upgrade advice from celestron 130 slt

[ausastronomer (John Bambury)]

Originally Posted by Camelopardalis

Interesting aside that Damian Peach often chooses to image with a C9.25...the Celestron SCT with the largest diameter secondary obstruction

For you to even make that comment Dunk, you're learning something from this thread. viz. The size of the central obstruction has minimal to no impact for imaging. It has a much greater impact for visual astronomy. Did you actually take the time to have a look at the simulation Damien himself provided in regard to the effects of the different sized Central Obstructions?

Cheers,
John B

[brian nordstrom (As avatar)]

Smallest , I think Dunk being an f2.5 primary as apposed to the f2 of every other Meade and Celestron SCT made so its light cone is narrower , hence smaller .
Sorry mate but you are wrong on this . . A simple ray trace will confirm this .
Brian

Originally Posted by Camelopardalis

Interesting aside that Damian Peach often chooses to image with a C9.25...the Celestron SCT with the largest diameter secondary obstruction

[Astro_Bot]

Originally Posted by Rodstar

BOTTOM LINE - The views through the SCTs I used were quite obviously inferior to the views through the same or similar sized dob. Some nights I ended up pretty upset, wondering why the f..k I had spent $5.2K for my LX200 when Mike had spent only $900 for his, and the views through his scope were quite obviously superior. Galaxies that were a mere blob in my scope were more clearly defined in his scope. Doubles were more clearly split in his scope etc. etc.

And yet my experience, and that of many others, is quite different.

An SCT has a longer focal length than a dob of similar aperture. This will result in the SCT showing a higher power view (smaller portion of sky) than a dob with the same eyepiece. The problem is that the quality of that higher power view is inferior.

Who said you had to use the same eyepiece?! I can comfortably get 1.1 deg TFOV with, say, a 41mm Panoptic and there's not much to see that's wider than that. At the other end of the scale, high power views are more difficult on a Dob - try looking at Jupiter on a good night at 300x in a 12" Dob and see how often you have to "chase it" by moving the Dob or suffer the "step stair" tracking at that power. It's not a comfortable viewing experience! The smoothness of tracking of an SCT on say an EQ6 is outstanding (but pretty good even on a fork mount) allowing a comfortable and lengthy study of any target at high power (seeing permitting). The high-power view is not, in my experience, inferior in any way. In fact, in my experience, it's superior, especially since you can focus on it for such a long time. That's not to say that there aren't better-than-average Dobs out there that can't give a good high-power view, but it's not, typically, going to be easy or comfortable.

SCT's suffer badly from dew, as their design involves glass against the open air. This can be reduced with a dew shield, but even still, this is far more vulnerable than having the primary mirror at the base of a dob.

At a noteably dewey star party last year, where no-one had dew heaters, only home-made dew shields, my SCT was the "last scope standing" with all others, including ALL of the Dobs, being dewed up well before mine. You simply can't make that generalisation and I think it's a little disingenious to claim that dew affects SCTs more than Dobs when a $10 DIY dew shield is all that's needed to turn the tables. Why do so many people add fans if Dobs are so good with dew? My experience (and not just based on that night) is that typical Dobs have no advantage at all when it comes to dew. Then there's the chipboard base's susceptibility to moisture ...

I found the mirror shift from using the focuser very irritating, requiring constant refocusing.

Mirror locks, microfocusers, zero-image shift focusers, crayfords, etc., have well and truly addressed that problem. On the other hand, there are plenty of shaky Newtonian focusers (on mass-produced Dobs) out there. I don't think you can claim a typical Newtonian's focuser as any kind of advantage. And there's no shortage of people who want to upgrade the focuser on their stock-standard Dob.

If you really want to talk about irritating, how about having to much more frequently re-centre your target or hunt for it in the first place (though, truth be told, some people enjoy that challenge)? And what about people bumping the Dob at a star party? That's not a problem you'll ever have with a sturdily-mounted SCT.

If I was looking to purchase a 10" for visual use again, and was planning to keep the scope I purchase for more than a year or two, I would (without hesitation) go for a dob over an SCT.

You're welcome to your choice of course. But people who've grown used to SDMs, especially an amazing scope like the Mary Rose, might not be in the best position to accurately recount how a typical GSO/Bintel or Skywatcher performs. Again, I'm not saying they're bad, but is it possible there's a little cognitive bias going on? You and John love your SDMs (and quite rightly so). Perhaps that's colouring your memory of cheaper, mass-produced Dobs? Just a suggestion.

