Scope advice sought

[greglloyd]

I've been observing the sky on and off for more than 20 years now and have progressed from small refactor to 6", 8", and 10" dobs. The 10" scope was sold off last year as I found it staying stored away more than anything with family life taking priority most of the time.

So... Last August I bought a pair of Pentax PCF WP ii 10x50 binos for a quick grab and go setup and these have been fab. Have seen many DSO's with them (Beyond the obvious.. M51, M101, M33, North American Nebula, many globulars, etc). In fact, the Pentax's are the first time I've ever seen the NA Nebula - so these are defo my current wide field instrument of choice right now.

However, I'm looking a scope again. Not a large scope - it must be very portable this time round. I'm looking the scope for closer inspection (i.e. full resolution) of the planets, tight clusters such as M11 / The Auriga clusters / NGC star clusters, plus partial resolution of the brightest Globs (e.g. M13, M3, etc).

The scope I have in mind at the moment is a MAK 127 (either Celestron or Skywatcher - they are essentially the same) but I'm just not 100% sure if this scope if the right choice.

I was wondering if anyone could give a little advice on these scopes. I'm aware of the long focal length and narrow field of view, but I still suspect that most DSOs will fit into the FOV with a 25 / 32mm eyepiece. I'm not concerned about large DSOs as that is what I'm using the binos for.

If possible, could someone give me an idea of what can be seen with the more obvious DSOs? I'm trying to gauge FOV, brightness (I'm aware the effective aperture is around 120mm) and contrast. Other than the MAKs what other choices are there? I'm not really looking to get an EQ mount as I mostly observe from my home location (which is blessed with magnitude 6+ skies on good nights!) and have been used to the quick 'point and shoot' approach the DOB's take - so would prefer a AZ GOTO tracking setup for quick and easy visual observing (not interested in AP).

If you have a 127 MAK and decently dark skies - objects I'm interested in hearing reports for are :-

M27

M57

M51 (Can you see the two seperate components? The 10" scope I had could show spiral structure from here - though I do not expect that in the MAK!)

M11

M38

M36, 37, 38

Other planetary nebs (e.g. Eskimo)

The brightest globs (M13, M3, M5, etc) - can you partially resolve the outer regions with the 127mm MAK?

M81 / 82 - Can you see mottling on M82? (I was able to see clear structure in M82 in 8" and above from my location)

M42 - What detail can you see? Can M43 be seen (as a seperate component)?

How do the planets look (Jupiter, Saturn, Mars)?

Virgo Supercluster (can you pick up many of the fuzzes here?). With the DOBs I could see lots. What about the MAK?

NGC starclusters in and around Cassiopeia (e.g. NGC7789)

Please note, I'm not expecting the same views as the DOBs gave. I've previously looked through a 5 inch reflector (a fairly cheap one) before and know the difference in brightness and resolution. But the MAKs are of higher quality than the 5" I used before and so I'm curious to hear from experienced observers what exactly they can see with theirs? For reference, I can easily find all the objects I detailed above in my 10x50's to give you an idea of the sky darkness I have here.

[knobby]

Good luck with your choice!

I'm no expert but do have a 10 inch dob and a 4 inch mak !

As a very rough guide, the orion neb from my garden looks about half the size and brightness through the mak.

[John]

I have a 120mm ED refractor and, until recently, a 10" newtonian so I'm sort of familiar with how the objects you list compare in scopes of around the apertures you are interested in.

Looking down your list I'd say that the 120mm refractor would achieve more or less what you have described from my moderately light polluted back garden. It does better under really dark skies of course.

I actually prefer the views of the planets through the refractor rather than the 10" newtonian - the ED120 produces some of the best views of Saturn, Mars and Jupiter that I've seen in any scope I've used.

On deep sky objects the 4x light gathering power of the 10" newtonian scores heavily as you would expect although the 120 does show M51 with 2 cores and a hazy halo around them and some mottling in M82.

A 127mm mak-cassegrain might not quite rival the ED120 but it should come quite close once cooled and assuming good collimation.

