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Trikeflyer

Double star scope and mount

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I'm looking to get the skywatcher ED 100 DS pro refractor for double stars and general use (moon and planets) mostly from a suburban back garden.  Thinking about the mount and balancing ease of use with accuracy, are good doubles do able with an AZ4 manual mount and will this take the weight of this scope or should I invest in an eq5 goto? 

I'd value an opinion from anyone with experience in the double star in light polluted skies.

Steve 

 

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I have saw loads of double stars from my backyard. I have had to make this after a street light was installed. I have a Tal 100rs on a EQ5 mount. 

I use sissy hass which was recommended by Nick (Cotterless45)

20171023_182347.jpg

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I cannot speak about the AZ4 but, as far as using your scope on an Altaz mount goes,  I have used my Tal100RS on the Skytee2 and have found it stable, easy to find objects, easy to keep the objects in the field of view up to magnifications of around 200x, beyond this you will benfit from a tracking mount or slow motion controls in my opinion. For double star work, not sure goto is required, but a tracking mount might help with really tricky doubles by keeping  them in the centre of the FOV and steady. The trade off is EQ's take longer to set up so you may end up doing less observing.

Edited by RobertI
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A heavy duty driven equatorial is essential. For tight doubles you'll be using high power and you want something stable. Trying to track at high power with alt-az can be very frustrating.

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I often look for doubles as they are one of the things readily visible from a light polluted site. I have to say I rely heavily on GoTo for this as I use lists that include objects well below naked eye visibility. If all goes well I press the buttons and then I can see a star looking double, or assume which star needs more magnification if it's listed as a close double.

If you go for the Alt-az mount, I recommend fitting a good finder, e.g. a 9x50 RACI which may look pricey but will save a lot of grief and neck-ache.

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I would have to agree with Mr.Spock, when going after close/ very close doubles a stable EQ mount is needed. 

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I have the same scope on AZ4. I like it now but it took a bit of getting used to not having slow motion controls. My 10mm ortho gives me beautiful stars at 90x and I prefer the views to my 6mm at 150x. It's still doable on the mount with a bit of practice. I'm actually just waiting for the clouds to pass during an Orion doubles session. Very satisfying and I might not have set up tonight with a more complicated set-up.

Edit- actually it's a little bit annoying at 150x but no probs at 90. I've just been outside again for a small gap in the clouds.

Edited by domstar
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I think a goto mount can be very useful for doubles, particularly if you want to crack through a list of them. Even with goto it can still be a challenge to locate the correct star, but as Michael says, a nice solid mount that tracks can really help you concentrate on splitting the tight ones.

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I've decided to get a goto mount. Thanks guys for the input. I have decided to go for something solid that can take my Meade etx 125 and also potentially my revelation astro 8 inch newt ( currently I use it as a dob). I have a 12 inch revelation which I will keep as a dob. I don't yet have the skywatcher frac and I'm interested to know from domstar if he is delighted with the scope? Any other opinions also welcome! I'm thinking of getting a used neq6 pro. Is that overkill or a reasonable option? 

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Hi, yes I love it more and more. The clear and icy conditions here  last week really showed what it can do on beautiful doubles and it always gives lovely views of the moon. I should mention that it's only the second scope I've used so you should talk to some of the more experienced members. I chose it for reasons of portability and balcony space and the longer I use it the more I appreciate it (even though I sometimes dream of a big dob). I'm one of life's cheapskates and it's unusual (and satisfying) for me to own something that feels so luxurious.

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I'm currently using a 150 f/6 Newtonian on a Losmandy AZ8 atop a Berlebach Planet. This manual alt-az mount has slow motion control - something I would not want to do without when manually tracking tight multiples at 300x. :icon_biggrin: So I do it all manually, and it's lots of fun and very satisfying. I do have the benefit of a couple of years of practice.

I have yet to try an EQ mount, or anything motorized. This was a conscious decision to keep things simple from the outset and in my case it has paid off and continues to do so.

I'm sure the benefits of a properly aligned EQ mount and/or a motorized one which automatically (acquires and) tracks the target are worthwhile, so don't take this the wrong way, it's just my approach to do without.

:happy11:

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For doubles, virtually any scope and mount will do I suspect. With my 180 Mak at high mag, I use either my SkyTee2 alt-az mount or my Vixen SP equatorial; each has its advantages and disadvantages. At say x400, the double will remain in the field for long enough with alt-az to get a good look, and if you can reach the slo-mo controls easily, with practice you'll be able to keep the star in the field. With my long frac, it is more difficult as my arms aren't long enough.......

Chris

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@chiltonstar Wow 400x that's pretty impressive. What stars are you looking at at that magnification? What sort of separation can you get down to? How sharp are the stars? 

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59 minutes ago, domstar said:

@chiltonstar Wow 400x that's pretty impressive. What stars are you looking at at that magnification? What sort of separation can you get down to? How sharp are the stars? 

I find that the scope will go up to about ca. x400 in excellent seeing (warm hazy nights usually) and resolve down to separations of about 0.7 arcsec for objects well above the horizon (On "another forum" there are quite a few test doubles for scopes of different apertures). I've been looking at a range of doubles with separations between 0.7 and 1.0 arcsec - when the conditions are good enough, these resolve as sharp disks, whereas at x540 (5mm EP) signs of slight lack of sharpness begin to appear.

Chris

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High powers work well on doubles. I use x392 on my C9.25. Despite being an SCT it will split quite close doubles.

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