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jayfish
journeyman
Reged: 08/28/08
Posts: 5
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Hello Everyone,
I have the opportunity to pick up a used scope and eyepiece kit and was wondering if anyone in the group had any opinions on the deal. The scope is a Nexstar 80GTL and the eyepiece kit is a Celestron #94303. I can get them both for $225.00. This seems like a pretty good deal to me but I can't find any user generated info on this scope. I can find some on the GT which has a 400mm fl but none on the GTL which has a 900mm focal length. I would hope to use this scope mainly with my kids for lunar and planetary viewing with an occasional try at a DSO.
Thanks In Advance
Jay
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Tel
Carpal Tunnel
Reged: 03/31/06
Posts: 2631
Loc: Wallingford England
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Hi Jay,
And a very warm welcome to CN and this forum in particular!
As to your question / dilemma, and at the risk of being contraversial, my own view is that I would not buy this 'scope but put the available cash toward something more suited to the purposes you outlined.
In the first instance, bear in mind that the aperture of this 'scope is not at all large (80mm) and that according to one source I came across, has a useful magnification of only X90.
If this is true, (and I have no reason to suppose it is not), then this rules out the use of the 4mm and 6mm eyepieces supplied with the #94303 kit.
Equally, any combination of even the longer focal length eyepieces with the X2 Barlow, will, in my view, be almost useless for the following reasons :
Acknowledging the 4mm and the 6mm are totally unsuitable for this 'scope, the 15mm ; Barlowed ; will give a 7.5mm which, in all reality, will be no better than the straight 6mm while Barlow-ing the 32mm will give you 16mm when you've already got a straight 15mm.
Turning now to the 'scope and the application you want to put it to, I personally think it has too small an aperture for any appealing planetary views.
Lunar observations will of course be possible due to the excess light available but again resolution will be limited.
As to DSOs, the 32mm Ploessl will give you a possible 2degs. field of view, but again, you will be limited by the 'scope's small aperture and thus low light gathering power.
Sorry to be pessimistic Jay, but just this guy's opinion. I would like to hear others.
Best Regards,
Tel
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Truth is the cubed root of Verbosity.
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jayfish
journeyman
Reged: 08/28/08
Posts: 5
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Thanks for the welcome and the well thought-out reply. I'm still on the fence.
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Bob Griffiths
Post Laureate
Reged: 10/10/05
Posts: 4195
Loc: Frederick Maryland
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Jay
A quick look at the specs and I do see it is listed as 900 mm f/11
with an OTA that is 35 inches in length... Highest useful magnification is 189x ....Which like Tel mentioned would still render the 4 mm Eyepiece in the kit completely useless and most likely the 6 mm as well unless the seeing conditions are darn good...
The scope also has in my opinion a fairly small FOV for a refracrtor (1.4 degrees)... Tough call because it is cheap enough to get your :kids interested .
BUT not big enough to really enjoy DSO,s and .too narrow a FOV to enjoy wide field sweeping views either...IF The FOV is larger then 1.4 degrees then I would have to sit down and think about the purchase some more...as for my opinion today...I'd say NAH !
BTW...my first GOTO scope was a 114 GT ...cost me $50
in a pawn shop...much more flexible scope then the 80 GTL
Bob G.
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CPC1100
Nexstar 8i + GPS & Rays Brackets
Denk S1 power switch
Orion 100 mm Refractor
Meade LXD 55 ...AR-5 127 mm Refractor
Exploradome Observatory S.I.E. (Smiling Irish Eyes)
39*21'03" N
77*28'12" W
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Midnight Dan
professor emeritus
Reged: 01/23/08
Posts: 619
Loc: Brockport, NY
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Hi Jay,
Welcome to Cloudy Nights! You did the right thing coming here before making a buying decision. There's a lot of folks here with an enormous amount of experience that will be eager to offer their help.
