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Equipment Discussions >> Refractors

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Yamato
member


Reged: 07/17/13

Low price guiding scope? new
      #6174911 - 11/04/13 06:19 AM

Hi.

I'm new to astrophoto. Actually only interested in doubles and open clusters.

Well, the point here is that i'm going to buy a CCD camera for this task, but I realize that I would need a guiding scope, or at least a scope mounted "piggyback" the main scope to know if I'm pointing to the correct place in the sky. The "guiding" will be done visually, or even call it "aiming secondary scope".

Astrophoto will not be my main interest per-se, but I will use it as a tool for measuring and "recording" observations and such. I don't like to get beautiful astrophotographs.
So, I'm looking for a very low budget but funcional guiding/aiming scope.

I had in mind a very short tube, refractor-type, as light as possible, and even allowing me to grag&go it for fast observations when I don't want to carry my longish refractor. The main scope is a 100mm f/10 achromat over an EQ5 (this OTA is 3.5Kg).


So, I have been looking arround, and found these two cute scopes:

either the SkyWatcher Startravel 70/500 or the Startravel 80/400:

http://www.skywatcher.com/product.php?cat=3&id=7
(The scopes will be bought as OTA, don't take their mount into account)


Bresser, SkyWatcher or whatever brand, I don't mind at all.

The point is, the 70/500 is only 0.9 Kg (1.98 pounds) weight, which is really low weight, rising everything to barely 4.5 Kg, but this offers slightly less FOV.
And the 80/400 is 1.5 Kg (3.3 pounds) wich will rise the total weight to 5Kg, but this scope offers slightly more FOV.

So, I'm stuck here, don't know what to do exactly. I would say that the 70/500 would be better because of the noticeable lower weight, even when the fov will be slightly less.
But in the other hand, the 80/400 would be maybe a better option for a fast grab&go scope over an EQ3 mount or even a "kid's scope".

Also, both scopes costs roughtly the same, around 100 - 120 or $

So finally, any other option would be also taken into account.

So, any tip?

Thanks a lot.


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obin robinson
Carpal Tunnel
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Reged: 10/25/12

Loc: League City, TX
Re: Low price guiding scope? new [Re: Yamato]
      #6174915 - 11/04/13 06:33 AM

Consider building one using a binocular objective lens. Binoculars have a fast focal ratio so the scope doesn't need to be very long. It should not be hard to find a broken set of binoculars to get the lens from.

obin


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cloud_cover
professor emeritus


Reged: 08/17/10

Loc: Restaurant at the End of the U...
Re: Low price guiding scope? new [Re: obin robinson]
      #6176706 - 11/05/13 01:47 AM

Have you considered getting a 50mm finder/guider? At 1000mm focal length (primary imaging scope) it should work and is very light.

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Yamato
member


Reged: 07/17/13

Re: Low price guiding scope? new [Re: cloud_cover]
      #6176789 - 11/05/13 04:48 AM

Quote:

Have you considered getting a 50mm finder/guider? At 1000mm focal length (primary imaging scope) it should work and is very light.




Do you mean something like this?

That is basically a 55/205 mini-refractor.

Definetely, that would be a better option.


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*skyguy*
Carpal Tunnel
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Reged: 12/31/08

Loc: Western New York
Re: Low price guiding scope? new [Re: Yamato]
      #6177210 - 11/05/13 11:37 AM

The Celestron 70mm Travel Scope would make a good guidescope. The opics are very good, it's very lightweight and it even has a lock down screw on the focuser. Always available in Europe on eBay for around 55 Euros.

Celestron 70mm Travel Scope


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desertlens
scholastic sledgehammer
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Reged: 12/06/10

Loc: 36N 105W
Re: Low price guiding scope? new [Re: Yamato]
      #6177374 - 11/05/13 01:15 PM

Check out this one from Stellarvue. There's no link from their home to this page at the moment but I fished this one out of my history. Available soon...

Edited by desertlens (11/05/13 01:16 PM)


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rkayakr
sage
*****

Reged: 10/27/10

Loc: Northeast Ohio
Re: Low price guiding scope? new [Re: desertlens]
      #6177993 - 11/05/13 06:49 PM

ZWO, who make the popular ASI120 cameras, sell a light, inexpensive 60 mm / 240 mm guide scope for $99 including rings and dovetail.

