Double star grab and go style set up?

[leo82]

Hi all, 

I keep thinking about concentrating  more on observing double stars, but then do nothing about it.

I’m looking for a simple set up that I can whip out at the drop of a hat, but good enough to split easy to medium double stars, I don’t state hard ones because my budget is £500.

 I did think about the sky max 127 but the long cool down time didn’t really fit into the grab and go style I’m looking for.

What do you all use? 

I look forward to hearing your responses.

Many thanks.

[Stu]

You could do alot worse than a used 100ED. Well corrected, quickish cool down and will cut through poorer seeing fairly well.

What mount would you use? An AZ5 Might do the trick if you don't want/need goto?

[Ben the Ignorant]

Funny, last night I did chase double and triple stars (Iota Cassiopeia was the queen) with my 127mm catadioptric. Powers up to 266x and 312x were possible thanks to rather good seeing. Mine is a Schmidt-Cass with a larger secondary housing/baffle than the 127mm mak.

Izar was a bit difficult because the primary star's diffraction ring was brightish, and close to the secondary star's core, but increasing the power separated them enough for a more comfortable view.

Apos and semiapos rule the steady views contest but I wouldn't want to lose the convenience of a shorter and larger tube that costed less, to boot. Except for exceptional cases like Izar where the combination of diffraction ring luminosity and angular distance is unlucky, a 127mm mak will do very well. I never had issues with cooldown in my 127, it's too compact to store much heat.

Apos excel in contrast and steadiness but splitting bright dots against a black background doesn't require much fine contrast like when looking for planetary features, it is more a sheer resolving power question, so more aperture is good to have.  

[leo82]

I would love an 100ed but the £500 would be for scope and mount/tripod, I don’t mind going down the used route if I’m going to get more for my money.

I don’t want to go down the goto route as I want everything to be as simple as possible.

If the cooldowns ain’t bad for the man then it’s a serious contender, especially how short it is compared to its focal length.

[dweller25]

@leo82

If you wrap a couple of layers of metallic silver insulation material (from B&Q) around a 127 Mak it will be ready for viewing immediately when you bring it out and it will take much longer than normal for the corrector to dew up.

I have been using a thermally wrapped C6 since Christmas and it has transformed the usability of the scope

[vlaiv]

Gonna throw in interesting suggestion - not sure if it had a chance to prove it self in the field, but it does tick right marks:

1. short tube (and relatively small weight) - can be mounted on AZ4 class mount.

2. small(ish) CO

3. long FL for ease of going high mag

4. Should be able to fit budget with az mount? (not sure, check VAT and import duties if applicable)

https://www.teleskop-express.de/shop/product_info.php/info/p10748_TS-Optics-6--f-12-Cassegrain-telescope-154-1848-mm-OTA.html

[Stu]

 

You could do alot worse than a used 100ED. Well corrected, quickish cool down and will cut through poorer seeing fairly well.

What mount would you use? An AZ5 Might do the trick if you don't want/need goto?

As an example though, there is a used Celestron 100ED in the classifieds for £325. This leaves you a decent amount for a mount.

[Stu]

 

@leo82

If you wrap a couple of layers of metallic silver insulation material (from B&Q) around a 127 Mak it will be ready for viewing immediately when you bring it out and it will take much longer than normal for the correctot to dew up.

I have been using a thermally wrapped C6 since Christmas and it has transformed the usability of the scope

I've often wanted to give this a try with my mak, I think I've got some insulation around somewhere so will give it a go. Hate the look of it but I guess if the views are better that is what matters.

[dweller25]

6 minutes ago, Stu said:

I've often wanted to give this a try with my mak, I think I've got some insulation around somewhere so will give it a go. Hate the look of it but I guess if the views are better that is what matters.

@Stu

it’s important to use 2 layers ?

[Stu]

 

@Stu

it’s important to use 2 layers ?

I'll give it a go. Since it came back from hospital, I've been far more impressed with the views and if this can take it a step further that would be great. I get hints of lovely clean diffraction rings when the tube currents and/or seeing stabilise.