I'm seriously not making it up when I say that my SCT is frequently regarded as "best on the field" against GSO/Bintel and Skywatcher Dobs. I have no doubt it wouldn't hold a candle (visually) to any SDM, but then that's not what Richard was asking about.

This is quicky devolving into tit-for-tat and a preference argument. I think there's little value to be gained in arguing further.

Poor Richard is probably wondering what he's let himself in for! We're much nicer in person. Really!

[barx1963 (Malcolm)]

Guys!
How about a little respect for the OP? He came on here asking about possible upgrades from a 130mm newt with a budget of $2000 and here we are arguing about the optical merits of LX 200's and SDM's.
There are lots of different scopes out there and each has its merits, drawbacks, strengths, weaknesses etc. And it is human nature once we have made a choice (especially if it involves large quantities of cash) to defend that choice vigorously. That applies to scopes, footy teams, cars, spouses etc.
So I suggest we all calm down, have a read of our previous posts and think to ourselves are we actually helping Richard? What he needs are some idea to spend his $2k and what the strengths and weaknesses of the various options are.
Here is a quick summary of my views.

8" Go To SCT
Strengths
Small portable scope
Usually good go to performance
OTA can be deforked and attached to a EQ mount for imaging if required
Eyepiece is always at a comfortable height for viewing
Long focal length makes high power observing easy

Weaknesses
Relatively high cost per inch of aperture so less $$ left to accesorise
Corrector plate is susceptible to dew (but this as with most dew problems can be solved with dew shields or heaters!)
Longer cool down time that open tube models
Relies on electronics, motors etc. which may fail from time to time necessitating repairs
Long focal length can mean that for the same EP, the view is degraded compared to a shorter scope.

8" or 10" dob
Strengths
Low cost per inch of aperture so $$ are available to spend on accessories or to get a Go To version
Smaller dobs are still compact instruments
Solid tube dobs can be used on an EQ mount if desired.
Primary mirror is not usually susceptible to dewing especially in solid tube models. (as an aside here, I have used both solid and truss tube dobs and only once had a dew issue on my primary and that was on the solid tube 12", and I never use the fan while observing, only while cooling!)
Non go to dobs have simple mechanics and even the go to versions can still be used in manual mode if electronics or motors break down or fail
Non goto dobs are easy to upgrade to push to systems such as Argo Navis
Collimation is an easy thing to learn and fairly painless in small dobs
A non go to dob is a great way to learn your way around the sky
Eyepiece height is usually at a comfortable position and can be used which seated if chair has adjustable height
Optically robust system that can give wonderful views

Weaknesses
Larger dobs can be quite large and heavy
Go to performance in some go to dobs has been less than stellar I have heard and as with all go to scopes there are electronics and motors that may breakdown or fail then requiring repair
Non go to dobs require charts and star hopping which is not everyones cup of tea
Require collimation on regular basis
Secondary, finder and eyepieces can be susceptible to dew ( but this as with most dew problems can be solved with dew shields or heaters!)
Eyepiece height can be uncomfortable at low elevations and in larger dobs (eg 16" plus) may need a stepladder.
Many cheaper dobs come with chipboard mounts that are susceptible to damage and moisture (although my old 12" GSO survived several years with no issues)
Shorter focal length means best views are at low to medium power. I found with my 12" f5 that I rarely pushed it much beyond 115X, but then I rarely needed to!

This list obviously is based on my experience and knowledge and there are MANY others with more of both. Note I have not mentioned collimation in regard to an SCT as I have no experience of how often it is needed or how easy it is. Also my comments on optical performance is not based on a rigorous analysis, only on what I have found but in relation to SCTs is based on a very limited sample that I have looked through at star parties.
Also I have tried to keep the points relevant to smaller apertures, although I have mentioned larger dobs in a couple of places for clarity. IMHO in larger apertures is where dobs really come into their own but the OP is budget limited.

Malcolm

[mental4astro (Alexander)]

Ditto Malcolm's sage words.

Cool head, Malcolm. Thank you.

Ranting and dissecting people's posts is just not cool.

It is not nice how some posts have developed.

[richard2600 (Richard)]

Thanks all info guys I think I get the pros and cons of each scope. Its been good reading better than any mags from the paper shop lol. I think which ever way I go so long as I got big aperture and its a quality scope from good brand im sure it will be upgrade, Well I hope it is anyway. Just hope weather gest better been crap all week im itching to get it out for some viewing

[iceman (Mike)]

Let's not make this thread a SCT v Newt bashing thread. The OP didn't ask for a comparison.

I think the OP has lots of info with which to make a decision.

