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8" SCT for a grab and go setup

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#1 Michael11

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Posted 29 November 2019 - 09:07 AM

Hi all

I'm considering to replace my 80mm ED with a 8" Meade or Celestron SCT as a grab and go setup, and trying to figure out a few things.

 

Can I fit a 8" SCT in on my Vixen porta 2 mount? Or should I consider a single fork solution like Nextstar ?

 

Is it worth investing in a corrected design like ACF? On-axis performance is more important for me, but I wouldn't like to have more coma than in a F/5 Newtonian (assuming same FOV of 1.2°)

 

I'll probably want to add an external low profile focuser and a 2" diagonal - is there any difference between Meade and Celestron models for this modification?

 

What is a faster setup in terms of setup time and amount to things to carry - a 8" SCT on an alt-az mount, or a simple  8" collapsible dobsonian? 

 

Is it possible to travel with a 8" SCT in carry in luggage?


Edited by Michael11, 29 November 2019 - 09:11 AM.


#2 whizbang

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Posted 29 November 2019 - 10:23 AM

Define "GO".  I consider my EVO 8 my real scope.  The 127mm Mak on the SE mount is my grab n go.  Personally, I would not take an 8 inch on an airplane.

 

I was looking at either Twilight 1 or Porta mount for my Mak.  I ended up with a GOTO SE mount.  I can still star hop with the arrow buttons, or, use the GOTO in light polluted areas.

 

The DOB is a much faster setup.  Plunk down the base.  Set the tube on it and start viewing.  A SCT or MAK on a tripod is a little more time consuming, but goes fast enough once you get the hang of it.  Stringing dew heaters and such in cold damp weather doubles the set-up time.


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#3 treadmarks

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Posted 29 November 2019 - 10:42 AM

Hello, I have a grab-and-go mount for my C8. I can recommend the VersaGo II for the C8. The VersaGo II weighs only 13 lbs and it handles the C8 very nicely. Just remember to always mount it "high" (pushed forward) for balance reasons. Most of the weight of the C8 is at the bottom of the scope because of the mirror. I mainly opt for the VersaGo II when I'm doing planets and don't need to use my Nexstar to find DSO, although the VersaGo II does have setting circles.

 

Can't speak to differences between Meade and Celestron, but as to your other questions... If you are able to leave the C8 put together on the mount and carry it around as a unit, which should also be possible with an 8" Dob, their setup time would be the same of course. Ideally, either of these would be stored in an unheated garage which also helps with the cool down issue.

 

The setup steps for the G&G setup are screwing it onto the dovetail, and putting on a dew shield if you're doing a session more than 1 or 2 hours. But G&G doesn't make sense to me for longer sessions, if you're investing a lot of time it makes sense to me to use your best mounts and scopes etc.

 

Re: airline travel, I would say a qualified yes. My C8 fits in my carry-on bag that has gone through airline security many a time, just not with the C8 in it. In fact I use that bag to transport my C8 a lot of the time. The issues are that it takes up the whole bag, so you're not going to be carrying on much else, and it may not be well-protected in the bag. Protecting it would be very much your responsibility. Personally I would prefer carry-on over checking my telescope every time.



#4 luxo II

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Posted 29 November 2019 - 06:36 PM

It is possible - I've flown interstate before with a C8 OTA inside a sleeping bag cover, it fitted in the overhead locker. The rest was dismantled and went in the checked luggage... the bag was way, way overweight though to the point they asked what was inside. Not much room for anything else so it was definitely an "astro" trip.

 

Also many years ago flying internationally to see an eclipse, I was astounded by how many americans had shipped their C8s complete - in the original coffin cases, with the old wedge and crutch tripod and drive system.

 

However these days for that kind of travel I'd say a C8 is a bit much - and I'd suggest a smaller SCT or mak, possibly up to the Intes M615 Mak (which I have).


Edited by luxo II, 29 November 2019 - 06:41 PM.

