, just enjoy using the scope and gradually gaining some good eyepieces.

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I have used eight and ten inch scopes and given your needs above I wouldn't even have to think about this. I'd get the 10.

I have a GSO 880 10 inch dob and it is such little hassle to put out, barely any effort at all. So let's suppose the forecast is iffy. I put the dob out to cool down. Takes me about two minutes to pop it out. If it stays cloudy, takes me two minutes to put away again. This is a scope that gets a lot of use due to the sweet aperture to effort ratio!

So in your case I can't really see much point going for the 8. I wouldn't put an 8 dob out any more than I do the 10. It's like virtually no effort versus vritually no effort...

Collimation - I collimate my dob about twice per year, and it takes about three minutes... And sometimes it is not out much at all after 6 months :D Six minutes or so per year, I can live with that!

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If you plan to observe from home, get the 10, only reason to get the 8 would be the budget. Coma is not that bad for a lot of objects when the important is in the middle of the eyepiece, and you can buy good eyepieces gradually and a coma corrector maybe, but a lot of people lives without it. Collimation won't be a problem if you don't move it a lot, and you can take it out, go back inside, and a cup of tea later you will have a cooled down telescope waiting for you.

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Well thank you all very much indeed, the above makes what I thought was a difficult decision remarkably easy - 10" it is. I had my heart set on a 10" from the start (9 months ago) and have spent all the intervening time trying to talk myself out of it for a variety of reasons, real or imagined. But if collimation is no great faff, and that's the resounding conclusion of the above, then it's a no brainer really. I shall order one as soon as I can be sure someone will be home to collect it.

I will be taking it in stages by just getting the scope and a cheshire to start with. This way I'll get to know my way around the kit and start to get an understanding of what FoV and magnification I want from my EPs I want before spending even more money.

Thanks to all!

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I had a 8" inch and 10" dob once too. For home use they are both virtually the same for ease of set-up from house to garden. But you'll be rewarded with the aperture increase. Funnily enough, I'm about to start a new thread about the merits of 10" v's 12" (so whatever you do, now you've made your mind up stay well clear of the thread!)

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