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Stew57
Carpal Tunnel
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Reged: 05/03/09

Loc: Silsbee Texas
Re: Low price guiding scope? new [Re: rkayakr]
      #6178407 - 11/05/13 11:35 PM

Take your finder and make it do double duty.
http://s906.photobucket.com/user/mstew57/library/Finder%20modifications%20for...


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MooEy
member


Reged: 10/02/07

Re: Low price guiding scope? new [Re: Stew57]
      #6178708 - 11/06/13 07:35 AM

50mm finders are some of the best guiders you can get. Lightweight, all threaded connections, very fine focusing and the focus stays fixed forever.

Modern Astronomy sell adapters for the finders. Stellarvue sells some of the best finder rings. Either the starshoot autoguider or the qhy5 is good. ASI 120mm is good too.


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mamamia
super member
*****

Reged: 10/11/13

Re: Low price guiding scope? new [Re: MooEy]
      #6178979 - 11/06/13 10:55 AM

How about buying the Mini Auto-guider package from Orion? I think its cheaper than building your own using spare parts.

Stellarvue Guider Scope - $99
Stellarvue Guider Rings - $45
QHY5 Camera - $270

Orion Mini $350

Unless taking build your own provides better performance than Orion Mini Guider.


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Wmacky
Carpal Tunnel
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Reged: 11/24/07

Loc: Florida
Re: Low price guiding scope? [Re: MooEy]
      #6180741 - 11/07/13 10:39 AM

Quote:

50mm finders are some of the best guiders you can get. Lightweight, all threaded connections, very fine focusing and the focus stays fixed forever.

Modern Astronomy sell adapters for the finders. Stellarvue sells some of the best finder rings. Either the starshoot autoguider or the qhy5 is good. ASI 120mm is good too.




Adapters for the Synta / Skywatcher / Celestron 50mm finders are available from Agena Astro for $29. BUT - If the finder is more the a couple years old you MUST check the mating thread on the finder, and confirm that it is 2" SCT thread. The thread was changed,and used to be much finer. I just did mine. No work at all other than 5 seconds to screw in the adapter. As stated, all threaded connections, so no sag / flex issues. ( this with cams that have a T2 threaded connection - ASI120, SSAG ETC.

Mooey - Your also dead on about the Stellarview guide rings! Last month I searched for the very best stable guide rings with a vixen type shoe, and those were the rings. I love them, and they are on the guider now. The Orion holder is not recomended, Nor any rings with a rubber o-ring. I'll post up a pic when I get home today.

Edited by Wmacky (11/07/13 11:02 AM)


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Yamato
member


Reged: 07/17/13

Re: Low price guiding scope? new [Re: Yamato]
      #6182296 - 11/08/13 05:32 AM

The problem I found just yesterday with a viewfinder is that my OTA has two holes to screw the actual 6x30 finder pier. This is: my viewfinder pier is not attached to a "standard" base, it is directly screwed to the OTA.

The distance between those two holes is 39 milimeters, and after looking and asking in several online shops and local dealer, the closest finder base I could find had the holes with a distance of 40.5 milimeters, so it won't fit the actual holes and I'm not drilling new holes to the OTA, so unless I find a compatible base, the viewfinder will not be an option.

Also I asked for clamp rings the diameter of the new viewfinder to attach the viewfinder to the main OTA with a new dovetail, but there aren't so small clamp rings.

So I think that a short focal, lightweight refractor mounted over the main OTA is the best option.

I would probably get the SkyWatcher 70/500 since it is ~300 grams less than the SW 80/400, the aperture is basically the same and I can use it also as a grab&go scope.


I'm waiting for a local dealer to ask prices to distributor.
He told me that he may be able to find a short Pentaflex OTA that is a bit lighter than the Skywatcher. But shivers run through my body when hearing "Pentaflex"...

I have been searching around google but I couldn't find any Pentaflex short tube. Anyone has some information? I won't be interested in a plastic lens toy scope, but maybe it could be a decent scope.


