22 replies to this topic

[drneilmb]

I bought an ST80 (okay, a Meade Adventurer 80) for under $100 new and I love it for quick nights on a homemade wooden tripod and pipe mount or on a nice old photo tripod (bought used here for $70) when camping.

The only thing that it doesn't do splendidly is high-magnification for moon and planets. My shortest eyepiece is a 5mm for 80x at 1mm exit pupil and I know from my bigger dobs that the moon and jupiter are much more impressive at 120-150x. Since that's often what I want to show people at a campground or party, I wonder if there's an inexpensive grab-and-go alternative for bright objects like the moon, Jupiter, Mizar/Alcor, M42, etc.?

I know it'll have narrow FOV, but as long as I can get the whole moon in the widest FOV and aim it with a red dot sight, I'll be happy. Will it need an eq. mount to be usable? Am I misunderstanding exit pupil and I should just get a 3.2mm or 2.5mm eyepiece and have the same performance as something with a longer focal length? I know people here rave about their long old refractors or their tiny little Cassegrains, but do they have some inherent advantage? Maybe a used C90?

Sorry I can't be more clear on this question, I fear that I am muddling what little I've learned in my two years in the hobby. Thanks for any advice you can offer.

-Neil

[Jim1804]

A C90. The combo of a ST80 (also the Meade model) and a C90 gets most of my G&G use. For the most part they can ride on the same tripod - I use a Twilight 1, which to be honest is overkill. If I’m going DSO or just scanning, it’s the ST80. For the moon or planets, it’s the C90 - a great combination! Check out the storied “Something for Nothing” thread if you need more convincing.

The weather last summer was so bad, if it weren’t for the C90, I wouldn’t have seen much of the “Summer of planets”.

[Jim1804]

And the moon is spectacular in a C90. Get one of the new models, though - the older orange models are hit or miss as far as I understand (although they have a big following).

[GoFish]

6” f/5 Newt. 150x at 1mm exit pupil, 5mm EP

 

5” SCT f/10. 125x at 1mm exit pupil. 10mm EP. 

 

ST120 f/5. 120x at 1mm exit pupil. 5mm EP. 

 

Many folks seem comfortable with dropping below 1mm pupil with an apo refractor on a steady night. Just doesn’t work for me, though. 

 

I have a 6” Omni XLT Newt that I like for EAA. I think it may also make a good GnG with a Porta II mount? Looking forward to trying it out later in the summer. 

[John Rogers]

You might want to check out a Meade ETX90.  I recently picked up one up from shopgoodwill.com for under $80 delivered (non-computerized 1st generation.)  I was pleasantly surprised with the performance on the Moon and planets.  Given its 1250mm focal length, it is 3x your ST80, so gives you greater magnification from the get-go.

 

I have an old Edmund 4mm Orthoscopic that I purchased new over 40 years ago.  It never performed well in any of my telescopes, so it has been relegated as a dust cover for many years.  For kicks, I dropped it in the ETX90 and was pleasantly surprised at the nice views it produced, especially during moments of good seeing.  It is now part of the eyepieces stored with the ETX90.

[Mitrovarr]

You could get a C6. I know, it sounds large, but it's a scope you can easily hold in one hand. A lot of the small mounts can carry it. And it's still 6" of aperture, even if it's a pretty small and light scope.

 

Someone up above mentioned a ST120 - that's a fine grab and go scope for wide fields, but you really don't want that one for the moon and planets. Too much chromatic aberration, even if you can tolerate some.

Edited by Mitrovarr, 24 June 2019 - 11:36 PM.

[BFaucett]

A C90. The combo of a ST80 (also the Meade model) and a C90 gets most of my G&G use. For the most part they can ride on the same tripod - I use a Twilight 1, which to be honest is overkill. If I’m going DSO or just scanning, it’s the ST80. For the moon or planets, it’s the C90 - a great combination! Check out the storied “Something for Nothing” thread if you need more convincing.

The weather last summer was so bad, if it weren’t for the C90, I wouldn’t have seen much of the “Summer of planets”.

 

+1 on the ST80 (whatever brand) and the C90 Mak combination.    Two relatively inexpensive scopes that compliment each other very well, IMHO.  That “Something for Nothing” thread is what convinced me to buy the C90 Mak.  I love my little Meade AS80 and Celestron C90 Mak. 

 

(The tripod/mount shown in photos is the one that came with my Celestron Omni XLT AZ 102 f/6.5 achromat.  The tripod actually works very well with the AS80 and the C90.  My C102AZ now rides on a Vixen Porta II.)

 

Cheers!  Bob F.  

 

 

Edited by BFaucett, 25 June 2019 - 12:05 AM.

[tony_spina]

The ST80 and the C90 or 102 Mak make a great grab and go combo.  I just picked up a used Orion102 Mak for $100 in great condition 

[Mitrovarr]

Yeah you can often find 102 and 125mm maksutovs for ~200 used if you look. Also a good choice. The C90 is inexpensive and feels like a quality instrument but I found it was a little bit low on aperture for what I wanted it for.

