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Deciding Between Alt/Az & GEM

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#1 JeepGuy

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Posted 23 April 2019 - 09:31 PM

Searching for a 1st telescope and after tons of reading I’ve almost abandoned the alt/az mount in favor of a GEM. My question is, if I want to “run” out in the backyard and relatively quickly look at a blood moon or a bright comet or something, do I have to go through polar alignment and a 1, 2, or 3 star alignment before I can look at the something?

 

FYI: I’m considering the Celestron CGEM II 800 EdgeHD w/40 lbs load capacity and 14 lbs OTA. I foresee wanting to get into astrophotography at some point... probably 5 minutes after the ‘scope arrives! roflmao.gif

 

Thanks!



#2 Richard O'Neill

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Posted 23 April 2019 - 09:41 PM

I think you've answered your own question. Don't be timid, jump in the deep water. shocked.gif


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#3 Cajundaddy

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Posted 23 April 2019 - 10:04 PM

Two choices:  

 

1. Dive in and order your gear.

2. Keep reading.

 

Some of us have been playing this game for a good long while and have discovered that some scopes are great for quick looks, some are great for planetary views, some are great for faint galaxies, and some are great for astrophotography.  The trouble is it rarely seems to be the same scope.  Choose wisely.


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#4 John Fitzgerald

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Posted 23 April 2019 - 10:08 PM

Alt Az is better for grab and go, quick looks.  GEM is better IMO for longer sessions, and certainly better for AP.  You do not have to accurately align a GEM for short visual sessions, just point it as near north as you can, with the correct latitude setting on the scale.  AP requires more precise polar alignment.


Edited by John Fitzgerald, 23 April 2019 - 10:09 PM.

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#5 Sketcher

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Posted 23 April 2019 - 10:40 PM

Option (A):  Decide where your priorities lie and choose accordingly.

 

Option (B):  If you must have multiple capabilities, be prepared to purchase multiple setups.

 

Option ©:  ?

 

This hobby can be as complicated (and expensive) or as simple (and cheap) as one wants to make it.


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#6 Napp

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Posted 23 April 2019 - 11:46 PM

Hopefully you are getting the message that no scope does all well.  It seems that most in this hobby for any length of time have multiple scopes to satisfy multiple requirements.  I do hope you understand that you are not going to just run out and set up a CGEM.  It’s no small task to assemble the mount and scope.  You then have to balance the rig in both axes.  You have to do this regardless of whether you polar align.  Trying to point an equatorial is not so straightforward because the scope can only move around the two axes which doesn’t translate easily into horizontal and vertical.  Just so you know I have an 8” LX200 that I mount on a CGX mount.  It’s really just too much trouble for quick viewing unless you can leave it assembled and roll it out on a dolly.  

 

I also have a 16” DOB which I can assemble and be viewing with quicker than I can the SCT and equatorial mount.  But it’s still too much trouble for quick viewing at home.  I just don’t have room in the garage to leave it assembled.  So I just bought a used 10” DOB for quick observing at home.  I carry out the base and then the OTA and set the OTA on the base.  I’m observing.  Of course this ignores mirror cool down.  A friend of mine has a 8” Orion DOB.  It can be lifted totally assembled and moved easily.  The point here is that unless you intend to leave the CGEM and scope assembled and balanced and roll them out you will find that that rig won’t be very good for quick viewing.



#7 SeattleScott

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Posted 23 April 2019 - 11:55 PM

Correct, while Celestron GEM mounts do not require an alignment process for using tracking, that is a big heavy mount that is not well suited for short observing sessions.

Scott

#8 qaiden

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Posted 24 April 2019 - 06:15 AM

Hi

 

I started with a GEM mount (manual scope) in the optic of upgrading it later to goto for AP ... and I did not use this scope very long.

The problem with the balacing configuration, the polar alignment was too much trouble for me before every session.

 

Now I have a SCT with starsense, and it does everything for me, I just pick auto align and wait. (I gave up on AP for now)

 

BUT, SCT is an alt/az mount, and that is a no go for astrophotography.

 

So if you are sure about going into AP, which is a whole other topic with a lot of knowledge involved, then there is no way around a GEM mount.



#9 Sarkikos

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Posted 24 April 2019 - 07:01 AM

If you want to get into AP, get a GEM.  Otherwise, get an alt-az.

 

I am not into AP, so I got rid of all my GEMs.  I do not miss them at all.

 

Mike


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#10 RaulTheRat

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Posted 24 April 2019 - 07:15 AM

AZ-EQ-6 ftw. Now actually, if you've the funds, it's even better to have a GEM for photography and a separate alt-az (maybe a dob or something) for visual use, to avoid the inconvenience of switching back and forth, but as a do everything mount with reasonable load capacity at a reasonable price, I've been satisfied with mine.

