Testing an 80mm refractor with some tough doubles, have a go!

[IB20]

I scalped this list off another forum as it was a suggested doubles list for testing an 80mm refractor. They are all 2” separation or less and both components within 1 mag brightness of each other. 

After some star hopping last night I pinned down HR8040, a blueish white primary in Cygnus. At 80x I couldn’t really see any split but increasing to 100x a greyish blue secondary popped out. Further increasing the magnification to 133x and 160x presented a really pleasing double split with two nice airy discs. An excellent result! 

I aim to work my way through the list decreasing in separation and see where the 80mm gives up!

Would welcome other members having a go and if there are any other similar double targets people can recommend, I’d be all ears.
 

[Knighty2112]

Getting this close to the summer solstice chasing down doubles is a good thing to aim for. Did a few lat night, but was really testing out a new goto mount so was kind of all over the place with objects to view. 

[John]

Some of my personal "tough tests" at this time of the year are Zeta Hercules, Pi Aquilae and Lambda Cygni. 

Eta Draconis is also a challenge for 100mm and below. The split there is 4 arc seconds but the brightness difference between the primary and the rather dim secondary star make the challenge.

 

 

 

[IB20]

21 minutes ago, John said:

Some of my personal "tough tests" at this time of the year are Zeta Hercules, Pi Aquilae and Lambda Cygni. 

Eta Draconis is also a challenge for 100mm and below. The split there is 4 arc seconds but the brightness difference between the primary and the rather dim secondary star make the challenge.

 

 

 

Thanks John, I’ll add them to my to try list. At least with brighter primaries it is possible to try earlier in the evening!

[John]

28 minutes ago, IB20 said:

Thanks John, I’ll add them to my to try list. At least with brighter primaries it is possible to try earlier in the evening!

A clear split of Pi Aquillae would be a very fine achievement with an 80mm with a 1.41 arc second separation. 

Delta Cygni is another good one. The split is 2.8 arc seconds but there is a large brightness difference.

Edited June 16, 2021 by John

[IB20]

13 minutes ago, John said:

A clear split of Pi Aquillae would be a very fine achievement with an 80mm with a 1.41 arc second separation. 

Delta Cygni is another good one. The split is 2.8 arc seconds but there is a large brightness difference.

I did try and split HR6329 which is 1.4” in Ophiuchus and it just looked like a single point of light. I need to try again as I’m not absolutely certain I was on the correct star. The 2” was tight, but a certain split. I’d fancy getting it down to 1.8” “comfortably” and be it’ll be interesting to see if I can push it further.

[John]

7 hours ago, IB20 said:

I did try and split HR6329 which is 1.4” in Ophiuchus and it just looked like a single point of light. I need to try again as I’m not absolutely certain I was on the correct star. The 2” was tight, but a certain split. I’d fancy getting it down to 1.8” “comfortably” and be it’ll be interesting to see if I can push it further.

You should be able to get an elongated or even a notched pair at 1.4 arc seconds if everything else comes together.

[Pixies]

I've set that list into a Sky Safari observing list and I'll give them a shot over the next few weeks (hopefully)!

[Pixies]

On 16/06/2021 at 08:28, IB20 said:

I scalped this list off another forum as it was a suggested doubles list for testing an 80mm refractor. They are all 2” separation or less and both components within 1 mag brightness of each other. 

After some star hopping last night I pinned down HR8040, a blueish white primary in Cygnus. At 80x I couldn’t really see any split but increasing to 100x a greyish blue secondary popped out. Further increasing the magnification to 133x and 160x presented a really pleasing double split with two nice airy discs. An excellent result! 

I aim to work my way through the list decreasing in separation and see where the 80mm gives up!

Would welcome other members having a go and if there are any other similar double targets people can recommend, I’d be all ears.
 

Had a try at some tonight in my Vixen 80 f11.3

STF 2741 (HR 8040) - split at x113 with a cool blue/grey secondary to North-East of primary

STF 2751 (HR 8065) - notched at x113, secondary to North-West. Uncomfortable viewing position!

STF 2583 (Pi Aquilae) - even at x130, elongated and notched occasionally. Secondary to West, primary trailing.

Seeing was pretty average and the skies light. This long (for me) refractor is a new acquisition and I am still to work out how best to mount/position it. At times it was very uncomfortable looking towards the Zenith. I still have to work out a good height and seating arrangement, my drum stool doesn't go low enough and my Manfrotto is not tall enough without becoming too wobbly.

 

[John]

Nice report

Very cloudy here so no observing. I got Pi Aquilae a couple of nights ago with my 120mm refractor. But then, it should.

Great piece on this binary from John Nansen at the Star Splitters website:

https://bestdoubles.wordpress.com/2011/08/03/a-slice-of-aquiline-pi-pi-π-aquilae-σ-2583/

 

[IB20]

5 hours ago, Pixies said:

Had a try at some tonight in my Vixen 80 f11.3

STF 2741 (HR 8040) - split at x113 with a cool blue/grey secondary to North-East of primary

STF 2751 (HR 8065) - notched at x113, secondary to North-West. Uncomfortable viewing position!

STF 2583 (Pi Aquilae) - even at x130, elongated and notched occasionally. Secondary to West, primary trailing.

Seeing was pretty average and the skies light. This long (for me) refractor is a new acquisition and I am still to work out how best to mount/position it. At times it was very uncomfortable looking towards the Zenith. I still have to work out a good height and seating arrangement, my drum stool doesn't go low enough and my Manfrotto is not tall enough without becoming too wobbly.

 

Great stuff @Pixies! Yes, these longer achros can sometimes lend themselves to some contortionist viewing in higher targets. I sometimes don’t extend the tripod legs and sit on the floor. 

Sounds like a good effort at Pi Aquilae. Can I ask what eyepieces you were using?

I’m clouded out here at the moment but can’t wait to get stuck in at the next opportunity.

 

[Pixies]

On 18/06/2021 at 07:53, IB20 said:

Sounds like a good effort at Pi Aquilae. Can I ask what eyepieces you were using?

I was using a Baader zoom to help locate and find a good magnification. Of course, all these need quite high magnification, so it was mainly a 8mm Vixen LVW and a 7mm University Optics ortho. I tried with 6mm and 4mm orthos, but the seeing wasn't good enough and contrast was poor too.

[IB20]

Amazingly I have a clear night so whipped the Starbase 80 out. Revisiting the double challenge headed straight for Pi Aql as it is in a favourable southern view for me at this moment. Nice and easily to locate near Tarazed and above HD187284. Switched to the 6mm Starbase ortho and could make out an elongated pair. In occasional moments this would improve to a notched pair which was easier to detect in the 5mm BST. There were times when it seemed that I could make out a dark separation line, and I found that easier to see than two stars if that makes sense? Feel I am pushing my eyesight to the absolute limit however. Tried the 3.2mm BST but gave too mushy and too dim an image to improve anything.

[John]

I'm about to have a look at Pi Aql now it's risen above the conifers here. I've got a 130mm refractor out tonight though so it should be no problem for that. Sounds like your 80mm got really close to a split though.

Sometimes waiting until the target rises a little higher in the sky can make the difference.

 

[IB20]

Having just gone back I think you’re right. With it being stiller and darker I can see two stars. I think the scope has fully cooled now too. To my eye I can see a secondary star at about 4 o clock; the primary looks white and the secondary looks yellow. Cracking target!