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A beginner’s take on the 80mm ED refractor versus the 150mm Mak

cassegrain catadioptric Maksutov Orion refractor beginner equipment eyepieces observing
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#1 Escape Pod

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Posted 01 November 2020 - 09:20 AM

PRELUDE

 

 

Besides a star party hosted by my college astronomy professor two decades ago, I hadn’t spent any real time behind a telescope since I was a boy. Blame COVID. Or chalk it up to mid-life crisis. But when my wife and I decided to book a camping trip to Big Bend for this winter and I started imagining all those clear, ink-dark skies, I became obsessed with the idea of getting back into astronomy.

 

So for the past three weeks I have been frequenting (at least one guy would say, pestering) this community as I planned my return. It began with the inevitable (infuriating, I now realize) question: which telescope?

 

In my defense, my question did have some parameters. First, the scope should be capable of graduating to astrophotography down the road. I’m an amateur landscape photographer, you see. It is inevitable that I will end up trying to press some kind of sensor up against the light path of this thing eventually. Second, it needed to be semi-portable. Specifically, it had to be able to fit inside the 26”x22” bin underneath the bed of our camper trailer.

 

It will come as no surprise to any of the regulars on here, but very quickly I was thrown into the Frac versus Cass debate—between those who value the magnification and light-gathering capability of a medium-sized Cassegrain versus those who praise the resolution, color and contrast of the refractors. I learned so much from both sides. I had decided that I probably would want both, a widefield explorer and a “planet killer.” But that my first scope would be the 80mm ED refractor. It was wide enough to take in much of the deep sky, but with the resolving capability to do some serious magnification for planets and more under good seeing. The focal ratio (f/7.5) was fast enough to eventually do some deep space astrophotography with, but just slow enough that it would be merciful to the budget eyepieces that I’d be using on it for visual astronomy. I put myself on the waiting list for a backordered Orion ED80 with all the trimmings.

 

But while I was eagerly awaiting the next sleigh to arrive from Santa’s telescope workshop in China, a 150mm Mak, also by Orion, popped up used on the classifieds here. It had the mount that I wanted but couldn’t afford a-la-carte, an alt-az GoTo mount called the StarSeeker IV that easily switches between manual and guided. I thought it would be the perfect Grab-and-Go mount. (More on that below). Moreover, for the price of a new 127mm Mak, I could get the extra light-gathering capability of a 6-incher. I pulled the trigger.

 

And almost immediately regretted it.

 

You see, in my mind’s eye I imagined staging a minimalist, old school return to stargazing. Light, breezy scope and mount. Hand-cranked, so that I could learn my way through the night sky through star-hopping rather than computer guidance. The GPS in my car had already proven to me just how dumb automatic guidance makes me. Analog, not digital. LPs, not MP3s. Simple, not sophisticated.

 

Instead, when the scope came in I found myself in possession of an unwieldy marvel of 21st century digital technology. Like I said, I am a photographer of sorts. I’m used to hauling kit. But even I was astounded at how big and heavy a 12 pound Mak with a 14-pound alt-az GoTo mount really feels. Lifting the tripod and mount out of the box, I felt like I was holding a 3 foot long cast iron skillet. Awkwardly cradling the Mak in both arms as I tried to slide its dovetail onto the mount for the first time quickly turned to clutching onto it with no small amount of terror as I removed one hand to tighten the set screw on the Vixen mount. “Is this thing really only 12 pounds???” I puzzled.

 

Biding my time as the inevitable cloudy skies rolled in with the new toy, I observed myself with equal regret as my inner techie went to work downloading SkySafari Pro and getting the mount synced up with my iPad for point-and-click astro-targeting. “I better order a lithium ion battery,” I thought, so I can power the mount without burning through AAs.

 

On the one hand, I could see my 13 year old computer nerd self, fumbling in the backyard on a warm summer night with his planisphere, his dot matrix star map printouts and his 60mm drug store scope. That kid would have been in total awe over the technology that was in front of me right now.

 

But this wasn’t what I had imagined.

 

There were further complications:

  • How in the hell do you build a winter jacket for the Mak so that you don’t get air currents inside the tube disrupting your viewing?
  • How wide (long) of an eyepiece can you put on a Mak for observing the beauties of the deep sky before you start bumping up against the limits of minimum magnification and exit pupil size? Back to the forums, where I discovered Astronomy.Tools

FF741477-88FF-461A-B4EB-1B2A9C74C6D2.jpeg

 

And in the back of my mind, there was still this question of Mak versus Frac in terms of optical performance. So when I saw a good deal on a used 80mm ED pop up on the classifieds page, I messaged the seller before I even finished reading the advertisement. Four days later, on Halloween, I was in possession of both the Mak and a Sky-Watcher Evostar 80ED. And somewhat miraculously, the clouds had parted.

 

There was going to be a shootout tonight.


Edited by Escape Pod, 01 November 2020 - 10:57 AM.

 

#2 Escape Pod

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Posted 01 November 2020 - 10:41 AM

FIRST LIGHT

 

With my chores done, I got the go-ahead from my increasingly perplexed and concerned wife to load up the car and head out into the fields just south of Columbus.

 

I decided to mount the 80mm refractor first. In theory, the silver blanket of Reflectix that I had made for the Mak tube would mean that it wouldn’t require thermal acclimation. But I wasn’t sure. So I bolted the refractor to the mount. Weighing in at 7 pounds, the refractor is definitely less unwieldy. But the oversized tube on these Synta version of the 80ED like the Sky-Watcher or the Orion copies is definitely not what I would call compact. I find myself wondering if they did it for better baffling, or because they had a bunch of 4inch refractor tubes laying around. 

