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Realistic refractors for an Az GTi mount?

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#1 25585



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Posted 01 August 2020 - 05:14 AM

What refractors have, do, or might you use with an Az GTi mount or the Star Discovery?


I have a TV Pronto & 85, 66 & 80 Equinox, plus a Vixen A80M in its weight capacity. However I use heavy optics, diagonals and eyepieces, plus the usual 8x50 finder & RDF.


Wanting to dip my toe into GOTO, to gain experience before deciding on a larger mount.   



Edited by 25585, 01 August 2020 - 05:39 AM.

#2 starryhtx



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Posted 01 August 2020 - 07:59 AM

60-80mm doublets, or even a 4" doublet, i wouldn't put a triplet on one of those. 

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#3 AaronF


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Posted 01 August 2020 - 10:14 AM


I recently finished assembling a travel telescope kit with the AZ-GTi mount:



The telescope is the TS 80mm f/7 doublet with FPL-53 which weighs 3kg.

The mount handles it, but I wouldn't want to put anything heaver on it, as I feel it would start to struggle.


I usually use it with a Baader T2 flip mirror which is quite light, but have some balancing issues with some heavier eyepieces, so I tend to use my 17.5mm Morpheus as my main low power eyepiece.


(I haven't tried using my Maxvision 40mm with it, either - I think I'll de-cloak it first! :D )


I don't have many decent photos of it, only this one from a few weeks ago - hunting Comet Neowise without a diagonal:

Oh, and here's having found it :D
c/2020 f3 neowise median stacked stretched


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#4 J_D_Metzger


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Posted 01 August 2020 - 01:11 PM

I have a Sky-Watcher EvoStar 72 72mm APO on my AZ-GTi, and am very pleased with it.  The looks match the mount too.. smile.gif


Here's a pic I found on the web.  It looks just like my setup...



Edited by J_D_Metzger, 01 August 2020 - 01:19 PM.

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#5 25585



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Posted 01 August 2020 - 02:13 PM

Thank you for replies so far. My 66, 70 & 80, all being short tubed seem appropriate. Keeping to 1.25" eyepieces probably.

#6 Robhatherton


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Posted 01 August 2020 - 05:35 PM

I’m using an Altair Astro Ascent 102ed f7. It weighs about 4kg and I use a 9x50 finderscope and 2” diagonal. For visual the mount copes perfectly well as long as the scope is balanced front to rear. 

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#7 MJB



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Posted 02 August 2020 - 12:51 AM

i'm using the AZ-GTi with a Tak FC-100DZ. I would't go much heavier than that, but it seems to cope with that load (plus binoviewer) without much problem. Anything over a slight breeze can get things moving. so next move for me is a tripod upgrade from stock. However, I'm really liking the grab and go nature of the setup. It should work fine with your OTAs, and for the price it's a lot of fun. 

#8 Robhatherton


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Posted 02 August 2020 - 01:45 AM

Sorry forgot to mention, mine is mounted on a heavier tripod the one by Skywatcher similar to the eq5 just with a different bolt on top.

#9 sg6



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Posted 02 August 2020 - 08:25 AM

I use a 72ED mainly as I have a 72ED.

Do not intend to try the 81 triplet and by weight the Megrez 90 should fit but it looks a bit more then I feel safe with - don't care about the mount, do care about the scope.


80mm doublets seem common, thinking the Skywatcher 80ED here.


People have tried 102's but I have a 102 and it looks way too much, even if it is less then the quoted 5Kg, just not a lot less.


So 80mm doublet of reasonable length for moments of inertia and the motors, seem to be the sensible.

However as I sit saying that - when has sensible ever really come in to things?

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#10 Bowlerhat


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Posted 02 August 2020 - 09:15 AM

On the long thread there's a pic of converted AZ GTi with a wedge with astrophotography setup, quite amazing (davidpark's)



The problem is not being able to use it in alt/az, but rather how much load you can put until the gear gave in. The quality control seems to be varied, some people having problem with the slouch, some people can use it accurately even for non guided AP. I have seen people opening it up to give modification to address it. However I'm not sure if they've rolled another update for it.


I also have seen people mounting SCTs, think 5/6"? You can also plug in a weight on side to balance it out. 

Use a long bolt (was it m12/16?) on side, put weight on it. I heard using suppression pads with added weights improves it's load.

Edited by Bowlerhat, 02 August 2020 - 09:16 AM.

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#11 Droro


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Posted 02 August 2020 - 01:46 PM

I use a es80ed, handles it easily on modified az3. Plus I replaced for the adm bracket.
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#12 cst4



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Posted 04 August 2020 - 01:55 PM

I use a 4" F/7 on my AZ-GTi quite often.  I have mine on a sturdier Bogen 475 tripod which I'm sure makes a difference compared to the stock one.  I can use 2" accessories no problem, although most of my 2" EPs are not terribly heavy and I doubt the full weight ever tops 10 lbs. I also sometimes shoot relatively long exposures with my DSLR through this type of refractor and I can get 1 minute subs with no star trailing if the AZ-GTi is aligned and tracking right.  Below is an example shot taken in alt-az with a skyglow filter.  I also use a C6 on it with 2" accessories which is about 2 more pounds than the F/7 4" and it handles it fine.  I've put my Vixen VMC200L on it a few times as well and it worked but I think that was pushing the gears a little much.


Overall I love my AZ-GTi and highly recommend it.  But consider purchasing a better tripod for it if you don't have one.  And also a nice addition is a pan-head to go under the AZ-GTi... the mount does not move very well manually in the horizontal direction, but adding a pan head under it allows you to keep the GTi clutch locked at all times and it is much smoother.  









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#13 ALPHA31


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Posted 06 August 2020 - 05:10 PM

After my ExploreScientific iEXOS 100, also wifi, I found this AZ GTI excellent: quality-price-weight ratio, very complete software. A little trouble all the same to make it run with SkySafari6Plus ... (I only got there once, but how? ...).

Mounted on a Rolleï carbon tripod, and on an EQ base, it easily supports my TS Optic 80mm (3kg), both visually and in photo, with a manufactured bar + 1Kg weight.

For the battery, a tiny Omega (€ 15) of only 4000 mh (with converter cable from 5V to 12V), is enough to power it over several sessions, amazing!

In addition, the SynScanPro app has everything you need for night-time SHOOTING (intervalometer, Time-laps ...), in my opinion, put in EQ mode, it buries the StarAdventurer from afar, on which I had made my choice beforehand.

Perhaps the tripod proposed by SW seems inappropriate, otherwise only happiness in terms of ultra-nomadism


#14 Starman81



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Posted 07 August 2020 - 12:00 PM

The biggest 'frac I put on it was the SV102 Access which is an f/7 and about 10 lbs or so. The mount could handle it but I recall there being shakes, since I was using the stock tripod. I think for heavier refractors you should probably do the counterweight mod and perhaps a sturdier tripod and vibration suppression pads just for good measure. And thrown in an ADM saddle of your choice for more solid mating with the mount. 

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