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First scope - skywatcher 200p or 250px


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I think, as this is my first rodeo... I'll start off with viewing. when it comes to imaging i might have to look into a small refractor like an evostar 120. but for now i am quite content with viewing.

from what I have heard a 10 inch dob doesn't really cut it for DSO's unless you particularly enjoy looking at grey blobs the size of a thumbnail or less. so i would have to say the planetary observing would be my first point of call. Unless you can correct me on that statement.

it sounds as if I am leaning towards the Mak... Decisions decisions.

Thank you for the tips Mike! you have been very useful indeed!

"turn left at orion" is on it's way. I shall have a good read through and take a look at the sketches and hopefully i will come to a decision.

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Hi DrNeb,

You're welcome. Turn Left and Orion is really useful. It's not a straight-through read as one might expect but more of a working book with the majority of the book being literally a reference to most of the popular objects and views through the finder and the eyepiece.

RE: Mak - apologies if this isn't quite appropriate, but take a look here: http://stargazerslounge.com/sale/114653-fs-skywatcher-mak-127-synscan-goto-black-diamond-edition-only-7-weeks-old.html - I can't actually part with it at the moment as the mount is with the distributor getting fixed (it had the typical Synta slowdown) and I'll refresh the for sale listing later.

Plus, if you want DSO for lowest possible cost you probably want a big dob.

It's all swings and roundabouts and a game of compromise. That's why a lot of people around here have more than one telescope :)

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mmm the dob or the 200p with the eq5. Having recently got the 200p with the eq5 mount I have to say I would not if I had the choice go for the dob as the 200p does everthing I want. No I would go for the 200p first and then get a dob later on because I wanted to get into astrophotography and i wanted to get a mount that I could upgrade to motor drive or go to. But if your not going to get into astrophotography and just want to observe then the dob wins hands down. Its up to you but l really love my 200p and the eq5 mount and if I had the choice again would still go for the 200p what ever you chose I hope it really gives you a lot of pleasure and great viewing.

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Imo getting a 200 or 250px is the least "risky" of all, you will get better views from the 200 or 250 than anything else at this price range, both of these scopes will beat a 5" mak on planets and will also be great on dso's. nothing else at this price range can do that.

these scopes are great all rounders

if you can get a good second hand one i recommend it, you will normally save 50% on the new price, but you must be aware of what to look for.

maks and sct's are good scopes but the main advantage of these designs is size and not always cost or performance.

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Thanks again all.

i think i know where i am heading now.

But i do have just one last question and for that i apologise!

if i were to buy the dob 250px and wanted to get into photography would you go for a smaller refractor and eq mount. or would adding the top end eq6 pro mount work with such a large scope?

im going to have a look at some dobs at my local shop tomorrow!

I would also like to say that you have all shown great patience and i truly appreciate it.

ps. I'd love to see the items you had for sale mike but i havent hit the magicaly 50 posts yet lol.

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If imaging is a later consideration, I would probably consider getting a new scope and mount, a little ED80 or something on a Heq5. a 200 or 250 is not required for imaging and will probably be a burden on you and the mount.

At least if you do imagine you will have a dob to play with while waiting.

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Well! i went to a little shop in frome called MC2 and the very nice fellow in the store unpacked a 250px for me to have a look at.

it is no where near as big as i had imagined. (although is wasn't mounted)

I was getting worried about its portability but it has put my mind at ease! I've been nosing through "turn left at orion" and i must say it is a fantastic book for the beginner.

I'd just like to say thank you for all your help, i'll be picking up the 250px In december as a Birthday prezzie to myself. I believe orion is best viewed from december - march so here's hoping for clear skys!

I know it's a way off, but it gives me alot of time to look into barlows/EP's and filters. Plus i'm still learning my way around the big black!

I will report with my first light when i get it. Not sure if i should pay the extra and pick it up at the store or buy it through FLO though.....

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Just want to say that if you buy it through FLO and you ordered it right now, you'd probably get it tomorrow. And their customer service is excellent.

The 250px is a nice scope, I take it you are getting it on a dob base?

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Aye. it's a dob. the EQ mounts for such a large scope are a tad out of my budget.

The shop i was planning on buying it from is more expensive... by around 30 quid!