 

Anyways, I fired up the GoTo alignment procedure, and immediately came to realize why astronomers hate full moons. “Where are all the stars?”

 

After a few minutes of fumbling with the planisphere trying in vein to locate a constellation to perform the two-star alignment with, I gave up and decided tonight would be a night of planet and moon-gazing.

 

I flicked on the red-dot finder, loosened the clutch on the mount, and swung over to Jupiter.

 

Lesson One: The StarSeeker alt-az GoTo mount is really not designed for manual use. It will get you in the neighborhood. But there is enough slop (backlash?) in the gears that you really need to use the electronic motor to make precision adjustments. In this moment I was grateful that I had the hand controller with physical buttons rather than relying on a mobile device. 

 

I hadn’t had a chance to re-align the red dot finder to the new scope during the daylight hours, so I crossed my fingers, got the red dot centered on Jupiter, and moved my eyes to the eyepiece (Orion’s new, inexpensive 7-21mm zoom). And there it was. A slightly out-of-focus Jupiter flanked by her moons. All of a sudden the slightly notchy two-speed Crayford focuser that I’d worried about when unboxing the scope earlier that day now felt like butter in my hands as the planet snapped into focus. Small, but sharp.

 

I quickly reached for the 2.4x Dakin Barlow and dialed up the magnification on the zoom. But the gas giant was somewhat low in the sky, and clear views of the clouds were few and far between. I found my eyes (and brain) doing some of the “lucky imaging” interpolation that I’d read about in planetary astrophotography.

 

Cool, I thought. Where’s Saturn?

 

I took off the Barlow, dialed the EP back to 21mm, and manually swung the scope around to get the red dot on Saturn. And like magic, there she was. Back to the Barlow, back to 7mm. There were a couple of moments where I convinced myself that I could make out the Cassini division. But Saturn was also low in the sky, so the seeing was not ideal.

 

Okay, I thought. Time to break out the Planet Killer. With my Vixen mount dexterity improving ever so slightly, I was able to get the refractor back in its case and, without too much trepidation, re-mount the Mak. Once diagonals and EPs were back in place—this time without the Barlow, since the Mak is 1800mm in focal length to the refractor’s 600mm—I decided to start again with Jupiter. 

 

Red dot on the planet, and back out to 21mm with the zoom, and there it was! A blurry mess. No problem, I thought. I started fumbling with the focuser. And fumbling. And fumbling. And one second I thought I had it in focus, the next, Jupiter and its moons were blurry and elongated. Fighting and fighting to work the focuser, I became frustrated that each time I’d make a small adjustment to the focuser I would have to wait a couple of seconds for the scope to settle down. Nowhere near as intuitive as the two-speed Crayford on the refractor felt. And even when I finally had the planet in some semblance of focus and dialed up the magnification, it didn’t seem like the image was producing those moments of “lucky seeing” that had convinced me I’d seen some cloud structure on the 80ED. 

 

“Bad thermals? Out of collimation? Too much magnification? Good old fashioned user error?” I didn’t know. 

 

Where’s Saturn?

 

I swung the Mak over, centered the red dot on the dimmer planet, moved to the EP and.....nothing. I rechecked the finder. I rechecked that the eyepiece was set to 21mm instead of 7. I panned around (clumsily) for several minutes, but never managed to get it in the finder. User error is surely at play here. Obviously there is some technique involved with panning and searching. But this was the first moment where I found myself wishing I had an optical finder scope rather that a red dot finder. With the narrow field of view on my Mak, it just seemed to imprecise. The Mak itself, more unforgiving of a rookie. 

 

B02DAE06-6F0D-47FA-9078-6266ECA6A922.jpeg

Caption: Comparing the “zoomed out” 21mm FOV on the Mak with that of the Frac, there is little wonder why I had more difficulty finding Saturn with the Mak. 

 

Giving up on Saturn, I decided it was time to look at the moon. I mounted a polarizing filter on the eyepiece to cut down on the glare and spun the scope around, aligned the red dot and.....big blurry white dot with what looked like the secondary mirror projected in the middle of it. Ahh...I thought. Must be a radically different focus point from my last target, Jupiter. So I moved my hand to the shifting knob and turned. And turned. And turned. And started second-guessing myself and turning it the other way. And turning it. And turning it.

 

This must’ve gone on for 5 minutes or so, but it felt like an eternity. I started noticing how cold it was getting. I started regretting purchasing the Mak. I contemplated throwing in the towel on and re-mounting the refractor. But then I remembered a phrase I’d read here in the forums: “Adult-sized patience.” So I recommitted to finding focus on the Mak and seeing this moon. 

 

And with three twists of my wrist, suddenly I found myself suspended in lunar orbit like the command module in Apollo 13. My jaw dropped. The dopamine receptors in my brain started going crazy. I located a semblance of a termination line crossing the craters around Mare Frigolis and began to zoom in. Suddenly, it felt like I was base jumping onto the lunar surface. 

 

“Okay,” I thought. “This Mak is definitely collimated.”

 

I don’t know how much time I spent scanning the lunar surface with the Mak before I decided to swap the refractor back in. What I do know is that it served up a more “killer” view of this solar system object than I could have ever imagined. Maybe the Mak can stay, I thought....

 

Then I mounted the refractor. With a few twists of the big focus knob and a small twist of the little one, I was quickly where I wanted to be. So far, I find the two-speed Crayford so much faster and more intuitive to focus with a rookie’s hands and eyes. 

 

No surpise, the lunar surface was just as stunning with the 80ED as was with the Mak. I forgot to look for chromatic aberration, but I am a photographer. So if the doublet was serving up any objectionable false color I’m sure I would’ve noticed. 