#11 Jeff Morgan

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Posted 24 April 2019 - 09:15 AM

If you want to get into AP, get a GEM.  Otherwise, get an alt-az.

 

I am not into AP, so I got rid of all my GEMs.  I do not miss them at all.

 

Mike

 

A GEM is essentially a alt-az that has the alt axis tipped towards the pole. Tipping a mount requires extra weight to balance, and has to be more rigid. Thus, it quickly becomes heavy and expensive compared to an alt-az of the same load capacity.

 

GEM set-up time is longer. The mount needs to leveled and polar aligned. Required alignment accuracy depends upon use. Visual or imaging? More accuracy = more set-up time. You can buy a device that will do the alignment for you. If you don't mind spending the money and giving Chinese software access to your computer and hard drive (no cyber risks there ...)

 

Additionally, the user ergonomics can be very poor for a GEM. Somewhat solved by rotating rings (more weight and money). Meridian flip is still annoying though. Now you can see why people like alt-az.

 

 

But the place to start is to consider the weight capacity and features you need. For example, do you want digital setting circles? Tracking? GOTO operation? Imaging?

 

After you get those requirements, then look at the mount(s) available in your budget. There are alt-az mounts that can do everything a GEM does - for a price.


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#12 markb

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Posted 24 April 2019 - 09:28 AM

I use 2 friction less alt-az mounts, EzTouch (AYO Swiss knock off) and a Sergio Bonilla, for casual viewing, with a green pistol laser for accurate aiming and less hunting. Both work even for high power as long as I use the laser to aim. Now 1/2 hour sessions are a breeze. I use a surveyors tripod.

I don't do AP so I settled on Nexstar GPS/non-GPS alt-az mounts for everything else, converting a GPS11 to hold my refractors and c8. Still a really fast set up, just heavy.

My GEMs are sold or about to be listed. Heavy and unwieldy.
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#13 rottielover

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Posted 24 April 2019 - 10:00 AM

All great advice.  No one asked what type of astrophotography you were interested in?     I am one of those who jumped into the deep end and nearly drowned.

 

My current rig is a GEM (Orion Atlas) and I'm doing DSO photos.  This rig does work for doing planets but it's not ideal.  You'll find that folks who do a lot of planetary work seem to be all be using alt/az with SC's and webcams for "lucky imaging".   Where-as DSO's are usually long exposures and you need excellent guiding.

 

I'm seriously thinking about getting a 2nd rig to do just planets, and if I do it's going to be an Alt/Az with an Sc etc.

 

So, if you're wanting to "run out and setup real quick" and then maybe later get into planets, moon, maybe solar (get the right filter!!!), then you may want to start with the alt/az style with an SC and go GEM later if you want to get into DSO's.

 

If nebula and galaxy's are more your thing maybe you should jump in the deep end ?

 

Just some added thoughts for ya, hope it helps!!



#14 Spikey131

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Posted 24 April 2019 - 10:08 AM

This is a common question.  Something like, “What mount can do everything well?”

 

The answer is that you do not yet understand the question.

 

Deep sky astrophotography is a very different pursuit than visual astronomy.  It demands different equipment.

 

I would suggest starting small, do some observing, and then figure out what you want to do.

 

So I guess a medium price, medium size GEM makes sense right now.  It would work for visual and introductory AP.  But what you will end up wanting/needing will depend upon where that takes you.


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#15 qaiden

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Posted 24 April 2019 - 11:31 AM

Deep sky astrophotography is a very different pursuit than visual astronomy.  It demands different equipment.

Fully agree with that, a friend of mine is into AP and I am only visual, he doesnt understand what I say and I dont understand what he says, different equipment, different needs, different knowledge required.


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#16 Sarkikos

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Posted 24 April 2019 - 11:38 AM

Fully agree with that, a friend of mine is into AP and I am only visual, he doesnt understand what I say and I dont understand what he says, different equipment, different needs, different knowledge required.

I agree as well.  Last year I was observing at my dark site.  A young man there who was new into AP and gungho about it asked me what f number I was running at.  No question about aperture or what type of telescope.  What f number.

 

AP is another world.  Not mine.  

 

:grin:

Mike


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#17 DavidWasch

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Posted 24 April 2019 - 12:22 PM

I think pretty much everyone thinks they might "get into telephotography at some point," myself included.

 

If your budget has few constraints, go ahead and pick up a GEM-- you can always sell it if you find it doesn't work for you. If you have relatively limited funds (ie. spending more than a couple hundred takes some time to digest), I would recommend that you stick with whatever puts you under the stars now. Don't have a possible interest in AP slow down your observing as a beginner.



