Baffled by my Mak orientation

[SwiMatt]

After 6 months of use, I thought I would get deeper into the "litterature" to try and understand my Maksutov a bit better. I am very happy with it: the stars are very sharp and I got amazing views of the brightest DSOs. One thing that has been frustrating me is that, despite all my attempts, planetary observation still does not give me views rich in detail, but... I guess it will come.

Digging deeper into the details, I realized something that has me baffled, to say the least: the views in my Mak aren't flipped - but I seem to understand that it should revert right and left when used with a star diagonal. 

If this is indeed unusual, I figure that when I got it from FLO (discounted, a customer return) they must have included an erecting prism instead of a star diagonal,  and this got me wondering: am I taking full advantage of my optics? Am I losing precious photons and contrast? Might this explain why I have such troubles with observing planetary details? In short: should I buy a star diagonal?

[Stu]

10 hours ago, SwiMatt said:

After 6 months of use, I thought I would get deeper into the "litterature" to try and understand my Maksutov a bit better. I am very happy with it: the stars are very sharp and I got amazing views of the brightest DSOs. One thing that has been frustrating me is that, despite all my attempts, planetary observation still does not give me views rich in detail, but... I guess it will come.

Digging deeper into the details, I realized something that has me baffled, to say the least: the views in my Mak aren't flipped - but I seem to understand that it should revert right and left when used with a star diagonal. 

If this is indeed unusual, I figure that when I got it from FLO (discounted, a customer return) they must have included an erecting prism instead of a star diagonal,  and this got me wondering: am I taking full advantage of my optics? Am I losing precious photons and contrast? Might this explain why I have such troubles with observing planetary details? In short: should I buy a star diagonal?

In short, yes. Although there are some excellent erecting prisms, I suspect the one you have is not top notch, so a decent mirror diagonal should show you an improvement in higher power views.

EDITed to say NOT top notch, DOH!

[SwiMatt]

14 hours ago, Stu said:

In short, yes. Although there are some excellent erecting prisms, I suspect the one you have is not top notch, so a decent mirror diagonal should show you an improvement in higher power views.

EDITed to say NOT top notch, DOH!

Dammit 🥲

And also, I will have to relearn my handles directions... thanks @Stu. Any suggestions on what to look for if I wanted a good diagonal that doesn't break my bank? 

[Zermelo]

https://www.firstlightoptics.com/diagonals/stellamira-1-25-90-di-electric-diagonal.html

[Louis D]

Just be aware that type of diagonal often has a restriction to about 23mm clear aperture:

If you do buy one, check it immediately to make sure it doesn't have a stopped down clear aperture.

I bought one used to use with a 22mm clear aperture binoviewer, so I'm okay with the aperture restriction.

Edited February 23 by Louis D

[SwiMatt]

Thanks for the recommendation @Zermelo and the warning @Louis D!

[SwiMatt]

For additional info, I found out that the particular bundle I got (Skymax 127 with AZ5) comes with an erecting prism, not a star diagonal. I wonder why SW would make this choice, considering that on the page of the SW erecting prims it says that it is designed primarily for terrestrial observing. It seems to beat the point of a beginner bundle at that price point...

[The60mmKid]

My guess is that they package the Mak with an erecting diagonal because people also use Maks as spotting scopes to observe nature.

To add to what's already been suggested, I recommend looking into other factors that could be impacting the planetary performance of the scope. The diagonal may be the issue, but it's also quite possible that what's getting in the way of satisfying planetary views are seeing (i.e.,, atmospheric turbulence) and/or thermal acclimation of the telescope. Seeing is always a factor, and thermal acclimation is an often overlooked consideration. The good news is that we can learn to identify good seeing (and, thus, observe planets under those favorable conditions), and small Maks aren't too tricky to thermally acclimate. (It's also worth noting that small telescopes can provide enjoyable planetary views, but cannot provide as much detail as larger telescopes because resolution is related to aperture... So, experience with various instruments over time helps us learn what we can and can't expect from any given telescope.)

My suggestion would be to try a star diagonal that's intended for astronomy (per the suggestions above) but to also take into account the other factors that may be impacting the views (seeing, thermals, collimation, etc.). We're able to get to most our of our equipment when we consider all of these together.

And it's great to hear that you've been enjoying your Mak 🙂 They can be great telescopes!

[dweller25]

Hello @SwiMatt

One factor that can drastically effect planetary views is thermal equilibrium of the primary mirror. It can take a long time for the thin boundary layer of residual heat to disappear from the surface of the primary.

To overcome this you could try putting a couple of layers of reflectix around the OTA. This will effectively lag the scope preventing the temperature gradient between the optics and the cooler OTA walls.

This will allow you to use scope immediately when you take it out and will prevent dew formation on the corrector for much longer.

 

 

 

 

 

Edited February 24 by dweller25

[Stu]

1 hour ago, SwiMatt said:

For additional info, I found out that the particular bundle I got (Skymax 127 with AZ5) comes with an erecting prism, not a star diagonal. I wonder why SW would make this choice, considering that on the page of the SW erecting prims it says that it is designed primarily for terrestrial observing. It seems to beat the point of a beginner bundle at that price point...

