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Second telescope dilema


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Hi Guys,

Would like some advice please. I have been interested in Astronomy for a few years & bought a 200p Dob after spending time on this forum etc. Had some good sites through this - especially plants as well as some stars but have failed to really view many DSOs. My problem is I can't star hop well. I know the advice is going to be stick with it, it takes time, I couldn't do it to start etc but I have limited time to master this. 

I visited my nearest astronomy shop to discuss alternatives - I was particularly interested in n Nexstar evolution 8. I thought that the GOTO function would be great to see some of the DSOs & help me see more of the wonders of the solar system! They tried to put me off this - saying that a SCT is not good for DSOs & only for planetary stuff & that I should get a used GOTO 200p Dob that they had in as an ex-demo - a skywatcher flex-tube.

I have read mixed reviews on this & still am keen on the Evo.

I have some star maps & a Tetrad but really struggle to see the same view in the viewfinder as the map. I can find stars reasonably well but then get lost! I really on sat nav in my car & wonder if GOTO would help. I am not interested in AP - the most I may do is get a webcam type device.

Any thoughts or advice?

Thanks,

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Had thought of that - was thinking that a equatorial mount me be too complicated & hard to set up? I like the relative 'simplicity' of the Nexstar setup. Would it fit on a Celestron Advanced VX mount? Is that easier to align?

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Hi Ya Drnat, first thing when I read your post was how much Light Pollution do you suffer from ? - This is probably the single most problem we all suffer with to a certain extent - If you have bad LP then any DSO will probably look far from its best.  Its all about Background sky and transparency, Yes the GOTO will help put the object in or near to the centre FOV - but if you have very light background skies (due to LP) each object will be very difficult to see - Bad Light pollution makes most of the objects up there virtually invisible which ever type of scope you have, also, if your trying with a standard finder on the scope you have to reverse things to actually locate objects, under light pollution, you can't really sweep the sky for the object because the sky id just too bright.  You could help things along a little by using a RACI (Right Angled Correct Image ) finder - this would give you the correct orientation when using a star chart - so say the object is to the right of a bright star - this is where you point the finder where as if you have a standard finder you have to put it to the left - yes I know its confusing - with a standard straight through finder you have to mirror and invert things so they show upside down and back to front - see very confusing - also to add to things if you have a bright sky - it makes things virtually impossible to find.

Once aligned GOTO's are now very accurate - so a slew to your desired object will soon tell you how the LP is - If you can actually see the object or not - once you've done a few tours of the sky each month you get to know which objects are doable and which are just too faint/Light Polluted out!

Also this time of year the sky never gets truly dark - so your fighting against this as well  - best time is mid winter waiting for each object to culminate (get to its highest point in the sky away from the LP)

I know its very frustrating for you, but getting a few things in your head regarding finder orientation, Light Pollution happens to us all !!

When I started, I used to have a look in the Sky Atlas for the brightest objects around at the time, pick these objects that are really high in the sky towards the Zenith (overhead) where the sky is at its darkest with the least amount of atmosphere to look through, using a low power, I would then sweep the sky to see if anything "pops out" as a little "misty" patch for DSO's - re check in the finder for correct position, try to invert and swap around for the correct orientation - if nothing - check back to the chart/book and have another go.  Try for objects that are covering the smallest area in the sky as the much larger Nebulae/Galaxies are really tough for LP'ed skies - and stick with the Messiers - these tend to be the most observed and the most observable.

Stick at it mate - you'll soon be swinging that thing around the sky!!

Paul.

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To someone to tell you that an 8" SCT is no good for DSO observing is simply not true. A 8" SCT is a terrific DSO scope but has a limited field, so large dso's can not be observed in their entirety in one go. M31 for example, shows spectacular dust lane detail but you'd have to scan the object and M13 will knock your socks off. If that's the scope that's calling to you, then go for it.

Some advantages of an SCT are : there's no coma, no spider diffraction, short physical tube, never needs re aluminizing and there's no need for expensive eyepieces. On the down side, and there's always a down side with every scope, SCTs are more sensitive to internal heat and can take over 3hrs to become truly thermally stable, if they've been stored in a warm room.

Mike

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There are only subtle differences between my 9.25" SCT and my 300P Dob under my skies. Aside from the FOV already mentioned above the Dob brings up fainter stuff and resolves stars slightly better. However, both are used equally when friends are round for a star party.

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I have a 9.25 SCT on the AVX mount and I have had no issues with DSO. I also use a field reducer.