[leo82]

4 hours ago, dweller25 said:

@leo82

If you wrap a couple of layers of metallic silver insulation material (from B&Q) around a 127 Mak it will be ready for viewing immediately when you bring it out and it will take much longer than normal for the correctot to dew up.

I have been using a thermally wrapped C6 since Christmas and it has transformed the usability of the scope

Thanks for the tip, I'm definitely rethinking my options now!

[leo82]

3 hours ago, vlaiv said:

Gonna throw in interesting suggestion - not sure if it had a chance to prove it self in the field, but it does tick right marks:

1. short tube (and relatively small weight) - can be mounted on AZ4 class mount.

2. small(ish) CO

3. long FL for ease of going high mag

4. Should be able to fit budget with az mount? (not sure, check VAT and import duties if applicable)

https://www.teleskop-express.de/shop/product_info.php/info/p10748_TS-Optics-6--f-12-Cassegrain-telescope-154-1848-mm-OTA.html

This looks an amazing scope, I know nothing about them, may need to do some research on it!

[leo82]

2 hours ago, Stu said:

As an example though, there is a used Celestron 100ED in the classifieds for £325. This leaves you a decent amount for a mount.

The other 2 scopes above seem to be more grab and go style with them being short tubes, is the 100ed better than them or are they all similar?

[dweller25]

Personally for double stars, between a 100ed, a 127 Mak and  the as yet unknown TS  cassegrain I would go  for a Skywatcher 100ed

[Stu]

1 hour ago, leo82 said:

The other 2 scopes above seem to be more grab and go style with them being short tubes, is the 100ed better than them or are they all similar?

Well, your request was for something with quick cooldown, which a doublet will certainly have. I have a Tak FC-100DC which is a 100mm f7.4 Fluorite scope, lovely, and expensive. The 100ED has a longer focal length and is a nicely corrected objective so will not be a million miles away from the Tak. Longer focal length scopes tend to have a greater depth of focus and will cope with variable  seeing conditions well which is what you need for doubles. Larger aperture will ultimately split tighter doubles, but you can do a lot of ‘damage’ with a 4” pea shooter if the optics are good, and the 100ED fits in that category.

I think SCTs and Mak CAN be good for this sort of observing, but cooling needs to be right, collimation needs to be spot on, and the larger aperture can be a little more susceptible to the seeing conditions.  Some people swear by them, others swear at them!

Just to back up the collimation question though, I have had one 200mm and two 140mm Maks, and bought, sold and re-bought the latest one of them . I was never convinced that I was getting the best out of them, and in the case of the one I have just re-acquired I sent it away to be properly aligned. Turns out it had a loose primary and a corrector that was too tightly packed, causing distortions. The difference now is significant, with good seeing it really does perform well with nice star shapes and an ability to split tight doubles. It does however need substantial cooldown time still, and I just love the clean and stable delivery you get from a good refractor, so often the Tak is my first choice. It seems to split down to a similar level under most conditions anyway, they will both manage Pi Aquilae for instance which is 1.4” separation, quite tight. I’m sure under excellent conditions the Mak might sneak ahead, but for quick grab and go simplicity, a decent quality 4” ED doublet is hard to beat.

Sorry, I rambled somewhat.....

 

[chiltonstar]

I use either my ED80 or 127 Mak on a Vixen Porta2 mount for "grab 'n go". Each has advantages and disadvantages; the ED80 is simple to use, gives clean visual images of doubles, but of course is of limited aperture, so it will split Epsilon Lyrae nicely but not eg Zeta Herculis. The 127 Mak is much more portable (shorter) and allows me to use the mount tripod un-extended for greater stability, the view is much more cluttered though as scopes with secondary obstruction put more light into the diffraction rings, resulting sometimes in a jumble of overlapping diffraction patterns. It gives a much brighter visual image of fainter stars or secondary stars (119mm true aperture cpd with 80mm for the frac) so will pick up fainter companions. Cooling time? Less of a problem than is sometimes stated I believe.

So, which is better? IMO depends on the phrase in the original post..... "easy to medium double stars". You perhaps need to define the limit of separation in arcsecs, and the magnitude levels you wish to reach. If you can borrow a copy of the Sissy Haas book "Double Stars for Small Telescopes", this gives a good idea of what aperture you need to see each well known double star at its best.

