Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_30_second_exp_2_winners.thumb.jpg.b5430b40547c40d344fd4493776ab99f.jpg

JOC

What do I need to buy please?

Recommended Posts

This page in the thread I mention is useful because Nigel G has imaged the same DSO using different camera lenses and telescope. So it shows what the difference is. I particularly like the camera with a 135mm lens. That is the star discovery mount that Nigel uses. I will stress it again the 150p that comes with that mount does not natively focus with a dslr, the focuser needed a hack to acheive this with a hack saw and other changes, so camera lenses do open up a spectrum of use and as you do not use auto focusing old manual lenses are fine for this.

link here

Only you know how serious you want to be about imaging and whether you have the budget, space and circumstances to go the EQ route.

Edited by happy-kat

Share this post


Link to post
Share on other sites

You cannot do everything with one telescope and you cannot make your final choice of equipment with your first purchase unless it happens to do exactly, and all of, what you want. This is not impossible but it is highly unlikely. A first scope is one to enjoy and to allow you to find your areas of interest. Keep that first choice simple and keep astrophotograhy well clear of the discussion. (I say that as someone who makes most of his living via astrophotograhy but I still say keep it out of the equation.)

A warning about instant gratification in this game. It is in very short supply. Most scopes will give you a mighty WOW factor on the moon and most will do likewise on Jupiter and Saturn. For the rest you need due diligence and carefully managed expectations.

Folks have already said on this thread that cash soon spirals out of control. What really spirals out of control, as the evolution of the thread confirms, is not cash but expectation. The first responders said, 'Skywatcher 8 inch Dob.' I will join them. This instrument will give good planetary views and the best views of fainter objects as can be had on budget. The electronics-dominated alternatives are all about making the gratification more instant at the expense of the view. But in this game the gratification, after a few nights out, will never be instant whatever you choose.

You may be happy to stick with the simple and rewarding 8 inch Dob or you may, like me, end up chucking in your job and becoming the proprietor of about 2000 kilometres of cable and enough computing power to run Paris.

Think carefully!!!!

Olly

  • Like 5

Share this post


Link to post
Share on other sites

OK, back to the 8" Dob.  An instrument on a tripod sounds attractive due to the ease of moving it and setting it up - With the one the ex had we took it from inside to outside and set it up on the tripod and it wasn't a difficult task.  I am still a little perplexed as to what an instrument like the 8" DOB sits on - is a suitable object to mount the white stand in its photo supplied with the scope or does the owner need to create something from scratch?  Assuming a suitable mounting base becomes part of the equation how portable does it all then become to store and then to use.  Sorry if this is a 'durrr' moment, but has any got a picture of one of these style of telescopes in use so that I can see what the whole unit from floor to instrument looks like please?

Edited by JOC

Share this post


Link to post
Share on other sites
10 minutes ago, JOC said:

OK, back to the 8" Dob.  An instrument on a tripod sounds attractive due to the ease of moving it and setting it up - With the one the ex had we took it from inside to outside and set it up on the tripod and it wasn't a difficult task.  I am still a little perplexed as to what an instrument like the 8" DOB sits on - is a suitable object to mount the white stand in its photo supplied with the scope or does the owner need to create something from scratch?  Assuming a suitable mounting base becomes part of the equation how portable does it all then become to store and then to use.  Sorry if this is a 'durrr' moment, but has any got a picture of one of these style of telescopes in use so that I can see what the whole unit from floor to instrument looks like please?

The dob just sits on the ground generally. You can sit down to observe at the eyepiece which is at the top of the tube, on the side so is quite easy to look into. It is literally a grab and plonk outside job.

Benefits over what we've discussed before are that the aperture will make objects appear brighter (that's not strictly true but assume it is for the moment), and they will have better resolution (more detail). The setup is much quicker and easier, no alignment necessary other than making sure the base is fairly level.

Negatives are that you have to manually find objects and track them yourself as the base has just a simple alt az manual movement. More of your cash is going on the optics rather than on any electronics.

  • Like 1

Share this post


Link to post
Share on other sites
17 minutes ago, JOC said:

OK, back to the 8" Dob.  An instrument on a tripod sounds attractive due to the ease of moving it and setting it up - With the one the ex had we took it from inside to outside and set it up on the tripod and it wasn't a difficult task.  I am still a little perplexed as to what an instrument like the 8" DOB sits on - is a suitable object to mount the white stand in its photo supplied with the scope or does the owner need to create something from scratch?  Assuming a suitable mounting base becomes part of the equation how portable does it all then become to store and then to use.  Sorry if this is a 'durrr' moment, but has any got a picture of one of these style of telescopes in use so that I can see what the whole unit from floor to instrument looks like please?

ok, here you go, here is the base on its own:

WP_20160918_20_49_28_Pro.jpg

You don't have to make this yourself, it comes with the telescope, but it is flat-packed, so you do have to put it together. It isn't too difficult to carry either:

WP_20160918_20_50_17_Pro.jpg

As Stu says, plonk that on the ground, put the OTA in it (the OTA has circular protusions about half way down the tube, and it rests on 2 plastic knobs - one of which you can see on the back surface of the mount in the first picture), there are then a couple of clutch controls to screw in and away you go.

