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Old 03-09-2019, 11:20 PM
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Astrofriend (Lars)
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Small not to expensive GOTO mounts

Hi,
After my positive test with a Canon 300 mm lens on my Star Adventurer mount I'm now looking for a small and easy transportable GOTO mount and not too expensive.

Demands:
Low cost, < 500 Euro
Load: < 5 kg
High precision: < ? max one minute exposure time and a 300 mm high quality lens
Weight: < 5 kg

I like the iOptron CubePro which is said to have worm gear of brass. The SkyWatcher allview mount looks good to me, but I think the gears are too simple. Or any of you who have diassembled and look into what's there?

I have made a list of links to small GOTO mounts:

http://www.astrofriend.eu/links/link...oto-mount.html

Some of them are for sure toys. Some mounts that cost more and weight more than my demands above.

/Lars
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Old 04-09-2019, 11:11 AM
Wavytone (Nick)
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I had an AllView - bought it thinking of going to see the 2017 solar eclipse, as it can do a 1-star alignment using the sun and will track that quite well if the base is accurately levelled. Perfect for scopes up to a refractor 102mm f/7, a 127mm mak or C5. I sold mine after buying a 180mm mak (which was way too big for it).

It is IMHO quite nice and under-estimated, the gears are fine BTW - I had it tracking planets with a 70mm quad APO (heavy beast weighing 3.5kg) at 200X with no issues at all so for guiding a DSLR and any lens within reason it is fine.

But... it has three issues:

1. The UGLY factor - it really IS plug ugly. Skywatcher really need to find an industrial designer.
2. The tripod supplied is very flimsy and inadequate. You can replace that but it ups the cost to the point you may as well consider an iOptron Cube.
3. It eats batteries. If instead you power it via the wall-wart or a battery below, watch out for the cable while it slews in azimuth - it has a tendency to rip it out of the plug.

But for a small grab & go scope it is a pretty good solution and, for airline travel, could fit on a solid camera tripod if you have one.

It also comes with several brackets for attaching cameras, upto DSLRs; Trying to by equivalents separately will cost another $100-200.

Last edited by Wavytone; 04-09-2019 at 11:27 AM.
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Old 04-09-2019, 11:55 AM
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Astrofriend (Lars)
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Hi,
Thanks for the long answer with info.

I'm going to use it for astro photography, then I need to mount it on a wedge to tilt RA axis in parallel with Earth axis. Is it possible to setup it in the menu for equatorial mode. Or maybe it can be setup as if it where on the northpol. Any experience from that ?

Lars
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Old 04-09-2019, 12:04 PM
Wavytone (Nick)
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Couple more for your list

https://www.rothervalleyoptics.co.uk...ing-mount.html

Astrotac 360 - which has been vapourware for 2-3 years, maybe it will ship, maybe not. I suspect they found it harder than it seemed to make a friction drive that works reliably. https://www.astrotrac.com
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Old 04-09-2019, 12:06 PM
Wavytone (Nick)
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Lars the AllView is not for equatorial operation, though I suppose you could tilt it on a wedge/tripod, and set the position as the north/south pole and it should work. I'd want to try that before buying though, because in software funny things happen at 90 degrees. Might be fine, might not.

If you're just doing photography (ie no telescope and no visual use) I'd suggest the Fornax tracker is a more appropriate match - it has been well tested, works well, smaller and more compact if you're travelling with it.
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Old 04-09-2019, 12:13 PM
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GoTo Mount = Any suitable mount (mechanicals) + OnSTEP

Last edited by bojan; 04-09-2019 at 07:10 PM.
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Old 04-09-2019, 05:52 PM
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bojan, your link goes straight to an Ice In Space page not found.
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Old 04-09-2019, 07:10 PM
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oops..

Corrected.

http://www.stellarjourney.com/index....uipment_onstep
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Old 05-09-2019, 05:30 AM
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Hi,
Thanks for all comments.

Note, not looking for only tracker, I looking for two axis trackers with GOTO. I already have the Star Adventurer when going with lgiht package.

The latest I found is that the Celestron Nexstar Evolution has bras worm gear. But hard to find one without telescope I think.

The small iOptron cube pro also has bras worm gears and that one is prepaired for EQ mount.

The SkyWatcher Allview seems tricky to get to work in EQ mode. Part of the sky in the software will be below the horizon if doing the trick I mentioned. Don't know if it will refuse to goto that stars. Maybe best to not go for this mount, but do any knows if it has bras worm gear or only spur gears?

