Would a Meade 5000 100* 10mm EP be too big in a 127 Mak?

[cloudsweeper]

Just thought I'd splash out on a nice, wide angle EP.  

I tried a Celestron Ultima LX which weighed in at 580g, was absurdly large on my tube, so went back.

The Meade is a mere 417g.

I've experimented with plastic bottles of water at exactly the right weights to get some idea!

Any of you knowledgeable and experienced folk out there like to give me the benefit?

Thanks,

Doug.

[John]

One little point with that eyepiece is that I believe the Meade 5000 100 degree eyepieces don't actually deliver a full 100 degree field of view. It's around 92 degrees. Not the end of the world but worth knowing.

 

[Northern Soul man]

Hi Ya Doug, may be worth you having a think about the focal length? - 10mm what x 150 I think in the Mak - due to the optical design your going to get a relative narrow FOV and your only going to be able to use it on the very best of nights regarding seeing and sky conditions - a 20 or 17mm may be a better option, but I'm not sure what other EP's you have in your collection - not a problem, but just making you aware of the limits of the Mak - I have one and find it a great planetary/Luna scope for its size, but I find the better contrast in using a lower FL EP, especially for the small deep sky objects.

Just a Thought Doug - hope you don't take it the wrong way mate - just a pointer so to speak.

 

Paul.

[cloudsweeper]

3 hours ago, Northern Soul man said:

Hi Ya Doug, may be worth you having a think about the focal length? - 10mm what x 150 I think in the Mak - due to the optical design your going to get a relative narrow FOV and your only going to be able to use it on the very best of nights regarding seeing and sky conditions - a 20 or 17mm may be a better option, but I'm not sure what other EP's you have in your collection - not a problem, but just making you aware of the limits of the Mak - I have one and find it a great planetary/Luna scope for its size, but I find the better contrast in using a lower FL EP, especially for the small deep sky objects.

Just a Thought Doug - hope you don't take it the wrong way mate - just a pointer so to speak.

 

Paul.

Not at all, Paul - I'm glad of any input from people who've been doing this so much longer than me!  I have 40, 32, 24, 18, 14, 12, and lower, so thought I'd plug a gap so to speak, and do it with something with a nice wide FOV.  

But you're right - I might not get much more out of it.  

However - looking ahead - if I get an 8SE with focal reducer, it would give me x128 @ 0.78*.  Do you reckon that would be more worthwhile?  And I'm guessing that 'scope could accommodate a large EP better than the 127 can.

Doug.

[Northern Soul man]

Hi Doug nice 1 thanks yeah probably be better in the 8, EP's are really a personal thing and its only with trial and error that you get to what you want as aperture increases you can push the mag higher, I've tried a lot of different focal lengths over the years, the sweet spot in my 11" I find is around 12mm especially on the planets, but after a while I tend to drop the power to around the 17mm mark and get a smaller but much brighter image with much more contrast visible at this mag, if the seeing is poor the lower mag works much better, even for the deep sky I back the power right down and prefer a much smaller image with much better contrast, but thats just me, I tend to spend more time with the lower power views and have stuck with a bino viewer for planetary and this has been a much better set up for me with my max mag on Jupiter of x225 its just using two eyes far out weighs a mono view, I just see so much more with the viewers than mono ever gave me.

Paul.

[Don Pensack]

This scope has a small fully-illuminated field and, in my opinion, doesn't work well with 2" eyepieces.

There's no point as the wider field stops result in visible vignetting.

The maximum true field is easily obtained with 1.25" eyepieces that have a field stop the full width of the barrel, such as a 40mm or 32mm Plossl or a 24-25mm widefield.

Under the best seeing conditions, the scope might be usable on double stars up to about 300x or so, but will really perform best from 150x and down.

Due to the long f/ratio, achieving lower powers is difficult, but a full degree of field is achievable with 38-64x.

A good range for this scope would be a 32mm Plossl,  a 20mm 68°, a 14mm 82°, and a 10mm 

There is a way to eke out a bit more true field in the instrument, and that is to shorten the visual back.  The part of the scope that threads onto the back of the scope

has a threaded protrusion that can be cut off to move the star diagonal about a centimeter closer to the back of the scope.

As is the case with catadioptric scopes, moving the primary mirror changes the focal length of the scope.  In this case, the shorter the visual back, the shorter is the focal length.

In this case, shortening the visual back 1 centimeter shortens the focal length about 4 centimeters, reducing a 1540mm focal length to about 1500mm.

[I would also note that the instrument's clear aperture is really only about 121mm, so figure the f/ratio accordingly]