 

Share this post


Link to post
Share on other sites

The 200p dob is arround 15 kilos for the base and 11 kilos for the tube on First Light Optiocs product page.

Share this post


Link to post
Share on other sites

Thanks all, that all makes much more sense now - The whole thing is actually much larger in total than I envisaged from the catalogue shot (the photos speak a thousand words).  I hadn't imagined that it could sit on the ground and be the 'whole object'.  The base appears big, but as it separates from the instrument I imagine that I could store the base in dry shed and the rest of the instrument inside.  The base appears to have a double floor - it rotates like a cake icing stand - yes?  I presume you set the angle of the scope to coincide with the degree of up/down-ess (Y axis) of the astrological object and then move it manually on the X axis pivot to track the object across the sky - yes?  Though I'm not certain that can be entirely it as I am pretty sure astrological objects  appear to move across the sky relative to where we stand in an arc and therefore a single Y axis setting wouldn't track them would it?  How much effort is it to track objects with it?  I must admit I like the notion that its 8" and not just 6" As a novice you tend to have a notion that a wider telescope collects more light and is therefore better - perhaps this isn't correct, but 8" sounds better than 6".

Share this post


Link to post
Share on other sites
10 minutes ago, JOC said:

Thanks all, that all makes much more sense now - The whole thing is actually much larger in total than I envisaged from the catalogue shot (the photos speak a thousand words).  I hadn't imagined that it could sit on the ground and be the 'whole object'.  The base appears big, but as it separates from the instrument I imagine that I could store the base in dry shed and the rest of the instrument inside.  The base appears to have a double floor - it rotates like a cake icing stand - yes?  I presume you set the angle of the scope to coincide with the degree of up/down-ess (Y axis) of the astrological object and then move it manually on the X axis pivot to track the object across the sky - yes?  Though I'm not certain that can be entirely it as I am pretty sure astrological objects  appear to move across the sky relative to where we stand in an arc and therefore a single Y axis setting wouldn't track them would it?  How much effort is it to track objects with it?  I must admit I like the notion that its 8" and not just 6" As a novice you tend to have a notion that a wider telescope collects more light and is therefore better - perhaps this isn't correct, but 8" sounds better than 6".

Yes, the base rotates just as you suggest to give you Azimuth adjustment, and the scope tilts up and down to give you Altitude.

You have to track objects in both axes as they do not just follow a straight path, but with practice this is quite straightforward.

Speaking very simply, 8" is better, and will show you more than 6". As I said it has more resolution and effectively allows things to appear brighter at the same size, or larger at the same brightness than in a 6". Planets will definitely show more detail assuming good seeing conditions.

Negatives are size/weight, additional cool down time for the mirror and lack the of tracking as we already mentioned. To be honest, the cool down will probably only be ten or fifteen minutes more.

EDIT Astronomical not astrological!!

Share this post


Link to post
Share on other sites

Correct, it doesn't track, so you have to nudge it in both axis. It's easier with eyepieces that have a wider FOV, i use 76º and I was sketching double stars, so needed to keep it view for about 10 minutes.

Share this post


Link to post
Share on other sites

Ah, so I was right it will need a nudge to make it track - I recall needing to do that with the ex's old one as objects drifted out of frame, I know that I've never used a computerised drive before so perhaps what I have never tried I won't miss.  

The mirrors get hot?   I am surprised that there is that much energy entering the system to make things hot - even focussed to one point!  However, if they take 10-15 mins to cool down they must get quite hot.  I must admit I think I'd rather see as much as possible for my cash and cope with any downsides and I'm sure that this collimation thing can't be beyond me.  Perhaps I'd learn more needing to manually find things too. 

This decision making thing requires a good bit of thought.........

Share this post


Link to post
Share on other sites

I'm  back now :icon_biggrin: These Dobsonian telescopes really work, very very stable. Collimation is easy- buy a Cheshire collimation tool The 8" will show you much more than a 130mm scope. The primary mirror holds heat and needs a bit of time to cool down, refractor objective lenses do to, not as long usually and SCT's can have long cooldowns. The 200mm f6 will be really easy to find a widefield to work with OIII filters.

