Doubles trouble..scope choice

[Jimboscotland]

Wow! Lots to consider. Thanks all. 

My main interest in doubles lies not in the toughest split,one can always find tougher and tougher pairs requiring  bigger and bigger scopes...hey why stop there  take up spectrographs..you get the idea. I like studying stellar evolution and doubles provide this and aesthetic differences as well. So colours are important. That favors the ED or All scopes . But if say the 72mm is doable budget wise the small focal length only gives 45x's for a 10mm eyepiece. Does a Barlow which introduces more glass surfaces take away some of the visual quality?

More to think about

Cheers

[Stu]

17 minutes ago, Jimboscotland said:

Wow! Lots to consider. Thanks all. 

My main interest in doubles lies not in the toughest split,one can always find tougher and tougher pairs requiring  bigger and bigger scopes...hey why stop there  take up spectrographs..you get the idea. I like studying stellar evolution and doubles provide this and aesthetic differences as well. So colours are important. That favors the ED or All scopes . But if say the 72mm is doable budget wise the small focal length only gives 45x's for a 10mm eyepiece. Does a Barlow which introduces more glass surfaces take away some of the visual quality?

More to think about

Cheers

Barlows used to have a very bad reputation, but decent ones these days take away little or nothing, other than adding focal length.

A 72mm should cope with much higher mags than x45 too, I’ve had them up to x120 or more and they perform very well. The main consideration then is the small exit pupils and how well your eyes cope with it, floaters can become an issue but not necessarily a problem for doubles. Which eyepieces do you currently have?

[Jimboscotland]

Just starting over, so I'd need the whole kit. But that's better in the long run than getting a scope pkg. and replacing things, I'd have what I like from the get go.

1 1/4 dialectic mirror diagonal and 1 1/4 eye pieces. Not sure of the finder as a long focal length eye piece could make it it's own finder.?? Recommended barlow??

[lunator]

Hi @Jimboscotland, I would just like to add my experience with observing doubles.

At present I have 3 scopes. OMC250, Orion Optics 200mm F6 Newt. and an ST80.

The OMC250 gives the best resolution but lives in an observatory I wouldn't want to have to drag it around, it is pretty heavy.

The Newt was originally on an EQ5 and was portable around the garden but was a little unwieldy. It is now on a dob base so is very easy to move around the garden and set up to avoid obstructions. This scope gives fantastic views and combined with a quality eyepiece like an orthoscopic will provide a true colour view.

The ST80 is on a photo tripod. It is very portable, a true grab and go. The colour correction is ok. It does limit the fainter stars in light polluted skies.

Each of these scopes has it's place but if I had to choose one it would be the Newt. I have had it since 2005 and will never sell it. It is a great all-rounder.

Cheers

Ian

 

[RobertI]

8 hours ago, Jimboscotland said:

I like studying stellar evolution

You’d probably enjoy carbons stars too then? Quite a few of those around, which increases the number of interesting objects available to a smaller scope. If stars are your thing, it’s hard to beat a refractor for aesthetic pleasure. So for doubles and carbon stars, would I choose my 100mm F10 achro or my previously owned 72mm ED refractor? The achro has better resolving power but introduces a yellow cast and is pretty unwieldy at 1000mm FL and therefore not always fun to use. However the purple halo typical of achros is only visible on really bright stars. The yellow cast can be annoying in some situations, but actually it can highlight the colours of orange and red stars, even if not totally accurate. The 72mm gave lovely pinpoint views, superb contrast and was just so easy to use. If you can get a used 80mm ED perhaps that’s the best of both worlds?

[RobertI]

This looks decent value…  https://www.altairastro.com/starwave-ascent-80ed-f7-refractor-telescope-geared-focuser-469-p.asp

 

[Jimboscotland]

Thanks Rob for the suggestion of the Starwave 80mm ED. Worth considering.

[ScouseSpaceCadet]

10 minutes ago, Jimboscotland said:

Thanks Rob for the suggestion of the Starwave 80mm ED. Worth considering.

The primary targets in my light polluted urban garden are doubles using the 102ED version. I've owned the scope about twenty months and it consider it a bargain (£495 at the time)... During this period I've also owned a 102mm Mak and have a 127 Mak. On doubles, the little maksutovs are out performed in every way by the refractor.

[bomberbaz]

On 15/08/2022 at 11:42, dweller25 said:

Here is a writeup/review of the Starbase 80

https://www.cloudynights.com/topic/696578-takahashi-starbase-80-first-impressions/

I am so glad you posted this review up about the scopetech. Note the review is for a Tak version which is identical to the scopetech. 

I had been wondering about the performance of this. The fact it is made in Japan and the same standard as a Tak says an awful lot. 

Seems near ED performance from an F10 achro is possible when done right. I can only assume they are using top quality glass to get such good results. 

Comes with 2 quality ortho's as well, what's not to like. 

If I didn't already have an 80mm frac, I would be very, very tempted to buy one of these. 

