What type of scope + size could be my next telescope?

[Linda]

Hi.

Currently I have a Skywatcher 127mm Maksutov, bought in October, so I'm still pretty much a beginner. I use it for planet viewing, hunting bright DSOs and occasional sun viewing with a Baader filter. I am purely a visual observer. Maybe I should add that I so far have been able to find 35 Messier objects and 24 H400 objects with my current scope.

When looking at sketches made by others who own big Dobsons, I see them sketching DSOs with much more details on them than the small grey fuzzies that I can see. I would also like to see more of that, like the spiral arms of NGC2903. So I have started thinking about a future bigger telescope, but I'm very uncertain about which type and size. So the main focus is on seeing more details on DSOs. But I wouldn't mind seeing more details on planets too and be able to split double stars.

The other thing I have been thinking about it that a 5" Maksutov has about equally big aperture as a 90mm refractor, because of the central obstruction. So I could buy a 5" refractor and still have more aperture than today. I have understood that it is a good idea to buy a bigger scope that is more than just a little bigger and that really makes a difference. 

Some requirements:

* My most used observing spot is a wooden terrace which isn't equally solid as sitting on the ground. I must be able to use the scope on it, even though it is not ideal.

* It will be used mainly at my house. I can keep the Mak for when traveling. But I want to be able to carry it in and out of the house by myself, as a woman who is not particularly strong. A cart could be an option. Carrying it in a pieces could also be an option, but is more fuss. It would be nice if it could fit into an otherwise full car, but not an absolute requirement.

* The scope must have equally sharp image quality as my current scope. Or better.

* I don't want strange colours when looking at a planet.

* I would prefer not to have to collimate the scope before each use. But as many of you can live with that, that requirement has lower priority.

* Budget for scope/OTA: I would appreciate to keep it under 1000 euros, but that might not be realistic. But prices like 4000 euro are not an option.

* I don't want a very wide field telescope. I want to be able to use large magnification when circumstances allow it. For wide field I will use my 10x50 bino.

* Telescope for visual observing

 

I have started making a list in Excel with possible scopes, but I am not sure of the limitations and differences in quality of the different scope models.

Scopes/models that I consider:

* 10" closed tube Dobson, e.g. Skywatcher Skyliner 250PX. This is the cheapest solution. Weights quite a lot. With a standard quality mirror. Does this mirror live up to my requirements for good optics?

* 10" or 12" truss Dobson, with optionally a custom made mirror (that last option makes it expensive, but is perhaps worth it). This type of Dob is transportable, although that is not high priority requirement, but nice to have.

* 8" Maksutov, like the Vixen VMC200L, which is light weight and small.

* 5" ED refractor, e.g. Explore Scientific Triplet APO 127mm for 1500 euros and only 4 kg. A 6" ED refractor might be better, but is too expensive.

* 7,5" Maksutov Newtonian, e.g. Skywatcher Explorer 190. But this is probably not a big enough step forwards from my current scope. Also quite heavy to set onto a EQ type mount.

* 9,25 " SCT from e.g. Celestron. But also this comes with a standard quality mirror.

I think the Edge HD SCTs are above budget.

 

Could those of you who have experience with different types of scopes please give me some recommendations? And tell me which of this list I should not have because the quality might disappoint me. Or is there a type of scope that I haven't considered that I should definitively consider?

[dweller25]

Hello Linda.

I had the 10" Skywatcher closed tube Dob and found it quite heavy (but I have a bad back) - the truss version is even heavier !!

In fact all the scopes you mention are quite heavy ! The Vixen VMC200L is the lightest  - I had one and have to say it's the worst scope I ever had as contrast was terrible.

If you want good optical quality my thoughts are that a lightweight 8" Dobsonian as made by Orion optics in the UK would be a good compromise ..... http://www.orionoptics.co.uk/VX/vx8-8l.html

Or perhaps the Skywatcher 120ED is worth considering .... http://www.firstlightoptics.com/pro-series/skywatcher-evostar-120ed-ds-pro-outfit.html

Good luck

 

 

 

[Linda]

7 minutes ago, dweller25 said:

 

[Peter Drew]

I'm struggling with a recommendation here. . As usual the wish list underlines that it is difficult to cover it with one telescope. I think you should keep your excellent Maksutov and add a conveniently larger Dobsonian for your deep sky interests. As far as planetary detail is concerned, you cannot easily buy extra performance, this tends to come from practice. You say that you are a beginner so why not continue with your Mak, the experience gained will stand you in good stead for the future.

