A couple of pairs to compare

[John]

With plenty of high level cloud around last night, after a session observing the moon I turned to easy to find double stars as they showed in the gaps in the cloud cover.

I was using my 130mm refractor.

Eta Draconis has become one of my favourites lately being easy to find and well presented in my sky. The A-B pair of this binary system  makes an interesting challenge for the seeing conditions and the scope. The component stars are magnitude 2.8 and 8.2 respectively. The separation is currently 4.4 arc seconds. The large brightness difference and the relatively small separation make seeing the B component quite challenging - I had to look for it very carefully before I spotted it at around the 7 o'clock position (refractor with diagonal view).

I had a rather half-hearted look at this one a couple of nights earlier (also under hazy / thin cloud conditions) with my 100mm refractor and could not spot the B star then. I'll give it a try with my 120mm refractor soon and see if that can winkle it out. I reckon the seeing conditions are a lot to do with success vs failure on this target, more so perhaps than scope aperture ?. We will see.

The comparison I mentioned in the thread title is with our old friend Polaris. As most know, Polaris has a 9th magnitude companion and personally I enjoy seeing the pair of them pop into view when I'm star testing a scope. As I recall, all my scopes, even the 60mm refractor, have showed the 9th  magnitude companion star which lies around 19 arc seconds from the magnitude 2.04 Polaris. And there is the thing, the brightness difference between Polaris A and B is a little greater even than that between Eta Draconis A & B although they are in the same "ball park". The separation between Eta Drac is over 4 times tighter and that turns it into a much more challenging pair to split.

Eta Draconis is well worth the trouble though

Close to Eta Drac is another binary, STF 2054 which is a very tight 1 arc second pair of magnitudes 6 and 7. Another sort of challenge !

This is adapted from an illustration by Bob King for Sky & Telescope. It shows the refractor / mak-cassegrain / SCT orientation:

   

 

Edited April 24, 2021 by John

[cotterless45]

Excellent , Draco is so lovely . Got over to Lynx the other night , although high in the west  , managed the fishhook leading yo that most distant twinkle of NGC 2419, careful now ,

Nick.

[wookie1965]

When I get out again and that could be tonight my son has said he will come over set my kit up for me and stay with me for a couple of hours then pack my kit away. 

Could not ask for more from him may try Eta Draco see how the 127mm performs. 

[John]

I've been able to split A and B Eta Draconis with my ED120 refractor this evening at both 225x and 257x (slightly easier at the latter).

 

[Pixies]

Seeing is pretty average here and a thin layer of high cloud has just arrived. I'll have a beer and try later.

[Pixies]

Think I got it in the 8" dob.

With the Baader zoom, I had no luck. Seeing wasn't great but seemed to be improving from earlier.  Tried the higher powered orthos, but no luck there, either.

Then I got out the Vixen LVW 8mm, which hasn't seen much action since last October when Mars was near opposition. I barlowed that with the x2.25 - to give me x337 magnification. This was a bit of a mess, but at least the wider angle could let me watch the star for a while. I could see something behind the star as it drifted West. I removed the barlow and it popped into occasional clarity:

 x150 magnification

I tried the 7mm ortho again, and the zoom, but it was only the 8mm Vixen that would show it. 

[John]

19 minutes ago, Pixies said:

Think I got it in the 8" dob.

With the Baader zoom, I had no luck. Seeing wasn't great but seemed to be improving from earlier.  Tried the higher powered orthos, but no luck there, either.

Then I got out the Vixen LVW 8mm, which hasn't seen much action since last October when Mars was near opposition. I barlowed that with the x2.25 - to give me x337 magnification. This was a bit of a mess, but at least the wider angle could let me watch the star for a while. I could see something behind the star as it drifted West. I removed the barlow and it popped into occasional clarity:

 x150 magnification

I tried the 7mm ortho again, and the zoom, but it was only the 8mm Vixen that would show it. 

That looks to be in the right position for the newtonian view. I reckon you got it

It's not an easy one, especially if the seeing is a bit variable.

[John]

23 hours ago, John said:

I've been able to split A and B Eta Draconis with my ED120 refractor this evening at both 225x and 257x (slightly easier at the latter).

 

Well I'm going to try with the 100mm refractor tonight. Last time with this aperture I didn't get it but the seeing wasn't great then. Fingers crossed for tonight.

 

[John]

2 hours ago, John said:

Well I'm going to try with the 100mm refractor tonight. Last time with this aperture I didn't get it but the seeing wasn't great then. Fingers crossed for tonight.

 

Eta Draconis can be split with a 100mm refractor. At 225x the faint B star was visible during steady periods. Blustery wind not helping. Getting sharp focus is important with this one.

 

[Zermelo]

I've tried for this one twice in recent nights - failed both times - though the seeing was average at best.
It will stay on the list.

[John]

43 minutes ago, Zermelo said:

I've tried for this one twice in recent nights - failed both times - though the seeing was average at best.
It will stay on the list.