Using a Dob becomes intuitive, you become "part" of the telescope.

Edited by jetstream
more info

Share this post


Link to post
Share on other sites
On 9/17/2016 at 15:46, jetstream said:

I would bet the SW 150P has better optics...at least as a system. The SCT uses more elements in its design and each one has the possibility to degrade the view. The long FL of the SCT has pro's and cons as well.

Having used both I would disagree. You would need to throw fairly expensive eyepieces at the fast f/5 Newtonian to make it compete with the slow f10 SCT with cheap eyepieces. 

Can't you also say that the short focal length of the Newt has pro's and cons as well?

 Isn't it easier to achieve a higher Strehl with slow optics?

 

 I would choose the Newt for larger DSO's, but the SCT for everything else.

got to admit dew control can be more of a pain with the SCT though, with a closed tube Newt I can often get away with no dew shield at all, but its a must with an SCT!   

  • Like 1

Share this post


Link to post
Share on other sites
19 minutes ago, Chris Lock said:

... Isn't it easier to achieve a higher Strehl with slow optics?

This is a bit of a tangent but SCT's typically have primary mirrors of around F/2.0, with a spherical figure. The corrector and the secondary create the F/10 optical system.

More on topic for the original poster, I moved from a Celestron C8 (8" SCT) to an 8" dobsonian a few years back freeing up some £'s for other projects. The F/6 8" dob rather surprised me by performing at least as well as the SCT on every thing I pointed it at. I did have to do that pointing myself though with the dob, and the tracking, but it does become 2nd nature quickly and today I can track at 300x plus with my 12" dobsonian quite easily.

After 30+ years in the hobby and having owned 25+ scopes I do find this posted by Olly earlier in this thread very much hits the nail on the head:

"A warning about instant gratification in this game. It is in very short supply. Most scopes will give you a mighty WOW factor on the moon and most will do likewise on Jupiter and Saturn. For the rest you need due diligence and carefully managed expectations..."

 

 

 

Edited by John
  • Like 1

Share this post


Link to post
Share on other sites
3 hours ago, Chris Lock said:

Having used both I would disagree. You would need to throw fairly expensive eyepieces at the fast f/5 Newtonian to make it compete with the slow f10 SCT with cheap eyepieces. 

Can't you also say that the short focal length of the Newt has pro's and cons as well?

 Isn't it easier to achieve a higher Strehl with slow optics?

 

 I would choose the Newt for larger DSO's, but the SCT for everything else.

got to admit dew control can be more of a pain with the SCT though, with a closed tube Newt I can often get away with no dew shield at all, but its a must with an SCT!   

I was thinking of the f8 SW 150P dob when I made the comment as I'm a dob guy, no doubt SCT's can give great images. Yes I think that the simple 2 element f8 SW dob could be easier to get a good Strehl, the 200mm f6 as well. Telescopes with a large central obstruction need VG optics to mitigate the effects the obstruction has on things IMHO.

Many people use and like their SCT's, personally I like reflectors, my 10"& 15" gives excellent high power lunar and planetary views. To each his own for sure.:thumbsup:

Share this post


Link to post
Share on other sites
5 hours ago, JOC said:

Ah, so I was right it will need a nudge to make it track - I recall needing to do that with the ex's old one as objects drifted out of frame, I know that I've never used a computerised drive before so perhaps what I have never tried I won't miss.  

The mirrors get hot?   I am surprised that there is that much energy entering the system to make things hot - even focussed to one point!  However, if they take 10-15 mins to cool down they must get quite hot.  I must admit I think I'd rather see as much as possible for my cash and cope with any downsides and I'm sure that this collimation thing can't be beyond me.  Perhaps I'd learn more needing to manually find things too. 

This decision making thing requires a good bit of thought.........

To be clear, the mirrors don't get hot in use, but they do absorb heat during the day, quite a lot if in a warm house or in a hot shed or observatory.

The best imagescarent seen until the mirror has cooled to ambient temperature, otherwise you get convection currents in the tube which spoil the view, especially at high power.

Cool down can take 45 mins or so, so it is best to get the scope out early and leave it in the shade so it is ready for you, although the low power views should be ok after 15 mins or so. The larger the mirror, the longer it takes to cool.

Share this post


Link to post
Share on other sites
7 hours ago, Chris Lock said:

Having used both I would disagree. You would need to throw fairly expensive eyepieces at the fast f/5 Newtonian to make it compete with the slow f10 SCT with cheap eyepieces. 

Can't you also say that the short focal length of the Newt has pro's and cons as well?