By the way, your 127mm aperture has more of an advantage over a 90mm refractor than you suspect. If you work out the area of the 127mm and then subtract the area of its obstruction I think you will find that the residual will be greater than that of the 90mm refractor.

[scarp15]

I quite agree with David, dweller25, comments, consider an Orion Optics UK dobsonian such as a VX8L. Very good all-rounder and light to handle even as one unit.

[Linda]

@dweller25: Thanks for your feedback on the Vixen.

@Peter Drew: When I calculate the surface area of the Mak compared to refractors, my Mak comes close to a 120mm refractor. That would make a 127mm refractor uninteresting, because of the small difference. I also had in mind to keep practicing with the Mak until I had found most of the bright DSOs on my atlas. But I am orientating on the next scope, because I need a really long time to decide anything like this. :-)

I will indeed consider Orion Optics with a good quality mirror. A light weight other option is Sumerian Optics, who makes 10" Truss Dobs at 12 kg, where you can optionally bring your own custom made mirror.

[vlaiv]

For deep sky observing I would either go with dob or 9.25 SCT - later being out of your specified budget at least two times. For that SCT you would like at least HEQ5 type of mount (15kg and upwards carrying capability). SCT being light in itself (under 10kg), mount will be bulk of total weight (that you need to carry and setup).

I own a skywatcher 200p dob (solid tube), and it is really easy to carry and setup (for me at least, but mind you I can haul quite a bit). Quality wise, unfortunately, I can't give experienced view of things as I did not have a chance to look thru more than 2-3 telescopes so far. But I can say following: either I've got fluke mirror that is by chance this good, or you don't have to worry about quality issues with such scopes (if all are being this good). I did not see any problems with this mirror. Image is sharp, I observed Jupiter and Saturn at over x400 with no image degradation only more features as mag went up (seeing permitted of course). Most troubling for me while observing planets are diffraction spikes that scatter some of the light. Light gathering increase is quite noticeable in comparison to 130mm newton and 4" wide field frac. I usually observe from red zone, but I think this dob really delivers even in such conditions.

And yes, about collimation, I collimated my scope only once for past 6 months, just finishing touch when I received it (it was already collimated pretty good). It holds collimation exceptionally well. I did not transport it for long distances, or by any other means other than carrying it in hands, but I did use it both on dob mount and on HEQ5 mount (I carry it each time a short distance - about 20m from my basement to back yard).

[cloudsweeper]

Hi - 

I have a similar 'scope, a Celestron Nexstar 127 Mak, also bought about the same time as yours.  

I am now aiming for a Celestron 8SE (weight 15kg) as my next one.  With a focal reducer it would give low mags at a slightly larger angle (about 1.3 degrees) than at present, and the highest mags are greater because the focal length is that much larger.  

As for DSOs, the 8 would gather about 2.56 times the light of a 5 inch.

I ruled out an Evolution 8 or 9.25 because of the bulk and the fancy extra features I don't really want.

I did seriously consider a Dob, but again thought them a bit bulky.  Also, I like the GoTo and tracking facilities of the Mak/SCT 'scopes.

Linda, these are just my thoughts.  I fully recognise that there are many helpful and knowledgeable folk on SGL who might not agree with me!

And anyway - it's going to be a while before I commit, so maybe I'll take on other ideas!

Doug.

[Linda]

Now I have read some more about Orion UK and their Dobson, maybe with an upgrade mirror option, seems like a good idea. I think I'd prefer the 10", though. I then move it on a cart at home...

@cloudsweeper: I don't care about Goto as I am used to hunt manually.

I am just wondering what is best, the shorter version of the longer version? The longer version has more focus length. Is it so that the longer version can have more magnification on the days when that is possible? Are their any good argument in buying the one or the other? I see that the longer one has a smaller secondary mirror.

http://www.orionoptics.co.uk/VX/vxspecifications.html

I haven't really looked at the price yet, so things might change again... I would first like to see what is possible and what would be preferred.