My personal opinion is that you could probably do better with a different scope for about that same amount of money. Take a look at Orion's site:
http://www.telescope.com
They have a Starblast 4.5 inch dobsonian reflector for $135, and a Starblast 6 inch dobsonian for $250. Each comes with a couple of eyepieces that should be enough to get you started. And they both have MUCH more light gathering capability than the 3 inch aperture of the scope you're considering. You'll get better planetary views as well as being able to see nebulae and galaxies.
These are both great beginner scopes (I've seen good reviews on both) and will give the kids great views of interesting stuff.
-Dan
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Scopes: Celestron NexStar 8, Orion EON 72mm ED/APO on Astroview mount (EQ3)
Eyepieces: Celestron 40mm, 25mm, Baader Hyperion 13mm, 8mm, 5mm
Other: Telrad, 2x Barlow, 0.63x Focal Reducer, Dew-not strips, DewBuster controller
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coutleef
scholastic sledgehammer
Reged: 02/21/08
Posts: 823
Loc: Montreal and St-Donat, Québec,...
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Completely agree and the 6 inch dob has had good reviews in S T
Francois
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François
Nexstar 8 SE
50mm StellarVue finderscope, Astronomik UHC-E and Orion OIII filters
WO Swan 40mm; TV Pan 22mm; TV Nagler 9T6, 12T4, 17T4; TV Plossl 11mm and 15mm.
WO 2" dielectric diagonal retrofitted with Denk Power Switch (and now reach the zenith with the shorty adapter).
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jayfish
journeyman
Reged: 08/28/08
Posts: 5
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Thanks for your input everyone. I'm now checking out another scope.
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Av8torjim
member
Reged: 07/14/08
Posts: 39
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Funny, I was going to make the same scope recommendations. The deals on the Orions right now are very attractive. I also think a younger child will get very frustrated with go-to technology. Being able to just push the scope around and look at whatever appears in the EP is very attractive.
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Celestron N8i Hybrid/Ray's Bracket/9x50 RACI
TV Nagler 13T6, 9T6 & 7T1
TV Panoptic 24 & 19
TV Plossl 32, 11 & 8
Meade 5000 Plossl 14
Lumicon Deep Sky (SCT), Orion Ultrablock (SCT), Lumicon OIII
Celestron f6.3 Reducer
TV Everbrite Diagonal
Celestron Ultima 2x Barlow
1970s Selsi Model 247 80mm f11.4 refractor on GEM
Minolta Standard EZ 10x50 Wide Angle Binoculars
Orion 15x70 GiantView Binoculars
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Rad
newbie
Reged: 09/01/08
Posts: 4
Loc: Saint Petersburg, Florida
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Quote:
Hi Jay,
And a very warm welcome to CN and this forum in particular!
As to your question / dilemma, and at the risk of being contraversial, my own view is that I would not buy this 'scope but put the available cash toward something more suited to the purposes you outlined.
In the first instance, bear in mind that the aperture of this 'scope is not at all large (80mm) and that according to one source I came across, has a useful magnification of only X90.
If this is true, (and I have no reason to suppose it is not), then this rules out the use of the 4mm and 6mm eyepieces supplied with the #94303 kit.
Equally, any combination of even the longer focal length eyepieces with the X2 Barlow, will, in my view, be almost useless for the following reasons :
Acknowledging the 4mm and the 6mm are totally unsuitable for this 'scope, the 15mm ; Barlowed ; will give a 7.5mm which, in all reality, will be no better than the straight 6mm while Barlow-ing the 32mm will give you 16mm when you've already got a straight 15mm.
Turning now to the 'scope and the application you want to put it to, I personally think it has too small an aperture for any appealing planetary views.
Lunar observations will of course be possible due to the excess light available but again resolution will be limited.
As to DSOs, the 32mm Ploessl will give you a possible 2degs. field of view, but again, you will be limited by the 'scope's small aperture and thus low light gathering power.
Sorry to be pessimistic Jay, but just this guy's opinion. I would like to hear others.