You ask about other options and I suppose a 6" schmidt-cassegrain might be one that would give you a little more aperture in return for not a lot of additional weight / bulk.

[greglloyd]

Thanks for that John. So, do you now exclusively use 5" of aperture? And if so, do you find it enough to give you satisfying views for the most part on the bright DSO's? With the 10" I found that you ended up going for more difficult DSOs which mostly looked dim with little detail just because the aperture let you do so. I wouldn't be inclined to do the same with the 5". I'd be using it more on the showcase objects.

Also, do you get partial resolution of the outer regions of any globs with the 120? The 10" would resolve a lot of the outer parts of M13 even at 85x with a nice bright view. 150x would resolve to the core but the image was somewhat dimmer. Obviously the 5" scope will give dimmer views but how much so at 85x and even though the resolution of the scope will be less, can it have a good go at resolving the outer parts at 85x? (I suspect at 150x it will appear too dim to be enjoyable).

John, I did also look at the Nexstar 6SE but it is around £800 compared with £380 and I'm not sure I would get £420 worth of extra satisfaction from the difference in the view considering I had previously had 10" of aperture and know I would not be getting the same views in either of the new scopes. Is there any compelling reason to go for a 6" Schmidt over a 5" Mak that I have't though about? Both are same 1500mm focal length so should give same eyepiece powers but with the Schmidt being a little brighter at any given power is all I'm thinking?

How would a 120mm achro refractor compare to the Mak? (Cost of APO is out of the question). e.g. Evostar or Omni Xlt? I know that CA would be an issue.

Finally, can anyone give me more info on the FOV with the 127 Mak? I understand it is around 1 degree but I still cannot picture how this would look compared with my previous 1200mm F5 Dob? I'm not bothered about getting rich field views with the scope as my binos are doing a great job at that. I just want to be sure that most DSOs can be framed in the view. For example, how does the double cluster look at 47x (32mm eyepiece)? How does the apparent field of view appear? Some older posts I've read would give you the impression that a Mak's view is claustrophobic! Yet a lot of the more expensive and serious level scopes have long focal lengths ranging from 1500 to 2850mm focal length so must give similarly restricted field of views, right?

[greglloyd]

One last thing! Scope would be stored outside in the shed. What would the cool down time be of a Mak? 30 mins or less? Shed is usually pretty close to the outside temp during autumn / winter - though heats up quite a bit in the summer.

I've heard of very long cool down times with closed tube scopes such as Mak's which would defeat any grab a go ability I am looking for but I'm thinking those guys keep their scopes indoors in the house hence the long cool down times

[Dunkster]

From what I understand (and read posts of), it's hard to beat a good decent sized refractor especially if you're not upset by the CA.

I've come somewhat of a circuitous route to the conclusion that an 8" is a good aperture in my light polluted suburb. I started off with a 127 SLT. It's a great little scope, showed me many firsts including M57 and M13 and Uranus. Then I was offered a 6SE by a colleague getting out of the hobby. A good chunk of the proceeds go on the tripod/mount. The 6SE is nice and solid, whereas the SLT is wobbly by comparison (although I was oblivious to this when getting started, I was having getting a lot of enjoyment from my 127). The mount of the 6SE is the same as that of 8SE. The 6SE is very light and so long as you don't have any particularly narrow doors to navigate it can be carried in one piece.

Visually, I couldn't tell them apart on planetary but that time overlaps with the last opposition of Jupiter. Saturn came and went and I loved the views with the 6SE - but this was my first Saturn with my own scope, so it will always be biased in my memory. When it comes to DSOs, the 6SE is certainly brighter, I managed to see the faint smudge that is M1 Crab Nebula one night without a filter! (remember, light polluted suburb!). I also enjoyed M42 with and without a filter with this scope. Unfortunately my location does prevent real benchmarking of the fainter objects.