[scarp15]

This would be a good choice to consider, perhaps the VX10 F4.8, the mirror upgrade option is equally very worth considering and they are first class. Perhaps Gerry, Jetstream will provide some comments and he has until quite recently excelled with using his VX10 dobsonian equally on planetary and DSO observing.

[vlaiv]

I would go for a longer version, reasoning being: slower scope - less coma and other aberrations, probably finer mirror (not necessarily but slower mirrors are easier to make with greater precision), smaller secondary (more light but difference some would argue is negligible), better on planets (higher mag possible and smaller central obstruction), more forgiving on eyepieces. Faster scope on the other hand - wider field possible, maybe somewhat lighter setup (less tube - smaller weight), might require coma corrector and more expensive eyepieces.

Just saw that you are interested in 10" version. Then short version has another benefit - more comfortable viewing position. I can observe in every position (full alt range) while sitting down with my 8" - 1200mm focal length. 1600mm focal length is at least 30-40cm taller than 1200mm one. Depending on your height, with 1600mm one, targets near zenith may require standing up, or some type of height adjustable observing chair.

[scarp15]

The VX10 is proportionally fairly comparable to the VX8L, so this level of portability is not compromised.  A coma corrector is a personal choice at this focal ratio and ought not necessarily be a given requirement, well corrected good quality eyepieces will be a benefit. However once you have settled on the scope, eyepiece obsession commences.

 

[jetstream]

The VX10 f4.8 is a superb telescope IMHO. I am continually surprised at the quality of the optics and the view they provide and I still observe with it despite my recent infatuation with more aperture.

The longer version may have balance issues, this may be worth checking out. What the f4.8 ratio does is put the scope right in the strike zone for higher mag viewing at a better exit pupil. It also allows the use of a 30mm eyepiece without the exit pupil becoming too big, for me anyway.

The mirror cell on these telescopes are excellent and holds collimation extremely well - they must have spent a fair bit of money on its design utilizing small nylon(?) tips the mirrors rests on. Zero astig ever shows in my telescope even as it goes through extreme temp changes, the mirror does not " stick" to the nylon allowing free movement. It is a nice open design too with the fan working nicely. The primary is only as good as the cell its on...

The focuser... no deflection in this focuser and it holds hvy eyepieces well.But... my version will have the tension set screw unwind itself from repeated use, lessening tension. OOUK may have updated this focuser now. Other than this I like it a lot.

The tube is aluminum and will dent, but the benefits of it outweigh this and it is very light. This tube will deflect under very hvy weight changing collimation as recent tests have shown. I have not detected this with any eyepiece used during star tests which included the monster 30ES 82. Binoviewers might be a different story.

The dob base is excellent, cast aluminum, light and easy to carry as is the scope tube by holding a ring in one hand.

The VX10 f4.8 is a fantastic telescope, mine has the 1/8PV upgrade and I'm completely satisfied with the mirror and telescope in general.

 

Make sure you ask about the balance of the longer version....IMHO

[ecuador]

My vote would be for the C9.25. It is simply the best planetary scope that you will be able to carry by yourself (9kg). Not sure what you mean by "standard quality mirror", the difference between it and the Edge HD version is the coma at the edge of the field, but you are not interested in wide fields anyway (and there is a cheap reducer/corrector that sort of takes care of that anyway) and it is really a problem for photography, not visual. Otherwise it is considered an extremely sharp optical instrument. I usually match it with the lightest mount that can lift it, an iOptron ZEQ25, but as that is a goto mount for astrophotography, it is not cheap. A simple EQ5 mount would also be able to lift it though just for visual use and that one is cheap. The HEQ5 starts to get heavy for me and I am an average man. Head + legs are about 15-16kg so you can lift them but it is not something you will "want" to do often (and separating the 10kg head does not really make it easier as it means extra trip + assembly/disassembly), so whatever you buy I suggest you keep it up to 10kg max for either tube or mount.

