Double Stars - Don't be afraid to use ludicrous magnification

[Moonshane]

Hi all

I have just been outside looking at Saturn and a few double stars. 'Just for a laugh' I decided to have a go at my maximum magnification of 533x on three doubles - the Double Double in Lyra, Izar in Bootes and Porrima in Virgo. Saturn was reasonable with seeing allowing decent images at about 180x.

They all split easily with my OOUK 6" f11 planetary dob using my 6-3mm Nagler zoom at 6mm (267x) and as I cranked up from 6-5-4-3mm I was amazed that they remained split all the way through and with nice obvious airy disks given the small exit pupils (0.27mm at the 3mm end). These doubles are quite high and I suppose not too challenging but I thought I'd mention it in case anyone assumes they cannot use such high magnifications in any circumstances.

In fairness, my equatorial platform helps with this as manually tracking at these mags would be a pain without it.

So have a go your scope may surprise you.

Cheers

Shane

[Moonshane]

as the cloud has cleared again I just had a look at Delta Cygni and the same story with the bright primary and tiny quite close secondary well split and easily resolved. seeing must be better than I thought!

[Nexus 6]

Looks like around 180x is a sweetspot for observing Saturn, my best views this time around have been with the 925 and 13mm Nagler.

Can't imagine 533x although I believe that figure is around the supposed max limit for a cpc 925

highest I have tried was using a 6mm Vixen LV giving 391x

Saturn was looming large through the ep but detail was difficult to pick out.

regarding doubles...think I will try and max out the power when I get a chance to use a barlow, using the 7mm BGO with a standard 2x I would have 671.428571x

[Moonshane]

Hi Alan, I agree about Saturn. my best images have generally been with my 9mm BGO = 177x although occasionally I can use 8mm & 7mm.

try the mad mags on doubles though, using 50x aperture in inches, my 6" should 'only' be capable of 300x but this is patently not the case with doubles.

[Telrad]

Shane, thanks for sharing that. I got into splitting doubles recently - my main interest for a long time has been star clusters, so I have quite a few I like. Last year I tried putting together a list for myself of all the NGC -designated deep sky objects with a 10" scope from my location.

[Moonshane]

you know that next question don't you!? any chance of a copy please? might be very useful

[Merlin66]

Would also be interested to hear what is the Minimum magnification required to split a double...I saw the Double double in Lyra split with only x48 on a 4" Genesis.

[Moonshane]

I think the answer is 1x - you can do Alcor and Mizar with the naked eye

good point though as I would suspect being able to split doubles with less magnification would equate to better optics, conditions and eyes.

[bish]

Would also be interested to hear what is the Minimum magnification required to split a double...I saw the Double double in Lyra split with only x48 on a 4" Genesis.

That's good going. I looked at it a couple of nights ago and really needed about x150.

[Merlin66]

My eyes are pretty shot so it must be down to seeing and practise. When you split it with a higher magnification, try with a lower....I'm sure you'll find it just separating...

[Telrad]

you know that next question don't you!? any chance of a copy please? might be very useful

It's on disc so I'll need to upload it Shane

Some of my considerations and logs include:

1. Do the components differ in colour, and what colours do you see?

2. Are they of different magnitude, and how obvious is that difference?

3. How much magnification was required for a clean split?

4. Does a change in magnification alter whatever colours you see

Hope this helps?

[Moonshane]

It's on disc so I'll need to upload it Shane

Some of my considerations and logs include:

1. Do the components differ in colour, and what colours do you see?

2. Are they of different magnitude, and how obvious is that difference?

3. How much magnification was required for a clean split?

4. Does a change in magnification alter whatever colours you see

Hope this helps?

cool.

[Moonshane]

My eyes are pretty shot so it must be down to seeing and practise. When you split it with a higher magnification, try with a lower....I'm sure you'll find it just separating...

might try this. I bet refractors can often split at much lower mags that flecs?

[Hypernova]

I tend to have mixed success with double splitting using the dob, I believe it is mainly down to seeing conditions. I have usually found the DD a pain to split at all but my highest mags (200x) but I managed it a week ago and got doubleness at 87x with the Speers-Waler and it was more defined at 133x with 9mm Ultrawide.

I haven't managed (or rather tried) to try anything closer than the DD, I did manage to get a hint of a split on Porrima using my long gone C100ED at SGL6 using the 7mm ortho. I thought the seeing and transparency on the Saturday night was a bit pants TBH, everything dewed up after a few hours and there was a little high cloud if I remember rightly.