 

What I did notice was that the refractor could go almost toe-to-toe with the Mak when it comes to magnification on the lunar surface. Reaching for the 2.4x Barlow that would give my zoom EP a magnification of just over 200X at 7mm, it could resolve almost (but not quite) the same level of detail as I could see with my Mak at 7mm (256x). At least, that was my impression. 

 

Lastly, I turned to Mars. As we are still fairly close to opposition, I had high hopes of making out some planetary detail, if not the polar ice field. No such luck. It was only faintly red. It was close to the moon, so I’m not sure if that was a confounding variable. But overall a bit of disappointment. I started to swing the scope back to the moon for more lunar gazing. But when I nearly blinded myself remembering that I’d have to re-attach the polarizing filter, I all of a sudden noticed that it was getting really cold and late and decided to pack up. 

 

I drove home elated, feeling like that 13 year old boy under the Oregon skies with his dot matrix star chart and a dream. 

 

My initial conclusion is that I can’t draw any conclusions just yet. Clearly the refractor, with its lower magnification and more intuitive 2-speed focuser, is more forgiving of a beginner’s technique. Had I gone out into the field with only the 80ED, I don’t think I would’ve felt disappointed that I didn’t have a proper “planet killer.” Armed with a good Barlow, the views of Jupiter and Saturn were quite satisfying even though they were low in the sky. 

 

Had I gone out into the field with just the Mak, I honestly don’t know how I would have felt. My difficulty resolving Jupiter to the same degree as the refractor (perhaps I was over-magnified? Or maybe the seeing had deteriorated?) was disappointing. My failure to even locate Saturn with the red dot finder was crushing. But the feeling I had when I finally managed to get the moon into focus—I will remember that moment for the rest of my life. For that alone, the Mak deserves to advance to Round 2. 

 

228EB99C-905B-41E0-85A7-A629A0E5716B.jpeg

Caption: Obligatory crappy afocal smartphone photo of my first moon view. Note that I believe the chromatic aberration visible in this shot was introduced by my iPhone. I didn’t see it through the EP. 

 

Next week we are heading down to the hill country south of Columbus for a couple of nights of camping. The sky is dark, the forecast is clear, the temps are bearable, and there is a cool observing site called the John Glenn Astronomy Park that I am dying to check out. By then the moon will be coming up later in the night, so I should have a bit of time to try Mak and Frac out on some easy DSOs. 

 

Stay Tuned. 


Edited by Escape Pod, 01 November 2020 - 01:16 PM.

 

#3 Starman27

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Posted 01 November 2020 - 10:41 AM

Can't wait for your first light report.. 


 

#4 B 26354

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Posted 01 November 2020 - 11:09 AM

Can't wait for your first light report.. 

Me too!!! waytogo.gif


 

#5 csrlice12

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Posted 01 November 2020 - 11:24 AM

I recommend you buy a RACI finder for the Mak.  A red dot works ok with a wide field scope, but can be very frustrating for a narrow fov mak.  Even on a wider field scope, the red dot gets you to the general area, a RACI is for finding your target.


 

#6 Escape Pod

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Posted 01 November 2020 - 12:40 PM

I recommend you buy a RACI finder for the Mak.  A red dot works ok with a wide field scope, but can be very frustrating for a narrow fov mak.  Even on a wider field scope, the red dot gets you to the general area, a RACI is for finding your target.

So you would recommend one of those—dovetail is it called?—attachments that allow you to have both the red dot and the RACI optical finder?


 

#7 csrlice12

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Posted 01 November 2020 - 03:01 PM

I wouldn't use a red dot on a mak or SCT at all.  That's just me though, others may use both.  A RACI will likely use a Vixen finder shoe instead of a dovetail unless you go high end, which you might consider if you use it as a guiding scope for astrophotography.


 

#8 sg6

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Posted 01 November 2020 - 03:29 PM

Something you have done is wrong. No 150mm Mak with a 2.5mm eyepiece is going to give a magnification of 60x and a field of view of just under the Plaides - wheich is just over 2 degrees.

 

So whatever you have fed into the tool is plain wrong.

 

The 150 Orion is given as f/12 and 1800mm focal length.

 

A 2.5mm eyepiece would give 720x magnification, and even with an 82 degree eyepiece that would be 0.11 degree view. You might get one star of the M45 cluster in view. Certainly not what the image indicates.

 

A 1.75mm eyepiece would give 1028x, and 0.08 field. Both of which are simply not feasible.

 

What did you set up in the tool as something is wrong. Those numbers just are not right for the equipment.


 

#9 Escape Pod

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Posted 01 November 2020 - 03:51 PM

Something you have done is wrong. No 150mm Mak with a 2.5mm eyepiece is going to give a magnification of 60x and a field of view of just under the Plaides - wheich is just over 2 degrees.

So whatever you have fed into the tool is plain wrong.

The 150 Orion is given as f/12 and 1800mm focal length.

A 2.5mm eyepiece would give 720x magnification, and even with an 82 degree eyepiece that would be 0.11 degree view. You might get one star of the M45 cluster in view. Certainly not what the image indicates.

A 1.75mm eyepiece would give 1028x, and 0.08 field. Both of which are simply not feasible.

What did you set up in the tool as something is wrong. Those numbers just are not right for the equipment.


EP in the astronomy.tools example you’re referring to measures the size of the exit pupil. Confusing, I know. That figure is for a 21mm 40* eyepiece on the 1800mm scope.
 

#10 Echolight

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Posted 01 November 2020 - 04:27 PM

I think until you've been at this game for awhile and have used every type of scope and mount there will always be some second guessing as to what equipment is right for any certain individual.