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MooEy
member


Reged: 10/02/07

Re: Low price guiding scope? new [Re: Yamato]
      #6182298 - 11/08/13 05:44 AM

I can't see why there would be any reason that you can't fit a dovetail base onto it. There are many options.

http://www.optcorp.com/os-vfs-vixen-style-dovetail-finder-shoe.html

http://www.telescope.com/Orion-Dovetail-Base-for-Finder-Scope/p/7214.uts

http://www.scopestuff.com/ss_rdpq.htm

And the stellarvue finder brackets pretty much work on vixen/synta style finder dovetail base. Get the R50D.

http://www.stellarvue.com/f50.html


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MooEy
member


Reged: 10/02/07

Re: Low price guiding scope? new [Re: mamamia]
      #6182308 - 11/08/13 06:00 AM

There's no comparison between diy and the orion package. Unfortunately all the parts in the orion package is of a lower grade and you will eventually want to replace all of them.

The finder rings is spring loaded and has only 3 points, expect it to move around.

The guider camera is of a yesterday sensor, the newer ASI-120MM and qhy5-II has a better and more sensitive sensor.

The focusing mechanism is the same as other finders. But the rear end of the scope is a standard 1.25" attachment with 2 set screws. Set screws can never hold as well as T-Threads. And to reach focus, you will have to slide the barrel of the guider out by a little. There is a tendency to dismantle after every session.

Time wasted in refocusing, readjustment of the finder bracket could be better spend on getting more starlight. For all purpose, threaded adapters to use existing finders are significantly more robust. And there's a likelihood that there's already a 50mm finder somewhere in your drybox.


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Yamato
member


Reged: 07/17/13

Re: Low price guiding scope? new [Re: MooEy]
      #6182358 - 11/08/13 07:11 AM

Quote:

I can't see why there would be any reason that you can't fit a dovetail base onto it. There are many options.

http://www.optcorp.com/os-vfs-vixen-style-dovetail-finder-shoe.html

http://www.telescope.com/Orion-Dovetail-Base-for-Finder-Scope/p/7214.uts

http://www.scopestuff.com/ss_rdpq.htm

And the stellarvue finder brackets pretty much work on vixen/synta style finder dovetail base. Get the R50D.

http://www.stellarvue.com/f50.html





Ok, wait, I think I will post images of the problem.

This is how my 6x30 finder is fixed to the OTA:




And those are the holes in the OTA to scren the finder's pier:





The pier shoes commonly sold don't have that exact distance between screw holes, so I would need to phisically modify the OTA itself to adapt it to the new pier shoe.

The only option I see here is the one from scopestuff.com, http://www.scopestuff.com/ss_rdpq.htm.
The only thing I don't like about it is the fact that it is only fixed with a single screw.


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Wmacky
Carpal Tunnel
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Reged: 11/24/07

Loc: Florida
Re: Low price guiding scope? new [Re: Yamato]
      #6182392 - 11/08/13 08:00 AM

I have a refractor with a single hole Vixen style base. It hold fine as the OTAs curve locks it in place. Not sure about large guide scopes though. For that I would only use scope rings mounted to a dovetail bar which in turn was mounted to the top of the main scopes rings.

Edited by Wmacky (11/08/13 08:05 AM)


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Yamato
member


Reged: 07/17/13

Re: Low price guiding scope? new [Re: Wmacky]
      #6182623 - 11/08/13 10:12 AM

Quote:

I have a refractor with a single hole Vixen style base. It hold fine as the OTAs curve locks it in place. Not sure about large guide scopes though. For that I would only use scope rings mounted to a dovetail bar which in turn was mounted to the top of the main scopes rings.




Yes, the dovetail thing is what I want to do:



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mamamia
super member
*****

Reged: 10/11/13

Re: Low price guiding scope? new [Re: MooEy]
      #6183855 - 11/08/13 11:32 PM

Quote:

There's no comparison between diy and the orion package. Unfortunately all the parts in the orion package is of a lower grade and you will eventually want to replace all of them.

The finder rings is spring loaded and has only 3 points, expect it to move around.

The guider camera is of a yesterday sensor, the newer ASI-120MM and qhy5-II has a better and more sensitive sensor.

The focusing mechanism is the same as other finders. But the rear end of the scope is a standard 1.25" attachment with 2 set screws. Set screws can never hold as well as T-Threads. And to reach focus, you will have to slide the barrel of the guider out by a little. There is a tendency to dismantle after every session.

Time wasted in refocusing, readjustment of the finder bracket could be better spend on getting more starlight. For all purpose, threaded adapters to use existing finders are significantly more robust. And there's a likelihood that there's already a 50mm finder somewhere in your drybox.