 Isn't it easier to achieve a higher Strehl with slow optics?

 

 I would choose the Newt for larger DSO's, but the SCT for everything else.

got to admit dew control can be more of a pain with the SCT though, with a closed tube Newt I can often get away with no dew shield at all, but its a must with an SCT!   

Chris, the 200P is f6 so should be relatively easy on eyepieces.

I'm mindful of budget in this. A 6SE had already blown the budget, an 8" SCT is significantly more so from a cost perspective the 200p is a much cheaper way of getting 8" performance.

@JOC the 200p is a relatively simple design, basically a rolled steel tube with the mirror held in a cell at the bottom, and a secondary mirror at the top with a focuser. This is mounted on simple bearings and the base is laminated mdf I believe. The SCT is a more complex design with a primary mirror, secondary and also an optical front corrector plate. This is all held in a more substantial tube with focusing done by moving the primary mirror. I think because of the narrower field of view, these scopes are often supplied with goto mounts and so the cost goes up again. There are many differences but there is no doubt that the 200P is the cheapest entry to 8"observing.

I always try to be guided by the requirements given in original questions, but also try not to put too much of 'me' into my answers i.e. I present the facts as asked without loading too much 'buy this one!' Into it. That hopefully lets you make your own decisions more freely.

In this case the choice largely comes down to how important goto and tracking are for you, plus of course budget. You will be observing more quickly with the 200p, whilst a goto scope needs setup and aligning, but then obviously to see anything you have to find it yourself. That is a skill which needs learning so will take a little time; it's very rewarding when you do though.

Dare I present another option? The 200p Flextube Goto. This combines the 8" dob with goto. You can find things yourself and still have tracking or let the goto find things

https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-flextube-goto.html

I guess the negative on this may be weight as the unit has to be carried all as one I believe. Worth checking out though.

Share this post


Link to post
Share on other sites

.....that's an extra 479 notes for some fancy electronics, though once mastered (  setting up and alignment ) it should work just as well, and will follow/track your target, and if your unsure of where your target is, will find it from the data base, but its critical to get the scope aligned first, every-time.
The  end result optically will be the same, for visual observations, though I would suspect the GoTo would fare better if you have a camera  in the focuser tube. The 200P Skyliner will not fail due to electrical issues?

JOC...........you stated " I have no time to get involved in visiting experts and societies - I just want a semi-decent set-up I can use in my own time in my own garden.  Can this forum help please? "
The forum will help, but to be honest each setup is a personal choice and a learning curve too. Not sure you can just buy off the shelf,  a one stop system, that will provide all your needs, unless you have seen  or maybe tried something yourself?
I have found that the  200P  is a great scope for my needs, and possibly the only scope I`ll need now! However, a bigger scope will offer me more in the way of light capture and image scale, something I want/need to increase? There are other merits and some pitfalls with a larger scope though, which is why for now, the 200P remains.
This is actually my second telescope, the 1st being a Celestron 127EQ   That particular scope  should be avoided IMHO, but at the time I thought it was cheap enough to get started. It was, but performance  was poor in comparison and usability was  just so cumbersome and frustrating, even  when mastered, its still frustrating and slow to operate. The 200P satisfies my needs and requirements, especially now, as my understanding of how it all works,  and to what is achievable and capable under my skies.

Edited by Charic

Share this post


Link to post
Share on other sites

@jetstream Yep agree the f/8 version would probably be better optically (other than diffraction spikes) and close to the field of view/ focal length of the 6" SCT, so probably a close match in that respect.

@Stu Was just aiming the comment at Gerry rather than the OP really, I thought he was talking about F/5 6" Newt being inherently better optically than an f10 6" SCT which I felt I had to stand against :) 

I went to bed thinking I would link exactly the same scope you have in the morning i.e the 8" goto Dob. Yes it's 750 quid but he'll struggle to share the sights with others if he's relying on nudging the scope. I think for a family scope you are missing a trick if you don't at least have tracking.

Edited by Chris Lock
  • Like 1

Share this post


Link to post
Share on other sites

The history of the Dobsonian telescope really says it all. John Dobson was an interesting mixture of monk and scientist who wanted to make big telescopes to show remote galaxies to the general public. He knew that making big Newtoian optical tubes and mirrors was possible and that amateurs did so.  What could not be done easily was engineer the massive mounts needed to carry them. Everyone before him had thought in terms of ponderous structures of steel running in ballbearings in the Victorian tradition.  Dobson thought outside this box and realized that you could create a minimalist wooden alt-azimuth (up-down, side to side) system with bearings consisting simply of teflon pads running on textured formica. The simplicity is breathtaking. The performance is a dream. The natural damping of the wood and the slight residual friction in the bearings conspire to give a system which, though it moves easily, is vibration free. The Dobsonian mount is not only cheaper and easier to make than the traditionally engineered one, it is also better as a manual mount.