Then a couple of months back I picked up a C8 ota. I feel this was something of a watershed moment in broadening my observing because I could suddenly resolve lots of stars in globs, M13 and M92 were beautiful, and open clusters such as M11 and Caroline's Rose were also really lovely (I'd expect the oc to be in the grasp of the 6SE but I haven't tried it for comparison). Regarding M13 I was able to resolve stars to the core with my ES82 14mm on one occasion (conditions must have been good, or my technique is improving), but there was still background fuzziness. I couldn't count them all but there must have been hundreds sparkling in the EP.

The C8 has much greater light grasp than the 6 so this is not unexpected. The C8 is only just over 1kg heavier than the C6, but this extra weight (and my application of heavier EPs!) is noticeable, as there is a small amount of focussing wobble, but not as much as with the 127.

Regarding FOV... the 127 and 6SE have the same limitation at just a little under 1.1 degrees, but you can get there in different ways. You could also add a focal reducer (at least to the SCT) to widen it to about 1.3 degrees. The C8 with its wider baffle tube can show a little more...I use a 30mm 82 degree EP with mine to pleasing effect... the double cluster fits in really nicely the 82 degree EPs help alleviate the "looking down a straw" claustrophobia.

Jupiter - hard to discern any difference

Mars - one good night could see polar cap and dark patch with 6SE

M57 - smoke ring in 127, brighter in 6SE, some element of texture in 8SE

M13 - fuzzy patch with brighter core in 127 and 6SE, resolves many stars in 8SE

M51 - only seen with C11 from here

M81/82 - I've not managed these with any, but I have a streetlight and some trees in that general direction

With much darker skies than I, you may have more luck. Is the 6SE worth the extra? Hard to say, but it might be worth keeping an eye on the used market for one, likewise the 8SE if you're inclined. Which ever scope you go for, plan for a heated dew shield and a power supply with enough juice to last you a session. Cool down should be very minimal if kept outside...I find it gives me time enough to get comfortable and do my star align. In the US you can buy "cat coolers", essentially just a tube with a small fan at the end with blows a gentle stream of air up the baffle tube, but even given all my frivolous spending I've not felt the need as I stage my scope in the porch.

One little aside about the goto... I personally prefer the Celestron Nexstar software to the SW Synscan (that I have on the EQ6), mostly because it requires fewer key presses! Sometimes it's the little details

Anyhow, I hope this gives you something useful, although I appreciate that your sky is much darker than mine so this may not be all that applicable

[John]

....Thanks for that John. So, do you now exclusively use 5" of aperture? And if so, do you find it enough to give you satisfying views for the most part on the bright DSO's? ......

I've sold my 10" newtonian because I have a 12" F/5.3 Orion Optics tube which will shortly be going onto a dobsonian mount. That will then be my largest aperture instrument.

A 5" scope gives nice views of DSO's but once you have tried a 10" you realise it's limitations. Globular clusters such as M13 and M92 are resolved right across the core with the 10" and under good seeing conditions are starting to look like their photographic images. The 5" just can't do that.

1 degree will frame most deep sky objects - it's around 2 moon diameters.

[rowan46]

I used to use a 5" sct and it's a good portable scope It will show a lot of dso's but sadly detail is not something it was good at . Planets were good at least the bright ones were but glob clusters remained small bright blobs or large grey splodges you can make out general charecteristics but not detail

[greglloyd]

I've come somewhat of a circuitous route to the conclusion that an 8" is a good aperture in my light polluted suburb.

Believe it or not, I'd say the same from my dark sky location. The 200P I used to own gave very similar views to the 250px. The upgrade to the 250px was not that great to be honest. Should have went to 12" for more impact! I went from having the very slightest hint of spiral structure in M51 in the 8" to being able to see stronger hints of the too brighter main arms in M51 on a few occasions in the 10 inch. But never a clear enough view though to rule out that it may be partly my imagination filling in the gaps at times!

An 8" scope would be ideal, but it must be smaller this time round for portability, storage, and the fact my wife is sick to death of me selling scopes and then buying again!

[greglloyd]

The words I got this morning by the way were "there better not be another one of those skywatcher thingies coming in this house again!"

That says it all!