The equatorial is a little more complex to set up but not impossible...another myth to be busted along with the light pollutuion issue on bigger scopes.

If the work you are doing is visual then a polar align based on an inclinometer (or just set latitude on the scale), compass to get north and a level base will be fine. There are also loads of You Tube videos showing how to balance an EQ mount.

I have a 300P goto as well (az mount) and it too is simple to set up and aquires targets very easily, which under UK skies is a boon.

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First off, you state your finder view differs from the charts? Okay, that's not unusual. Assuming you have set up the finder during the day on a distant object - church steeple, radio tower, etc.- then you must realize the scale is going to be different, between charts and finder-scopes and main scopes;, in real time. You could use a compass to draw a circle on the chart to emulate what you see in the main scope based on the magnification you're using. Or use a map/chart whose size you can easily change to better match what's showing in your eyepiece. This can be done easier than you may think - I'll get to this in a moment.

When you are trying to find a specific object out there, start at your lowest possible magnification. The lower the mag. - the wider the field of view (FOV) you will be seeing. To match (it'll never be exact) the FOV, select the brightest stars. All the dimmer stars would drive you crazy if you tried to 100% duplicate on the chart or in the eyepiece. Go brighter. And here's where a software-program you can make bigger or smaller is more convenient, and realistic, than the printed chart. So I will now, yet again, shamelessly plug Stellarium.....

Stellarium is a VERY big planetarium (sky-charting) software-program developed and written by a large team of astronomers from all over the Earth. With it you start by setting your location - or selecting it from the large list on-board - and time. Then read the manual, either on-line or a downloaded one, and set up the rest of the parameters you'll need (as will be clearer once you are looking at it on your screen). Then you can move to the area of the sky where what you wish to find is in. And then you can simply make the view on the computer match (almost) what you can expect to be seeing at the eyepiece. Larger or smaller - it makes this as simple as rolling the center-wheel in your mouse. Once you see this thing in front of you, you'll know this is extremely over-simplified. Stellarium is capable of so many things that even long-time users (like me) are constantly finding new things it can do.

And yes - all this takes time. So I council relaxing, having a cup of tea, and study at your own pace. It took the known Universe about 13.6 billion years to get like it does today. It's not going to go away any time soon. So now, if you'll allow, I'll toss out a few links to follow.

Stellarium - which is 100% FREE - can be downloaded via this site:

http://www.stellarium.org/

A Pdf. manual you can download to read leisurely is to be found here:

http://barry.sarcasmogerdes.com/stellarium/stellarium_user_guide-new.pdf

And the most recent manual with the latest additions and fixes live on-line only at present is:

http://www.stellarium.org/wiki/index.php/Stellarium_User_Guide

Stellarium is an ongoing project. As more discoveries are made, new things are incorporated into the program. So check back often to view the latest updates.

Oh - one of the developers is a member here in SGL. You could drop him a line with a suggestion at some time. Who knows? You might be responsible for another addition! :grin:

As for that guy who told you SCT's are no good for DSO's? Perhaps he should tell that to this little puppy:

post-38438-0-07210800-1440659789.jpg

Relax, it's not a road-race,

Dave

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Wise words mate ! Trouble in the UK is that the weather is not fit for purpose. We get a procession of weather systems with short gaps between them. These arrive usually at gibbous and full Moon. Some parts of the country have had their worst summer weather for thirty years.

All this considerably narrows the time for observing. Locating easy targets by star hopping and you'll soon whizz around the old same.

Finding new stuff particularly faint stuff takes time and patience. This is more so with light pollution where low magnification searching is required. This can give little contrast to faint objects. As I've spent time searching, it's always against cloud arriving !

I'd suggest a GOTO equatorial mount able to take your choice of ota. Once you're used to it, setting up can take a few minutes and will give you immediate access to targets and tracking for as long as is required.

Choice of ota will depend on what you'd like to see . I use frac and Newts.

If you buy the mount new, then ota's can be picked up, even some super classics , by scouring the used market,

Nick.

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You don't need to get a new scope to just to find things, you can fit a push to system. I use Astro Devices Nexus system. You use a phone, iPad or tablet as a handset to view the sky and where your scope is pointing, then push the scope to the target, it's brilliant, you'll be able to find anything your scope is capable of seeing within a minute, even in a light polluted sky. It'll probably cost between £300 to £400 to fit it including the encoders.

http://www.astrodevices.com/products/Nexus/Nexus.html

Edited by Scooot
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Thanks guys. Nexus looks interesting. If not a goto is the way forward. Like the look of the avx mount but slightly intimidated by it. Need to have a look at one in a shop!