It is not unheard of, I believe the ST80 also comes with an erecting prism. As said, I doubt it’s particularly high quality as it is just bundled with the scope. I have a fairly expensive 2” William Optics erecting prism and although it is decent, I can still see an improvement at high power if I switch to a normal diagonal. The benefits are obviously the correct image and 45 degree angle which makes use as a spotting scope more comfortable but for Astro, use a proper diagonal.

[F15Rules]

It might also be worth noting the following, as posted on the USA site..

"I found that the few Chinese Mak-Cass I tested were roughly 1/2" smaller in true aperture than advertised. They are probably the same optical system with different branding/packaging. The culprits are the undersized 2nd surface on the corrector and the undersized primary mirror."

It does seem that  these entry level Maks from China have a 127mm corrector plate, but that the primary mirror is only c 118mm in diameter, so a noticeable difference. Add to that the poor quality (and possibly also stopped down) erecting prism, your Mak might only be operating more like a 4 -4.5" scope..

I've used several high quality Russian Maksutovs of 150mm aperture (not stopped down) and their planetary performance rivalled a 5" apo refractor..but they do cost a lot more to buy.

Dave

[Zermelo]

1 hour ago, F15Rules said:

It does seem that  these entry level Maks from China have a 127mm corrector plate, but that the primary mirror is only c 118mm in diameter, so a noticeable difference.

This "feature" of the Synta 127 Maks has been discussed before here. Clearly you will be losing some light grasp, and hence the limiting magnitude of the faintest objects will be the poorer for it. I'm not sure how much that would make a noticeable difference to the view of brighter objects like Jupiter.

There is also the question of the effect on resolving power of the undersized mirror. With a refractor, it's a simple function of the size of the objective lens, but for a catadioptric with mis-matched elements? I asked the question here, but didn't get an answer.  Logic suggests that the smallest aperture in the system will be the limiting factor, yet I've split doubles down to the theoretical limits for 127mm several times, so I'm not sure that any such effect is noticeable. @SwiMatt, have you tried splitting tighter doubles with yours? Or doing a star test? 

With Jupiter, seeing detail is as much about teasing out the subtle contrast between adjacent regions. I suspect that, most of the time, (i) observing conditions, (ii) prior observer experience and (iii) the loss of contrast caused by the Mak's central obstruction may swamp any difference in the effective aperture loss of the undersized mirror. And a sub-optimal diagonal may outweigh all of those.

 

Edited February 24 by Zermelo

[Peter Drew]

Unless someone has measured one of these "undersized" Mak mirrors I suspect that they are the size as specified from the manufacturer.  The undersize issue is due to the fact that light passing through the corrector diverges on its way to the primary mirror, so to achieve the full entrance aperture the primary mirror needs to be oversize.    

[F15Rules]

45 minutes ago, Peter Drew said:

The undersize issue is due to the fact that light passing through the corrector diverges on its way to the primary mirror, so to achieve the full entrance aperture the primary mirror needs to be oversize.    

I think that was the point being made on the CN site Peter..several primary mirrors being physically measured as 118mm diameter,  not the 127mm advertised.

We have seen similar misleading specs in chinese Binoculars.. Steve Tonkin of Binocular Sky fame has reported on a number of allegedly 50mm or 60mm aperture binoculars being significantly stopped down, leading to inferior performance.

[SwiMatt]

Thank you all for the answers!

Actually, I was aware of the undersize aperture when I bought it, believe it or not. I had read about it but don't remember where. I haven't tried to split many double stars, the lowest I have gone is probably 4 arcseconds (Algieba comes to mind), so cannot confirm what @Zermelo says. I'm not the most avid double stars observer. And no star tests either.

I observed the planet in all sorts of conditions and one thing that I can tease out is when seeing is bad 😂 and in terms of cooling, for my planetary sessions I normally put the Mak out well in advance to cool it down (even 1 or 2 hours sometimes), I'm not sure if temperature gradients would be so strong to actually affect the optics once the scope is acclimated, but maybe this is something to account for.

Let's put it like this: after few long sessions (probably more than 10 sessions at this point), I find Jupiter quite boring since I can never tease out more than just the equatorial bands. I have seen possible traces of festoons and GRS, but far from conclusive certainty. So far, I thought I didn't have enough optical quality of the OTA or experience: now I am starting to think that the erecting prism might exacerbate the other limits. I will buy a star diagonal and come back with answers as soon as possible (when the weather allows again)

 

[Cosmic Geoff]

My experience of the similar Celestron 127mm Mak is that it performs well on splitting close doubles (with a decent eyepiece and diagonal), but the visual performance on planets was such as to prompt me to buy a bigger scope. 

On the other hand, planetary imaging with both the 127mm Mak and the 203mm SCT revealed a lot of detail I could not see through the eyepiece. 