Chris

[leo82]

Now I’m confused!

I was talking to a chap at work earlier about astronomy etc and he bought a second hand mount which came with an evostar 90, he has no use for the scope so it’s sitting in his garage in its original box in as new condition and said I could have it for £20.

I have to buy a mount anyway for whichever scope I buy so was wandering whether a 90mm might be worth a punt at that price or would it be a waste of money if it ain’t as good as the scope I currently have?

 

[Ags]

I am thinking of getting a SkyWatcher ED 72 for general grab and go and particularly doubles, but for me the most important consideration is: will it split the double double?

[vlaiv]

37 minutes ago, leo82 said:

Now I’m confused!

I was talking to a chap at work earlier about astronomy etc and he bought a second hand mount which came with an evostar 90, he has no use for the scope so it’s sitting in his garage in its original box in as new condition and said I could have it for £20.

I have to buy a mount anyway for whichever scope I buy so was wandering whether a 90mm might be worth a punt at that price or would it be a waste of money if it ain’t as good as the scope I currently have?

 

Honestly, I would jump on that without much thinking. It might prove less than suitable for your needs, but again 90mm F/10 achromat for £20 - let's face it, you can't get half decent eyepiece of that sort of money. IMO, just experience of trying out a new scope, and toying with it for a while is worth that sort of money. In the end if you don't find the use for it, it can be a nice present for someone.

[Stu]

17 minutes ago, vlaiv said:

Honestly, I would jump on that without much thinking. It might prove less than suitable for your needs, but again 90mm F/10 achromat for £20 - let's face it, you can't get half decent eyepiece of that sort of money. IMO, just experience of trying out a new scope, and toying with it for a while is worth that sort of money. In the end if you don't find the use for it, it can be a nice present for someone.

I agree!

22 minutes ago, Ags said:

 

I am thinking of getting a SkyWatcher ED 72 for general grab and go and particularly doubles, but for me the most important consideration is: will it split the double double?

 

Should do, I’ve done it with a 60mm Tak and 66mm Willam Optics SD 66mm so I would expect the 72 to do it.

[Red Dwarfer]

I can use my 127 Mak after 15 to 20 minutes cool down as long as it's at low power 32 or 40mm ... hard to find doubles like Struve 3052 ( near 10 Cass ) seem easier to hunt down in a frac because of the wider field ?

[chiltonstar]

1 hour ago, Stu said:

I agree!

Should do, I’ve done it with a 60mm Tak and 66mm Willam Optics SD 66mm so I would expect the 72 to do it.

Limit to split the closer pair of Epsilon Lyrae should be 50mm (just touching) based on Dawes. 

Chris

[Stu]

28 minutes ago, chiltonstar said:

Limit to split the closer pair of Epsilon Lyrae should be 50mm (just touching) based on Dawes. 

Chris

Who will be the first to split it with an ED50?

[chiltonstar]

On 08/08/2018 at 18:17, Stu said:

Who will be the first to split it with an ED50?

No ED50 to hand, so I put the 50mm aperture cap on my ED80!

The wider pair (2.4 arcsec) were just split at nearly the Dawes limit, with a darker band between the two Airy disks. The closer pair (2.3 arcsec) could just be split for a second or two every now and then with a darker band between them, otherwise the two merged as a rod. So, theory & practice agree.

Chris

[michaelmorris]

On 07/08/2018 at 15:08, vlaiv said:

Gonna throw in interesting suggestion - not sure if it had a chance to prove it self in the field, but it does tick right marks:

1. short tube (and relatively small weight) - can be mounted on AZ4 class mount.

2. small(ish) CO

3. long FL for ease of going high mag

4. Should be able to fit budget with az mount? (not sure, check VAT and import duties if applicable)

https://www.teleskop-express.de/shop/product_info.php/info/p10748_TS-Optics-6--f-12-Cassegrain-telescope-154-1848-mm-OTA.html

That certainly looks like a very interesting little scope and may well fit all the OP's specification.