SCT v MCT Beginner Question

[Leedsgreen]

Dear All,

I realise there might be a few groans with this age old question but after reading as many reviews as possible (including a good number here on SL), I still have a few outstanding queries. I hope it is OK to check my thinking out?

First of all, a little about my requirements: I currently own an APO 66mm refrator and am looking for a SCT or Mak to allow me a more detailed and closer look at the moon and planets. (I haven't yet looked at DSOs but may do in the future). I have in mind a 5" SCT or MCT becuase it will be light enough for my current mount, fairly cheap but also offer a substantial increase in resolution compared to my refractor.

Regarding SCT v Mak, what I have found is:

1. Due to its slightly larger secondary, an SCT will show an image with less contrast compared to the Mak (with the same aperture).

2. However, due to the thinner front plate, SCTs are usually lighter and cool down quicker than Maks.

OK, that is what seems definate. However, with regard to point 1, what I can not determine is if the resolving power of an SCT is less than a MCT of the same size. In other words, does a 5" SCT display an inferior optical image compared to a 127mm MCT? There appears to be a difference of opinion. For sure, many say that a MCT is sharper and more contrasty than an SCT (including Rod Mollise in his new CAT book) but there are others who say this is a myth and when the two are compared side-to-side there is no observable difference.

I would really welcome any advice with regard the above. I am currently leaning towards the Celestron C5 becuase it is 1/2 Kg lighter and has a shorter FL but would not buy it if I could get a better image of the moon and planets with the MCT. Has anyone owned/tried both so that they can give their opinion?

Thanks very much for any help,

Nick

[johninderby]

The SCT is the better all-round general purpose design that basically does everything well, but if it's purely lunar/planetary then the MCT would normaly have a small advantage. One other important point in comparing SCT vs. MCT is to compare equivalent quality scopes. For instance don't compare a top quality MCT with premium optics to a standard mass produced SCT. As the MCT design is easier for small manufacturers to produce, you do tend to see some very high quality MCTs form smaller manufacturers. SCT corrector plates are more difficult to produce and require expensive production equipment so most SCTs are of the standard mass production type.

I've owned the 127 MCT and the C5 and preferred the 127 (but it was close). However I've also owned the Skymax 150 MCT and the C6 and preferred the C6 on luinar/planetary.

John

[Leedsgreen]

John,

Thanks for your helpful reply. I think that about wraps it up for me (in that I will go for an MCT at 5" size. The 6" is to big for my mount and I don't wish to spend too much at the moment). BTW did you try any imaging with the 5" scopes? I plan to use both afocal and web-cam. I presume your results remained constant (i.e. for lunar/planetary, the MCT just pulled ahead of the SCT)?

Nick

[johninderby]

Hi Nick

You won't be disappointed in the 127, lovely little scope. I didn't do much imaging with it, but on purely imaging there was little difference between the 127 and the C5 from what I remember, but on visual the 127 had a slight edge. The one real advantage of the 127 is that it maintains collimation very well are rarely needs collimating whereas the C5 needs collimating regularly. The downside of the 127 is that it takes longer to cool down due to the thicker corrector.

When you get the 127 do get a decent diagonal, the standard one is rubbish. A 1.25" dielectric will be fine, or if you do want to go to a 2" diagonal you can get an adaptor that screws onto the back of the 127 and lets you use standard SCT bits.

John

PS

I used the 127 on an SLT mount which was ideal, and now Skywatcher does the same thing.

[Leedsgreen]

Cheers John, and thanks for all your advice, much appreciated.

Nick