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Old 19-06-2016, 02:37 AM
Neil
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Skywatchers EQ8

Is anyone using this mount with tripod/pier set-up?, if so what scope( type,weight) r u using? and what results are you getting?
I'm thinking of buying a EQ8 head only, mounting it on my permanent obs/pier .I intend to De-fork a 12" Meade LX 90.I'm told this will weigh about 18kg,plus focused,finder, guide scope and cameras will bring the weight up.
Skywatchers are claiming 50 kg capacity( minus 20 kg counterweights) that would leave about 12 kg for camera and other gear( hope to come in around 5 kg. A margin 7 kg to mount limit(14%).
So I'm asking for comments and opinions on this plan and mount, thank you for any replies .
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Old 19-06-2016, 06:58 AM
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Astroman (Andrew Wall)
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Why minus the counterweights? most manufacturers, including SW rate their mounts to what it can carry. So if the EQ8 is rated at 50kg, then that is what it can carry. Off the Bintel website it says "50 kg Payload Capacity " So this would leave you a little more than 7kg to play with... I have seen a video on youtube of a 16" RC on an EQ8, so it can carry a fair amount of weight by the looks.. I have also seen a GSO12" RC (almost 24kg) on an EQ8. So the mount is definitely capable, but as for operation and usage, I will leave that to others who have the mount to tell you how it performs.
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Old 19-06-2016, 07:18 AM
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Neil,

The 50kg quoted is the weight of OTA etc without the counterweights. I've got a 10" Schmidt Newt, 50mm guide scope, QSI683ws8, parallax rings and Losmandy dovetails on my EQ8. All up it would be in excess of 20kg of imaging equipment. It takes two 10kg counterweights to balance this. Here's a link to a photo of my gear before I got the EQ8.

http://www.iceinspace.com.au/forum/a...e.php?a=193547

I'm getting good guiding results with mine - RA RMS 0.8-1.0 arc seconds, peak 2.7-3.4 arc seconds. I think seeing plays quite a significant part for me as I'm in a built up inner city location.
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Last edited by peter_4059; 19-06-2016 at 07:28 AM.
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Old 19-06-2016, 09:06 AM
Neil
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Thanks Andrew,Peter,
It seems I'm mistaken and I can breath a little easier with it appears only 50% capacity used. I would think a 16" RC would weigh 30kg?
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Old 19-06-2016, 09:31 AM
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Quote:
Originally Posted by peter_4059 View Post
Neil,

The 50kg quoted is the weight of OTA etc without the counterweights. I've got a 10" Schmidt Newt, 50mm guide scope, QSI683ws8, parallax rings and Losmandy dovetails on my EQ8. All up it would be in excess of 20kg of imaging equipment. It takes two 10kg counterweights to balance this. Here's a link to a photo of my gear before I got the EQ8.

http://www.iceinspace.com.au/forum/a...e.php?a=193547

I'm getting good guiding results with mine - RA RMS 0.8-1.0 arc seconds, peak 2.7-3.4 arc seconds. I think seeing plays quite a significant part for me as I'm in a built up inner city location.

I Peter - I wonder how it would go with an OAG?
I have an EQ6 & I find that 1 in 20 frames is lost because I see the guide graph
goes off by 2 to 3 divisions where as it's normally +/- 1 division.
It must be because by an inaccurate worm drive but it's still more then usable.
At least I can see the guide graph when that happens & immediately cancel the shot & delete it.
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Old 19-06-2016, 09:44 AM
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Alan,

I'm not really sure how an OAG would help with seeing? I have considered getting the replacement front casing for my QSI683 with the integrated guider however I don't have a rotator and I don't want to be stuck framing the image to get a guide star.
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Old 19-06-2016, 12:09 PM
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Quote:
Originally Posted by peter_4059 View Post
Alan,

I'm not really sure how an OAG would help with seeing? I have considered getting the replacement front casing for my QSI683 with the integrated guider however I don't have a rotator and I don't want to be stuck framing the image to get a guide star.

I know that I couldn't do the job properly without an OAG as
there would always be differential flexure between the guide camera & the main camera sensor.
Not only that - an OAG is working at the native focal length &
so is far more accurate than a little guide scope.
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Old 19-06-2016, 12:24 PM
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Quote:
Originally Posted by alpal View Post
Not only that - an OAG is working at the native focal length &
so is far more accurate than a little guide scope.
That seems intuitive, but I don't think that it is any longer the case Alan - Craig Stark explains why in http://www.stark-labs.com/craig/reso...raig-Stark.pdf

Back in the days of film imaging and
manual guiding, there used to be a rule of
thumb that the guide scope should be at
least half the focal length if not the same
focal length as your imaging scope. ...With CCD-based
autoguiding this rule can be thrown away.
Computers are far better at spotting very
small movements and far faster and more
accurate in their reactions.
With modern guide software, motions
that are small fractions of a pixel can be
accurately estimated....
Personally, I use a 66-mm telescope with a
388-mm focal length (William Optics
Zenithstar 66 SD doublet). I know many
who use scopes of similar focal lengths and
have even seen excellent results from an
8x50 finderscope that had been converted
into a guide scope (200-mm focal length).
The SBIG eFinder accessory for their STV
guider is even shorter at only 100 mm! The
days of very long focal length guidescopes
are over

FWIW, I use a 180mm fl guidescope with a QHY5L2. At times it keeps the EQ8 within 0.4 arcsecRMS, normally about 0.7 RMS and in bad seeing it is >1arcsec RMS - and then I don't usually bother with imaging. With 8 inch wheels, the EQ8 is inherently better than the EQ6, since minor fluctuations in mesh due to surface and/or grease irregularities (dirt etc) are less noticeable. An EQ8 will handle the Meade with ease.

Last edited by Shiraz; 19-06-2016 at 02:54 PM.
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Old 19-06-2016, 04:31 PM
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Hi Ray,
Craig Stark is a heavy hitter so I don't want to argue with him.
His advice is not based on any scientific test but is more subjective.
I mainly used an OAG to stop differential flexure problems.

cheers
Allan
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Old 20-06-2016, 10:56 AM
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rustigsmed (Russell)
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hi Neil,

I use a 12" newt on my eq8 - it handles the weight with ease.
I think a 14" scope is likely fine and I would guess a 16" is pushing it to the limits. they do have a bit of backlash but are strong.

might be worth looking at the yahoo group https://groups.yahoo.com/neo/groups/SkywatcherEQ8/info

Cheers

Rusty
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Old 20-06-2016, 12:12 PM
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billdan (Bill)
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If anyone is interested in repairing the DEC backlash on an EQ8, there is a strip down video on SGL.
The owner manages to reduce the DEC backlash from 1.8 sec to 330mS, as reported by PHD assistant.


https://stargazerslounge.com/topic/2...8-users-video/

Cheers
Bill

Last edited by billdan; 20-06-2016 at 12:28 PM.
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Old 20-06-2016, 01:19 PM
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I wouldn't go to all that trouble to adjust the dec backlash. There is a procedure to adjust the backlash that is much more straightforward.
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File Type: pdf Adjusting the Declination Axis Backlash - Orion.pdf (340.8 KB, 35 views)
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Old 20-06-2016, 07:03 PM
Neil
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Thanks Ray, Russell and Bill for the info and advice. It looks like I will be investing in a EQ8, thanks to all.
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