36 replies to this topic

[RAKing]

My favorite double star scope is a refractor, but since I cannot handle a large refractor any more I also have good success with my 6-inch f/12 Mak (sub-30% CO).

 

I am a double star guy and I have had fun with every scope design I owned.  My first split of Sirius was about ten years ago when it was tighter - and I had an 8-inch SCT at the time.  The optical quality wasn't so hot, but the scope was sharp enough to give me a clean split.

 

My favorite eyepieces have been my Leica and Baader Zooms with the appropriate Barlows to match the focal length of the scope.  The zoom allows me to "push in" to the maximum magnification the atmosphere allows on any given night.  And I still use and enjoy Tele Vue, Pentax, and Baader fixed focal length eyepieces.

 

The main key to success IMHO is a solid mount.  This will allow you to push the magnification up to the maximum allowable for the conditions no matter what scope and eyepiece you are using.

 

Cheers,

 

Ron

[aa6ww]

I've always had lots of fun with my 80mm F/15 Towa for double star splitting. You definitely need long focal length to achieve high magnification with good eyepieces.

I don't consider myself a double star aficionado but I always look for them when I'm out observing.

I visit double stars more in my back yard where the skies aren't to dark and stars are easy to find, as compared to deep space objects.

I'm only comfortable using refractors for double star observing. I don't need to split the tightest ones to enjoy them, not at all.

Since you put a limit on cost, I cant recommend my 152ED refractor, so instead I will recommend a long tube classic.

I do like Thomas's 4" F11 ED refractor, the focal length is nice as well as the optics.

For me however, if I'm not using my 152ED, which I'm mostly using these days now that the weather has improved, I like my 80mm F/15 with a 2" focuser.

200x and above is no problem with 1200mm FL.

This is my Towa F/15 80mm I had out last weekend during some solar observing, but it also makes for and excellent double star splitter.

 

...Ralph

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[Mike W]

I use my Televue 102 f/8.6, good scope for doubles!

 

[aa6ww]

Best Star splitter under $700, fudging the price just a little:

 

https://www.apm-tele...ed-focuser.html

 

 

 

Best star splitter scope under $2000:

 

https://www.skywatch...0-apo-refractor

 

 

Always a Refractor, Always!

 

When  you use those two scopes, any quality eyepiece is going to give  you excellent performance. Aside from Televue and Explorer Scientific eyepieces, APM and Stellarvue also sell excellent high magnification, short FL eyepieces.

 

 

...Ralph

 

 

 

 

I'm adding DS searching as a criteria for my next scope. 

 

Best scope for DS under $1K with mount or $700 without. 

Best scope under $2K

Bonus Question: favorite eyepiece.

[sg6]

In a way traditionally a refractor is going to be the scope.

I have never had a good view through an SCT - not sure why.

MAK's are supposed to be sharp so maybe one of those. So long since I used my MAK I cannot recall much.

Newtonians have the obstruction and the spider both of which generally degrade seperating critical doubles.

 

Of those given the one AstroJensen has looks pretty good for doubles.

I generally use a shorter ED but not usually on anything close. Just the nature of the viewing and use. A Tal 100 when the mood takes me is the other.

 

I know people that have built a 6 inch f/10 newtonian for doubles and planets but they also used a premium mirror. Afraid a Skywatcher or whatever will not match a Zambuto.

 

Eyepieces, suppose in an ideal world Delites or Delos. However TV Plossls are an option, known for clear and sharp.

[barbie]

My classic Celestron/Vixen SP C102 refractor does extremely well on close doubles and also on the more colorful ones as well.

[EastAnglian]

My old Celestron C102 HD (102x1000) used with a 2” Revelation Quartz diagonal and various eyepieces is my own favourite for doubles. Having said that because I’m getting old and less athletic  I’m starting to use an ETX 105 with its right angle finder, which lessens the need for bending about and contorting to uncomfortable angles. I haven’t had a chance to do a side by side comparison yet between the two, so am not sure how they’ll compare. 

