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robbymain

Struggling to split the double-double with my 150P

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Hello all

I picked up a used 150P on an undriven EQ3-2 a few weeks ago (upgrading from a Heritage 130P - nice optics but wanted something with a little more light gathering power and a proper focuser) and after a good clean, mount rebuild and careful collimation (including squaring the Crayford which was quite out of true) I had it out the back garden on Saturday night. I enjoyed some very pleasing views of M44 in a Baader 32mm Plossl after which I failed to detect locate any of the clusters in Auriga due to the local urban North Bristol LP - can't wait for some dark sky outings!

Anyway I switched my attention to Vega and the nearby double-double which I found I couldn't split with a 6mm Ortho. In fact I didn't feel I was achieving very satisfactory focus at x125. A star test showed fairly concentric diffraction rings, not perfect but close enough. 

Am I simply experiencing poor seeing? Or am I suffering from unrealistic expectations having once owned a 1/8PV, Hilux Orion Optics 8" reflector and remembering how capable that was?! 

Thanks to anyone with experience of the 150P who can comment ?

Rob

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I dont have experiance with the 150,but you should be able to split them ok,if collimation was good then i would put it down to seeing.

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Hello Rob.

A 6” reflector should very easily split the double-double into its 4 components at 125x or higher.

It sounds like you’ve been into astronomy for a long time having owned the 8” OO and also know how to collimate.

But how high an elevation was Lyra when you viewed it ?   In May it’s rising in the NE as it gets dark. Poor seeing will be worse if your target is not high up.  Some will say a 6” doesn’t need much cooldown, but if it’s just come from a warm house it will take while for that to happen.

If it were me, I’d recheck collimation, make sure the scope is fully cooled then try again when Lyra is higher. If that doesn’t work, a consolation prize is the “double-double’s double”, Struve 2474, also in Lyra, easily split into 4 components at much lower magnification.

Good luck with your 6” scope, very capable and low hassle.

Ed.

 

 

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Posted (edited)
On 06/05/2019 at 17:32, robbymain said:

Hello all

I picked up a used 150P on an undriven EQ3-2 a few weeks ago (upgrading from a Heritage 130P - nice optics but wanted something with a little more light gathering power and a proper focuser) and after a good clean, mount rebuild and careful collimation (including squaring the Crayford which was quite out of true) I had it out the back garden on Saturday night. I enjoyed some very pleasing views of M44 in a Baader 32mm Plossl after which I failed to detect locate any of the clusters in Auriga due to the local urban North Bristol LP - can't wait for some dark sky outings!

Anyway I switched my attention to Vega and the nearby double-double which I found I couldn't split with a 6mm Ortho. In fact I didn't feel I was achieving very satisfactory focus at x125. A star test showed fairly concentric diffraction rings, not perfect but close enough. 

Am I simply experiencing poor seeing? Or am I suffering from unrealistic expectations having once owned a 1/8PV, Hilux Orion Optics 8" reflector and remembering how capable that was?! 

Thanks to anyone with experience of the 150P who can comment ?

Rob

If you cannot get good focus at x125 then one or all of the following may be the cause:

1. Scope needs collimating - how does the airy disk look at perfect focus .

2. Scope needs longer to cool down

3. Very active Jet stream

I suspect it’s number 3 - it may be best to do an online check of the Jetstream before observing

Edited by dweller25

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If the target is low in the sky, it will be harder to split. Let Epsilon Lyra rise up well above the horizon and it should split quite easily at 100x or more with your scope provided that the scope is cooled and in reasonable collimation. Tight double splits are not always as clearly defined with newtonians because of diffraction from the secondary and it's supports which is why I prefer refractors for this purpose but the splits can be made none the less.

My 70mm refractor splits this target once it's in a decent position in the sky.

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I currently own a Skywatcher 150P and I have split the double double many times with this scope. When using this scope for doubles I use my TeleVue 8-24 zoom together with a Baader 2.25X barlow.

If its clear over the next few nights I will have a look and try and pick up the double when its low in the sky to see what I can detect.

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Until Vega and the D-D are quite high in the sky (>15 degrees up) I find the seeing often quite poor in this (E) direction. Once up a bit higher, and the D-D are clearly separated with any of my four scopes and a delight! Persevere! All of us who looked at Saturn last year will be aware of the problems of near-horizon viewing.

Chris

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Just to echo the previous comments, your scope is more than capable of splitting the Double Double provided the conditions are right. I've done it quite easily with a Heritage 130P and the 150 is significantly better in a number of aspects.

I suspect it was probably low down when you tried, so as others have said, wait for it to get higher and hopefully it will split then.

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These stars are  not too difficult to separate into two components. As good optical alignment is essential, 
you would ensure that is a given. Atmospheric conditions will also have a bearing on success or otherwise, so if it's
not good, don't give yourself a night of torment, give it a go another night when all is as good as it can get in the UK,
you may have a wait ?.  Get the two main components in your eyepiece, and take you powers up gradually.
Don't be too hasty in deciding they won't split, If they don't dance about, concentrate on one  of the stars,
and ramp your power up a bit more, let your scope settle down, as it will have movement from handling the focuser.
don't stare too long at the target, but look away, and rest your eye, then go back to look again.
the double component  will reveal itself, because the telescope has that ability.
When the split becomes apparent, carefully put more power on, (be careful changing eyepiece though, because if you lose the
image, you'll have the devils own job getting it back in the field of view.) If the seeing is perfect,
you can go very high power, and drive a bus through the gap between them. ?.
Persevere, you will crack it.

Ron.

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As above could be seeing or collimation. My first scope was the 150p I easily split the double double with a BST 12mm.

I have seen the ice caps on Mars the cassini division in Saturn's rings and E and F stars in the Trapezium in Orion.

It is a brilliant scope I had a friend flock the inside for me as I was a Newby after that I flocked a 200p.

As people have said double check everything leave to cool longer this does help and persevere.

 

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 Nice one Rob, small scope but attention to detail with colimation, or should I say calibration. Never thought to check the square of the focuser!

I have so much to learn from the details of conversations like this. I have to say that Ron ‘barkis’ sorry if I have your name wrong, has the kind of experience and calm educational teaching that makes me look out for his input.

Supernova, well deserved.

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My 2p worth: I was unable to split e1 and e2 Lyrae with my 127mm Mak until I got a couple of decent eyepieces for it to replace the poor 9mm sold with it.

These stars should be splittable with a 70mm refractor, and IIRC I managed it with my vintage 70mm Ross.

x125 seems a bit low - I used x150, x 180 or more.

With a Newtonian, good collimation makes a significant difference to the ability to split double stars. 

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Many thanks indeed to everyone who weighed in with advice on my query! I'm fairly confident in the collimation (all carefully redone again as I flocked the scope this weekend) and was able to use some satisfyingly high mags on the moon on Friday night so I will persevere.

 

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