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#5 PXR-5

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Posted 29 November 2019 - 10:17 PM

A C8 will not play with a Vixen Porta, a C6 would be the max.
I picked up an SE mount for my C8.
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#6 Bataleon

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Posted 30 November 2019 - 01:15 AM

Only 8" SCTs I can really think of that I'd call "grab and go" are ones on Celestron's SE or Evolution mounts.

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#7 SloMoe

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Posted 30 November 2019 - 09:28 AM

I still don't get this "Grab n Go" race against time, this has never been a hurry up and go hobby in my opinion.

 

Every "G'N'G set up I've seen mentioned is a compromise of our first scope views, in your case you'll be losing FOV but will gain detail in light gathering and no CA,

 

I think it's more of an excuse to purchase another scope, and there's nothing wrong with that either. cool.gif

 

Every type of scope, Newt, Cat/Mak, & Refrac have a particular quality to them, other wise we would all be using just one type of scope,

 

Go ahead and buy another scope, after all "Black Friday" sales are on right now, if you miss them you'll have to wait t'till Christmas for a new scope. lol.gif



#8 Bataleon

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Posted 30 November 2019 - 09:31 AM

I still don't get this "Grab n Go" race against time, this has never been a hurry up and go hobby in my opinion.

Every "G'N'G set up I've seen mentioned is a compromise of our first scope views, in your case you'll be losing FOV but will gain detail in light gathering and no CA,

I think it's more of an excuse to purchase another scope, and there's nothing wrong with that either. cool.gif

Every type of scope, Newt, Cat/Mak, & Refrac have a particular quality to them, other wise we would all be using just one type of scope,

Go ahead and buy another scope, after all "Black Friday" sales are on right now, if you miss them you'll have to wait t'till Christmas for a new scope. lol.gif

To be fair, there are nights when I just want to peek at a few favorites and call it a night and the cost/reward of lugging out my heavy equipment is a motivation killer. This is usually more in the winter months though. Unfortunately, some of the best non-planetary targets in the northern hemisphere are best viewed in the cold months. Orion being the most obvious...

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#9 Eddgie

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Posted 30 November 2019 - 11:01 AM

 

 

What is a faster setup in terms of setup time and amount to things to carry - a 8" SCT on an alt-az mount, or a simple  8" collapsible dobsonian? 

 

 

If the 8" collapsable dob is small enough (though clearly not air line carry on size), this is the path I recommend and for a great variety of reasons. 

 

More stable

No need for coma correction

Better light transmission

Better planetary performance

Wider field

More dew resistant

Binoviewer friendly (though probably not at full aperture, but that may be the case with the C8 as well depending on the configuration.  The C8 though is also binoviewer friendly, but with the very long focal length, a much narrower true field of view)

Ease of using printed az circle and digital inclinometer

 

Now the 8" retractable dob will not be as compact as the C8 of course but the tripod and mount for the C8 are not particularly small either especially if it is something that is going to match the stability of the dob.  For 200x, you need 2" tripod legs and a pretty solid Alt-az mount and by the time you measure out the tripod and mount size and weight, we are not talking about a lot of difference.

 

If it really does have to be able to fly though, the C8 is probably a better pick, but the mount will probably have to go in checked baggage. 



#10 whizbang

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Posted 30 November 2019 - 11:39 AM

I agree with Bataleon.  Sometimes you just want to take a quick peek at a few objects.

 

Also too, here in the Northwest, the weather forecast frequently predicts ten days of solid clouds or rain.  Occasionally there is a surprise cloud break.  GRAB n GO and look at something.  In the time it takes to set up the real scope, the clouds are back.



#11 jgraham

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Posted 30 November 2019 - 12:52 PM

I have used a couple of different 8" SCTs on my Twilight I for grab'n go and they work fine. You gotta use a light touch to minimize vibrations, but they settle fairly quickly.

 

My SC8 on the Twilight I...

 

SC8 TW1-2j.jpg

 


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#12 SeattleScott

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Posted 30 November 2019 - 01:30 PM

Some issues. No I would not take a C8 on a plane. Those corrector lenses are thin. If you can pack your scope well enough that someone could play football with it without breaking it, you are safe taking it on a plane. By comparison a 6” SCT or Mak or 4” refractor can ride in the overhead bin. Or an 8” SCT, wrapped in a couple sheets of newspaper for protection when you hit turbulence...

