MaK Eyepiece Suggestions
Posted 08 May 2013 - 11:54 AM
Looking for input from Mak-Cass owners on the best eyepieces to use to fully utilize the scopes potential. What eyepieces would compliment the Orion or Meade Mak-Cass 180mm ,( 7inch ) OTA. I understand that these OTA's have long f/l as I m interested in planetary viewing with the occasional deep sky.
Posted 08 May 2013 - 04:27 PM
OK, 2700mm focal length.
Looking for input from Mak-Cass owners on the best eyepieces to use to fully utilize the scope's potential. What eyepieces would complement the Orion or Meade Mak-Cass 180mm ,( 7inch ) OTA. I understand that these OTA's have long f/l as I'm interested in planetary viewing with the occasional deep sky.
Primary interest lunar and planetary but also deepsky.
f/ratio = 15, so 7mm exit pupil with a 105mm eyepiece and a 0.5mm exit pupil with a 7.5mm eyepiece (the range of exit pupils for the scope). Nominal "high power" would be a 15mm eyepiece.
So, because a 41mm Panoptic (or similar) with a 46mm field stop has just about the largest possible field of view, if you modified the rear of the scope to accept 2" eyepieces, you could achieve a low power of 66X and a true field of 0.98 degrees. It would not be well-illuminated, though, so a better low power choice would have a smaller field and be 30-32mm in 2"
If we stick with the original 1.25" visual back, the largest field 1.25" eyepiece becomes a 40mm Plossl or 24mm Widefield. The 40mm would yield 68X and a true field of 0.57 degrees, about the same size as the full Moon.
Exit pupil would be 40/15=2.7mm, kind of small for a low power, but this is an f/15 scope after all. Exit pupils are always small on an f/15 scope.
A reasonable complement would be a 25-27mm eyepiece, yielding around 100X. But if you stick with a Plossl, the true field would be a little less than 0.5 degrees. A 60 degree 25mm would yield 108X and a true field of 0.53 degrees, or a little wider. Since the interest is lunar and planetary, a 25mm AT Paradigm might be a good choice here. An alternative would be a 24mm widefield, like the 24mm TeleVue Panoptic if your budget is much bigger.
If you get a good 2X barlow (like the ES or the TeleVue), then you have 132X (20mm) and 216X (12.5mm), so now your set is 40/25/20/12.5. What follows that up would be a good 16mm for the in-between magnification and an even higher high power. 8mm (the 16 barlowed) would be pretty close to the minimum exit pupil for your scope, and the 16 would be a nominal high-power eyepiece.
Now the true field at those really high powers with a 50-60 degree eyepiece would be kind of restricted--OK for a planet, not so great for the Moon or globulars or planetaries. So I recommend a wider apparent field eyepiece for the 16mm, like: Explore Scientific 16mm 68 degree (on the narrow side), or TeleVue Nagler 16mm Type 5 82 degree (I use this barlowed all the time in my 5" Mak, where it is my favorite eyepiece for Saturn and Mars, and it is really sharp--and not heavy, either). Of course, you could go +/- a millimeter and use anything from 15-17mm, which would give you many, many choices. The 16 Nagler would yield 169X and a true field of 0.47 degrees.
All 3 of these eyepieces would yield nearly the same size true field of view. Interesting.
I am just presuming, here, that you don't necessarily want to view a drinking-straw-narrow field, and that you might occasionally want to use the scope for the Moon (where a wider, well-corrected field is really nice) and other objects, like double stars or globulars, etc.
So, that set with barlow would be 40/25/20/16/12.5/8 and cover all the bases for the scope.
On that scope, something else to be aware of: a 2X barlow, used in front of the star diagonal instead of under the eyepiece, might yield as much as 3X, so you have additional magnifications. Vignetting might start to be a problem in that position, but it works with some eyepieces in superb seeing.
