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SW Mak 127 - Am I expecting too much ?


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Well I picked one of these up used a couple of months ago - all looks in pretty good shape and as far as I can see reasonably collimated though I’m no expert.  Used it a few times especially as we’ve had Jupiter and Saturn up and about, but tbh on these I can’t seem to get great focus on any ep of 20mm and below, and not much detail and contrast which is disappointing considering what great planetary scopes they are supposed to be. Am I expecting too much ? For comparison (and yes I know it’s got more light grasp but is of course a slower scope) my 150 dob blows it out of the water on these two gas giants ! I even I think prefer the view through my little SW mak 90. Thoughts ? 

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1 hour ago, johninderby said:

What sort of diagonal are you using?

The 127 mak should be giving very sharp images. They don’t usually need collimation. Have you done a star test which will show how well collimated it is.

I’ve got a fairly stock standard 90 degree mirror and a 45 degree prism. Must say I haven’t done a star test, bit remiss of me….I’ll do so and see what transpires. 

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50 minutes ago, GazOC said:

If you're observing in the UK then Jupiter and especially Saturn are placed too low for the Mak to really show it's stuff

Yes I had considered that but still a bit surprised at the low quality visuals especially compared to the dob.

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The Mak 127 was more or less my first scope. It was superb, and most people’s reaction to it is the opposite of yours. IE they’re surprised how good it is compared to expectations for something so inexpensive. I only don’t have mine now as someone offered a one-to-one swap for its bigger sibling, the Mak 150. That in itself shows how well-regarded it is.

Which leads me to suppose yours has somehow got itself miscollimated, or (hopefully not) worse (dropped it damaged), unless the culprit is the diagonal or the eyepieces.

Hooe you sort it,

Magnus

 

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2 hours ago, chrisdg1968 said:

I’ve got a fairly stock standard 90 degree mirror and a 45 degree prism.

Amber alert! The 45 degree prism is probably not fit for astro use unless explicitly designed and sold for that purpose. 

I have a 127mm Celestron Mak and the star test with it is superb provided a decent eyepiece is used and not the 'starter eyepieces that come with it (the 9 or 10mm are especially poor).  I used my Mak for imaging Jupiter once or twice and got an image showing the size and shape of the Great Red Spot, which proves there was nothing at all wrong with that particular instrument for planetary observation.

The Maksutovs in gereral have a fine reputation so your problem may not be with the instrument itself but with the eyepiece or diagonal(s) or the length of time allowed for cooling.

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29 minutes ago, Merlin said:

I recall reading somewhere that a good Newtonian reflector is superior to any folded-beam instrument.

It's a sweeping statement to say that one design is unequivocally better than the other and they all have their strengths and weaknesses. The ideal scope would probably be an unobstructed three-mirror anastigmat but there are currently no commercially available telescopes of this type.

A Newtonanian can't be as well corrected as two or three-mirror designs without additional optics but for planetary observing things like off-axis coma isn't a major problem so designs like the Newtonian and the Dall-Kirkham work very well. Having two or more curved mirrors has its advantages but it can also make the scope more sensitive to collimation errors and harder to collimate. At a given price point you'll also get a bigger and/or better instrument with a Newtonian due to its simplicity and in long focal ratio models the mirror is relatively easy to fabricate well and allows for a small secondary which is an advantage, especially for the planetary observer.

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16 hours ago, chrisdg1968 said:

Yes I had considered that but still a bit surprised at the low quality visuals especially compared to the dob.

If you are using similar focal lengths on the Mak and dob. Unless your getting bad seeing when using the Mak. It suggests a scope problem. Or very poor diagonal. Check the Maks collimation for sure

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Okay managed a star test before clouds rolled in…which showed collimation to be a bit off at one side of focus, but at the other side of focus clearly quite a bit off so there seems to lie the issue.  I’ve collimated a newt quite a few times but really don’t fancy messing about with the mak tbh so I think I may just move it on (as a scope which needs some adjustment) and try to recoup some of the outlay.

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Before I bought my mak I did a lot of online research, and bookmarked this about collimating them (I've not needed it yet, but you never know ... ) It doesn't look incredibly difficult , just a bit of a faff to do in the dark.

https://www.cloudynights.com/topic/476371-how-to-collimate-new-production-c90/#entry6217519

 

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23 hours ago, seven_legs said:

silly question but are you using a dew shield or some type of dew prevention? 

as I would guess the front corrector plate would get dewed up and misty really quickly this time of year in the UK

I have checked for dewing and it wasn’t the issue.

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On 08/11/2021 at 23:51, Tiny Clanger said:

Before I bought my mak I did a lot of online research, and bookmarked this about collimating them (I've not needed it yet, but you never know ... ) It doesn't look incredibly difficult , just a bit of a faff to do in the dark.

https://www.cloudynights.com/topic/476371-how-to-collimate-new-production-c90/#entry6217519

 

I too have now bookmarked this, thank you @Tiny Clanger

Edited by SuburbanMak
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