 

I've had the same feelings about the fat tube SW 80ED. Although I really love using the scope, and appreciate it's slightly longer and more forgiving f7.5 focal ratio. And I got a great deal.

But think if I were buying new, and paying full price, I'd appreciate a more compact form factor and likely order a TS 80 f7 fpl-53 apo with the 2.5 inch r&p geared focuser a la SV80 Access and Zenithstar 81 for a more travel-friendly smallest scope in my arsenal.
Still I'm happy with the performance and ease of use of the SW 80ED. And particularly love it as a widefield scope, as this is where it really shines.

But then I think as a widefield scope that an ST120 must be better. So yeah, a combination of the TS 80 apo and the ST120 would be most ideal.

 

My old used Nexstar 8 that I bought has a similarly very long focusing mechanism and is similarly shaky on that mount. But I have it set up for my AVX now where it is much more stable. Although I'm now finding that for purely visual purposes I greatly prefer a manual mount. And I think the super stable manual mount is a reason, along with pure economics, that an 8 inch dob is nearly unanimously suggested as a beginner scope.

Eventually I'll use the AVX for some long exposure snapshots though. So I'm glad I have it I guess.
 

My 6 inch f8 achro is a sweet scope that's always ready and easy to use. Needs an extra tall extra sturdy mount. But I tell myself that it's combination of aperture, always in collimation, never needs acclimation, and durable closed tube design makes the yard cannon a lifetime scope for me. I'm not bothered by the CA.

Still I'd like a little dob for it's low stable mount and probably easier eyepiece acquisition. Though I know they don't like to be pointed at zenith where I often find myself looking with the refractors.

 

Everything is a compromise.


Edited by Echolight, 01 November 2020 - 04:29 PM.

 

#11 MalVeauX

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Posted 01 November 2020 - 04:58 PM

Heya,

 

Good report, and it really does echo the experiences that almost anyone would have when it comes to attempting with little experience to use a really long focal length visually with minimal sight aids and it exposes just how difficult it is to put even a large object into the FOV of a really tight angle FOV long focal length instrument, with high magnification on top of that. Think of the Mak like a sky microscope. A short refractor will always be easier to use on every subject, especially manually, visually, by anyone from no experience to highly experienced. That said, the 150mm Mak will show off on planets if it's thermally acclimated and the atmospheric seeing is good, and eat the little frac's lunch on planetary resolution; of course, when used with a little experience on putting it on the subject. I say this as the 150mm aperture is just such an advantage (especially if binoviewing!) compared to smaller aperture Maks. The 80mm would be a force to contend with if the Mak were 102mm and 127mm, but 150mm just is too far for the 80mm to reach to, if conditions allow it to show off.

 

Both are great scopes to have and compliment very well together.

 

Another great scope to start with, that will be more like the small short refractor experience, is a 150mm F5 or 150mm F6 newtonian, and they're very inexpensive for what they are:

 

https://agenaastro.c...lector-ota.html

 

Very best,


Edited by MalVeauX, 01 November 2020 - 05:02 PM.

 

#12 Escape Pod

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Posted 01 November 2020 - 05:09 PM

I think until you've been at this game for awhile and have used every type of scope and mount there will always be some second guessing as to what equipment is right for any certain individual.

 

I've had the same feelings about the fat tube SW 80ED. Although I really love using the scope, and appreciate it's slightly longer and more forgiving f7.5 focal ratio. And I got a great deal.

But think if I were buying new, and paying full price, I'd appreciate a more compact form factor and likely order a TS 80 f7 fpl-53 apo with the 2.5 inch r&p geared focuser a la SV80 Access and Zenithstar 81 for a more travel-friendly smallest scope in my arsenal.
Still I'm happy with the performance and ease of use of the SW 80ED. And particularly love it as a widefield scope, as this is where it really shines.

But then I think as a widefield scope that an ST120 must be better. So yeah, a combination of the TS 80 apo and the ST120 would be most ideal.

 

My old used Nexstar 8 that I bought has a similarly very long focusing mechanism and is similarly shaky on that mount. But I have it set up for my AVX now where it is much more stable. Although I'm now finding that for purely visual purposes I greatly prefer a manual mount. And I think the super stable manual mount is a reason, along with pure economics, that an 8 inch dob is nearly unanimously suggested as a beginner scope.

Eventually I'll use the AVX for some long exposure snapshots though. So I'm glad I have it I guess.
 

My 6 inch f8 achro is a sweet scope that's always ready and easy to use. Needs an extra tall extra sturdy mount. But I tell myself that it's combination of aperture, always in collimation, never needs acclimation, and durable closed tube design makes the yard cannon a lifetime scope for me. I'm not bothered by the CA.

Still I'd like a little dob for it's low stable mount and probably easier eyepiece acquisition. Though I know they don't like to be pointed at zenith where I often find myself looking with the refractors.

 

Everything is a compromise.

Great points all around. It’s really too bad that we have so many choices. In photography we call this gear acquisition syndrome (GAS for short). There must be some equivalent in astronomy. Something beyond aperture fever. Where one becomes more a collector than a stargazer. Not that there’s anything wrong with being a collector. But I am fortunate to have the constraints of a 26”x22” box to rein in my impulse to get a 12” Dob. Maybe once we have that farmhouse in the country....

