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Telescope buying decision - YOUR HELP NEEDED :-)


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I need your help & advice please!!

I'm trying to decide which telescope is the best scope for my needs, and to help me make this decision I'd like to have descriptions of the ACTUAL VIEW you would get when looking at the following objects through a 150-200mm Reflector and a 120-150mm Refractor:

Please go into as much detail as you can about what kind of colours and details you would see with both scopes, even if you only have experience of one scope i'd apriciate it.

TARGETS:

1) Moon

2) Jupiter

3) Saturn

4) Mars

5) Orion Nebula

6) Andromeda Galaxy

7) M101 - Pinwheel Galaxy

8) Cats Eye Nebula

9) M15 Globular Cluster

Any other target you'd like to describe.

(Assume clear skies and low(ish) light pollution and a semi decent EP)

Thank you so much and I hope I can make a decision soon...

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(Assume clear skies and low(ish) light pollution and a semi decent EP)

That's a big assumption, particularly the bit about "decent EP", as the eyepiece used with a scope can make as much difference to the viewing experience as the scope itself. Combine that with the range of scopes covered by your criteria, and I doubt very much that you'll get any information that will really help you decide on a scope. It will be impossible for you to compare one person't experience with a equatorial mounted Takahashi refractor to another person's experience with a 8" SkyWatcher dobsonian.

The list of objects you mention also encompasses a vast range of different subjects, of hugely different brightnesses and sizes, and I don't think I'd be alone in telling you that no single scope will work well on all of them.

My suggestion would be to think of the subjects in order of priority - which objects are you more keen to see? - and maybe renumber them in that order. That will help to work out what sort of instrument would suit your needs early on, perhaps with the understanding that some of the other objects might have to wait until your experience has broadened, your wallet is refilled, and you are able to consider your next scope to tackle the next group of objects.

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I think what you are asking is virtually impossible to be honest. What I see though one of the scopes you list, with my observing conditions, my eyes and applying what I've learned over the years I've been in the hobby is likely to be quite different to what you, or possibly other folks might see.

Observing conditions are by far the biggest variable in that list so I could say that X scope will show Y details of object Z and then you will probably find things quite different when you observe.

Also to describe fully the details that are potentially visible, under ideal conditions, to the experienced eye, in the scope types you list for the objects you list would take pages to be honest.

I also feel that discovering what you can see through your scope on a particular occasion is all part of the appeal of the hobby - if someone was able to give you chapter and verse then what is left for you to go "wow" about when you encounter it for yourself ?.

One piece of advice I can give is that you won't see colours in deep sky objects apart from possibly very faint tinges of lime green in M42.

To get some idea of what people have seen in scopes it's worth looking at the sketching section of the forum but bear in mind that, as they say, "your mileage may vary".

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Ouch, thats some list I have a 10" sct, 127mm frac, 120mm st frac. You would be better off going to local astro group and seeing for yourself through different scopes. At least that way you will be relying on your mk1 eyeball. Everyone here will have their favourite ep, barlow, so its very personal!.

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I understand that what I'm asking is extreemely open ended and with massive difference in target types...but...

I suppose the simple question that i could ask is:

GENERALLY, Which scope type will give me the best planetary & lunar detail (SW 150mm reflector or SW 120mm refractor)? And roughly how much a difference would there be between the two?

AND: I've heared that DSO's are very difficult to spot, Do most DSO's look like 'fuzzy blobs' through either type of scope? If so i'll just concentrate on planets during my observation sessions...

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Most of the stuff you'll see will be black/white/grey except the planets and some double stars. To answer your question you need to download CCDCalc by New Astronomy. It's free and will show you fov's, camera images, and direct observations. It's an approximation but reasonably accurate if you input your telescope and eyepiece details and choose either "Telescope view" or "Camera view". Then choose a target from the list. Hope that helps :)

New Astronomy CCDCalc Software Informer: Latest version download, news and info about this Multimedia Madness, Inc. program. The New Astronomy CCDCalc is a virtual astrophotography imaging software.