[OzStarGazer]

I would wait a bit if I were you, Richard. If I remember correctly from another thread you had your (first) scope for just over 2 months. Maybe you can join an astronomy club for example, try out different scopes yourself and then take a decision.

[Amaranthus (Barry)]

As I mentioned earlier, don't neglect an eyepiece upgrade as a first option to improve your current scope!

[OzStarGazer]

Have you got a Barlow lens by the way? You will definitely see more details on clear nights with good atmospheric conditions with a Barlow lens.

[Marios (Marios)]

Hi Buddy

If you do go the Newt route with the NeQ6, get the Orion ST80 for a guiding scope with a $35 Solar filter it can be used to observe the Sun Disc in its full glory. Saves you a few dollars buying specialized solar telescopes, spend that money on the accessories field flatners,heaters etc..

[richard2600 (Richard)]

Originally Posted by OzStarGazer

I would wait a bit if I were you, Richard. If I remember correctly from another thread you had your (first) scope for just over 2 months. Maybe you can join an astronomy club for example, try out different scopes yourself and then take a decision.

Hi yep that's good point I will def go to some night viewings and get a look at some scopes first and also get bit more of a handle on things as im only new to it all I wont rush out just yet buying a scope.

[richard2600 (Richard)]

Originally Posted by OzStarGazer

Have you got a Barlow lens by the way? You will definitely see more details on clear nights with good atmospheric conditions with a Barlow lens.

No not yet I only got the standard 25mm that come with scope. I just ordered a Orion edge on planetary 12.5 mm fully coated from a shop online for $100 delivered Its suppose to be a good upgrade from the one I got

[richard2600 (Richard)]

Originally Posted by Amaranthus

As I mentioned earlier, don't neglect an eyepiece upgrade as a first option to improve your current scope!

Yep I just did that orion edge on planetary 12.5mm should be up grand on my standard 25mm that come with the scope

[OzStarGazer]

Originally Posted by richard2600

No not yet I only got the standard 25mm that come with scope. I just ordered a Orion edge on planetary 12.5 mm fully coated from a shop online for $100 delivered Its suppose to be a good upgrade from the one I got

Oh, with the 25 mm one you won't see many details of planets. It is more to recognize constellations and see stars with small telescopes.
You will see much more with the 12.5 mm one (and possibly a Barlow lens). I see many details with the 10 mm one and the Barlow lens. Wait and see!

[Amaranthus (Barry)]

Good choice, the Orion Edge On is a good eyepiece, and you'll see quite a difference compared to your 25mm (and twice the magnification, of course)

[barx1963 (Malcolm)]

Richard
A 12.5 is probably a good choice for that scope. As you have a 25mm that will give you low power view at 26x and the 12.5 gives you 52x.
Personally if you have only had the scope a short while I would suggest holding of spending much on eyepieces or new scopes but spend as much time as possible getting to know your scope.
I assume the scope is one of these? http://www.celestron.com/astronomy/c...ar-130slt.html
How have you found the Go To capability of these? and how are the views that you have seen so far?

Malcolm

[OzStarGazer]

At any rate don't buy a new scope only to have more magnification without first trying more powerful eyepieces. But first, yes, learn all the tricks of your scope and enjoy your new great 12.5mm eyepiece.
With your scope (which has the same specs like mine) the maximum useful/useable magnification is about 162.5x from what they told me, so it is much higher than the 26x magnification you have seen up to now. It has a lot of potential.

[multiweb (Marc)]

Originally Posted by richard2600

Hi yep that's good point I will def go to some night viewings and get a look at some scopes first and also get bit more of a handle on things as im only new to it all I wont rush out just yet buying a scope.

That's the best advice. Have a look around before buying more stuff. A couple of nights out with a club looking at other scopes is the best way to make up your mind. For visual you can't beat a big(ger) DOB IMHO. They're the best value for money in term of aperture.

[richard2600 (Richard)]

Originally Posted by barx1963

Richard
A 12.5 is probably a good choice for that scope. As you have a 25mm that will give you low power view at 26x and the 12.5 gives you 52x.
Personally if you have only had the scope a short while I would suggest holding of spending much on eyepieces or new scopes but spend as much time as possible getting to know your scope.
I assume the scope is one of these? http://www.celestron.com/astronomy/c...ar-130slt.html
How have you found the Go To capability of these? and how are the views that you have seen so far?

Malcolm

Hi yep that's the scope and its pretty good Jupiter and the moon look stunning jupiter is not quite as good as the pic but the moon is way better than those pics with the scope. The goto im still trying to work it out. It gives me a list of stars to line it up to but I don't know what any of the stars are or were just yet. I use the remote to just move it around at the moment but im learning all the time