 

Heya,

 

Good report, and it really does echo the experiences that almost anyone would have when it comes to attempting with little experience to use a really long focal length visually with minimal sight aids and it exposes just how difficult it is to put even a large object into the FOV of a really tight angle FOV long focal length instrument, with high magnification on top of that. Think of the Mak like a sky microscope. A short refractor will always be easier to use on every subject, especially manually, visually, by anyone from no experience to highly experienced. That said, the 150mm Mak will show off on planets if it's thermally acclimated and the atmospheric seeing is good, and eat the little frac's lunch on planetary resolution; of course, when used with a little experience on putting it on the subject. I say this as the 150mm aperture is just such an advantage (especially if binoviewing!) compared to smaller aperture Maks. The 80mm would be a force to contend with if the Mak were 102mm and 127mm, but 150mm just is too far for the 80mm to reach to, if conditions allow it to show off.

 

Both are great scopes to have and compliment very well together.

 

Very best,

That’s really exciting, Marty. I’m really looking forward to spending more time with the Mak and getting to a place where I can experience what you have seen. 
 

Do you agree with CSRLice12 that a RACI finder is a must for the Mak? Or do I need to pop in my 38mm 2” and practice my panning?


 

#13 MalVeauX

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Posted 01 November 2020 - 05:15 PM

 

That’s really exciting, Marty. I’m really looking forward to spending more time with the Mak and getting to a place where I can experience what you have seen. 
 

Do you agree with CSRLice12 that a RACI finder is a must for the Mak? Or do I need to pop in my 38mm 2” and practice my panning?

I use a 50mm RACI on my Mak as well, when I'm only using the Mak. I usually have both a refractor and a Mak side by side on my mount(s) and they're aligned though (no finder needed, the refractor is the finder in my case typically). That said, I often move between an ED80 or a 120mm F5 refractor for the wide field. I prefer a 50mm RACI on the Mak though on its own simply because the RACI is a 50mm little refractor that gives a lovely wide FOV that is just like having a little refractor, you can see a great wide field of rich stars and locate objects quickly but while still getting an appreciable view while you're at it. The 50mm RACI is also a good viewing device (I removed the cross hairs from mine, so its a clear unobstructed view). If you align your RACI to your Mak, it will dead center a subject in either. So it's nice to get something dead center in the RACI and then when you view through your Mak, it's there in the middle pretty closely which is great. I don't have to pan and hunt around with the Mak unless I just feel like cruising with it. I use a 7~21mm zoom in my Mak, so my minimum magnification is pretty high already and using a big 2" eyepiece with wide FOV really won't help anything on a Mak, or any long focal-length instrument, as it will always induce high magnification. But I prefer a RACI over red dot, telrad, etc, on the Mak because again it compliments it by giving you a wide FOV that is from a 50mm aperture, much brighter than your naked eyes, which gives you another great view to enjoy on large subjects. A 50mm RAC is like having a little refractor side by side with your Mak. Great compliment. And if you want to go beyond the RACI, just get a ST80 or 60mm refractor with a diagonal and wide eyepiece and strap it piggy back to your Mak and truly have both.

 

Very best,


Edited by MalVeauX, 01 November 2020 - 05:16 PM.

 

#14 kjkrum

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Posted 01 November 2020 - 06:15 PM

Just a quick take on your first post. One thing I like about my MK67 is the built in carry handle. It helps a lot with getting it on the mount. If yours is in rings, you might consider adding a top rail. Even a single ring with a large cabinet knob might be nice. As for the limits of exit pupil, that depends on your eyes. For me, 1 mm is comfortable. I start to see a lot of floaties with a 2/3 mm ep, and 1/2 mm is unusable. Some eyepieces that work well on planets exhibit blackouts and kidney beaning on the moon.
 

#15 elwaine

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Posted 01 November 2020 - 06:15 PM

Loved reading your report and will definitely follow your progress. (You write well. It was like reading a good book.)

 

A few points I'd like to mention based on my experience with refractors from 60mm to 130mm and Maks from 90mm to 203mm. First and foremost, take a critical look at your mount and tripod. I'm not familiar with the StarSeeker Alt-Az mount, but I know what it means to under-mount a telescope. The StarSeeker ad indicates it has a payload capacity of 13 lb. Telescope companies are notorious for overstating the carrying capacity of their tripods and mounts. The real (practical) carrying capacity of your StarSeeker is closer to 8 lb. for visual astronomy and 6 lb for astrophotography. Your mount should work quite well with the 80mm refractor, but it is too small for the Mak, which weighs about 12 lb. without a diagonal or an eyepiece.

 

I'm not saying you absolutely cannot use your mount with your Mak. Of course you can (and did). But every time you touch the Mak's focuser the telescope is going to giggle for quite a while until it settles down. That makes focussing a real chore. I'd bet that it's not the Mak's focuser that was giving you trouble. It was the small mount and tripod. The reason the Crayford focuser was so much easier to use on the 80mm Frac is because that telescope works well with your tripod and mount.

 

And the same giggling will happen with the Mak if your eye touches the eyepiece. And if any wind stronger than a very slight breeze comes up, you won't be able to use your Mak on the StarSeeker. 


Edited by elwaine, 01 November 2020 - 06:18 PM.

 

#16 elwaine

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Posted 01 November 2020 - 07:13 PM

 What I did notice was that the refractor could go almost toe-to-toe with the Mak when it comes to magnification on the lunar surface.

 

Not surprising. But at the same magnification, the views will be about 3.5 times brighter in the Mak, and it is easier to see subtle details that are bright compared to the same details that appear dim. That's usually not a problem when viewing an object like the Moon, because the Moon is so bright. Regardless, magnification isn't the name of the game.

 

The name of the game is resolution; i.e., how much detail can you see? You will be able to see more details on the Moon, and on the planets, using a 150mm Mak than you will be able to see using an 80mm refractor. Resolution, like light gathering ability, is a function of aperture. But the differences in resolving power between an 80mm refractor and a 150mm Mak won't pop out at you. You will have to look for them. 