Personally I find tripods quite irritating to store. They have to be folded and collapsed and persuaded to keep still in a corner. With a mount head they are top heavy and don't seem inclined to stay where you put them. An 8 inch Dob has a small footprint and stands vertically in a corner. Job done. It takes up no more room than an umbrella stand but if you use umbrellas...  just don't!!!!!  :shocked:

That or an SCT? To quote John Dobson, 'Cassegrain Schassegrain.' And, boy, do they ever mist up in the UK. You need active dew heating. Passive will not always suffice by any means.

Olly

Edited by ollypenrice
Typo
  • Like 2

Share this post


Link to post
Share on other sites

Hi Charic - My problem is finding the time to get involved in societies etc.  I have spent my whole life involved in this and that society and they all take time and commitment to get the most out of membership and the communities knowledge.  I can't deny the huge amount that can be learned through the generosity of society members, but it is shame when I struggle to reciprocate by being a diligent member through pure lack of time.  Hence if I now want to try things out I limit my involvement to short courses and what I can achieve myself by using the marvellous resource of generous folks on the internet - forums to which I always do my best to respond to and try to help others in return when I gain sufficient knowledge to do so.  I am sure as a starter into this an off-the-shelf kit maybe with some additions as in the lovely shopping list so kindly provided at the start of this thread will help me find out if I am going to gel with it.  At least as Charic has done people can say you might be best avoiding X, or if I suggest something someone can say if it will be unsuitable

It does sound like these 8" DOB's might provide clearer views of the more 'family' friendly objects.  for example, I have a mother who would love to see the planets, but as noted by Chris just now nudging things by hand doesn't help to share what you have found if by the time you have swapped viewers the object has vanished from the view-finder and the person you are sharing with doesn't realise just how slight the movements need to be in order to track an object - we are already recalling an hilarious conversation from years ago with the ex's system and my father declaring "I can't see the ruddy moon" loudly on several occasions.  So that's the trade-off a the moment, get a scope that might be clearer - the 8" DOB or get a Newt with tracking, or blow the budget out of the water and get both!!

Hot mirrors - ah, they gain warmth from where they sit and need to cool before use - that makes far more sense.  It was doing my head in to comprehend the physics of them heating up in use on a cold night LOL

Dew shields - was there one of them in the shopping list?  Mind you looking at online pictures it seems that a home-made solution might be easy to achieve - they appear to resemble a long lampshade - I assume it doesn't really matter what they are made from as long as they are 'cone shaped' enough to avoid vignetting the image.

Share this post


Link to post
Share on other sites

Dew shields are "tube" shaped and just slip on over the end of your scope and fastened with a bit of velcro. You can make them cheaply from a £5 camping mat. Tracking is a great idea for your purposes - you don't necessarily need goto - and a tracking only dobsonian will save you some money. I used to have a 12" flextube tracking dob - to which I added a goto handset - so that remains a future option for whichever aperture size you choose. Hth :)

Share this post


Link to post
Share on other sites
8 minutes ago, brantuk said:

Dew shields are "tube" shaped and just slip on over the end of your scope and fastened with a bit of velcro. You can make them cheaply from a £5 camping mat. Tracking is a great idea for your purposes - you don't necessarily need goto - and a tracking only dobsonian will save you some money. I used to have a 12" flextube tracking dob - to which I added a goto handset - so that remains a future option for whichever aperture size you choose. Hth :)

I couldn't see a Flextube without Goto Kim, is there a 200P version? Might be a good middle ground, especially if upgradeable.

Share this post


Link to post
Share on other sites

To be honest Stu - seeing the 8" flextube goto was a pleasant surprise for me - I've always wondered why it's taken till now to produce one. Hopefully there will also be a "tracking only" version available - but I've not seen one yet which is why I hinted at the 12". Alternatively the OP could mount an 8" tube on a tracking only EQ mount.

The 12" tracking dob is large enough for people of various heights to peer in the eyepiece without too much back strain. Imho the 8" is a bit small and some folks will want to sit - others will kneel or stand - could be awkward with a crowd - an adjustable stool would be a good idea. But that's down to the OP's judgement I guess. :)

GoTo Dob Chart

Edited by brantuk
  • Like 2

Share this post


Link to post
Share on other sites

There is something very similar/same on the buy/sell pages of this forum, I can't justify £1000 - luckily I am about 400 miles from Oban!! 

  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.