Which of these two for planets...

[Ags]

In the one corner we have the Skymax 150 Pro, a respected planetary specialist.

In the other corner we have the 150PDS newtonian. An imaging scope, not made for planets.

Obviously they have the same aperture. As far as I can tell they have the same sized central obstruction (28% for the Mak according to SaN, and 29% for the newt). The 150PDS obviously exhibits coma at the edges of its full field, but at planetary magnifications you aren't using anywhere near the full field.

The PDS has several advantages: it uses one less reflective surface, and two less refractive surfaces. Secondly it has a dual-speed focusser while the Skymax only has the coarse single-speed mirror-shift mechanism.

I was all set to buy a skymax last month but family emergencies cancelled that plan. Now I'm having fun with some basic imaging but still looking to tick the planetary box...

[great_bear]

Neither (at least not for visual)

For really interesting planetary detail you need the 180 version of the Skymax.

But if you're really set on one or the other of the scopes above, then for planetary it has to be the Mak. A fast Newt just can't compare.

[Ags]

Bigger is usually better in astronomy, I can't argue with that. But I'm upgrading from 100mm... Besides, there is only an inch between the skymax 150 and 180 - as far as I can see the differences can only be incremental, not night and day.

[Nexus 6]

had a look through a 180 Skymax a few months back.

Saturn was a superb sight, I immediately thought how crisp and tight the view of it was.

Only the price is a stumbling block with them.

can imagine the 150 would still deliver some outstanding sights

[John]

I'd go for the Mak too, although I'd prefer a refractor but thats not on your list.

[spaceboy]

For what it's worth the PDS has a larger secondary mirror over the standard 150P. Central obstruction are considered contrast robbing on planets so the smaller the secondary the better. You may find the 150PL more geared up for planetary observing.

[Ags]

My point is that the secondary of the PDS is the same size as that of the mak.

Yes, I have been looking at refractors too...

I expect the mak is better, my question is why? On paper the scopes are not that far apart and as I point out the PDS has some things going for it, like a dual speed focusser and far less optical surfaces.

[A McEwan]

Somebody got a gold-tube 180 on AB&S the other day for £275.

Grr...

Ant

[nightfisher]

the mak has a MUCH longer focal length, making it so much better on planets

[Ags]

the mak has a MUCH longer focal length, making it so much better on planets

What do you mean? Surely it just means buying different focal length EPs. The resolution and contrast of a telescope are not related to its focal length.

[spaceboy]

What do you mean? Surely it just means buying different focal length EPs. The resolution and contrast of a telescope are not related to its focal length.

I think what Nightfisher means is that long focal length scopes can achieve a much higher magnification over short FL scopes meaning detail on planets will be more obvious. Unfortunately it's very rare UK seeing allows for such magnifications.

[Ags]

I'm not trying to argue that the PDS is better, but I am trying to understand why this is not the case. I think I'm coming across as a bit argumentative, which isn't my intention.

[spaceboy]

For example. A 6mm EP in the MAK will give you x250 magnification but only x125 in the 150PDS

[Ags]

Yes a point against the PDS is that I would have to buy a completely new set of planetary eyepieces.

[great_bear]

What do you mean? Surely it just means buying different focal length EPs. The resolution and contrast of a telescope are not related to its focal length.

The focal length of a telescope is generally perceived to have a significant effect on contrast. "On paper" in a theoretically perfect world of course it shouldn't, but in practice it seems to. Then there's the fact that eyepieces don't have to work so hard to get the magnification, and the added comfort you get from better eye relief of such eyepieces.

Unfortunately it's very rare UK seeing allows for such magnifications.

In most cases it's people's scopes that are the problem. It's no problem reaching 300x magnification in the binoviewer with the Mak 180 on most nights at about 1-2am,

Only lasts about 30 mins to an hour, oh but what an hour that is!

Outside of that time, 200x or thereabouts is pretty effortless on most nights.

[catburglar]

In addition to the secondary obstruction, which are similar in both scopes, the 150PDS will also have:

• Diffraction spikes which reduce contrast
  
• Narrower focal zone due to the faster focal ratio which makes focussing more critical
  

[Nillchill]

I have recently purchased a 150pl and have been very happy with the views i am getting esp of jupiter recently, i cannot wait to see saturn( next year) in it and the moon, damned clouds!!!

also using a webcam has been so easy, with plenty of focusser travel even with barlows .

i would definitely go for the skymax to be honest mate, the longer focal length will make all the difference. and so much easier to manouver around.

all the best with your choice

[Ags]

There is an Intes MK-67 on www.te-les-koop.nl for 400 euros at the moment, and an Intes MK-65 for just 300 euros, so that is all tempting, but not for me. I have to wait a few months.

But it does not answer my question as to why the newt performs less well. As regards the diffraction spikes I had thought these would affect contrast by I've been told by very knowledgeable members (sixela, where's he gone?) that these are not significant. It sounds counterintuitive to me, but he seemed to know his stuff.