But, i like supporting local businesses, i've heard from our local astronomy club that they provide aftercare/advice as well for free.

hmmm

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  • 3 weeks later...

Well! it's getting closer to my purchase date!

I do just have one more question though, would it be worth getting an erecting prism?

I'm getting really excited! and i cannot wait to share the details from my "first light".

One question, for a 250px do i need a dew shield? i was told by someone that because the large mirror is at the back it wouldn't be nessecary.

Thanks all

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Hi DRneb

I had the same question as you ask http://stargazerslounge.com/beginners-help-advice/113706-going-out-my-mind-advice-needed-200p-vs-dob.html In the end I got both second hand for a very reasonable price. I picked up a EQ5 & Helios 8" which is basically a SW 200p and a 1mth old 10" dob. I have a observatory so I required a "grab and go" hence why I ended up buying the two but if I had to choose between them I would go with the 200p as it is great on planets and DSO (given dark sky) and tracking is not so much an issue as you can easily to upgrade to motors with an EQ mount. The dob will only give slightly better views and will always require a nudge to track objects not to mention there is the considerable size difference. The only thing IMHO that lets reflectors & EQ mounts down is the eyepiece can end up in some real awkward positions so either you get some small steps or constantly adjust the tube to suit.

As long as you are careful buying second hand there are some deals to be had. I got both scopes for less than the one cost new and the views are the same as if they were new.

As for the dew shield I am curious about this also. I have seen many dobs with them on. Is this so the secondary doesn't dew up? or can the primary be at risk? or is it just to stop stray light?

SPACEBOY

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Very useful thread, I am looking at both these scopes but am settling on the 8" Dob instead of the 10". If it goes how I hope then I'll transplant the Dob to an Eq mount or just buy a better scope.

Oh and my advice is to buy from who ever you want and don't second guess your scope decision now you've made it (not that you've shown any signs you were) :)

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well i'd only go for an eq if i was imaging. and to do that with a 250px we are talking the eq6 pro and that is currently way way way out of my budget. so for imaging i will most likely go for a small refractor instead. But you never know! by the time i get into imaging the eq6 pro might be obsolete and cost a fraction of it's original price!

I'm more than happy to learn the sky and not rely on GOTO. more then that, i'm looking forward to it!

also i've seen a 250px in the flesh so to speak and it didn't really worry me, i have numerous "dark sites" around where i live within even walking distances.

I have been slightly confused however, some are saying that apature is the main concern where others are saying that have less apature will result in sharper more detailed images.

i think the term is "spoilt for choice"

Anyway, i would welcome some thoughts on the dew shield for the dob as well as an erecting prism.

Cheers again all.

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:p This is what I have learnt from browsing these forums for a while

If your purely intrested in observing go for the biggest

dobsonian u can get 0):) and remember even dob tubes can

be upgraded to more sophisticated mounts :eek: if your intrests

lie in planets and webcam imaging tbh the 127 mak has to be

the number 1 choice its an awsome planetary scope... ive said

it once and il say it again choosing scopes is hard work... :)

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...I have been slightly confused however, some are saying that apature is the main concern where others are saying that have less apature will result in sharper more detailed images...

I think larger aperture scopes can be more affected by poor seeing conditions than smaller ones so there are occasions when the smaller scope, particularly if it's a closed tube design like a refractor, will show planetary details and split double stars better than a larger one.

When seeing conditions are average or better then the larger aperture will deliver better views.

On the erecting prism - I've not heard of one being used with a newtonian - it's generally accepted that newts deliver traditional astro views, ie: north at the bottom. I'm also not sure it would come to focus when used with a newtonian anyway :)

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Cheers all.

now any thoughts about the dew shield?....

I use one on my 10" newtonian but not for dew - I use it as a light shield to keep stray light out of the top of the tube and off of the secondary mirror. I've got a few neighbourhood lights to contend with you see :)

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I think larger aperture scopes can be more affected by poor seeing conditions than smaller ones so there are occasions when the smaller scope, particularly if it's a closed tube design like a refractor, will show planetary details and split double stars better than a larger one.

I have read something about this. It is some thing to do with the smaller aperture cutting through the particles in the air better than a larger aperture can. The wider the aperture the more of the dust and c**p the light has to pass through. I had it compared to adjusting the beam of a tourch... the narrower you make the beam of light the more focused and brighter it is on a distant wall. It made sense when I read it but I can't think where it was I saw it :) I think this only relates to planetary viewing ?? as the light gathering of a large aperture is required for viewing of faint DSO's

I will try to find the article and post the details.