Best Regards,
Tel
HEY TEL . I am new to the site and have finally purchased a tele the nexstar 6 se , I am doing calculations on power for my eyepieces to aperture ratio,focal length too. I have a Barlow 2x now. So from what I understand you SUBTRACT from the barlow 2X? Say i have a 32mm it is actually a 16 X focal length of my tele? instead of 64? hence 32x2barlow? you would subtract power ? hence 32 x 2 barlow = - 16 mm x focal length. Thanks Rick 
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IN THE WIND HE'S STILL ALIVE ! FRED BEAR
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Tel
Carpal Tunnel
Reged: 03/31/06
Posts: 2631
Loc: Wallingford England
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Hi Rick,
A very warm welcome to CN and to this forum in particular. With your new 6SE I'm sure you'll find it very useful !
If you're slightly stuck on the various maths associated with power (magnification), perhaps the following may explain what you require.
Take the focal length of any 'scope, (in your case the 6SE has a focal length of 1500mm) and divide this figure by the focal length of any eyepiece (EP) you choose.
For example, if you have a 32mm EP, then 1500/32 gives you a magnification of about 47 (actually 46.875) and is expressed conventionally as X47.
Again, if say you had a 10mm EP, then your magnification would be X150. (i.e. 1500/10 = X150).
Now if you were to place a X2 Barlow lens between an eyepiece and your 'scope's diagonal, this will have the effect of doubling the normal magnification. provided according to the above calculation.
In other words and for example, 1500/32 = 47 x 2 = Magnification X94 (actually X93.75).
So, if you have a 32mm EP and use it in conjunction with a X2 Barlow, it will yield the same magnification in your 'scope (or any 'scope for that matter), had you have used a 16mm without the Barlow. (In your case, 1500/16 = X94 (actually X93.75). Thus a 32mm EP X2 "Barlowed", is the same as a 16mm "UnBarlowed" !
Similarly, a X2 "Barlowed" 10mm EP will behave as if it were a 5mm and thus produce double the magnification according to, (in the case of your 'scope 1500/10 = 150 x 2 = X300).
Does this explanation help?
Best regards,
Tel
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Truth is the cubed root of Verbosity.
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Rad
newbie
Reged: 09/01/08
Posts: 4
Loc: Saint Petersburg, Florida
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Hey Tel, thanks for the quick reply. Yes this does help alot ,I understand now that it doubles the magnification. Not the mm of the lens, This is a great help in determining my eyepieces and the usefull power of the 6" apeture. Thanks for the warm welcome also . Rick 
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IN THE WIND HE'S STILL ALIVE ! FRED BEAR
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Tel
Carpal Tunnel
Reged: 03/31/06
Posts: 2631
Loc: Wallingford England
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Hi Rick,
Well you are right to a certain extent about a X2 Barlow doubling the "length of the lens".
Looking at it the way you are perhaps seeing it, the use of the X2 Barlow doubles the focal length of your 6SE telescope from 1500mm to 3000mm, or, looking at it another way, it halves the focal length of any EP you choose to use.
You also made a point about useful power.
As you know there is a limit to the amount of power / magnification you can "wring" out of a particular 'scope.
I think the maximum useful magnification set for yours is X354 (according to Celestron) but in practice you will be very hard pushed to reach anywhere near this unless your seeing conditions are absolutely perfect.
Use high magnification by all means when the object demands and the conditions allow, but always aim to retain a sharp image. Pushing the magnification too high will only result in image deterioration.
Best regards,
Tel
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Truth is the cubed root of Verbosity.
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Talstarone
Vendor (Inner Planetary Products)
Reged: 09/12/06
Posts: 7597
Loc: Benson, North Carolina
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I purchased a new Celestron 80-GTL in mid 2006.
It was basically a GT model scope with a longer focal length optical tube. It did come with some bonuses such as a solar filter and a couple more I could not remember.