 

For example, with your naked eye, the smallest feature you will be able to resolve on the Moon will have a diameter of approximately 60 miles across. The smallest feature you can resolve using your 80mm refractor will have a diameter of about 3.5 miles across. That's quite a big difference, and that's what gives us the WOW factor looking through a telescope. The Mak, on the other hand, will be able to resolve individual features on the Moon having a diameter as small as about 1.8 miles across: certainly no where as dramatic as the comparison between the naked eye view and the 80mm refractor view. 

 

I agree with others who wrote that your two telescopes compliment each other quite nicely. All you need is a mount and tripod upgrade. (Sometimes just getting a beefier tripod and keeping the mount will result in enough improvement to make you happy with the Mak, but there is no substitute for a sturdy platform on which to mount your telescopes.)


 

#17 GeoffC47

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Posted 01 November 2020 - 07:55 PM

Nice writeup, Don, and an *engaging* read!!  For a beginner, you are certainly well along, much farther than me!!  Look forward to the next report. 


 

#18 Escape Pod

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Posted 01 November 2020 - 11:50 PM

Thanks for the kind words and comments, everyone.

 

Larry and Marty, you’ve definitely got me fired up to learn how to use the Mak. The optics lessons were really clear and useful. Your experience is much appreciated.
 

Larry, your insight that my Mak is under-mounted is an excellent one. I had noticed that weight issue before purchase, but decided to cross my fingers and hope that Orion knew what they were doing. Then I get into the field and figure I must be doing something wrong, or that the tube is an inferior design. But I think your explanation is closest to Occam’s razor. For now, at least,  I may experiment with lowering the tripod legs and modifying the focus knob as was suggested in another thread.

 

Clear skies and stay tuned for second light once I can get these scopes under some dark sky!

 

Best,

 

Don

 

 

 

 


 

#19 Escape Pod

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Posted 10 November 2020 - 03:08 PM

SECOND LIGHT

 

To distract ourselves from current events, last Weds my wife and I headed south to Ohio's Hocking Hills for a bit of camping and to try out the John Glenn Astronomical Park. Nominally a Bortle 3, someone with more experience than me assured me that it was at best a Bortle 4. Either way, a massive improvement from what we have around Columbus.

 

Eagerly racing off to the Astropark after a wolfed-down dinner on Wednesday night, I had a solid hour or so before the moon broke the horizon. Here was my chance to finally see enough stars to get the mount aligned and test out the two scopes on DSOs.

 

I had read the Turn Left at Orion section for October - December. I had jotted down several of the objects they recommended. I had further scoured Facebook astronomy groups for many more targets still. All in all, I had about a dozen DSOs that I was planning on seeing in that hour. Maybe I would cheat and use the GoTo, even though I had promised myself that I would restrict my target finding to star hopping and only use the mount for tracking them once I had them.

 

(Un)Fortunately, the mount did not cooperate. 

 

Lesson: I can't align a GoTo mount to save my life. But hey, now I know how to find Andromeda "by hand."

 

I mounted the 80mm refractor first, as I was going to be starting with widefield objects before pivoting to clusters and doubles that should favor the Mak.

 

I performed the recommended two-star alignment, or so I thought. I selected two planets for my bright stars as, even with the help of SkySafari, my constellation/star spotting knowledge is still weak. I used the mobile app rather than the hand controller so my phone could provide the mount with latitude and longitude. Mars was to the south, meanwhile Jupiter was setting to the west. Easy peasy. Time to go hunting for DSOs. 

 

The first target on my (laughably ambitious) SkySafari observation list was the North American Nebula. Way up towards the zenith, I thought this would be a perfect time to try and make out a nebula through the eyepiece. I hopped over to SkySafari, connected to the mount, selected NGC 7000, and hit GoTo. Sure enough, the telescope pointed straight up towards the zenith. So far up that I regretted not lengthening the legs of the tripod enough. I took my jacket off and used it as a seat cushion. Still hunched over, I leaned into the eyepiece and saw......just a bunch of stars. Hmm, I thought. Must need a nebula filter for this one. (Subsequent reading confirms this). 

 

I then told the scope to point to M31. Immediately I knew something was wrong. The mount swung the scope halfway across the sky and down to the horizon. Even my untrained eyes could see that this is not where Pegasus and Andromeda lived. "I'm losing dark sky time," I thought. We'll do this the old fashioned way.

 

First I reached for the well-regarded Pocket Sky Atlas . I must say that it did not immediately suggest to me how to go about star hopping. First of all, I had difficulty making out the box that is Pegasus. I tried using the planisphere, but here again I couldn't be sure what I was seeing. I was pointed south, and my only frame of reference--Polaris--was of no use. Feeling pressed for time, I quickly abandoned my analog charts and fired up SkySafari again. Here I could see that at this moment Mars was directly south of Algenib. Now I had Pegasus. So now I had a star-hopper's chance. 

 

I loosened the clutch and manually swung the telescope over to Mars and up to Alpheratz. From there I hopped along until the second star along Andromeda's northern leg, panned up, and.... hey, look at that faint fuzzy! It was quite faint, baring little resemblance to the image in Astronomy.Tools that suggested it  would barely fit in my Agena 2" 38mm FOV.  This  thing was much smaller in the eyepiece. Switching to the 30mm eyepiece, the Andromeda galaxy was just slightly larger but still quite faint and fuzzy. 