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Thank you, both of you for your help.

Very interesting. And a fantastic tip regarding the dew shield.

just had a pm from a previous poster, Mike regarding the 127 skywatcher mak! that thing looks pretty darn good too.

I'm going to lock myself in a room until i make the final decision lol...

or i could get blind drunk and get click happy on the FLO website.

Either way! i'll post my first light adventures once whatever i buy arrives.

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I think larger aperture scopes can be more affected by poor seeing conditions

In general, that's not true (it is theoretically possible, but it rarely ever happens). What happens is that the larger scope has a less aesthetically pleasing --less stable-- image, but you usually still see more details using the larger scope, and vastly more in the brief moments of better seeing. For the smaller scope to really see more, you almost have to hand-craft the convective cells in the atmosphere for it (and yield a speckle pattern that slowly shifts on the small scope but is blurry on the large scope; if you actually use small scopes and star test them at high powers, though, you rarely see such a small but shifting speckle pattern).

Of course, some people prefer seeing an aesthetically pleasing image to seeing a lot of detail but in a distractingly unstable image. It is, of course, their prerogative.

One aspect of "seeing" that really does cause more problems on large scopes is the seeing in the tube, and the couple of millimetres right above the mirror in particular. That's because large scopes usually have a mirror at the bottom that's thick and has trouble cooling. Improper thermal management is the bane of large scopes (and that's the reason I never pick a large scope when I only have ten minutes to look at a planet).

But too many people don't try to determine if the seeing's really bad or if it's jus their scope, despite the fact it's a lot easier to do something about cooling the mirror than changing the seeing.

What smaller scopes are good for is things like splitting bright doubles at low magnification (on large scopes, the larger exit pupil means more aberrations in the eye to make stars appear uglier, but of course increasing magnification solves thant handsomely and makes the split easier) and firs tand foremost observing things at low magnification (which are too large to fit in the field of view on the large scope with a magnification that makes the sky background pleasingly dark.)

it usually than smaller ones so there are occasions when the smaller scope, particularly if it's a closed tube design like a refractor, will show planetary details and split double stars better than a larger one.

I have encountered situations in which an off-axis mask showed more detail than the entire aperture, but these are extremely rare; so rare that I discarded the mask. Now the only thing I use is a tuned apodising mask for my 400mm Dob.

As for splitting double stars, that's usually only valid at equal magnifications, and the human eye's aberrations is the cause (it's generally unproductive to use exit pupils above 2mm, i.e. magnifications not at least half the millimetres of aperture).

But there's no reason to stick to the low magnification on the larger scope, so that's saying that the larger scope will be beaten by the smaller one if it has to run with its shoelaces tied.

it's generally accepted that newts deliver traditional astro views, ie: north at the bottom.
Minor nit: North is not always at the bottom (if you observe above the North celestial pole but with the scope pointing North, North is "down" naked eye but close to "up" in the scope.

Even "up" is not always at the bottom, as you don't always have the same orientation with respect to the eyepiece and as not all focusers are exactly horizontal. But yes, the view is mostly rotated close to 180°.

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HI found the article. It's in Philips stargazing with a telescope section regarding Lens Vs Mirror.

Quote:

One of the major reasons for the claimed supirior performance of refractors, and these days Maksutovs, lies not in their optical quality but simply in their smaller size. Atmospheric seeing acts a little like frosted glass windows - the sort with fluting or blobs, rather than a fine-ground surface. From a distance, when you are looking through a large area of the window, you have a very poor view of what lies beyond. However, get close-up and peer through a small section, and you can actually see through it rather better. Seeing is caused by air cells of different densities, constantly on the move. These cells are of the order of a few centimeters across, near ground level, so a small telescope, whether refractor, reflector or maksutov, will see through individual cells. But larger instrument, ofwhatever sort, often looks through several cells at once, resulting in blurring or even multiple images. When seeing settles down, however the larger telescope really comes into its own and reveals more detail.Generally speaking, larger telescopes are reflectors rather than refractors, hence the reports that a small refractor or maksutov can out perform a larger reflector or SCT.

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