Really?? what about software support? do you think one can build a superior guiding scope without having to get the package. If yes, I'm be interested to learn more. Reading raving reviews about Mini Guider I was under the impression that it was the best guider.


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LewisM
super member


Reged: 01/23/13

Re: Low price guiding scope? new [Re: mamamia]
      #6184130 - 11/09/13 06:40 AM

I use a Takahashi 7x50 finderscope (which is better optically than many bigger scopes!), married to the guidecam back from an Orion miniguider, plus a Lodestar. I have NEVER had an issue finding a guide star, the image is superb (I can easily see most nebulae and galaxies in the guider image, so I KNOW I am on target).

I currently have it mounted in an old Vixen 6 point finder bracket (hammertone green - shows how old it is) - I replaced the 3 "set screws" with another 3 adjustable screws from ANOTHER ixen bracket, and so it is 6 points holding it, FULLY adjustable, but ROCK solid (never showed even a skerick of flexure). I have had 2 aluminium rings of I.D 53mm, O.D 60mm made up so it can fit a set of small Borg tube rings I have, and will then mount it on a dovetail on the top. I do NOT need it to move (it will be aligned with the main tube), because as I said, ALWAYS can find a guidestar with the Tak and Lodestar.

The Orion miniguider is... well... useful for parts. The finder itself is rubbish (really poor optically, and I could NEVER get a decent star image with it), and the guidecam itself may as well be a calculator. Finding guidestars with that SSAG was like trying to find an old corroded needle in a wet haystack. It all works... JUST. I needed a good 2 inch extension with it when I replaced the SSAG for the Lodestar, but I was still not happy and finally found a used Tak finder at a good price. No extension piece, and it is a marriage made in heaven.

I have tried a lot of the guidescopes on the market, and disliked every one of them - either too bulky or optically poor. The Orion short tube guidescope needed a 4 inch extension tube for anything to come to focus with it - of course, optional extra.


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Yamato
member


Reged: 07/17/13

Re: Low price guiding scope? new [Re: LewisM]
      #6184217 - 11/09/13 08:45 AM

Quote:

I use a Takahashi 7x50 finderscope (which is better optically than many bigger scopes!), married to the guidecam back from an Orion miniguider, plus a Lodestar. I have NEVER had an issue finding a guide star, the image is superb (I can easily see most nebulae and galaxies in the guider image, so I KNOW I am on target).

I currently have it mounted in an old Vixen 6 point finder bracket (hammertone green - shows how old it is) - I replaced the 3 "set screws" with another 3 adjustable screws from ANOTHER ixen bracket, and so it is 6 points holding it, FULLY adjustable, but ROCK solid (never showed even a skerick of flexure). I have had 2 aluminium rings of I.D 53mm, O.D 60mm made up so it can fit a set of small Borg tube rings I have, and will then mount it on a dovetail on the top. I do NOT need it to move (it will be aligned with the main tube), because as I said, ALWAYS can find a guidestar with the Tak and Lodestar.

The Orion miniguider is... well... useful for parts. The finder itself is rubbish (really poor optically, and I could NEVER get a decent star image with it), and the guidecam itself may as well be a calculator. Finding guidestars with that SSAG was like trying to find an old corroded needle in a wet haystack. It all works... JUST. I needed a good 2 inch extension with it when I replaced the SSAG for the Lodestar, but I was still not happy and finally found a used Tak finder at a good price. No extension piece, and it is a marriage made in heaven.

I have tried a lot of the guidescopes on the market, and disliked every one of them - either too bulky or optically poor. The Orion short tube guidescope needed a 4 inch extension tube for anything to come to focus with it - of course, optional extra.




I will use a short refractor over a dovetail attached to the main OTA. Something like the SkyWatcher 70/500 that is 900 grams, including ring clamps. I find it the best option since I can use it as a lightweight guiding scope but also as a grab&go scope.

In addition, I can use it as a scope to photograph wide field since this scope is half the focal lenth as the main scope (1000mm focal lenght).
In this case, I tried yesterday to view the Pleiades, and even with a 25mm, 60 eyepiece the pleiades barely fit the field of vision. But with a shorter OTA I would be able to view them easily.


Also, someone has some info about any Pentaflex short tube? I get offered one, but I don't know how good is it optically.


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