 

astronomy_tools_fov-7.jpg

 

Realizing I was not going to be able to move through my list of winter DSOs before the moon rose, I decided to swap out the 80mm Frac for the 150mm Mak. After re-centering on M31, I thought I was able to make out a bit more faint fuzzy where M32 should be that I didn't see in the Frac. But to my very untrained eye (more on this below), the visual impression M31 made was quite similar between the two scopes. Certainly a remarkable performance for a refractor with nearly half the aperture of the Mak. But then again, not a fraction of the exhilaration I felt when studying the moon for the first time. All the things they always say about rookie astronomers were coming true for me. 

 

This was the source of another lesson. 

 

Lesson: For visual astronomy to be engaging, at least with this level of equipment, it requires both practice, imagination, and maybe a good dose of astro-knowledge. 

 

Following a brief but failed attempt to locate the next object on my list, Gamma Cassiopeiae Nubulae, my wife joined me. I swung back to M31, positioned her in front of the eyepiece, and asked her with more than a bit of sarcasm if she was ready to see the massive, spiraling galaxy next door. Pressing her eye to the telescope, her reaction was a predictable "hmm, oh yeah." After studying it for a minute she stepped back and probed, "How's it going? Is this what you expected to be able to see?"

 

In the moment I apologetically muttered something about maybe trying out Electronically Assisted Astronomy. Later, I even  looked into a couple of tools to achieve live stacking without hauling a computer into the field. Indeed, I found a couple promising avenues there: MallinCam through a monitor, or the ZWO ASIAIR PRO and an astrocam all controlled and viewed through an iPad. This could be really cool.

 

But immediately I sense the welling up of Gear Acquisition Syndrome (GAS), an affliction that I see in far too many of my brothers and sisters in photography. I've reached a good place with controlling GAS in that arena. But I could feel it creeping up on me here in my new hobby. And I didn't like that feeling. 

 

So rather than racing out to buy $500 in Astrophotography gear, which would've gotten me divorced anyways, I raced out to research and buy $50 worth of astronomy books. My hope here is to deepen my understanding of the cosmos and, in doing so, hopefully improve my ability to imagine and comprehend what I am seeing through my eyepieces. 

 

The first book I selected, SpaceTimeInfinity, talks about the long historical journey from our earliest understanding of the cosmos up through today. It is stuffed with beautiful photos and artwork. And at first glance, it appears to be very well written.  I hope it helps me feel connected to those who've came before, as well as appreciate how amazing an intermediate-level telescope of today is compared to many of the early instruments Astronomers wielded. 

 

F15A25D4-BA9E-4D8F-86EF-82ADE17FAB77.jpeg
57129BC3-0766-4B2F-911E-B5AB00E2E219.jpeg

 

The second book, The Stars, promises a constellation-based tour of DSOs as they appear to us in the night sky, as well as some introductory sections that help me understand how they're actually spread out in the universe. As I move through the constellations of the winter sky in coming months, I hope this will help me see what my eyes can't see through the eyepiece. And with the spatial maps, combined with an app called Our Galaxy, I hope to comprehend a small piece of where a given object fits into the incomprehensible expanse of our universe. 

 

A9C004A2-C1BC-4C23-AE3A-EA6D801E324A.jpeg

2D27B841-110E-4A01-9AE5-8E6F5275526C.jpeg

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Now if I can convince my wife to let me drag these ginormous books along with the two telescope cases, mount and all the other trimmings that I've acquired for our trip to the dark skies of Big Bend at the end of the month!

 

(and MAYBE a simplified all-manual Alt-Az mount laugh.gif)


Edited by Escape Pod, 10 November 2020 - 05:03 PM.

 

#20 Eddgie

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Posted 11 November 2020 - 09:29 AM

The North American Nebula is probably best using the naked eye and a nebula filter under Bortle 2 or 1 skies.

 

Aperture does not make extended targets like M31 brighter.  What makes galaxies brighter is exit pupil.  If you use the same exit pupil on the MCT.  Lets say you used 75x in both scopes.  Because the exit pupil in the larger scope is now bigger, it will show things brighter.  You can't compare the power, you have to compare the exit pupil.

 

And while you were at M31, you really should have tried one of the companion galaxies.  Both are easy to find and these would have been better for the MCT because you would have gotten a brighter image at the same image scale or a larger image at the same exit pupil.

 

A note though.  Refractors are more efficient with transmission so at the exact same exit pupil it might be a tiny tiny bit dimmer, but this is is easy to fix by using a tiny tiny tiny bit lower power.

 

In case you are not famaliar with exit pupil, if you use a 32mm Plossl in both scopes, the power would be 18.75x and the exit pupil in you 80mm ED would be 4.26mm but in the MCT, that same eyepiece would give 56x and the exit pupil would be 2.67mm.  That would mean a huge difference in brightness with the 80mm having a huge advantage.

 

But here is the problem with the MCT.  You can never get as big of an exit pupil with the MCT as you can get with the 80mm.

 

And here is the problem with the 80mm. When you are viewing things like the Ring Nebula at 100x when using both scopes, the ring will be much brighter in the MCT than in the 80mm, because at 100x, the exit pupil will be much bigger in the larger scope at the same power.