For the price the scope was a pretty good buy.It worked well enough on GOTO's and tracking considering its price.The scope was OK but not a great instrument.Though if you did replace the light aluminum tripod with a more stable tubular steel or wooden tripod the mount would be a good match for a WO or AT 66-80mm APO/Achro Refractor.
I traded mine back in about 20 days after purchase to buy a Celestron NexStar 102SLT(The newest edition with the round tubular tripod)That is a slightly better mount with a much better scope.
For the lower price of the scope and eyepiece kit I personally would give it consideration. But I would also seriously consider a Meade ETX-80AT or a Celestron NexStar 80 SLT for the price.They would include 2 eyepieces(which would be enough to start with).
So the final choice is yours but the GTL is a useable scope for the price,but there are also better scopes for the same(or close to the same)price.
GTL
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Todd C.
Celestron NexStar 4SE(102mm F/13)Maksutov-Cass
Meade ETX-80AT(80mm F/5)Achro Refractor
Meade ETX-60BB(60mm F/5.8)Achro Refractor
www.innerplanetaryproducts.com
Meteorites and More....
"Outer Space at Down to Earth Prices"
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jayfish
journeyman
Reged: 08/28/08
Posts: 5
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Thanks again everyone for the advice. I really wanted a scope for that weekend as I was going to dark sky country. I held off though. I finally pulled the trigger over this weekend though and picked up a very lightly used Powerseeker 114EQ for $50 and the aforementioned eyepiece kit for another $50. Everything is in fantastic condition (with the exception of a missing "The Sky" cd. I achieved first-light with the scope Saturday but due to the heavy LP from my site it was "meh" at best. That was until I decided to try Jupiter. I had to move everything to a different part of the yard to point the scope South w/o obstruction. I had a hunch that the large orange object to the SW was Jupiter so I gave it a shot. I started with my 32MM Plössl and 2x barlow. I lined it up and was , quite frankly, shocked by what I saw. At first I thought there was a problem with the scope and wanted to focus the large disk disk away to match the smaller ones on either side of it. About a split second later I realized I was looking at Jupiter and it's moons. I was ecstatic! I wanted to try every combination of every eyepiece and filter in the span of about 1 minute. I tried most of the the eyepieces and it was glorious. I could vaguely make out the cloud-bands but they seemed washed out. After checking Jupiter in Celestia it looked about the same. ...kinda washed out. It appears as though this is due to the direct sunlight washing out the colors and given a different night or by using an appropriate filter (I did not get to try any of mine) I would be able to make them out better. Is this the case?
Jay
Edited by jayfish (09/29/08 08:34 PM)
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Tel
Carpal Tunnel
Reged: 03/31/06
Posts: 2631
Loc: Wallingford England
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Hi Jay,
Absolutely ! Seeing and transparency will vary from night to night if not even from hour to hour to enhance or spoil our views.
With the use of colour filters I think it's a case of a need to expertiment on the night to see which, if any, work in your favour. Most times I personally think they are ineffective but then again, occasionally, their use surprises me. Try for example, a light blue filter when viewing Jupiter. For me, it can circumstantially tone down it's brightness to show the cloud bands more clearly.
For you interest, perhaps take a look at the attached link as a guide and explanation of "Seeing" and in particular the sub-link "Simulated Seeing Animation".
http://celestialwonders.com/articles/seeing
Best Regards,
Tel
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Truth is the cubed root of Verbosity.
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jayfish
journeyman
Reged: 08/28/08
Posts: 5
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That's a great page, thanks. The "poor seeing conditions" simulation of Jupiter in the "Simulated Seeing Animations" link was exactly what I was experiencing. Since that first post about Jupiter I've had a chance to go back to it and have had some better views. That being said, even though it's not a NexStar, I've had a great time with this scope so-far. I've done a few mods on it and have viewed some objects I never thought possible in my LP sky's. I'm hoping to get to a dark-sky site before winter kicks in here.
Thanks Again For Everyones Help,
Jay
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