Which also means the 250 Skyliner would be too heavy in my opinion with a 15kg tube (the length does not help either). Otherwise, if you were not more into high power views and you did not have the budget for the C9.25 I would also suggest a lighter dob as an alternative, like the truss tubes you are thinking about. Generally I prefer using an equatorial myself (either motorized or even just nice slow motion controls are fine with me), but for a newtonian this size the equatorial mount would be too heavy, so the dob makes sense, especially a truss type.

Personally, for planets, I also love looking through APOs. Their light-gathering is not that great, but they show higher contrast and color, so it takes quite a larger mirror to match them in enjoyment. But then for DSO's they lack the aperture so you'd also need a light-bucket still. That's why I suggested the C9.25 which has proven a significant improvement over my previous C8 and the 8" Newtonian I have for some wider fields.

Edit: I haven't used the Orion dobs, mainly Skywatcher, so I see their short solid tube is a bit lighter at 11kg. An 11kg 1.2m long scope is certainly harder to carry around a C9.25, but not by too much, so I'd say it is probably doable. It will be "harder" on eyepieces of course than slower scopes.

[Mr Spock]

For the money and convenience the 10" Dob is the way to go.

Just be aware that even in a 10" fuzzy grey blobs are still fuzzy grey blobs

[Linda]

Thank you all for your input. It does not make it easier. I am however convinced that I won't buy a good refractor before trying a light bucket.

An advantage of the Dob is that the mount is included. A heavy SCT requires a new mount.

Good information about the sitting options, so maybe the 8 inch is better. I don't have a telescope store anywhere near my house, so I need to collect knowledge from the internet only. I will definitively look at some youtube movies with poeple using them.

[jetstream]

and the views... I forgot to mention that the VX10 trounces my SW120ED under anything but poor seeing. The VX10 shows great ring features in Saturn, sharp colorful bands in Jupiter along with shades in the caps- and then there is the moon-fantastic. The performance of these dobs cannot be understated.

For me choosing one of these scopes is not about cheap aperture- it is about great optics... with a rock solid base. Yes, I belong to the dob mob

[Linda]

6 minutes ago, Mr Spock said:

For the money and convenience the 10" Dob is the way to go.

Just be aware that even in a 10" fuzzy grey blobs are still fuzzy grey blobs

I really hope to see a bit more details in some grey fuzzies, as I've seen in sketches. Today I only see grey blobs, sometimes as thin as a needle. But I have for example never seen a spiral arm. I do not expect to see astro photos.

But I realize that some sketches have been made by looking through a 18" scope. That is not an option.

[jetstream]

the mob is gathering Linda lol!

Dark skies are needed first and foremost for seeing detail like you describe. I see faint spirals in a few galaxies with the 10" from very dark, transparent skies. M51,M101 and M33 show spirals in this scope. The Needle galaxy will show its dust lane as will M31 (lanes). And then there are the DSO... Leo Triplet easy, Markarians Chain all there etc.

How are your skies Linda?

[scarp15]

20 minutes ago, Linda said:

Thank you all for your input. It does not make it easier. I am however convinced that I won't buy a good refractor before trying a light bucket.

An advantage of the Dob is that the mount is included. A heavy SCT requires a new mount.

Good information about the sitting options, so maybe the 8 inch is better. I don't have a telescope store anywhere near my house, so I need to collect knowledge from the internet only. I will definitively look at some youtube movies with poeple using them.

 

Yes cure the aperture fever first, in terms of grey fuzzies, as Gerry has said dark skies are needed, you will I expect have access to pure dark skies, the 10" dobsonian will have them reveal a little more definition.

[dweller25]

 

@Linda

I have had two Skywatcher 8" F/6 dobs - they gave excellent views and weight wise were easily manageable.

I wanted better views so I moved onto a 10" Skywatcher dob and it also was superb but VERY heavy for my ageing back

So I replaced it with an Orion Optics 8" F/6 dob which is very light. Still have this  - both the OTA and the base are excellent.

Had I done my homework properly I would have realised that the OO 10" F/4.8 weighs the same as the Skywatcher 8" F/6 !! 