Thanks,

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I started out visual only - no intention of doing AP.  But got a webcam as it was recommended (Philips SPC900NC) and the last batch being sold.  Now I only bother with AP as I can see far more on my computer screen than I ever did visually - and study the results afterwards.  As someone has said, with the weather being what it is time is of the essence so being able to find something quickly can be very useful.

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Had thought of that - was thinking that a equatorial mount me be too complicated & hard to set up? I like the relative 'simplicity' of the Nexstar setup. Would it fit on a Celestron Advanced VX mount? Is that easier to align?

Unless you're going to be imaging, I'd say stick to the Alt/Az Nexstar type setup, much quicker to setup. The AVX is a equatorial mount and you will need to spend time polar aligning it to a degree.

To someone to tell you that an 8" SCT is no good for DSO observing is simply not true. A 8" SCT is a terrific DSO scope but has a limited field, so large dso's can not be observed in their entirety in one go. M31 for example, shows spectacular dust lane detail but you'd have to scan the object and M13 will knock your socks off. If that's the scope that's calling to you, then go for it.

Some advantages of an SCT are : there's no coma, no spider diffraction, short physical tube, never needs re aluminizing and there's no need for expensive eyepieces. On the down side, and there's always a down side with every scope, SCTs are more sensitive to internal heat and can take over 3hrs to become truly thermally stable, if they've been stored in a warm room.

Mike

Completely agree there, it seems like they were trying to sell you something they had in the store rather than what you were truly after... the NexStar will be great... if you need a greater field of view, just use a f6.3 focal reducer and a 40mm eyepiece... There will be a lot of time you will want to magnify the DSO tho, for example, the best views of the Carina nebula I had was magnified 184X with a 11mm Televue type 6 nagler and a UHC filter.... of course wide views were also breath taking... 

Of course as mentioned above, light pollution will be a factor to how much you'll will see, but with the Nexstar your setup is easy and portable and it doesn't take much to go to dark sites and do a night of observing... I live in a quite a dark area, but there is, as everywhere there are people and their need for lighting, a level of LP... when I went to a dark site, and I'll tell you that what I saw there through the eyepiece was like my 8" SCT doubled in size!!! It was amazing.

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There is a myth that the slower the scope, the better it is for planets and the faster the scope the better it is for DSOs and this is often repeated even by people e.g. in shops who should know better. Visually the speed of a scope has no difference on the brightness of the image at the same magnification. In fact objects in the sky never get brighter with a telescope than they are naked eye as they have fixed brightness. What you get with more aperture is larger image scale at the same brightness. E.g. if you look at M42 with naked eyes, you may just see a fuzziness around the stars at x1 magnification. Within reason / seeing allowances a telescope of increasing aperture will show the same object at increasing size at the same brightness.

Naturally each design has it's pros and cons but they all show DSOs, planets and stars very well given that they can be squeezed within the field.

If you don't use a red dot finder/telrad and a right and corrected image finder then I'd say they improve the ability to find things no end although always subject to your local sky quality of course. buying a GOTO scope which can go to everything but where you can see little due to the objects being too faint to see them in your skies is, I imagine, more frustrating than what you currently have.

Imaging I know nothing about.

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For a cheap alternative why not add a wixey to the 200p dob with some home made ra scales round the bottom.

Cheap GOTO for a DOB in reality.

Absolutely, a Wixey with something like sky Safari is all you need. I don't think you even need az circles, just get near it with your red dot finder and once you're at the correct alt, you'll find what you're looking for

Barry

Edited by Bart
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  • 4 weeks later...

Finally been to a shop & had a really useful conversation with no had sell etc. I have decided that the Nexstar evolution is the way to go. Debating between the 8 & 9.25 but leaning towards the later at present...

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Finally been to a shop & had a really useful conversation with no had sell etc. I have decided that the Nexstar evolution is the way to go. Debating between the 8 & 9.25 but leaning towards the later at present...

I eventually got my scope too, opted for the Celestron Advanced VX 6"SCT, so far its amazing! If you can afford the bigger aperture go for it, just weigh up the practicalities/needs of it. My 6" is the perfect size for me, if it was any bigger i think i would struggle to use it as much because of moving it around.

Sent from my iPhone using Tapatalk

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