Yes it is harder to focus a 3mm EP at F5, but don't forget focusing on a mak can be pretty coarse too, as you are shifting an F2 mirror, while in comparison the newt has that dual speed focusser.

Nillchill, if it was just the quality of the view to consider, I would get the 150PL for planetary use rather that the mak. But that huge tube is off-putting to me.

[Nillchill]

Nillchill, if it was just the quality of the view to consider, I would get the 150PL for planetary use rather that the mak. But that huge tube is off-putting to me.

i was also due to purchase a skymax 150, and had to reconsider as had issue at home which ended up chewing up most of my funds, (maybe these skymax scopes are cursed, ) however the 150pl came up with a motorised eq5 for far less, and to be honest i couldn't really say no, to it.

i am learning to live with the rather large beast living in the corner of the dining room, but it has paid me back with change, with the views i've had so far with it. and my webcam is far easier to use than with my old 130p f5 tube.

one thing i am getting is a motor focusser, which if you go for the f5 pds scope I highly recommend you get also

[great_bear]

There is no issue focusing the Mak - just use a clothes peg.

[Ags]

In most cases it's people's scopes that are the problem. It's no problem reaching 300x magnification in the binoviewer with the Mak 180 on most nights at about 1-2am,

Only lasts about 30 mins to an hour, oh but what an hour that is!

Outside of that time, 200x or thereabouts is pretty effortless on most nights.

I certainly can reach over 200x with my little mak most nights. I pushed it to 330x on Saturn one evening (with a borrowed SR4 EP...!) and was rewarded with a sharp view of the Cassini Division. Lots of people seem to stick to 130-150x regardless of scope or conditions but I think that is being a bit conservative.

One thing I have read about Maks is that they correct extremely well for spherical aberation, perhaps this is an advantage over the newt?

And being all-spherical systems Maks can be figured to a higher accuracy than a parabolic newt. But SkyWatcher do not make any guarantees about the optics in the pro series.

[spaceboy]

The best advice I can offer is try before you buy. Put a request up on the forum and see if there is anyone with in driving distance.

If I may it appears that you have already made your mind up and you want convincing that the extra cost of the MAK is justifiable. If your main forte is planets then given the above choices I don't see how the MAK could fall short. I understand you already have a MAK and you may want to either sell it to fund the new scope or keep it adding the different design of the Newt to your collection. What ever you choose you will be gaining the advantage of increased aperture and resolution but most newts perform better on DSO's offering low power wide field views where as the MAK delivers much sharper high power views. DS focuser's are a more noticeable improvement on newts because the focus is so much harder to nail than it is in a well cooled MAK. Just think most newt owners spend £80 + to get good focus and MAK owners get away with 3p on a clothes peg. Goes with out saying.

What ever you choose the improvements will not be drastic over what you already have. With out rocking the boat too much 8" seems to be the when things start to get interesting and would be within your budget laid out for the MAK.

[Steve]

I expect the mak is better, my question is why?

The Maksutov design has a long focal length with optics made entirely from spherical surfaces. Spherical surfaces are perfect for mass production, they can easily and affordably be ground and polished to a very high surface accuracy. By comparison, a fast Newtonian's mirror must have steep parabolic curves that are considerably more difficult to manufacture so, unless you spend significantly more, you cannot expect anything like the same surface-finish accuracy. This and the Maksutov's relatively small central obstruction results in a high power, high contrast, high definition telescope with almost no chromatic aberration.

Perfect for observing or imaging planets.

HTH

[Moonshane]

one thing I don't understand is this. my experience with newts seems to confirm that a longer tube and slower focal ratio equates to a smaller secondary and that it is largely this latter point that generates the increase in contrast? there also seems to be more 'depth of field' (i.e. more range of focus where the image is sharp).

with a faster newt, the contrast is reduced I think due to the larger secondary and possibly more scattered light due to the shorter tube? the range of sharp focus is also much smaller.

what I don't understand is how a scope like a Mak or SCT with a long focal length and large secondary obstruction can have better contrast/detail than a slow newt of the same aperture?

to answer the question of the OP if it were me making this decision (and considering the scopes he has at the moment) I'd actually buy neither as the small frac covers the wider fields, the 4SE at 4" and f12 should presumably give nice planetary images(?) and therefore a larger aperture would provide the 'missing link'. obviously I'd suggest a mid-range auto dob (being dobsessed with them) of 8-10" with the tracking feature and I bet you could get this with the same cost as the Skymax OTA. with tracking, and when seeing allows, I'd suspect that this would provide far superior planetary images then either of the scopes mentioned.

just putting other suggestions in the mix to confuse further

[Alkaid]

Would a SW ED100 beat the 150 Mak on lunar and planets?

I e-mailed a respected retailer and they said that it would.

Sorry to hijack the thread and throw another scope into the bag for you. The refractor would be lighter to move and easier to store as it comes with the carry case.

I'm in the same boat - I'm also looking for a planetary scope but cannot decide, thank you for the interesting thread, great read.