[sg6]

Suspect EastAnglian knows but the Institute of Astronomy in Cambridge still performs double star observing - not sure of the purpose as in where their data is collected.

 

The "main" scope for this is the Thorowgood Cooke refractor, 8" and 114" focal length so f/14.

Think it is Dereck that does the observing when the sky is clear and the scope is not in use for other purposes.

https://www.ast.cam....wgood.telescope

 

Now the other one for double star observing (slight question on this now) is the 36" reflector, person for this is Roger Griffin. Unsure of the nature of his observing as the observatory has more equipment in it then "simple" observing. And no one dares ask Roger, and that includes security.

 

I see that the additional equipment appears to be for radial velocity spectrometer (?). Unsure where double star observing necessarily comes in but sure that is what I recall being informed.

https://www.ast.cam....-inch.telescope.

 

Assuming that spectroscophy is not applicable they basically utilise a long achro  for DS observing, and they also have a 16" Dal Kirkham available but it is the refractor that is the weapon of choice.

[EastAnglian]

Hi sg6

No, I didn’t know any of that! I had a look at the Thorowgood scope (I love that winter photo!) and will read the other info that you linked to. It sounds as though you have a somewhat intimate knowledge of the Cambridge ‘scene’, do you observe there yourself? I’m in north Cambridgeshire so it’s not exactly on my doorstep, and I’m not physically a young man anymore, but the opportunity to look through such a scope is extremely exciting!

It also sounds as though your way ahead of me not only in knowledge but also DS experience. I’ve only recently realised what an extraordinary opportunity DS observing gives. I’m really looking forward to the next clear night (aren’t we all!!) when I intend to see how my ETX 105 does on Polaris B. So much to see, so little time. 

[Jon Isaacs]

Best Star splitter under $700, fudging the price just a little:

 

https://www.apm-tele...ed-focuser.html

 

 

 

Best star splitter scope under $2000:

 

https://www.skywatch...0-apo-refractor

 

 

Always a Refractor, Always!

 

When  you use those two scopes, any quality eyepiece is going to give  you excellent performance. Aside from Televue and Explorer Scientific eyepieces, APM and Stellarvue also sell excellent high magnification, short FL eyepieces.

 

 

...Ralph

 

A couple of years ago, I was corresponding with a fellow with an 175mm Astro-Physics apo. I split some doubles he had tried without success.  My scope was a basic 10 inch Dob.

 

Two factors were important, the greater aperture and the location of the scope.

 

Refractors have several advantages as double star scopes but for folks like me, a Newtonian offers more performance in an affordable package.

 

Right now, there are no planets well situated during most of the evening so doubles it has to be..

 

Jon

[sg6]

Little experience really in DS observing. Really comes from knowing the IoA scopes and what they are usd for.

My very small knowledge of doubles is from outreach and knowing the pretty ones to aim a scope at for outreach to show people. I found a DS table of colored doubles from the Delaware AS some years ago that is nice simple and reasonable short.

 

Showing people some contrasting colored doubles and then showing where they are in a constellation (GLP) goes down well.

 

Interested in the ETX capabilities as I have an ETX-105 sat here next to me.

 

For the OP, better get back to the topic, one aspect is defining a "split" and that means a sharp image, or as sharp as possible. Did have a chart somewhere. Which likely brings in the quality of the optics. A long ED like that of AstroJensen will split them better/easier the a similar achro.

[Magnetic Field]

A couple of years ago, I was corresponding with a fellow with an 175mm Astro-Physics apo. I split some doubles he had tried without success.  My scope was a basic 10 inch Dob.

 

Two factors were important, the greater aperture and the location of the scope.

 

Refractors have several advantages as double star scopes but for folks like me, a Newtonian offers more performance in an affordable package.

 

Right now, there are no planets well situated during most of the evening so doubles it has to be..

 

Jon

Between a 10" Dobsonian and a 6" refractor there is quite a large gap in terms of resolution limit.

 

A 6" refractor is not a miracle worker.