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Dyptorden

Telescope for DSO photo

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Hi again,

Recently I had a post where I asked information about a telescope less than 600e.The budget is the same,yet after gathering some more information, I decided that my primary goal is to observe and photo DSOs. For the moment I want a telescope+mount that would help me observe DSOs and later, buy a tracking motor.(that's why I didn't take into consideration anymore the refractors which seem to be planetary oriented and the dobsons which can't be use for photo too well)

What I found in my country at that price would be:

1. Celestron - Omni XLT 150 which comes with a CG4 mount

2. Sky-Watcher 2001P-NEQ5 which comes with an EQ5 mount (I don't know why but this one is cheaper than the Celestron and has better aperture, and better mount... is better in everything... is it the brand only or the quality of the materials too?)

also some guys recommended me

3. Celestron - Omni XLT 127 which comes just as the XLT 150, with a CG4 mount but is a Schmidt-Cassergrain and not a Newtonian.Also this telescope is more expensive (~150e more) and i doubt i can go for it.

As far as I know, when thinking about DSO's, the most important characteristic is the apperture (the newtonians above 150mm and 203mm) but for photography its the focal distance (the Schmidt-Cassergrain which has 1250).

I don't know the importance of the f when regarding DSO's or photography... the Newtonians have f/5 and the Schmidt-Cassergrain has f/9,84

Could you please tell me your opinion about which of these should I go for (also some arguments would help). I am opened to suggestions towards other telescopes (but I want them to be new).

Thank you for your time,

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And two more similar telescopes :

4. Bresser N 150/1200 Messier which comes with a EXOS-2 mount, a 150mm aperture, 1200 focal distance and f/8

5. Orion N 203/1000 SkyViewPro which comes with a SkyViewPro mount, a 203mm aperture, 1000 focal distance and f/4.9

Yet I haven't heard too many things about "Bresser", and regarding the Orion, I haven't heard too many things about SkyViewPro mount (at least compared to the CG4 or EQ-5)

Again, thank you for your patience.

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You have a bit of a problem really to observe dso's requires a different scope to one that images them at least it does if you are not made of money.If you want to get a good view of them you need a big scope this can be relatively cheap  if you got a dobsonion scope but try putting an 18" scope on a mount and you are looking at some thing a small professional observatory would use probably costing in the tens of thousands of pound.  So what most imagers use is something smaller with good optics that can fit on a smaller cheaper mount and let the camera take the strain. this brings you back to the problem of not being able to see dso's visually. So if you are not a multi millionaire it is cheaper to get to get 2 outfits a relatively inexpensive big dob for visual and a relatively inexpensive small scope and mount for imaging.Of course this is only relatively inexpensive  it is still expensive to most of us. If you can't afford a heq5 mount the skywatcher eq5  with motors is usable and so is the celestron cg5 but not very effectively with a 200p on it. If you want to do both disciplines you are going to have to forget about buying bundled items none of the offered bundles  will do both disciplines. I would get a skywatcher 130pds and an eq5. Its more expensive than buying a bundle unless you can get a second hand eq5 and it will not be better than an imaging bundle like the ed80 on a heq5 or an observing bundle like the 200 on an eq5 but it may give you enough apparture to do some visual and be small and stable enough to do some imaging. Its a compromise and not even the best but its probably the cheapest that gives you a chance to do both.

Edited by rowan46
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As above, the 130pds is as close as you're going to get to a scope that's good for visual and photography.

I'd highly recommend you do some more reading into the importance of focal length and f-ratio (speed) and why aperture is not a main consideration when choosing a scope for astrophotography before you part with any cash.

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For imaging a faster scope really is a bonus - Earlier this year I gave imaging a go at f10 - It was mind numbingly slow going, I needed a lot of data to get anything decent. I was using a pretty sensitive mono CCD as well, if you are using a DSLR it will be much worse.

For me, my money would always be on a shortish focal length refractor such as an ED80 with the reducer.

