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Any idea on max and min mag on this model?

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#1 Atlantic Devil

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Posted 02 December 2020 - 10:05 AM

The website fails to mention it. A 12mm eyepiece is as strong as I’ll use, but what do you guys determine is the maximum and minimum useful magnification on it??

https://www.meade.co...html#additional

#2 Alrakis

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Posted 02 December 2020 - 10:25 AM

This is a classic 90mm Maksutov with the center spot on the inside of the corrector. I think you are practically limited to 1 1/4" eyepieces so max and min magnification (and true field of view, TFOV) are constrained by that particular limit.

 

For minimum magnification you have a few options, noting that with this telescope you really can't get to the minimum useful magnification due to the eyepiece limitation. Your basic options for a minimum eyepiece would be something like a 40mm Plossl, 32mm Plossl, or a 24mm Panoptic. This will produce the following magnifications, apparent field of view (AFOV), and true field of view (TFOV):

 

40mm Plossl:        31x mag, 43 degree AFOV, 1 degree 23 arcmin TFOV

32mm Plossl:        39x mag, 52 degree AFOV, 1 degree 20 arcmin TFOV

24mm Panoptic:   52x mag, 68 degree AFOV, 1 degree 18 arcmin TFOV

 

As you can see the numbers indicate that you are at about the maximum true field of view with any of these eyepieces. I would recommend the 32mm Plossl. This would give a decent AFOV and would work well with this type of telescope.

 

On the maximum magnification end you would select an eyepiece with approximately half the focal ratio of the telescope in mm. In this case the focal ratio is 13.9, so you would be looking at about 7mm. An example of this would be a 7mm Plossl or a 8mm Radian. This will produce the following magnifications, apparent field of view (AFOV), and true field of view (TFOV):

 

7mm Plossl:        179x mag, 52 degree AFOV, 17 arcmin TFOV

8mm Radian:       156x mag, 60 degree AFOV, 23 arcmin TFOV

 

In your case, however, I would just simply get the 32mm Plossl and your 12mm eyepiece along with a 2x barlow which would give you the following magnifications: 39x, 78x, 104x, 208x.

 

Chris


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#3 sg6

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Posted 02 December 2020 - 10:36 AM

90mm Meade Mak at f/13.9, I suggest the 12mm is the maximum sensible target so around 105x.

Will say friend had the equivalent and I lent him a 12mm and 8mm Paradigm - do you have any idea how much trouble I had getting those back off him? They worked well apparently. I suspect it was mainly the 12mm as the 8mm would I expect be a bit too much for comfort everyday.

 

So a nice 12mm and a nice 10mm would I suggest be a sensible pair. I say pair as what happens is the 10mm may work 40% of the time and the 12mm all the time. But that 10mm when it all fits will be nice.

 

It would give 125x and Saturn at 125x was one of my best views. But it was a long refractor not a Mak.

 

Safety is a 12mm for 105x. Remember that 105x would be around 0.5 degree field so the nice big things would be out of the field of the system. M45 is just over 1 degree, so you would nto get all that in one.


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#4 jefffed

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Posted 02 December 2020 - 10:45 AM

Maximum magnification is always dependent on seeing conditions. Only on nights of with great conditions can you use your scope's mathematically maximum magnification usually much less


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#5 peta62

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Posted 02 December 2020 - 10:50 AM

I was afraid of central obstruction with 40mm EP, since I see obvious darkness in the center with 50mm 2" EP in C9.25, so I went to check, but there is no problem with 40mm in Mak90. Maksutov works differently than Schmidt.


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#6 Atlantic Devil

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Posted 02 December 2020 - 01:10 PM

I'm not an expert on all the mathematical aspects. But thanks for the info! My idea of 12mm to 32mm has been pretty much confirmed.




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