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GENERALLY, Which scope type will give me the best planetary & lunar detail (SW 150mm reflector or SW 120mm refractor)? And roughly how much a difference would there be between the two?

AND: I've heared that DSO's are very difficult to spot, Do most DSO's look like 'fuzzy blobs' through either type of scope? If so i'll just concentrate on planets during my observation sessions...

On Q1: The views will be pretty similar. The 120mm refractor (assuming it's the Evostar) will show some false colour around the moon and brighter stars and planets. With both scopes, on a night of good seeing the detail and contrast will be seen, on a night of poor seeing you may see very little.

On Q2: Many (most ?) deep sky objects are "fuzzy blobs" even in larger scopes than you have listed. Still very fascinating "blobs" once you know what you are looking at. Again seeing conditions and light pollution will make a big difference to what you can see. A 100mm scope can see 100's of deep sky objects under decent, dark, conditions.

If you just concentrate on the planets you will be limiting your viewing to just a few objects which seems a shame to me.

You have to work at astronomy though - by that I mean spend time at the eyepiece, honing your skills and catching the moments of good seeing. Thats the way to get the best that your scope and the Universe can offer :)

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It sounds to me like you need to look through some telescopes before you buy. Your question can't be meaningfully answered because the telescope is just one variable out of many. It's not even clear what "lowish light pollution" means. I've often seen people state that they live somewhere with "no light pollution", then I look at that location on the maps and it's clear that this isn't the case. I think they're just defining light pollution in a different way.

You're basically asking "would I be happy with the views?" This is a hard question to answer. It depends on your expectations and your experience. Here's a story: Recently I set up my 18" next to a newer observer who had a lovely, fast, 3.5" refractor with really expensive eyepieces, etc. He'd not looked through a big scope before and so we compared views of M31 in the two instruments. He found it a negative experience because he was disappointing that his scope gave a relatively dim view. He couldn't see the dust lanes in the 3.5" whereas they are screamingly obvious in the 18". I, on the other hand, loved the view through the 3.5". My scope can't fit all of M31 into the field but the 3.5" can. That was a major selling point for me because, up to that point, I'd never seen it this way from dark skies. I could pick out the more prominent dust lane in the 3.5" but I think he couldn't because he had less experience. We ended up with him thinking of buying a Dob and refusing to look through my scope again, and me thinking of buying a small refractor and asking to look through his again.

DSOs will show plenty of detail in a reasonably large scope if you have experience and dark skies. The following link contains sketches made under such conditions with an 8" Newtonian: Deep Sky Sketches - Deep Sky Watch Those are accurate renditions of what you can expect to see in the eyepiece *if you have good skies*. It is for this reason that an 8" is often recommended as a good starter scope. They will show you plenty and they're cheap.

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Another point: you ask for a comparison of the views between refractors and reflectors. At the end of the day, aperture is aperture. Yes, the reflector has a secondary mirror and spider vanes. However, the effect of the secondary obstruction and the vanes is generally over-played.

Telescopes with obstructions under 20% by diameter produce images indistinguishable from unobstructed optics. This has been shown pretty rigorously in Suiter's book on star-testing astronomical telescopes. Spider vanes do add diffraction spikes to stars and some observers find these unpleasant. Refractors, SCTs, and Maks don't have these spikes and this gives the impression of tighter, prettier, star images. However, the impact of the spikes on things such as planetary detail is negligible. They mainly throw light outside of the planetary disk, rather than causing blurring of features within the disk. A large newt will still produce a smaller Airy disk than a 4" refractor. However, if you really don't like the spikes then that's enough reason to avoid Newtonians.

Probably the main difference between the designs is practical. Newtonians are prone thermal issues and require careful collimation. Refractors are more or less grab-and-go and produce nice images without any messing about. A reflector which isn't cooled down and/or is out of alignment will produce sub-par images. Perhaps even downright awful images. These effects are sometimes attributed incorrectly to the secondary obstruction. In reality, a well-tuned reflector can produce devastating planetary views, surpassing 1000x under rare steady skies (probably ain't going to happen where most of us live).

Thus, your choice of refractor or reflector is probably less influenced by the views but more influenced by practical considerations.

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