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Long focal length 80 mm achromat v 100 mm Maksutov.


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I have owned a long focal length 80 mm achromat doublet refractor. It gave really nice views of the planets and the Moon. I have recently been thinking about smaller Maksutov telescopes. Around the 100 mm diameter.

These are reputed to perform well on the Moon and planets. I did have a Meade ETX 125 mm Mak some time ago. It performed wonderfully well on Jupiter and Saturn.

Given good seeing conditions. Which would give the better planetary/Luna performance?

The 100 mm Mak or the longer focal length 80 mm refractor?

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  • Guest changed the title to Long focal length 80 mm achromat v 100 mm Maksutov.

I would go for the 100mm Mak most likely. Aperture counts on planets, and there is a definite benefit between 80mm and 100mm. I’ve seen that between the 80mm f15 Scopetech I’ve tested and my 100mm scopes. I’ve viewed Jupiter through a 4SE and was very impressed with the views. The Mak will be much more manageable too, more compact, and cool down time should not be too bad.

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4 minutes ago, Avocette said:

@Grumpy MartianI think I'm right in thinking that you used to have a SkyMax 150 Pro for planets and the moon? - how did you get on with it? I have seen a YT video which compares the SW Mak 127 versus Max 102 where the 127 certainly won.

Hi Avocette. You're right I did have the Skymax 150 mm. It gave some wonderful views. But I wish that it was a third of the weight. Robust and really heavy. I now have an AZ GTi mount and am enjoying lighter weight smaller telescopes.

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I've compared, not a Mak but a 100mm sct with a 76mm F/15 achromat and the refractor just inched it. The sct was a B&L 4000 but with a hand made replacement corrector and compared with the achromat for quality. I measured the sct obstruction at a hefty 38% which may have been the clincher. So, I would expect the 80mm achromat to just prevail assuming similar quality but probably there would be little in it.

Beautiful seeing last night and the little sct gave a razor sharp view of the moon at x180.

29 minutes ago, Grumpy Martian said:

I have owned a long focal length 80 mm achromat doublet refractor. It gave really nice views of the planets and the Moon. I have recently been thinking about smaller Maksutov telescopes. Around the 100 mm diameter.

These are reputed to perform well on the Moon and planets. I did have a Meade ETX 125 mm Mak some time ago. It performed wonderfully well on Jupiter and Saturn.

Given good seeing conditions. Which would give the better planetary/Luna performance?

The 100 mm Mak or the longer focal length 80 mm refractor?

David

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I think even a 90mm Mak would give a long 80mm Frac a close call and the Mak is much easier to mount, the other big benefit is no wobbly focusser, you can hang several kilos off the back of a Mak with no ill effects..

Alan 

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I would expect the maksutov to give better views due to aperture. It would be slower to cool down but it's small so that wouldn't be a big problem. The mak is also compact so good for storage and good for less vibes when on a light mount.

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How about the Celestron C6 SCT? Light weight (not much heavier than a 127 mak) and 150mm aperture.🤔

When I did a head to head between the C6 SCT and a Skymax 150 a few years ago it was a tie. Found no real difference in contrast between the two. 

Edited by johninderby
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1 hour ago, johninderby said:

How about the Celestron C6 SCT? Light weight (not much heavier than a 127 mak) and 150mm aperture.🤔

When I did a head to head between the C6 SCT and a Skymax 150 a few years ago it was a tie. Found no real difference in contrast between the two. 

I had a C6 and a Meade ETX-105 Mak. The Meade gave breathtaking views of the Moon and planets, as sharp as a top apo refractor, yet I never warmed to the C6. Maybe it was a poor example. Agree that it’s an easy to handle scope though.

But to answer Martin’s question, if you can track down a decent 105 ETX, I think you’ll love it. Often wish I’d kept mine.

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2 minutes ago, Highburymark said:

I had a C6 and a Meade ETX-105 Mak. The Meade gave breathtaking views of the Moon and planets, as sharp as a top apo refractor, yet I never warmed to the C6. Maybe it was a poor example. Agree that it’s an easy to handle scope though.

But to answer Martin’s question, if you can track down a decent 105 ETX, I think you’ll love it. Often wish I’d kept mine.

Interesting. I would love to know just how much variability there is between samples of various scopes. The comparisons vary person to person so it does seem like they vary quite a lot.

I think I viewed Saturn through an ETX 105 or 125 once and it was an excellent view!

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3 hours ago, Stu said:

What scopes do you have currently Martin?

Hi Stu. I use my OO VX8 in Dorset. But at home in Hertfordshire I enjoy my Equinox 80 mm and 120 mm Startravel. I have the AZ GTi mount which I like. I find that smaller stature telescopes. I wanted to add a small but capable planetary telescope to the set.

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22 minutes ago, Grumpy Martian said:

Hi Stu. I use my OO VX8 in Dorset. But at home in Hertfordshire I enjoy my Equinox 80 mm and 120 mm Startravel. I have the AZ GTi mount which I like. I find that smaller stature telescopes. I wanted to add a small but capable planetary telescope to the set.

I would think a 102 or even a 127mm Mak would suit very well in that case. The Bresser ones are worth a look I think, as they operate at full aperture unlike the Skymax 127. Should be within the capabilities of the AZGTI, but might need a better tripod if you still use the standard one which is quite flimsy.

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1 hour ago, Stu said:

I would think a 102 or even a 127mm Mak would suit very well in that case. The Bresser ones are worth a look I think, as they operate at full aperture unlike the Skymax 127. Should be within the capabilities of the AZGTI, but might need a better tripod if you still use the standard one which is quite flimsy.

I have the AZ GTi mount setup on an EQ5 tripod using the adapter. Works a treat. I was even considering an older Meade ETX deforked tube assembly if one were to become available. Or a Celestron Nexstar SE 102 mm tube.

I always wondered about the performance of a compound telescope with it's central obstruction and what would it's equivalent refractor be without a central obstruction.

I wanted it to use for planetary observing.

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5 hours ago, johninderby said:

How about the Celestron C6 SCT? Light weight (not much heavier than a 127 mak) and 150mm aperture.🤔

When I did a head to head between the C6 SCT and a Skymax 150 a few years ago it was a tie. Found no real difference in contrast between the two. 

Thanks John. The 150 km Mak was very good but so heavy. The C6 was tempting. But wonder how it would perform on the AZ GTi mount with a payload of 5 kgs?

The Celestron C6 is approx 4 1/2 kgs.

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I also use a Skymax 102 i addition to the C6. I prefer the mak for double stars, but the C6 wins on planets as my eyes don't cope with exit pupils below 1mm. For faint fuzzies the C6 wins as it has a wider FOV (I use a .63 reducer).

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