I would not tend to take a motorized GoTo mount on a plane for same reason. At least not without a very strong case.

I have flown with a 6” Mak overhead and a checked AZ4. Try and break that, baggage handlers.

You probably won’t be able to put an external focuser on a Nexstar 8SE. Not much clearance at the base. I would certainly inquire first.

For me GNG and GoTo don’t mix. I’m not going to spend 10-15 minutes leveling and aligning stuff for a 30 minute session. Nexstar is a GoTo mount. Isn’t really intended for manual operation.

Unfortunately an 8” SCT tube costs like $950 and you can get the Nexstar 8” for what, $1,000 on holiday sale? Almost dumb not to get the mount, even if you just sell it to offset the cost.

If you want to use an 8” SCT as a grab and go scope instead of a grab and wait scope, you will want to insulate it with Reflectix.

Scott

#13 Bataleon

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Posted 30 November 2019 - 01:35 PM

Yes. Maks or small refractors travel better than SCTs...

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#14 Michael11

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Posted 30 November 2019 - 05:48 PM

Thanks all for the answers.

 

 

 

You probably won’t be able to put an external focuser on a Nexstar 8SE. Not much clearance at the base

Even with a low profile SCT focuser? And what about LX65? 

Would using a quality helical focuser after a 2" diagonal be a good idea? I really hate image shifts...

 

 

 

Define "GO".  I consider my EVO 8 my real scope

 

Defintion of "GO" for me is a single trip to a car, and setup time of ~10 minutes. My main telescope is a 12" Newtonian on AZ-EQ6 ... The reason for grab and go is not only to save time... it's lack of motivation to carry and assemble the 12" Newt for a short session. Especially when you have little kids, and sometimes all you wanna do is just to relax and sit near an eyepiece. 

 

 

 

For me GNG and GoTo don’t mix

I only need GOTO for tracking. It takes me less than 5 minutes to align my AQ-EQ6, sice I don't really care for its GOTO accuracy, and alignment for tracking is much less demanding

 

 

 

Unfortunately an 8” SCT tube costs like $950 and you can get the Nexstar 8” for what, $1,000 on holiday sale? Almost dumb not to get the mount, even if you just sell it to offset the cost.

I'm not from US so sale isn't really relevant here... And I'm tending to lean towards Meade ACF (maybe with the LX65 mount) - it costs exactly the same as the "regular" C8 ... Can I mount Meade ACF on a Nextstar? I've read that Meade's SCTs are a bit heavier...

 

 


If you want to use an 8” SCT as a grab and go scope instead of a grab and wait scope, you will want to insulate it with Reflectix

Why? isn't waiting is for cool-down which reflectix would prevent?

 

Regarding air travel - I meant as a carry on of course. I think a 8" SCT should fit a padded camera bag. Anyway It's not a must.

 

The hardest part is over though, after I explained my wife for an hour "why that 3rd telescope is an absolute necessity" tongue2.gif


Edited by Michael11, 30 November 2019 - 05:51 PM.


#15 Bean614

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Posted 30 November 2019 - 10:08 PM

Thanks all for the answers.

 

 

 

Even with a low profile SCT focuser? And what about LX65? 

Would using a quality helical focuser after a 2" diagonal be a good idea? I really hate image shifts...

 

 

 

 

Defintion of "GO" for me is a single trip to a car, and setup time of ~10 minutes. My main telescope is a 12" Newtonian on AZ-EQ6 ... The reason for grab and go is not only to save time... it's lack of motivation to carry and assemble the 12" Newt for a short session. Especially when you have little kids, and sometimes all you wanna do is just to relax and sit near an eyepiece. 

 

 

 

I only need GOTO for tracking. It takes me less than 5 minutes to align my AQ-EQ6, sice I don't really care for its GOTO accuracy, and alignment for tracking is much less demanding

 

 

 

I'm not from US so sale isn't really relevant here... And I'm tending to lean towards Meade ACF (maybe with the LX65 mount) - it costs exactly the same as the "regular" C8 ... Can I mount Meade ACF on a Nextstar? I've read that Meade's SCTs are a bit heavier...