[petert913]

Yup.... small Mak is the answer

[Redbetter]

A ~100mm Mak sounds like what you are after.  I don't have one, so that is not a first hand recommendation.  It is based on what I have seen with a ES 127 Mak (which is a clone of the Meade 125 ETX but with a better backplate than the old Meade.)  The 127 is small but still probably somewhat larger than what you are seeking.

 

My suggestion in selecting a Mak would be to make sure it is one that can be easily collimated and that does not have flip mirrors or a back plate assembly that prevent easy access to the collimation screws.  Flip mirrors can present their own problems from what I have read of others.  Hopefully you will only need to collimate the OTA initially, but expect to need to fine tune the collimation before it puts up its sharpest views.  Disregard claims that Maks never need collimation, while that can be true if it happens to arrive perfectly collimated or if the observer is insensitive to a softer/less detailed planetary view, from what I saw with mine the view was pretty poor until I collimated it.  I would have shipped mine back immediately if I had not been able to figure out how to collimate it (there were no instructions of course.) 

[sg6]

Unless the mount tracks then 120-150 will have you at the eyepiece more then half the time recentering the planet. Seen it too often where it is literally operator once, observers twice (if quick), then recenter and go around the loop infinitely or until you run out of people.

 

At 120 you have 0.5 degree field, center to edge is therefore 0.25 degrees. So target is in view for 1 minute before it is out of view. So in that 1 minute window you have to jump in, take over and recenter the scope. Not a lot of time for the people to look, and in a way a poor impression.

 

For what sounds like outreach and people forget the astronomers idea that more magnification is better. In a way you are not observing, you are presenting. Different ball game.

 

Explain that you are using a lower magnification to make the viewing easier and less problematic because the image drifts across the view and off the edge faster with higher magnification. People like that, it gives them information and greater insight.

 

Concerning a shorter eyepiece, similar/worse problem with field and you will need a good scope. My 3.2mm is useless in my small 70mm f/5 achro. It does work well on the 60mm f/6 ED.

 

Never worked out why a small Mak is the "ideal" G&G scope. I have one, ETX-105. Never use the thing - either for myself or at outreach. OK did once = disaster   Too much trouble, not easy. And it tracks, still a pain.

[HellsKitchen]

I think it would be hard to go wrong with a 130mm F/5 newtonian. It'll do moon/planets very nicely as well as wide field. You can consider it the "jack of all trades". They are lightweight so a Porta 2 or GSO Skyview/AT Voyager type mount will hold them no worries. You'll be able to carry it outside fully assembled and I suspect cooldown will be quicker than a small mak owing to the open tube.  

 

A 90 or 102mm Mak will do planetary/ lunar well, and they are super compact and light, but they lack the wide field capabilites of the small newt and still need to cool down. To me, the small newt just makes more sense, it'll do planetary just as good as the small Mak, while offering the benefit of wide field DSO viewing aswell - the latter being a particularly useful attribute if you intend to show off DSOs to the public -  all in a larger aperture. The only genuine advantage I can see for the Mak is that they just about fit in your back pocket.

[Bowlerhat]

+1 for c90, it's really compact in size so it's comparable to ST80. Also, it can be a bit more versatile as it can be used for DSO hunting providing you have enough dark sky..

[Redbetter]

Unless the mount tracks then 120-150 will have you at the eyepiece more then half the time recentering the planet. Seen it too often where it is literally operator once, observers twice (if quick), then recenter and go around the loop infinitely or until you run out of people.

 

At 120 you have 0.5 degree field, center to edge is therefore 0.25 degrees. So target is in view for 1 minute before it is out of view. So in that 1 minute window you have to jump in, take over and recenter the scope. Not a lot of time for the people to look, and in a way a poor impression.

 

For what sounds like outreach and people forget the astronomers idea that more magnification is better. In a way you are not observing, you are presenting. Different ball game.

 

Explain that you are using a lower magnification to make the viewing easier and less problematic because the image drifts across the view and off the edge faster with higher magnification. People like that, it gives them information and greater insight.

 

Concerning a shorter eyepiece, similar/worse problem with field and you will need a good scope. My 3.2mm is useless in my small 70mm f/5 achro. It does work well on the 60mm f/6 ED.

 

Never worked out why a small Mak is the "ideal" G&G scope. I have one, ETX-105. Never use the thing - either for myself or at outreach. OK did once = disaster   Too much trouble, not easy. And it tracks, still a pain.

The OP didn't indicate that the crowds would be large, so I doubt re-centering would be much of an issue.  With small groups things are much easier.  And with a mount with any sort of slow motion controls looking at a planet (which is on more horizontal path anyway) it really shouldn't even require the operator to be at the eyepiece to track.  Then again as far as re-centering, I have handled crowds with hundreds doing manual tracking at over 200x with a 20"...and requiring a trip up a short ladder for DSO's.  And I encourage them to focus as well.  120x would be an eternity by comparison...  The most common comments are "Oh wow!" and "Oh my God!" so it seems to give a good impression of the targets.