And last, you will hear people say that you should be able to use 50x per inch of aperture. I would take that figure with a grain of salt. On extended subjects with low contrast, you may find your best view is at considerably lower power than 50x per inch.  This is because as the exit pupil gets smaller and the image gets dimmer, you reduce brightness on the fovea of the retina, and the fovea is where the cones are.   The cones give you far better resolution than the rods but they take more light over a given area to see the same brightness.  The more you magnify the image, the fewer photos that hit the cones, and the lower your contrast sensitivity becomes.  So, the power you can use will vary considerably by the contrast of the detail you are trying to see.  The Cassini Division is a very high contrast detail (as planetary detail goes) and can be seen at high powers in even small telescopes.  Festoons on Jupiter are very low contrast detail and are best seen using lower powers than would be possible on Cassini Division.   Shadow Transits of the Jovian moons are high contrast detail and can be easily seen in small telescopes at high power, but the belt structure on Saturn is rich in subtle shading and will be much better at lower powers in the larger scope.  The lunar surface has amazing high contrast shadow detail, but craterlets in Plato are small with small shadows and these can blur out with excessive magnification.  And this is one of the reasons why telescopes require different eyepieces.  By the way, I recommend a good zoom for planetary work in your MCT because it makes it easy to tell when you have the right magnification.  

 

You will learn these things but just like with bowling, you don't throw a perfect curve on your first roll.  You have to learn how to do it.

 

My advice is to study up on how exit pupil works for extended subjects.   


 

#21 Escape Pod

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Posted 11 November 2020 - 10:56 AM

Eddgie, I cannot thank you enough for this thoughtful reply. 

 

Others here introduced me to the concept of exit pupil and how it impacts things like viewing with an OIII filter or the maximum AFOV I can achieve with my Mak. But I hadn't realized what its full implications are for tackling the faint fuzzies. Your post moves me much further in the right direction. 

 

So for a given eyepiece (e.g. 38mm), the 80mm refractor will offer a larger exit pupil (EP). 

 

astronomy_tools_fov-10.jpg

 

But for a given magnification (~47x), the 150mm Mak (fitted with a 38mm eyepiece) will offer a larger exit pupil than the 80mm Frac (fitted with a ~13mm eyepiece). 

 

astronomy_tools_fov-11.jpg

 

And the larger exit pupil will show a brighter (more pleasing?) image up until the limits of our own pupil size? And as we approach that limit, averted viewing becomes more effective? Or am I confounding the optics of our eyes with exit pupil size?

 

 

Either way, I think I understand what I need to be thinking about next time I'm at the proverbial bowling alley in the sky:). Thanks again, Eddgie.

 

EDIT: One last question. Practically speaking, if we're observing nebulae with the assistance of a filter (I just picked up a used DGM NPB 2" from our classifieds section) do we generally want the largest exit pupil possible so that the brightness compensates for the dimming effect of the filter? Is that why folks say that the OIII wants larger exit pupil size?


Edited by Escape Pod, 11 November 2020 - 11:02 AM.

 

#22 Asbytec

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Posted 14 November 2020 - 05:30 PM

I paid some attention to your experience with the Mak because my Orion 150 became my longest owned and most used scope ever. Specifically for lunar and planetary and even some double star observations. It became my poor man's Questar.

Maks need a little TLC and preparation for high res observing. They need to be thermally stable and well collimated to work best, especially when seeing and observing conditions or dark skies permit. I tended to use mine in the higher magnification realm, say 300x on the Ring Nebula. It's not a wide field scope like the ED80.

It's not as easy as point and shoot, either. It does take some familiarity on the part of the observer. As does eeking out fine planetary detail. Observing is not only about the equipment. Scopes don't observe anything, we do. It will come. When both the scope and the observer are prepped, the Mak can take whatever you can throw at it.

 

Through my Mak at the appropriate magnification, prepped for observing, I have seen detail in the Martian polar caps, albedo features on Ganymede (including two craters as bright specks), craters less than a mile in diameter (7 craterlets of the Plato challenge), and the apparent elongation of Io (compared to the circular disc of Europa). Not bad for a 5.9" aperture. 

 

And Jove at 240x near the zenith a few years ago. The sketch is somewhat embellished in terms of contrast and hue so you don't have to work as hard as I did. But, it's all there. 

 

Jupiter 22 Dec 1600UT draft.jpg


Edited by Asbytec, 14 November 2020 - 06:01 PM.

 

#23 KBHornblower

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Posted 14 November 2020 - 08:48 PM

snip...

 

A note though.  Refractors are more efficient with transmission so at the exact same exit pupil it might be a tiny tiny bit dimmer, but this is is easy to fix by using a tiny tiny tiny bit lower power.

 

 

That's interesting.  I would expect the refractor to be a bit brighter.


 

#24 Asbytec

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Posted 14 November 2020 - 11:29 PM

That's interesting.  I would expect the refractor to be a bit brighter.

I think that is what he meant. I believe refractors can stand slightly smaller exit pupils. How much is anyone's guess. My guess is the (proportional?) obstruction shading,.i.e, the clear aperture, and throughput do play a role in the final image brightness. Maybe even our own acuity, earned or otherwise, makes a difference. 


Edited by Asbytec, 15 November 2020 - 12:20 AM.

 

#25 KBHornblower

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Posted 15 November 2020 - 02:50 PM

I think that is what he meant. I believe refractors can stand slightly smaller exit pupils. How much is anyone's guess. My guess is the (proportional?) obstruction shading,.i.e, the clear aperture, and throughput do play a role in the final image brightness. Maybe even our own acuity, earned or otherwise, makes a difference. 

My bold.  A telescope is an inanimate object that does not feel anything to do with the exit pupil.  My eyes are the components that stand a range of exit pupil size.  At 1mm or smaller I sometimes see floaters, and coincidentally I am getting into the realm of empty magnification of a planet, as the diffraction pattern is becoming apparent.  At 2mm or larger I start needing my glasses to correct my own astigmatism.  At 6mm or larger my eye pupil starts restricting the effective aperture.  That is a hard maximum for me because that is the size of my lens implants from my cataract surgery.


 


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