Also, some barlow lenses can be detached from the tubes they come in and screwed directly to the eyepiece, where the magnification is less (averaging 1.5X) and where vignetting is seldom an issue. Being used this close to the focal plane of the eyepiece, it is imperative to keep the barlow lens clean. This is usually not a popular position for a barlow.
I am not a believer in the super-narrow fields of view for planetary viewing unless you NEVER, EVER, want to look at the Moon or any other object. The 1.25" 40mm Plossl I mention is already a compromise, with a narrow 43 degree apparent field. If you find that too narrow, a 1.25" 32mm Plossl has a larger apparent field and the same true field as the 40mm. I recommended the 40mm to TRY to get some additional exit pupil for a brighter image and the true field isn't any smaller than the 32mm.
My Mak is f/12.7, so a little larger exit pupils can be achieved. The advantages of the Maksutov design is being able to use nearly all eyepieces and not see any aberrations induced by the f/ratio, and seeing a field in really tight focus from edge-to-edge. I've had my 5" for 10 years, and it has performed really well. A wide-field instrument it is not. But a nice sharp set of optics in a portable format it is.
Posted 08 May 2013 - 05:18 PM
That'd be *my* scope then :-)
Notes from the field:
So, because a 41mm Panoptic (or similar) with a 46mm field stop has just about the largest possible field of view, if you modified the rear of the scope to accept 2" eyepieces, you could achieve a low power of 66X and a true field of 0.98 degrees.
Doesn't work with a Titan II. :-( You just get a heavilly-vignetted view.
the 24mm TeleVue Panoptic if your budget is much bigger.
Also doesn't work well in the Mak 180 - the edge of the field *just* gets vignetted (but only just). The 68 degree Meade SWA 24mm - Ah... NOW that's just fine (just has that *tiny* TINY bit less field than the Pan for some reason, and so the field-stop remains crisp.) It lives on in the shape of the 68deg Explore Scientific 24mm.
The best eyepiece I've found BY FAR in the Mak 180 is the Meade Series 5000 14mm Plossl (other S5k Plossls being not so good) but the 14mm? Absolute star! Lovely, lovely eyepiece in this scope. Better than a 16mm Brandon.
Haven't found a "low-power" (sic) EP I'm happy with for this scope yet, the 24mm being just a little too dark, and a 40mm Plossl being too narrow and eye-relief unnaccceptably long. I've been "getting away" with a 32mm GSO plossl (with adjustable eyeguard) on trips, or simply using a different scope when at home.
I don't see the point in using a Barlow with a scope of this F/R
In summary, I pretty-much "live" in a 60deg 14mm all evening when this scope comes out, and rarely change to anything else.
Posted 08 May 2013 - 05:37 PM
It's interesting you use a 14mm so much in the 180. That's a <1mm exit pupil (kind of dark and in the range where floaters in the eye begin to be an issue), and high power 193X for a 7".
I had a couple nights with the 7" Meade Mak, and my favorite eyepiece in that 7" was a 25mm eyepiece (sharp, sharp, sharp!).
If you like the 32 Plossl, try a 30mm or 35mm Parks Gold Series Plossl (or the equivalent Orion/Antares/Celestron/Meade/Tuthill/Omcon/Takahashi/Baader, most of which are no longer available new but I see all the time used), or a TeleVue 32 Plossl. That last one is my "gold standard" 32mm Plossl (though I really liked the 35 Parks--I'd be afraid it would vignette, though, due to its 29mm field stop).
Posted 08 May 2013 - 08:42 PM
Yes. I guess it's all about targets really.
Living in smokey London, I pretty much only look at:
- 14mm: Planets / Moon
- 32mm: Globs
Floaters not a problem for me at 0.93 ex/P but yeah, not much below that and its like staring through dishwater...
Posted 09 May 2013 - 01:21 AM
The Mak though, once cooled, does seem less susceptible to wobbly atmosphere, possibly because its field of view is narrower and atmosphere cell effect is lessened. Thats just speculation. But at any rate I am often able to use higher power than I can with an F5 8" Newt. Theres some evidence that smaller fracs can often run at higher mag than a newt at least in the UK which is often attributed to the smaller aperture, narrower field haing less of an issue. Certainly on planets ai have often been able to push above the x235 limit which is generally considered the max under UK skies.