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As above, an 80ED is a good choice for the beginner. It will allow you get familiar with the various aspects of imaging (guiding, focus, framing, processing) without getting embroiled in the task of collimation or modification that reflectors sometimes need.

Once familiar, then you can move on to a reflector like a 130 or 150pds (Skywatcher). Avoid the Celestron (even though its the same company) because I dont rate the focuser on those (single speed only). The worst choice possible is the SCT, unbearably slow for imaging.

Bigger (or longer focal length) isnt always better, its just harder by quite a magnitude.

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http://www.12dstring.me.uk/fovcalc.php

If you play with the link above it will give you some feel for what can be captured through different combinations of equipment, particularly for imaging. As Wuthton says, it is worth investing more time in understanding field of view.

Edited by Owmuchonomy

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In general for AP you need a short fast scope, either reflector or refractor. For visual you want a large aperture scope but the large aperture counts against the AP aspect. They are physically bigger and the focal length is longer.

A short ED refractor may seem good, WO ZS71 for example, but they are generally fast and being a doublet can/will show some CA on things like stars, which as the milky way is made of stars causes a problem. A short fast apo triplet cost a lot more.

An SCT or Mak is no use, the focal length is just too long, so this causes trouble with tracking and with exposure length. They work on planets but that form of imaging is different - do not mix the 2 forms of imaging up you effectively use different equipment and they do not cross over in use.

One other aspect is that getting say an EQ5 now will allow you to image with just a scope and camera, if you then get into it deeper and add guide scope, guide camera, tube rings and whatever else you are increasing the weight and then the EQ5 is too lightweight so you need a heavier mount as well.

Starting in AP means deciding what it is that you re likely to actually end up with.

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FIrst you need to understand the key variables.

1) Aperture is important in itself for visual observing. It is not, in itself, at all important for imaging. This image was taken with about 50mm aperture (tiny) in a camera lens. http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-gfQmRVJ/0/X3/ORION%202014%20reprocessWEB-X3.jpg  For deep sky imaging forget about aperture on its own and think entirely about the next two variables.

2) Focal length. This determines your field of view. A long focal length reduces your field of view so that small targets will fill the frame. That is great for small targets but not for large ones, which won't fit on the chip. Many targets are large, some very large. Long focal lengths are difficult to guide because a small tracking error at the mount produces a huge error on the image. If you are using a basic mount and not autoguiding you really do need to keep focal lengths very short.

3) Focal ratio.  This is really only important in imaging, where it is very important indeed. A fast focal ratio gets more light onto your pixels in a given time than a slow one.  DSLR cameras in particular need this, as Sara said. F5 is four times faster than F10. (A small complication; only compare F ratios between scopes of the same focal length. If you compare scopes of different focal length and different focal ratio at the same time you are comparing double variables and can be easily misled.)

Some of what we are saying to you will seem unlikely and odd, but that is how it is.

Olly

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Thank you for your answers,

You told me above, about that Sky-watcher 130

In my first post, the second telescope seems similar to what you have shown me. It is a Sky-Watcher 2001P-NEQ5 which comes with an EQ-5 mount (as you have suggested it should do nice). It is exactly in my budget and has a 200mm aperture (which seems nice for observing) with f/5 (which seems the nice choice for photo). On the other side, the telescope number 1, the Omni XLT 150 has a shorter focal length which may offer me a wider field of view and a f/5 focal ratio.Yet this one has a CG4 mount which seems to be worse than the EQ-5.

Should I go for this Sky-Watcher maybe?

P.S.: the apo ED80 is in my budget without the mount.. When adding the mount it is too expensive... And just asking, being a refractor, isn't it worse than a reflector, when the DSO's are primary targets?

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The Skywatcher 200p would make an excellent scope for visual use on an EQ5. For astrophotography it would be a poor choice, the focal length is quite long and besides it is far too big and heavy for photographic use on an EQ5. A slight puff of wind would ruin your image.

I'm fairly certain that you wouldn't be able to achieve focus with a camera either. Thr PDS versions are for astrophotography.

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