[Louis D]

28 minutes ago, SwiMatt said:

Let's put it like this: after few long sessions (probably more than 10 sessions at this point), I find Jupiter quite boring since I can never tease out more than just the equatorial bands. I have seen possible traces of festoons and GRS, but far from conclusive certainty.

That's pretty much my experience with my 127 Mak as well.  I've only seen festoons and barges clearly starting at 8" of aperture (needs to be exceptionally well corrected and acclimated), becoming blatantly obvious by 12" of aperture in an exceptionally well corrected scope on nights of exceptional seeing.  If collimation, figure, polish, seeing conditions, etc. don't all align, fine, low contrast details will turn to mush guaranteed.  All you can do is buy or make the finest scope you can, use the best eyepieces possible, get yourself to places with the best seeing conditions, wait for opposition, make sure everything is well collimated and aligned, and then hope for the best if you want to see low contrast details on Jupiter.  When everything does align, it's hard to stop taking in the view because it's so mesmerizing to see such detail.  It's quite sublime.  Mars is the same way, except that dust storms on Mars can ruin our best laid plans here on Earth.

[Ratlet]

I had much the same experience as you @SwiMatt.  Ended up selling my mak and sticking with my much shorter fl 130pds.

Of course about 3 months later I ended up getting everything aligning perfectly and seeing some beautiful detail on Jupiter and Mars.  It just clicked why people do it.  What also clicked was regret at selling the mak lol.

The planets and the moon are dynamic things so I've seldom made a night of planetary observing, but I will always stick the scope at them a couple times through the night just to see what I can see.  When you see something special it just blows all the dust away 

[dweller25]

@SwiMatt

I see you are using your Skymax 127 on a light weight alt-az setup.

Is this because you need to travel to an observing site and need a small light setup ?

[SwiMatt]

11 minutes ago, dweller25 said:

@SwiMatt

I see you are using your Skymax 127 on a light weight alt-az setup.

Is this because you need to travel to an observing site and need a small light setup ?

It's the mount that came with the OTA. I did not have time and money to update yet - but I read good report of the AZ5 with the Mak 127. The weak point is the tripod which I will update soon for a carbon one. And yes, portability for me is paramount since I live in a light polluted neighborhood and at the third floor in a small apartment. That bundle gave me the best compromise between aperture and portability (although knowing what I know today, if I did that again I would go with smaller APO).

[Tiny Clanger]

If the focuser of your 127 annoys you as much as mine did, a relatively cheap way to get fine focus at the same time as buying a new diagonal is to get one of these :

https://www.firstlightoptics.com/diagonals/baader-t-2-90-prism-star-diagonal-with-focusing-eyepiece-holder-125-nosepiece.html

I find it works well .

[F15Rules]

2 hours ago, Tiny Clanger said:

If the focuser of your 127 annoys you as much as mine did, a relatively cheap way to get fine focus at the same time as buying a new diagonal is to get one of these :

https://www.firstlightoptics.com/diagonals/baader-t-2-90-prism-star-diagonal-with-focusing-eyepiece-holder-125-nosepiece.html

I find it works well .

+10 for that option..a great piece of kit!

Dave

[Stu]

4 hours ago, SwiMatt said:

Thank you all for the answers!

Actually, I was aware of the undersize aperture when I bought it, believe it or not. I had read about it but don't remember where. I haven't tried to split many double stars, the lowest I have gone is probably 4 arcseconds (Algieba comes to mind), so cannot confirm what @Zermelo says. I'm not the most avid double stars observer. And no star tests either.

I observed the planet in all sorts of conditions and one thing that I can tease out is when seeing is bad 😂 and in terms of cooling, for my planetary sessions I normally put the Mak out well in advance to cool it down (even 1 or 2 hours sometimes), I'm not sure if temperature gradients would be so strong to actually affect the optics once the scope is acclimated, but maybe this is something to account for.

Let's put it like this: after few long sessions (probably more than 10 sessions at this point), I find Jupiter quite boring since I can never tease out more than just the equatorial bands. I have seen possible traces of festoons and GRS, but far from conclusive certainty. So far, I thought I didn't have enough optical quality of the OTA or experience: now I am starting to think that the erecting prism might exacerbate the other limits. I will buy a star diagonal and come back with answers as soon as possible (when the weather allows again)

 

I can’t say for certain, but there is a good chance the erecting prism will be hurting some of that detail.

My understanding of the aperture is the same as Peter’s ie the mirror is full sized at 127mm, but the corrector plate diverges the light so that it overspills the mirror resulting in a smaller effective aperture.

[bosun21]

7 hours ago, Tiny Clanger said:

If the focuser of your 127 annoys you as much as mine did, a relatively cheap way to get fine focus at the same time as buying a new diagonal is to get one of these :

https://www.firstlightoptics.com/diagonals/baader-t-2-90-prism-star-diagonal-with-focusing-eyepiece-holder-125-nosepiece.html

I find it works well .

Exactly! I solved this by fitting an electric focuser. No more vibration while focusing.