/Lars
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Old 05-09-2019, 06:07 AM
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You should also consider friction-type reductor... No backlash, cheap and easy to fabricate.
Or stack of timing belt reductions...

See here.
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Old 05-09-2019, 06:29 AM
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Hi Bojan,
I thought about a only belt driven mount with stacks. But didn't feel it will get enough precision.

Say 120:10 x 60:10 x 60:10 (432:1) and a 400 step/rev stepper motor. Could that really work?

Thanks for the link, night time reading for me, looks very interesting.

/Lars
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Old 05-09-2019, 06:53 AM
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It will work, of course..

Tracking accuracy is not an issue with guiding in place.
As to pointing accuracy I don't know, it depends on manufacturing precision of course.. for visual probably not an issue at all, and you can check (plate solver) before you start actual exposure.
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Old 05-09-2019, 07:06 AM
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I mean, isn't the timing belt stretching and cause big errors?

With my 300 mm lens and a 50 Mpix camera the pixel scale is something like 3 arc second per pixel. Maybe a resolution and a guiding precision of 1" will be good enough. Not very high.

/Lars
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Old 05-09-2019, 07:23 AM
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Should be OK..

Actually as long as your target is somewhere on a sensor (say, 1/3 of sensor diagonal length away from centre), IMO it is still acceptable and easy to correct.
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Old 05-09-2019, 07:46 AM
Wavytone (Nick)
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Lars, Iím sorry but there is one glaring issue with attempting to use the AllView equatorially - it has no counterweight to balance the camera and lens. That means the gears will be straining against the full imbalanced load. While that might be ok with a compact like my LX5, thatís not going to work well with a DSLR.
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Old 05-09-2019, 07:53 AM
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For example, stack of 3 1:12 friction (or timing belt) reductors will give you overall reduction of 1:1728. With 200 steps motor, it is more than enough for 300mm lens.
My belt-modified EQ6 (as well as yours) has 1:900 reduction (180*5).. and 400steps/rev motor..


BTW, have a look at my mount for wides (including 300mm).
http://www.iceinspace.com.au/forum/s...&highlight=eq3
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Last edited by bojan; 05-09-2019 at 08:34 AM.
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Old 05-09-2019, 09:57 AM
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Quote:
Originally Posted by Wavytone View Post
Couple more for your list

https://www.rothervalleyoptics.co.uk...ing-mount.html

Astrotac 360 - which has been vapourware for 2-3 years, maybe it will ship, maybe not. I suspect they found it harder than it seemed to make a friction drive that works reliably. https://www.astrotrac.com
I read a post where they are starting to ship. I'd await confirmation though.

Greg.
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Old 06-09-2019, 07:14 AM
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Astrofriend (Lars)
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Hi,
@Wavytone,
That's the idea behind the Allview mount. You don't need the counter weight balance because it's design with a fork arm. You can move the camera to the center of RA axis and also to the center of DEC axis (if you have tilted it like a GE mount). All the brackets you need to do this are included with the mount.

@Bojan,
I'm very impressed of all things you have built, lot of smart details and looks good too. How many mounts?

/Lars
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Old 06-09-2019, 07:36 AM
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Quote:
Originally Posted by Astrofriend View Post
..... @Bojan,
I'm very impressed of all things you have built, lot of smart details and looks good too. How many mounts?

/Lars

I don't know the exact number :-)

It all started (officially) with the one shown on attached image, built (with some help from my father who organised machining of the RA shaft) for Republic and Federal competition back in 1968... It had terrible PE (even visible on images taken with 45mm FL Smena-8 camera), but it ensured me the 1st prize (transistor radio) on both :-)
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Last edited by bojan; 06-09-2019 at 07:59 AM.
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Old 06-09-2019, 08:50 AM
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Hi Lars,

This is a mount built by Rainbow Robotics in Korea, the RST-135 uses strain wave gears, weighs 3.3Kg and can handle a payload of 13.5Kg without counterweights or 18Kg with counterweights.

It can be used in ALT/AZ or EQ mode, comes with internal GPS, WiFi and an ASCOM driver plus hand controller.

http://www.rainbowastro.com/new/them...roduct-135.php

There is also a discussion on Cloudy Nights from those who have purchased this mount, explaining its pluses and minuses.

https://www.cloudynights.com/topic/6...imaging-mount/

Cheers
Bill
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