I have done wide field object like M42 with the Mak and Orthos and while you wont ever see an expansive view what you can see is very detailed and contrasted structures in the nebula, assuming good seeing. Likewise other compact objects like M13 show well.
I have also tried wide field EPs in the Mak but not often so I would hesitate to say much on that. Limited experience would conclude that the Es 14mm 100' works tolerably well with some vignetting/illumination issues. Not sure which as I have only ever used it in the Mak a few times and never really checked into issues. The 30mm ES82' is not nice at all in the Mak...it all too easily lurches into the ring if fire effect. Thats not damning on the eyepiece...its a wide field blob of glass and not at home in something like the Mak. Ai have yet to try the Pentax XW30 in the Mak so I cant say what the issues of that might be and whether they would be the same with other 2" widefields.
One thing I found when I first had the Mak was you have to readjust your notions on EPs if you come from a Newt background. The focal length is so large that a medium power EP in a newt is a monster mag EP in a big Mak. Intellectually I always knew that to be so but in a dark field when your absorbed with viewing its so easy go keep reaching for a 5mm
Corrected for typos and other stuff.
Posted 09 May 2013 - 04:16 PM
Regarding the comments about wide fields vignetting... I have found the 41 Panoptic to not work as well for that reason. I much prefer a TV 55 mm Plossl. The views of objects such as M42 and other large nebula are simply stunning. I am a huge Panoptic fan. The 27 mm hits all the sweet spots; 2.0 mm Exit Pupil, 0.7 degree true field and x89 (roughly). Magnificent on Globular Clusters.
Due to the long focal length, Maks are more forgiving on eyepiece design. For higher magnification, any of today's standards; Plossl, Ortho, Delos, etc. will work well, though a Mak doesn't take full advantage of what a Naglar or Ethos can deliver. Those are best with shorter focal ratio scopes.
The best planetary views through my instrument are in the x140 - x240 range depending on the seeing. Maks tend to excel on small planetary nebulae. You can really push the magnification.
Posted 09 May 2013 - 05:09 PM
Quite odd. Both of those eyepieces have identical field stops, and should vignette totally equally.
Regarding the comments about wide fields vignetting... I have found the 41 Panoptic to not work as well for that reason. I much prefer a TV 55 mm Plossl.
Posted 09 May 2013 - 06:06 PM
Posted 10 May 2013 - 12:24 AM
You can really push the magnification.
I've just started a separate thread prompted by your comment above.
Posted 10 May 2013 - 06:58 AM
Posted 10 May 2013 - 10:48 AM
Posted 10 May 2013 - 07:58 PM
Clear Skies.. WiL
Posted 13 May 2013 - 01:40 PM
On a GEM. Used for Moon, planets.
what I use,
University Optics "Volcano Top" orthoscopics.
25mm, 18mm, 12.5mm, 9mm, 7mm, 6mm.
Recently added an 8mm Carton Plossl.
Posted 13 May 2013 - 08:00 PM
Posted 14 May 2013 - 12:10 PM
For higher magnification, any of today's standards; Plossl, Ortho, Delos, etc. will work well, though a Mak doesn't take full advantage of what a Naglar or Ethos can deliver. Those are best with shorter focal ratio scopes.
Eyepiece aesthetics really are personal thing. My 10mm Ethos in my newly acquired M703 is incredible. That eyepiece is so sharp and gives the same TFOV as a 20mm Plossl, but at twice the magnification.
I have had a blast revisiting my favorite spring globular clusters at 180x in the 10mm Ethos. They just come alive in a way I used to associate with a 10" scope in darker skies.
Posted 14 May 2013 - 01:45 PM
Posted 14 May 2013 - 04:24 PM