 

 

Why? isn't waiting is for cool-down which reflectix would prevent?

 

Regarding air travel - I meant as a carry on of course. I think a 8" SCT should fit a padded camera bag. Anyway It's not a must.

 

The hardest part is over though, after I explained my wife for an hour "why that 3rd telescope is an absolute necessity" tongue2.gif

The idea is that you DON'T want cool down!  The rapid cooling going from a warm house, say 70F, to a cold outside  location, say 20F, is what causes the thermals which cause the lousy seeing.  On very cold nights your mirror will never cool to ambient.   However, Reflectix keeps the warmth from radiating out of the tube, thus reducing the thermals to negligible,  thus providing  excellent sharp views from the very moment you take it outside. 

   I have a Unistar mount on a Sirius  tripod, covered, right outside  my door.  We're  expecting 20 inches of snow in Western Massachusetts tomorrow. At sunset it was 24F, but clear.  I took out my Insulated  C6 to get a quick view of setting Jupiter, very sharp at 100X. Then Venus, quite clear.  Then Saturn at 187X, still sharp!  The Crescent Moon was next and terrific.   Then over towards the East for a nice Uranus at 100X, then at 187X one of the moons, Miranda according to my chart.  Finally back toward the South for Neptune, and as with the others, great at 100X and 187X.

    All in 45 minutes.  Without insulation,  this wouldn't have been possible!   Heck, even a 4 inch refractor would taken 20 minutes to reach semi-ambient with a 46 degree temperature delta (70 to 24).

  To me, this is the ultimate  GNG.  The Baader Zoom is already in the diagonal, the Reflectix always affixed to the scope AND the Dew Shield,  so it's  grab the OTA in one arm, out the door, pull the cover off the Uni, attach scope, start observing.  

How long was that??  2 minutes??


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#16 SeattleScott

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Posted 01 December 2019 - 12:00 AM

What Bean said.

Not sure about specific clearance details but I know some people have had difficulty using a 2” diagonal on a Nexstar 8 so I would think an external focuser wouldn’t work well. But best to hear from someone who owns one.

Scott

#17 Michael11

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Posted 01 December 2019 - 01:38 AM

I think baader has low profile diagonal which threads directly into OTA. but focuser is probably an issue 



#18 Michael11

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Posted 01 December 2019 - 07:08 AM

An interesting piece of info I found when trying to decide if coma correction is necessary.

from "amateur telescope optics" site:

 

 

the SCT linear field is, coma-wise, comparable to an ƒ/6 paraboloid. Angularly, coma in a paraboloid changes with the square of focal ratio, thus the SCT field compares to that of an ƒ/4.7 paraboloid

This quote is for 8" model with f/2 mirror. Since I have a lot of experience with a 8"  f/4.7 newt and it has the same amount of coma as the "regular" 8" SCT - I think I'll just order the Nexstar 8se as the cheapest option with tracking.


Edited by Michael11, 01 December 2019 - 07:10 AM.


#19 George Methvin

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Posted 01 December 2019 - 09:45 AM

If I want to just do a hour or two of viewing I use my C-6 on a Orion starseeker goto mount I can carry the whole thing out in one piece easy to set up and easy to carry back in when I am done. If I plan to be viewing most of the night I take out my C-8 mounted on a Celestron Nextstar SE goto mount a two trip process mount then the ota still very easy and quick to set up and take down. If the weather is going the be clear for a week or two I take out my Orion 14 inch goto dob and just leave it setup for a week or so of viewing keeping it covered during the day and viewing at night, this is what works for me diffract tools for diffract jobs.   



#20 Michael11

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Posted 01 December 2019 - 01:10 PM

Just ordered the 8SE while it's still on sale... blush.gif 

It's the most compact and cheapest option I could find.

 

I wonder if I can use my william optics 2" diagonal straight out of the box, or adapter is needed?

