A bit disappointed with Celestron 127SLT Mak

[jeffwjz]

Clear sky this evening (finally!), after I set up my astrophotography equipments and started tracking, I decided to do some visual observation on Jupiter in the meantime with a Celestron 127SLT Maksutov Cassergrain. I haven't really had a good use of this Mak before as I bought this mainly to bring little family members (nephews) into astronomy and have only used it to view the moon for some times.

I am using a TS 6mm planetary eyepiece but am surprised to find out that I could distinguish any details on Jupiter. From the eyepiece it is just a blurred orange disk. I used to view Jupiter with a Skyliner 200p and the view is awesome with crystal clear bands and zones. I didn't expect 127SLT to give me the same view (because of aperture size) but I did expect to see at least some details. I later on tried with a 80mm apo with same eyepiece and I can clearly see the bands. 

I always thought 127 Mak is a nice little scope for planetary observations. I was wondering if the blurred Jupiter is because I maybe pushed the scope beyond its power, or maybe the scope itself is out of collimation? Has anyone got any experience to share?

Thank you!

[Ibbo!]

A lot of your (and my) problems are due the low elevation of Jupiter & saturn.

Also the seeing has not been very good tonight.

[heliumstar]

I suspect the magnification was just too much on top of bad seing and low elevation?? You also didn't mention which eyepieces you used with two other scopes. Try less magnification next time. Like 200x or even less.

[Sunshine]

I have a 150 Mak, i find that on nights of average seeing i can comfortably use around 150x. If you are using the SLT and, a 6mm eyepiece as you mention then you are at 250x, which is really pushing that scope even on a good night. For comparison, the same eyepiece in a 200P will give you 200x but, with 8 inches of aperture it will be far better suited to handle that power. Any particular eyepiece behaves differently in different scopes depending on aperture and focal length for starters. Tone down the power and you may find it more rewarding, as for collimation, wait for a night of good seeing to do a star test, Mak's hold collimation very well.

Edited June 9, 2019 by Sunshine

[RT65CB-SWL]

Hi Jeff,

Did you let it cool down? - sounds crazy in late spring/early summer, but I do give my ETX105 & C6 a minimum of thirty minutes.  And as @Ibbo! & @heliumstar have said: "...low elevation...".

Below is a cropped image of Jupiter before collimation, etc., as viewed through my ETX105, (before the 're-mod'), star diagonal and a 6mm e/p.

Any 6mm e/p is pushing it to the Mak's max.

[alan potts]

Jupiter is very low from here and I am 10 degrees better off than anyone in the UK, don't be too hard on the scope, even my bigger one struggles, it's a lot of atmosphere to look through.

Alan 

[johninderby]

Agree with the above. Too much mag for the conditions. The 6mm is near the max you could use on the moon in great seeing.

Here’s a couple of charts from the Televue eyepiece calculator showing the magnifications various eyepieces would give you in your scopes. First is for the 127 mak and second is for the 200 dob.

 

Edited June 9, 2019 by johninderby

[Rob]

With Planets so low currently. I've found 70 to 100mm APO is definitively pulling the best results (hence your 80mm test). Also agree the 6mm is pushing to hard on the 127!

Rob

Edited June 9, 2019 by Rob

[nightfisher]

dont write the mak of they are very capable scopes, with the planets low and average seeing i would not be going below a 15m ep, more likely an 18mm

[MakeItSo]

I was observing last night and spent 4 hours looking at the moon and splitting doubles because of the perpetual twilight. Jupiter was no more that a bright disc with 4 moons. That was through an 11inch scope with a variety of good eyepieces. A 17mm Ethos was as far as I got and mostly stuck to a 41mm Panoptic. Wouldn’t write your scope off quite yet....

[ollypenrice]

If the seeing was allowing better views with a different scope then you are left with too much magnification and not enough temperature stabilization time. Since the two will work destructively together I think you have your answer.

Olly

[jeffwjz]

Thanks guys, for the advice. 

So it seems I was bit unfair with judging the 127Mak... I don't think the scope temperature is fully stablised as I used the telescope in the same room that I stored it (I left the backyard to astrophotography). I do realise Jupiter is quite low in the sky and would expect some influence considering the atmosphere. Also 6mm is a bad choice.. I would definitely try with some other magnifications later on.

I think I phrased the title wrong - I'm not saying 127Mak is a bad scope, I knew it is excellent when I was watching the moon. I think what I mean is I was a bit disappointed with using the scope to watch Jupiter at such non-ideal conditions.

2 hours ago, johninderby said:

Here’s a couple of charts from the Televue eyepiece calculator showing the magnifications various eyepieces would give you in your scopes. First is for the 127 mak and second is for the 200 dob.

Thanks for the chart, John, that's very good piece of information.

Lessons learned! - should've considered more factors before drawing conclusions.

[steveex2003]

2 hours ago, Rob said:

With Planets so low currently. I've found 70 to 100mm APO is definitively pulling the best results (hence your 80mm test). Also agree the 6mm is pushing to hard on the 127!

Rob

Absolutely concur with this. 
Had a (SW) Mak 127 and an 80mm Equinox pointed at Jupiter last night. The little frac gave much better views at 100x.

[jeffwjz]

3 hours ago, Rob said:

With Planets so low currently. I've found 70 to 100mm APO is definitively pulling the best results (hence your 80mm test).

Just out of interest, why is apo with (relatively) low aperture gives best results in such conditions?

[John]

The refractor cools to outside temps quickly and maintains that equilibrium and the smaller apertures seem to help make the most of the poorer seeing when a target is at low altitudes. I've noticed just the same with my 12 incn dob vs my refractors on the planets currently. When high in the sky the dob delivers superb planetary views but currently the fracs are the winners.

I don't think I'd make any judgements about a scope when observing targets anywhere near the horizon whether stars or planets.

The other thing that needs to be said is that planetary detail does not just jump out at the observer. It needs to be worked at though spending time at the eyepiece to allow the eye to adjust to the image. The more subtle details will start to show themselves if only momentarily and the more you observe, the more often that finer detail will show. This advice applies when the planets are high in the sky but you can still tease out more detail from low lying planets by careful observation. Jupiter can appear bland and relatively featureless at an initial glance but there is more detail to be seen if you work at it. Dropping the magnification back often helps enhance the contrast on the giant planet - a smaller but more contrasty disk is better than a larger washed out one.

 

 

[steveex2003]

For whatever it’s worth, as said previously, at 30 degrees, I have found details have to be observed over a period. What I assume is atmospheric conditions cause veils of intermittent disturbance to interfere with what can be a few seconds of very stable, static viewing. For whatever reason, or self-induced delusion* (delete as applicable) you care to apply, I am preferring the views my 80mm Frac offer over my 127 Mak, and my 120mm Frac over my 10” Dob are offering with regards to Jupiter and Saturn right now.

 

*Caveat, I only have my eyes/perception to base this on, and not 15 years of experience. Prefer, is the key word. I do have some reasonably pleasant WA EPs, Plossls, diagonals etc etc and do spend time mixing, matching, chasing that “view” and can only report as found.

Edited June 9, 2019 by steveex2003