[wookie1965]

On 15/08/2022 at 09:45, Knighty2112 said:

One extra thing to contemplate if you wanted to go down the Evo 102 ‘frac option you mentioned is to get a Baader semi-apo filter to use with it. I use the semi-apo filter on some of my achro ‘fracs (Celestron Omni 120, Bresser AR-102S) and it works very well at reducing/eliminating any CA on any stars/doubles etc, and also improves the images any planets too when used.

I use the same in my Tal and the Meade when I had it very very little CA present. 

[IB20]

On 15/08/2022 at 09:06, dweller25 said:

Hello @Jimboscotland and welcome to SGL.

In my experience the 4” F/10 refractor is a bit too long for an EQ3 type mount to hold it steady enough for higher power viewing.

Perhaps this may be a better balance, if you can live with an 80mm objective ……
https://www.firstlightoptics.com/scopetech-telescopes/starbase-80-refractor-and-mount-package.html

I have this scope (still do) and discuss here.

I loved having a 3” refractor so much I ended up getting a premium APO. I still use the mount and tripod from the Starbase too as it’s excellent. For doubles it splits epsilon lyrae at 80x and split Rigel and Izar without much fuss. A really capable achromat that comes with everything ready to go. 

[The60mmKid]

I recommend the refractor over the Mak in this case. A quality, thermally acclimated, well collimated Mak on a night of good seeing is a wonderful instrument. But that's four qualifiers...

First, the Mak needs to be of good optical quality. Thankfully, most current mass produced scopes are.

Second, it must be thermally acclimated. This is where it's easy to go wrong. Mismanaged thermals can be mistaken for poor optical quality and/or poor seeing. If you want to be able to go outside and split doubles immediately with your scope, I don't recommend the Mak unless you're storing it outside or planning ahead to acclimate it to the ambient temperature. Not good for spur of the moment observing, probably... A poorly acclimated scope yields fuzzy, warped stars at the eyepiece.

Third, the collimation needs to be dialed in. The good news is that it will probably hold for a long time. But this can be difficult if you haven't done it before. A poorly collimated scope yields fuzzy, warped stars at the eyepiece.

Fourth, the central obstruction of the Mak throws more light into the diffraction rings than with an unobstructed scope. The less concentrated image is more visible impacted when seeing is poor. A star appears as a sharp point of light in the refractor vs. a (slightly) larger target in the Mak. The difference at the eyepiece can be significant when bad seeing is making all of that light sway here and there. 

A friend of mine put it well... "When all the conditions align, a (larger) Mak will pull ahead of a (smaller) refractor. But on the other 29 days of the month..." In my experience, refractors offer real advantages when the conditions aren't ideal.

I'll add: There are so many doubles to observe that one doesn't necessarily need a 4" (or larger) refractor. An 70-80mm ED could keep you busy indefinitely. My 60mm refractor is a wonderful doubles scope.

These are merely my opinions, based on my experience, and we live in a beautifully subjective reality.

[jjohnson3803]

I bought a 72ED last winter and have just started observing doubles with it.  It seems to be quite capable with very crisp views. 

However, I confess I have yet to resolve Epsilon Lyrae¹ and Epsilon Lyrae² with it.  Not sure if that's partly due to the horrible LP I live in, seeing, or if I just haven't cranked up the magnification enough - my shortest EP is a 4mm and the scope fl is about 430mm.

I have to say the 72ED blows away my ST80 achro for sharpness and color on other doubles.

 

[John]

4 minutes ago, jjohnson3803 said:

I bought a 72ED last winter and have just started observing doubles with it.  It seems to be quite capable with very crisp views. 

However, I confess I have yet to resolve Epsilon Lyrae¹ and Epsilon Lyrae² with it.  Not sure if that's partly due to the horrible LP I live in, seeing, or if I just haven't cranked up the magnification enough - my shortest EP is a 4mm and the scope fl is about 430mm.

I have to say the 72ED blows away my ST80 achro for sharpness and color on other doubles.

 

I found Epsilon Lyrae quite a challenge with my 70mm ED refractor when I first tried the scope on it. I was being impatient though and found a couple of hours later, once the constellation had risen higher in the sky, that I could make the split of both pairs at around 150x magnification. So my tips are to allow the target to get higher in the sky and to use a bit more magnification if you can - a 3mm eyepiece or a barlow lens perhaps ?

The scope has a resolution capability of around 1.6 arc seconds under favourable conditions so that should be enough for both the Epsilon Lyrae pairs.

 

[Stu]

57 minutes ago, jjohnson3803 said:

I bought a 72ED last winter and have just started observing doubles with it.  It seems to be quite capable with very crisp views. 

However, I confess I have yet to resolve Epsilon Lyrae¹ and Epsilon Lyrae² with it.  Not sure if that's partly due to the horrible LP I live in, seeing, or if I just haven't cranked up the magnification enough - my shortest EP is a 4mm and the scope fl is about 430mm.

I have to say the 72ED blows away my ST80 achro for sharpness and color on other doubles.

 

I used to have a TS 72ED and always found the Double Double quite straightforward with it. I would think the 4mm would be enough, but John’s point is very valid in terms of letting it get to a decent altitude before judging if it’s possible or not. As ever, poor seeing can mess with these tighter doubles but LP shouldn’t be a problem; I did it from mag 19 skies near London.