I should have bought the 10" Orion Optics F/4.8 

Also this may be of interest ....

http://www.cloudynights.com/topic/529412-10-lightweight-travel-telescope-by-the-dobson-factory/

[Linda]

38 minutes ago, jetstream said:

the mob is gathering Linda lol!

Dark skies are needed first and foremost for seeing detail like you describe. I see faint spirals in a few galaxies with the 10" from very dark, transparent skies. M51,M101 and M33 show spirals in this scope. The Needle galaxy will show its dust lane as will M31 (lanes). And then there are the DSO... Leo Triplet easy, Markarians Chain all there etc.

How are your skies Linda?

I have quite a lot of stray lights from neighbours around my house. Last autumn I could just see the Milkyway in direction South. But when the snow came, that disappeared. At the snow will last to the spring. Now the sky is much lghter, blueish, not black at all. And my viewing area at home is due east, where I look out over the capital and it's light polution.

We also have a cabin in the country side with truely dark skies, but we don't go there often. And when we go there, the weather does not always cooperate. Last time I didn't even bother to bring the scope. I have only observed there once, around new year and then I was even less experienced than I am now.

I am in no hurry at all to buy the new scope. I should definitively try out my current scope more under dark skies and then look at familiar objects to compare with how they look at home.

But it is good that you mention it, because I am looking for a scope to use mainly at home. If a 10" Dob doesn't show much more there, then what is the point?

[jetstream]

When living in town with 19mag skies and bright local lights I could still make M13 out like Qualias sketch... Great idea to try your scope out under dark skies for sure. More aperture will show more regardless of LP...Under dark skies Rob and I saw M13 pretty much the same as in the sketch. M37's dust lanes, M42's wings etc.

 

[ecuador]

Yep, dark skies are the #1 "boost" in viewing. I was at my country house (in Greece) during the summer and while it is on a nice plateau in the mountains outside the city, there has been extensive street lighting installation the last 10 years (we are talking about in the middle of empty fields - it's crazy!), so it is not really dark. Anyway, I showed my wife some of the grey blobs we are talking about through an 8" skywatcher and the (new back then) C9.25 and she did enjoy it but after some point all started feeling similar to her and she went back inside. Then, there is a power outage in larger area and the entire plateau goes completely dark! Behold mag 6+ skies! I call her outside, and she was awestruck by the difference. Previously I could only describe to her that the two individual little fuzzies were interacting galaxies, but now she could actually see the spiral arm from M51 extending to the companion! Thanks to goto it took just a few seconds from object to object so we had time to enjoy over 12 targets in the half hour black-out (yeah, goto does come in handy sometimes!).

After all, Messier only had a poor quality 3" telescope. But he had dark skies.

Oh, and in your calculation of your Mak vs a refractor you were a bit off: The 127 Mak is 122mm real aperture (does not take advantage of the full 127mm mirror), its central obstruction is 42mm which brings us to equivalent light-gathering of 114.5mm. Next, while a refractor has a transmission in the area of 95% (ok a triplet might go less, but you get the point), for the Mak that's close to the transmission just for the meniscus corrector. The two mirrors further lose precious light. I am not sure of the exact mirror coatings, but as Celestron is not advertising special coatings (like the XLT on the SCTs) I would assume it is "standard" with a reflectivity around 0.9. This means two of such mirrors "lose" another 20% of light vs a refractor, making the effective aperture about 102mm. Now, this is only for light-gathering, as an Apo / ED refractor also has higher contrast and color which is the reason any inexperienced observer who viewed through my 80ED refractor and 127 Mak would say the 80ED is clearly better. Experienced observers would see that the Mak could show some more detail due to the resolution the 122mm true aperture offers over the 80mm, but still it means a refractor can hold its own over quite larger mirror systems. It's just that they start becoming way too expensive and heavy over 5" or so...

[Linda]

It must have been spectacular, that power outage. Last time we had one at home this winter it was cloudy .

 

I have been looking at some 10" dob you tube films and they don't seem too terribly big.

But as you mention dark skies, I must definitively consider a truss dob type so I can take it to darker skies. Whenever we travel to our cabin, we always have a car full of skies, clothes and other stuff. So a big full tube Dob wouldn't fit.