[greglloyd]

Thanks for all the info guys. I realise that the 5" aperture will not give anywhere near the views I had with the 10" scope but I'm not really expecting the same views as before anyway. You've all given me some great info regarding expected views, FOV, and the differences between the software on the GOTO solutions.

It's good to hear your comments regarding the expected views as the last time I personally used 5" and 6" scopes was more than 5 years ago. It's been 8 and 10" scopes since. However, I've really enjoyed the views through my binos since I got rid of the last scope and the intention for any new scope is to simply get some closer looks at some of the objects I can readily pick out in the dark skies here in the binos.

I'll have another mull over things before deciding what to go for

[twotter]

The words I got this morning by the way were "there better not be another one of those skywatcher thingies coming in this house again!"

Celestron it is then

[Marki]

My 125mm achro refractor does very well on planets, moon and brighter DSOs. It will resolve the edges of thngs like m13. And it is great for splitting doubles. I have a 200mm SCT (Nexstar 8SE), but I prefer generally to use the 'frac - nicer views in my eyes. Plus I have never really got on with the Celestron goto routine. On the other hand the nextstar packs away pretty tight - I keep the tube and mount in the two boxes they came in, one on top the other in my spare room, and the tripod lives in the shed. The refractor is a little harder to store/hide .

If I do use goto I tend to use my iOptron minitower (use that with an 80mm apo for "grab and go") - I find the alignment and tracking with that much easier and better than the Nexstar. I haven't used the skywatcher routine yet so can't compare with that. The minitower, at least in the minitower II or Pro version will take a reasonable load - it should cope with a decent size shorter tube refractor or 6" plus mak or sct, if you use the counterweights. It also packs down in to one flightcase, plus the tripod.

Goodluck with your choice!

[Mr Fiery Jack]

I gave both large and small scopes, a 10 inch 00 dob and a 4 inch refractor , both have their merits. The refractor, an ED100 produces the most consistently good views, but then you would expect that with a quality refractor and the seeing being what it is in this country. That said when the seeing us good (which isn't very often) those extra 6 inches just blow the refractor out of the water, especially M13, 15, 92 and the like, even Jupiter looks better on those rare nights of good seeing in the dob. It is however just amazing what you can see from your back yard with just 4 or 5 inches...incredible really. If I had to sell one, it would be the dob though.

[greglloyd]

Hi Fiery Jack,

Agree with all that you said. Here at my location in NI we actually get a lot of really transparent skies in the winter particularly, but more often than not there is decent turbulence above spoiling the chances up bumping up the magnification. An unfortunate consequence of the UK having a jet stream nearby so often!

[greglloyd]

_{Well I ordered the new scope this morning from FLO...}

_{Celestron C6SE}

_{I think this will be a happy medium between larger aperture and the portability / quality optics I am looking for.}

_{Hopefully will arrive within a few days in time for some first light before the moon starts to interfere again later this month :-)}

[greglloyd]

Sorry, typo before! I mean't I bought the NexStar 6SE

[Marki]

Hi Greg

Good choice I think - a neat balance between aperture, goto and size. Look forward to reading your first light (and lets hope FLO forgets to pack the complimentary box of clouds....)

[John]

Good choice Greg

[greglloyd]

Can anyone recommend any good eyepiece choices for a 6" F/10 SCT?

Would be looking for something around 32mm for lowest power with widest FOV, 6 - 8mm for planets (180 - 250x), and around 15mm for medium power (100x).

My budget would be no more than £100 per eyepiece

[Dunkster]

Congrats Greg, the 6SE is a great portable scope! Keep us posted with how you get on in your darker skies

My experience has been that something around 10 or 11 is useful too when the conditions aren't so great. I have a spread of the ES82 range and they work great... I imported from the US for about £100 each inc. taxes (less for some )

For a low power, it's hard to fault a TeleVue 32mm plossl is just a little over budget (10% sale on now), alternatively an ES68 24mm (again import, if you can find one) or the Baader Hyperion 24mm should all show the same amount of sky. Of course there are countless more and less expensive alternatives.... but good EPs should last a very long time.