 

And what is the largest recommended eyepiece for it? 40mm 70 degrees will do? Or a combination of a reducer and a smaller EP is better?



#21 Bataleon

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Posted 01 December 2019 - 01:17 PM

Just ordered the 8SE while it's still on sale... blush.gif
It's the most compact and cheapest option I could find.

I wonder if I can use my william optics 2" diagonal straight out of the box, or adapter is needed?

And what is the largest recommended eyepiece for it? 40mm 70 degrees will do? Or a combination of a reducer and a smaller EP is better?

The longest focal length you can reasonably expect to work in an 8" SCT is about 55. I use a 55 mm 2" Tele Vue plossl in mine for large DSO like the swan and lagoon nebulae. Any longer than that and you'll get pretty bad vignetting. You can use a pretty good range of focal length eyepieces in these scopes without using a reducer. My eyepiece kit ranges between a 7mm nagler and a 55mm plossl. The shortest I really use in the SCT is a 12mm. If I really need to go higher than that, I usually barlow up a 20 or 32mm

As for your William diagonal, does it have an SCT adapter or are you talking about screwing the mirror housing directly onto the visual back? I wouldn't recommend the latter because the thread stop on a lot of diagonals causes "tight" to be in an uncomfortable position for viewing or manipulating the focuser.

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Edited by Bataleon, 01 December 2019 - 01:20 PM.


#22 Michael11

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Posted 01 December 2019 - 03:16 PM

Regarding the eyepieces - my question was - what is the point of using focal reducer? If I can acheive maximum useable FOV with a 40-50mm eyepiece anyway...

Does ig reduce coma or field curvature ? 

 

I was planning to use the WO diagonal I have in my ED80. It has an eyepiece like 2" nosepiece.



#23 Bataleon

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Posted 01 December 2019 - 04:16 PM

Regarding the eyepieces - my question was - what is the point of using focal reducer? If I can acheive maximum useable FOV with a 40-50mm eyepiece anyway...
Does ig reduce coma or field curvature ?

I was planning to use the WO diagonal I have in my ED80. It has an eyepiece like 2" nosepiece.

The benefits of a reducer are less if you're already using 2" equipment. At that point, the main benefit would be field flattening for imaging. It sounds like your diagonal is a refractor style, so you'll need a 2" visual back adapter for SCTs.

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#24 SeattleScott

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Posted 02 December 2019 - 05:22 PM

Getting a 2” adapter adds length to the back, which can cause problems with clearing the base when viewing at zenith. Given the reputation for limited clearance on this model, I would be more inclined to get a separate SCT diagonal. Plus that way you don’t have to swap one diagonal between two scopes. Or arrive at your dark sky site and realize you forgot to swap and have no diagonal...

Honestly, I would wait awhile and see how it goes with standard equipment. Some people say they can balance the 8SE and have clearance for a 2” diagonal or focal reducer, others say they have to avoid zenith. I suppose it could depend on whether they use a dew strap or a heavier dew shield. And some people just run it unbalanced to get clearance, which they say works fine, but personally would make me nervous. So might spend a little time with it and check out the clearance before investing in a 2” SCT diagonal or focal reducer.

Scott

Edited by SeattleScott, 02 December 2019 - 05:28 PM.


#25 gjanke

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Posted 05 December 2019 - 07:43 AM

So, look, I am going to just say it; a SCT 8" isn't a grab and go scope. Its portable, sure, but grab and go? No.

 

Several factors that make a scope a grab and go.

 

1) One hand rule. Needs to be able to be picked up with one hand and walked out of the garage or house.

 

2) Quick cool down time, which traditionally isn't a 8" SCT. We're talking 10 to 20 minutes tops. Typically that's a 5" or less of diameter and more than likely, lenses instead of mirrors, but I don't want to rule out the MAKs.

 

3)Typically the mount is a push to Alt-AZ. Lightweight in nature. With everything mounted no more than 12lbs ( see rule 1).

 

4) Set up and break down no more than five minutes.


Edited by gjanke, 05 December 2019 - 07:45 AM.



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