 

The only time I use low powers like you suggest for outreach on planets is when the seeing is particularly unstable.  I typically don't go below 4" for outreach and that is part of why higher powers are useful, but the other aspect is that people's visual acuity is not that great on average, so having some scale helps. 

 

A 4" Mak on a tracking mount would be a cake walk for this sort of thing precisely because fairly pedestrian magnifications will still provide a bright enough image and resolution without being overly sensitive to seeing.  The other primary competition would be from small SCT's.  Either way I would probably go simple alt az if I was trying to minimize the size of what I needed to transport.

 

While I don't consider the Mak an ideal grab-n-go for various reasons, however, the scenario the OP described is not really simple grab-n-go or do-it-all.  It is more of one of needing a small package to be used for travel, but not necessarily immediate set up and service (such as quick looks in the yard), it is most likely for mild/warm weather, and for one that can do planets well with little concern about DSO's except the brightest.  If the OP wants to use even lower powers than 120x with it, there is no obstacle to do doing; but unlike the 80 f/5 achro it should be able to handle 100 to 150x well for planets.  I doubt cool down is likely to be a concern for this sort of scenario. 

 

I am wondering what you consider a good fit for the OP's scenario?  What sort of OTA do you see providing the combination of small form factor and good planetary images? 

[drneilmb]

Thanks everyone for the suggestions. I'll keep a C90 or ETX90 or 102 Mak on my radar on the classifieds.

 

I'm also working on an 8" travel dob that will be quite compact and grab-and-go, so I'm limited in my will to move up to something like a 5" or 6" newt. It's possible that a 4" cat won't win the portability contest compared to the 8" porta-dob, but that remains to be seen. That one has 1200mm of focal length, so the 120x-150x range is easy too.

 

What's Jon Isaac's line? "The best 6" f/8 is an 8" f/6"?

 

-Neil

[Thrifty1]

Love my ETX-105 for my grab and go scope to view the moon and planets. Easy to throw in the car and set up. I only use my 10” LX200R at home - too much work to break down, transport, and set up.

[JGass]

Amazon has the Nexstar 127 SLT for $430.

The extra aperture means more useful for small DSOs, like planetary neb. Would give you tracking, which is a big plus when pushing some magnification to tease out details of the planets in moments of good seeing.

The go to can get you to targets more quickly, meaning more targets viewed in a session.

[treadmarks]

I've been using a 102mm Mak for this purpose - cheap grab-and-go for solar system. On most nights, it is seeing limited. A couple nights ago I used it on Jupiter in poor seeing - magnifications less than 150X. Well, actually it seemed like good seeing because the night before I could barely manage 100X.

 

Anyway, I was able to see the GRS clearly, some structure in the equatorial belts, and vague hints of polar bands. In good seeing, all of those things are defined pretty sharply, and 200X is possible.

[clearwaterdave]

AWB Onesky.,130mm newtie,..tabletopper.,Check out the mile long thread in the beginners forum.,good luck with your choice.,

 

Mine with tweeks.,

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[Traveler]

-1 C90/ETX90.

 

In stead, think about a C5 or C6. They are a more substantional step on Moon and planets. A C6 however is here in Europe a little expensive. For a little more money, one could buy a C8....

Speaking about a C8  , it is also a great G&G scope on a Alt/Az mount...

[Eddgie]

If you really want to use powers up to 150x and a big part of your desire is to share the view, go as big as you can.  A 100mm MCT at 150x will have a pretty small exit pupil and a pretty dim image, and many of your guests will probably struggle with floaters (and of course you may too, but if you have not had this problem with your current scope, probably not).

 

If you can find a used one, my top recommendation would be an Intes Micro MN56.  This is not as compact as a small SCT or MCT, but it will run rings around them on planets, and will give excellent views of many wide field deep sky objects.  While you might not see one for sale, a classified wanted ad and some patience will probably turn one up.

 

And I promise you that nothing else mentioned here will produce a result nearly as good as the MN56, though it is heavier than anything else mentioned here and it is about as big as you can use on most light mounts but I would not recommend forcing your guests to have to focus a telescope on a shaky mount at 150x. 

 

And don't worry about the focal lenght of the eyepiece.  That is what Barlows are for.  An expensive wide field eyepiece with big eye relief is really not going to do any better than an inexpensive Plossl with a Barlow.  My own top recommendation would be to get a Hyperion Zoom and the Barlow for it.   There is nothing that says Grab and Go like a good zoom eyepiece. 

[IslandMusic]

Hi!

 

First post here but a long time reader.  When Celestron cleared out their 80mmED through Astronomers without Borders I bought one to use as a spotting scope for the rifle range.  I was very pleasantly surprised at its contrast and sharpness.  It's longer than the ST 80s but it's a real nice instrument.  If you could find one gently used it would be a good addition to your inventory.  It was originally a $500 scope.  It doesn't mind cranking the power up and has a FL of 600 mm.  The focuser takes 2" EPs and it came with a 1.25" adapter.

 

David

Edited by IslandMusic, 30 June 2019 - 05:44 PM.