#18 tony_spina

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Posted 24 April 2019 - 12:50 PM

Quick views = alt-az mounts with a small refractor or newtonian.

 

You will see in the CN forums that lots of people have more than one scope.  One of the reasons is exactly the grab-and-go,  quick views.  It's all about removing any obstacles that would prevent you from viewing. 

 

If you needed to setup a 40-50lb mount you are less inclined to go out on a whim


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#19 Astrojensen

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Posted 24 April 2019 - 02:15 PM

GEM set-up time is longer. The mount needs to leveled and polar aligned.

This is a widespread myth. For visual observing, it only needs to be reasonably level and a quick glance over the top of the mount to assure the RA axis is pointing roughly towards Polaris is all you need. I use my Zeiss Telemator a lot and it takes me about three seconds at the most to polar align it with the accuracy I need to keep objects in the field for long periods of time with the RA axis alone. People fuzz about this far too much and forget that the equatorial mount has other significant advantages, such as defining the cardinal directions, which is helpful to find objects, especially for the beginner. It's also much easier to reacquire an object again, even with an undriven equatorial, if you have to walk away from the scope for a while. Just push it westward again when you come back, while looking into the eyepiece and you'll quickly have the object in the field again. With an altaz, you might have to do the starhop all over again. 

 

The biggest drawback of the GEM is its significantly higher weight, but in a windy location, that might also count as an advantage. It can certainly be one in mine. 

 

 

Clear skies!
Thomas, Denmark


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#20 Sarkikos

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Posted 24 April 2019 - 02:20 PM

If Polaris is blocked by a tree or building where you usually observe by your house, then setting up a GEM is even more of a bother.  Yeah, I know there are ways to get around this.  But I don't want to bother with it.  For grab-n-go, I like quick, light and easy.

 

Mike


Edited by Sarkikos, 24 April 2019 - 02:21 PM.

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#21 tony_spina

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Posted 24 April 2019 - 04:01 PM

This is a widespread myth. For visual observing, it only needs to be reasonably level and a quick glance over the top of the mount to assure the RA axis is pointing roughly towards Polaris is all you need. I use my Zeiss Telemator a lot and it takes me about three seconds at the most to polar align it with the accuracy I need to keep objects in the field for long periods of time with the RA axis alone. People fuzz about this far too much and forget that the equatorial mount has other significant advantages, such as defining the cardinal directions, which is helpful to find objects, especially for the beginner. It's also much easier to reacquire an object again, even with an undriven equatorial, if you have to walk away from the scope for a while. Just push it westward again when you come back, while looking into the eyepiece and you'll quickly have the object in the field again. With an altaz, you might have to do the starhop all over again. 

 

The biggest drawback of the GEM is its significantly higher weight, but in a windy location, that might also count as an advantage. It can certainly be one in mine. 

 

 

Clear skies!
Thomas, Denmark

The issue is not the alignment needed with an EQ mount.  The issue is the weight and the awkwardness of carrying and navigating around walls and doors in the house.

 

A


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#22 Jeff Morgan

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Posted 24 April 2019 - 05:34 PM

If you can find one, the old Vixen Polaris and Super Polaris mounts were real gems (no pun intended). Light to medium duty (Celestron put 8" SCT's on them), but capable of EQ or Alt-AZ operation and very nice slow motion controls.

 

As Thomas mentioned, they are good for cardinal directions and star hopping.


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#23 vkhastro1

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Posted 24 April 2019 - 06:20 PM

I prefer to use alt-az mounts for most of my visual needs.

For best results use a bigger alt-az mount for your needs.

For example if the OTA is 10 lbs, I use a mount with a carrying capacity of 20lbs or more - makes balancing the OTA easier and reduces the risk of the mount tipping (or possibly falling over). This is especially advantageous with refractors with long momentum arms.


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#24 rkelley8493

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Posted 24 April 2019 - 07:10 PM

You could get the best of both worlds with the Orion Atlas Pro AZ/EQ-G or Sky-Watcher AZ-EQ6. They are the same mount, different color & name brand. Both can be used in Alt-AZ and Equatorial modes, and they have a 20 kilo [44 lb] load capacity. Perfect for astro-photo and/or heavy OTAs.


Edited by rkelley8493, 24 April 2019 - 07:13 PM.

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#25 tony_spina

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Posted 24 April 2019 - 07:38 PM

You could get the best of both worlds with the Orion Atlas Pro AZ/EQ-G or Sky-Watcher AZ-EQ6. They are the same mount, different color & name brand. Both can be used in Alt-AZ and Equatorial modes, and they have a 20 kilo [44 lb] load capacity. Perfect for astro-photo and/or heavy OTAs.

They are very good mounts, but a little heavy for grab and go.  just like tools, most of the times it is better to have a couple specific to the task at hand


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