Sky-Watcher 250PX versus SCT/MCT

[doubledoubleswifty]

Hello,

I have a Sky-Watcher 250PX (10 inches) and still quite a beginner to astronomy.  

I was having a look at FLO's website and wondered how would it compare to a SCT/MCT.

For example https://www.firstlightoptics.com/se-series/celestron-nexstar-8se.html or https://www.firstlightoptics.com/maksutov/skywatcher-skymax-180-pro.html

Would the views be much different on a SCT/MCT?

Thank you!

[John]

The views of the planets would be about the same but the views of deep sky objects would be a little dimmer with the smaller aperture SCT or MCT. The SCT or MCT should show slightly tighter star images which make double stars a touch easier to split.

The SCT / MCT would be more compact to store of course but would take longer to cool down (especially the MCT) to outside temperature, if stored indoors.

I moved from an 8 inch SCT to an 8 inch dobsonian and was pleasantly surprised that the less expensive and simpler dob gave just as nice views.

Others might have different experiences though and I'm sure they will chip in soon

 

 

[knobby]

Hi, I've had a 250px Dob and now a C8 edge. Completely agree with John, possibly teeny bit better on planets on the 250 but fairly noticeably better on DSO. The C8 however can be lifted and carried easily with 1 hand 😁

[Chris]

The only thing I can add to the above comments is that a dew shield is a must for SCT's and Maks, but on the plus side you can wave good bye to diffraction spikes on planets and stars!

[Louis D]

Since the 250PX has a 25% central obstruction by diameter compared to 31% for the 8SE, it should provide better contrast on planetary details.  However, the 180PRO has a 23% obstruction, and so should be slightly better than the 250PX.  On the other hand, there are far more surfaces involved with the two CATs than with the Newt, so it comes down to quality of figure and polish in each scope.  That, and the obvious aperture differences between them.

For reference, the best planetary views I've had were through a 12.5" Mag1 Portaball with a Zambuto primary under steady seeing conditions.  Jupiter looked about like one of those photographs created from lots of combined frames.  There were all sorts of ovals, festoons, and barges.

[Dr Strange]

The biggest difference is going to be the footprint and weight. The best telescope is the one you use. If you find yourself making excuses not to go outside and view then the 250 is not for you. The 8SE is going to be the Swiss Army Knife scope. It does everything for you, just not excellently. It is lightweight, easy to move and store, small in footprint, gives good overall views, and is a great option if you are not happy with how big and heavy the 250 is.

The other huge factor that can be a big bonus or a real negative is that the 8SE is a GOTO mount which means a computer and motors. You align it and then use the hand controller to select objects and the mount moves the scope to that object. No star hopping. It also tracks. 

 I would suggest a 72mm-80mm ED refractor that you mount on top of it. Something like the 72mm Evostar from Skywatcher for example. It is not expensive but does a good job with wide field objects that the 8SE will not do well on. It can also be used as a finder scope for the 8SE. 

[doubledoubleswifty]

Thanks for all your replies - I do find myself reluctant to go outside and set up the SW250PX.  

I would love to have something that does not involve downgrading the views but at the same time - I can lift up and carry outside in one go.

[alacant]

On 02/06/2020 at 18:46, doubledoubleswifty said:

reluctant to go outside and set up

Hi

Leave it out permanently? Is a cover/shed/roof protection viable for your climate?

Optics wise, I only do photography but FWIW, the 8se was among the worse I've ever tried. Our renovated blue tube 250p, one of the best.

Cheers.

Edited June 4, 2020 by alacant

[ollypenrice]

In terms of the view the biggest difference, for me, would be in field of view. I find myself boxed in by long focal lengths, particularly when the aperture is modest.

Olly

[Captain Scarlet]

On 07/05/2020 at 21:25, Louis D said:

Since the 250PX has a 25% central obstruction by diameter .... However, the 180PRO has a 23% obstruction, and so should be slightly better than the 250PX.  ....

Actually that's not quite true for the Mak 180. While the secondary mirror spot itself is indeed 23% of the aperture, the retaining ring around the middle of the primary mirror is 63mm across, meaning the "working CO" of this scope is actually 35% unfortunately.

Cheers, Magnus

[michael.h.f.wilkinson]

I have had a Celestron GP-C8 for nearly 25 years, and it is a great all-round visual scope, and no slouch on planetary imaging, although I do set it up in three stages (set up tripod, add mount, attach scope, which takes about 10 minutes). For most DSOs it is very good indeed, and only in some cases does my Meade SN6 6" F/5 Schmidt Newton provide better views, simply because of its huge field of view. Note, however that the C8 needs cool down time, which is short in my case, because I store it in a garage with little or no heating, but can easily be 30 minutes if stored inside. The SkyMax 180 will need a similar cool down time, if not longer, given its higher mass.

Regarding planetary detail and contrast, I would guess a 10" Newtonian has higher potential than either the 180 mm Mak or the 8" SCT, assuming good collimation and optical figure. Aperture is king, I find. The main issue is the seeing, however. At these aperture the atmosphere is the key factor in determining image quality. If seeing is poor, the best optics won't help. I remember seeing Jupiter through Olly's TEC 140, when it had just risen above the hills to the east, and the view was absolutely dreadful. Nothing to do with the scope, everything to do with the seeing.

[Owmuchonomy]

An SCT should hold collimation much better than the 250P and the Mak maybe even better.  I collimated my 12" Dob every second time I used it but the 9.25 SCT has only needed collimating a handful of times in 13 years.  My 5" Mak needed collimating from new but a well known retailer and sponsor of this forum kindly took it back and replaced it (the focuser was faulty too).