[Mr Fiery Jack]

_{Well I ordered the new scope this morning from FLO...}

_{Celestron C6SE}

_{I think this will be a happy medium between larger aperture and the portability / quality optics I am looking for.}

_{Hopefully will arrive within a few days in time for some first light before the moon starts to interfere again later this month :-)}

Good for you..enjoy.

[greglloyd]

Well, the NexStar 6SE arrived today and it's a really nice scope. Build quality seems absolutely amazing compared with my two previous Skywatcher Dobs (as you would expect).

I'll save the proper first light report for another night as conditions were not ideal this evening and I also moved the scope from +24c indoors to -1c outdoors and did all my observing within 1 hour (during which the scope was cooling down). Tonight was mainly about aligning the red dot finder, trying out the Sky Align (which worked fine), familiarising myself with the NexStar handset, and checking the optics.

Unfortunately, my 12mm eyepiece did not arrive today as expected (will arrive tomorrow) so I was left with the stock 25mm that came with the scope and the 7mm Celestron X-Cel LX which also arrived today. That gave me a choice of 60x and 214x - not ideal! After around 30 mins of cool down I tested out slewing to some objects and this worked really great. The views at 25mm were nice with sharp stars and nice contrast on Jupiter with 4 bands visible - however the scope was still cooling down and between that and the general turbulence in the atmosphere the seeing was very variable even at that power.

Bumped up to the 7mm to give 214x and the size of Jupiter increased considerably although the contrast was poor and at this point I noticed that the four Galilean moons were all looking like seagulls each side of the focus and I could not focus them to pinpoints. Decided to check out Capella and check the concentric circles at each side of the focus and noticed that the central point in the airey disk appeared slightly off centre towards the top. Decided to leave all alone and let the scope continue to cool down. This improved things somewhat but still at the end of the session (scope had been outside for approx 1 hour to 75 mins at this stage) the circles were not symmetrical with the central point bang centre.

Pointed back to Jupiter and noted that the detail and contrast had now increased somewhat after the scope had been out for an hour and enjoy the view. Moons still showed seagull effect but much less than before. Decided I should leave the scope optics alone and test again over a few more nights before determining if collimation is off in any way. Can anyone give me advice on all of the above.

Bar the apparent poor seeing, the sky in general was poor with lots of hazy (thin fog) really limiting the transparency. So generally not a good night to test the scope unfortunately. Did manage to view M36, M37. M38 and they were well resolved but the view was somewhat affected by the misty conditions.

Decided to call it a night about 1 hour into the session as it's freezing cold outside, misty, not great seeing, and black ice everywhere. Hopefully get a better chance to test the scope out soon. Could have done with having the 12mm eyepiece arrive today to give me a more mid power view to test with.

I'd appreciate feedback from any SCT owners out there with what I reported above about the seagull effect which was very noticable at 214x. Was this just because the scope needed to cool down more (remember, going from +24c in house to -1c outside and had the scope back inside around one hour afterwards) or do you think there may be a slight collimation issue?

[John]

You can check the collimation by looking at a star like Polaris and moving it a little out of focus in each direction, so it expands into a small "donut" of light with a circular black shadow in the centre. If this black circle is in the centre of the unfocused star "donut" on both sides of sharp focus then the collimation is OK.

My money would be on the scope not having cooled fully though. This can wreak havoc with the image at medium to high power and the SCT's and mak-cassegrains can take a long time to reach equilibrium with a large temperature change to deal with.

[greglloyd]

Thanks John. Yes, I decided not to touch anything at all and give it a few more sessions before making any changes. I defocused to both sides of the focus on the star Capella and could see the rings but they were not concentric - rather than were flaring somewhat in all directions and constantly changing so I suspect this was due to the tube not being fully cooled down. I did notice over time that the pattern was improving somewhat.

I also read last night that you should check collimation with a magnitude 2 / 3 star near the zenith so I'll follow your advice John and use Polaris the next session.