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Big Scope, Little Scope


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Bigger aperture scopes are far better suited at observing stationary objects due to their narrower field of view. Also, due to their greater aperture and magnification than a smaller scopes, they are suited for viewing objects at great distances such as stars, planets and the Moon. I hope that's answered your question?

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Thanks for your replies.

I have a 60mm and a 100mm refractor. At the moment the 60mm is being used on a more regular basis than the 100mm as it is very quick to set up and there is no real cool-down time. It doesn't take much longer to set up the 100mm but it is a triplet so the cool-down time is about 45 minutes. This isn't that long to wait but I am currently finding that the 60mm does a lot (enough for me) of what the 100mm does so the 100mm scope is not being used as much. This will probably change as Jupiter becomes better placed but it has got me thinking that if I am going to wait for a scope to cool down then maybe it should be for one with a larger aperture than 100mm, like a 180 or 200mm reflector.

Al

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Thanks for your replies.

I have a 60mm and a 100mm refractor. At the moment the 60mm is being used on a more regular basis than the 100mm as it is very quick to set up and there is no real cool-down time. It doesn't take much longer to set up the 100mm but it is a triplet so the cool-down time is about 45 minutes. This isn't that long to wait but I am currently finding that the 60mm does a lot (enough for me) of what the 100mm does so the 100mm scope is not being used as much. This will probably change as Jupiter becomes better placed but it has got me thinking that if I am going to wait for a scope to cool down then maybe it should be for one with a larger aperture than 100mm, like a 180 or 200mm reflector.

Al

That's a really good idea. The bigger the aperture the better.

The bigger telescope will show fainter objects than a smaller telescope with, and be able to show them at a higher resolution too. Double stars that are a challenge for the larger scope would never be resolved in a smaller telescope under the same conditions for example. Also, a larger telescope can be used at higher magnifications than a smaller telescope can before the image quality breaks down. Good Luck Al! :)

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Thanks Telrad.

I think I just need to find a good balance between aperture and usability within the context of my local seeing conditions. The 100mm refractor I own becomes diffraction limited from my location on a regular basis. The 60mm becomes diffraction limited more often (as you would expect) and its small aperture is offset (for me) by its ease of setup and the fact that it is just so much fun to use.

The last thing I want to do is buy a larger aperture scope and not use it very often, however my seeing log does suggest that a 180 or 200mm scope would get close to being diffraction limited on a fairly regular basis, just not as often as the 100mm. I like sharp images of the planets so I guess I just need to find that balance. The two scopes I have are probably too close in size but I just need to consider how large a departure from the 60mm I should go.

AL

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For those of you who, like me, don't have an permanent setup for your big scope; what is the number one motivating factor when choosing to use your big scope in preference to your little scope? Time, predicted seeing conditions or subject matter?

Al

Edited by astro_al
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For those of you who, like me, don't have an permanent setup for your big scope; what is the number one motivating factor for choosing big scope over little scope? Time, predicted seeing conditions or subject matter?

Al

Mine had to be subject matter. I opted for a large dob on the basis of DSOs. It has motivated me much more so since getting one, and I appreciate the beauty of them more now, rather than just a fuzzy blob :)

I agree with Russ too, the 250px is approximately the same as a 90mm refractor :)

Edited by Telrad
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Choice for me depends on all three things you mention. If I have time and the conditions look like they are going to be clear for a decent time then I will always choose to put the Sphinx mount out. If it's patchy cloud and looking like only a few quick peeks are possible then I'll use the Porta mount, or rather the Giro now I've got it.

Scope choice..... If the seeing is good then I'll choose the Mak, it's sensitive to poor seeing. If I'm trying for a bigger target, looking at doubles or clusters, or the seeing is a bit more marginal then I'll use the 106 refractor which will still give good views up to relatively high mags.

For quick sessions, I use the 66mm refractor which is set up in a minute or two and gives surprising good views still. Normally take this one away with my if I go abroad, with a camera tripod which is not great but just about does the job.

Ultimately a 10 or 12" will end up as my big scope. Or 14 or 16"........ Depends what I can get away with/afford :-)

Cheers

Stu

Sent from my GT-I9000 using Tapatalk

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For those of you who, like me, don't have an permanent setup for your big scope; what is the number one motivating factor for choosing big scope over little scope? Time, predicted seeing conditions or subject matter?

Al

For me it is the other way around. I have the binoculars and the little 70mm frac out in the back garden. I have a 10" newt and an neq6 which effectively is my grab and go.

There is not much quality in viewing from my garden.. I have access to a fabulous viewing spot and even if I only get a short time to view it is always worth the effort. It takes an hour from loading all the kit in to the van to getting set up..

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For real grab and go I use 20x60 binoculars on a camera tripod. If we are going away in the car overnight or something then I generally take the Skymax 127 and EQ3-2. My current 'big' scope is my 150P with the camera and laptop etc. but I have a Skyliner 250PX due for delivery tomorrow :)

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I have an 80 mm triplet APO, and a C8 at 203mm. The C8 does not have a permanent set up, but I can get it out in 5-10 minutes. Cool down time is short as I store it in an (almost) unheated garage. Only if the day-time temperatures are high do I need a cool-down time of 30-45 min. The C8 gets most use by quite a margin. It can see far more than the 80 mm both on planets and on DSOs. I will probably drag it out tonight to get another go at sn2011dh.

The 80 mm does get used for wide-field objects (NGC 7000, Pleiades, double cluster, Beehive, Rosette) and is excellent on those. And of course, it fits in the hand luggage.

Quickest of the grab-and-go brigade are the 15x70 bins I have.

Edited by michael.h.f.wilkinson
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SW 200P Newt is my big scope, and today I received an ETX70 bought for portability. As for which I'd use for a quick session - I only expect to use the ETX70 on its own away from my house, otherwise I'll still use both.

The other reason for the ETX is the GOTO mount. I plan to use the ETX70 in conjunction with my SW to assist me in locating objects - something I'm not doing as well as I should be.

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Hi Al

I have as in my sig a 10" grab n go Dob for quick sessions and when the moon prevents DS observing.

My main scope is a 16" Dob.

The criteria for which scope for me depends on the conditions or where I am going to observe from.

If I'm going long distance I always take the larger scope.

Local trips I normally take the 10".

Regards Steve

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I have 102mm and 125mm scopes which are pretty portable and 152mm and 250mm ones which can be moved around easily enough but I would not want to carry them far. I've tried a few 80mm grab and go's but ultimately I find that aperture limiting so 102mm is where the fun stars for me :)

Edited by John
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