It is quite difficult to see the dimmer star. Having observed it a few more times now I would modify the illustration I posted earlier to reflect this:

[Nik271]

I managed to see the secondary on Monday night with my 127mm Mak at 250x but it was very subtle and I could only see it for brief moments. It was breezy and a bit hazy so I will try again in better conditions. Hopefully this weekend we'll get some clear spells again.🤞

[John]

9 minutes ago, Nik271 said:

I managed to see the secondary on Monday night with my 127mm Mak at 250x but it was very subtle and I could only see it for brief moments. It was breezy and a bit hazy so I will try again in better conditions. Hopefully this weekend we'll get some clear spells again.🤞

Well done

Spotting the secondary star seems to be influenced a lot by the observing conditions. I only glimpsed it a couple of times the night before last when I was using my ED120 refractor but my conditions then were similar to the ones that you describe here.

Lets hope for some nice clear, transparent skies again soon

I've not been able to get a clear split of the nearby star STF 2054 as yet with any of my scopes. I get elongation and it's clearly a pair but no split yet.

 

 

[F15Rules]

I went out tonight at 10.45pm specifically to try eta draconis..as John said it's well placed at this time and the two end stars of Ursa Minor (one of them is Kochab) point nicely to eta nearby, if like me you've not looked for it before.

I tried various combinations and thought I could see the faint companion intermittently at about 220x, (Carton 10.5mm with Baader 2.25x zoom barlow), but it was only when I added my WO nosepiece (1.6x) to the stack that I could be sure it was there. It was faint but unmistakable and seemed to be just outside the 2nd or 3rd diffraction ring (seeing was pretty good but there was a bit of intermittent oscillation of the rings - I had to wait for short stable periods of several seconds, during which the image settled).

I'm thinking this must have been getting on for 350x, but the higher mag, coupled with short steady periods did seem to make all the difference.

Just for comparison I then turned to Polaris with the same high magnification and as John said, the companion star just stood out like a beacon, despite being fainter than eta drac's companion..Polaris B seemed miles away from Polaris at this magnification!

I also looked at Polaris with my new-to-me Axiom LX 31mm beast. At just 33x in the FS128, Polaris B was plainly visible. I was also struck by the lovely star field in the surrounds of Polaris - at 82 degrees, the field was very immersive.

A short but very satisfying session and thanks to John for sharing his initial impressions of this interesting but far from easy double 👍😉.

Dave

 

[John]

42 minutes ago, F15Rules said:

I went out tonight at 10.45pm specifically to try eta draconis..as John said it's well placed at this time and the two end stars of Ursa Minor (one of them is Kochab) point nicely to eta nearby, if like me you've not looked for it before.

I tried various combinations and thought I could see the faint companion intermittently at about 220x, (Carton 10.5mm with Baader 2.25x zoom barlow), but it was only when I added my WO nosepiece (1.6x) to the stack that I could be sure it was there. It was faint but unmistakable and seemed to be just outside the 2nd or 3rd diffraction ring (seeing was pretty good but there was a bit of intermittent oscillation of the rings - I had to wait for short stable periods of several seconds, during which the image settled).

I'm thinking this must have been getting on for 350x, but the higher mag, coupled with short steady periods did seem to make all the difference.

Just for comparison I then turned to Polaris with the same high magnification and as John said, the companion star just stood out like a beacon, despite being fainter than eta drac's companion..Polaris B seemed miles away from Polaris at this magnification!

I also looked at Polaris with my new-to-me Axiom LX 31mm beast. At just 33x in the FS128, Polaris B was plainly visible. I was also struck by the lovely star field in the surrounds of Polaris - at 82 degrees, the field was very immersive.

A short but very satisfying session and thanks to John for sharing his initial impressions of this interesting but far from easy double 👍😉.

Dave

 

Nice report Dave - thanks for adding it to this thread

Glad you got some clear sky - it's been rather poor here for the past couple of nights.

 

[Nik271]

I  had success last night at Eta Draconis, again with the 127 Mak but this time I was testing a cheap 7-21mm zoom I recently purchased. It works very well in my super slow scopes (at F12 probably any EP looks good ). There was plenty of cloud but in the gaps the seeing was excellent, the stars were perfect points with textbook diffraction rings. I started with Castor which was split already at 21mm (75x) and then chased the gaps in the clouds. Mars looked good but smallish, I think its only about 4 arcseconds now. Theta Aurigae was a good catch, first time with the small Mak, I had to go down to 200x to get a clean split. Then the eastern sky cleared up and I moved to Polaris first. As Dave @F15Rules said the companion was obvious even at my lowest mag (74x at 21mm). Finally it was clear enough to look at Eta Dra and I started to see a blue dot southeast of the primary at about 200x. It was more consistently visible that last time, beyond the diffraction rings as the seeing was way better. I didn't have time to try STF 2054 as some more cloud filled the gap.

I'm actually very thrilled by the success of the small Mak, it just keeps giving. The small zoom (cheapest of the SVbony line) also performed very well. It is sharp almost all the way to the edge (probably not a great achievement with a narrow FOV - 40 to 55 degrees) I will keep it in my arsenal for double stars.

Should be less cloud tonight, I hope the seeing stays good!

 

Nik

[F15Rules]

7 hours ago, John said:

Nice report Dave - thanks for adding it to this thread

Glad you got some clear sky - it's been rather poor here for the past couple of nights.

 

Thanks, John.

It was a nice night last night, but just so cold for the end of April! I'm actually wondering.. could the "wobbling" I saw be as much to do with the day/night ground temperature variations lately, as much as the atmospheric conditions?

During April almost every night has been at or close to zero.. but in the daytime the sun is now pretty high up (only c 7 weeks until midsummer's day 😱😂), and we've had some really warm temperatures when it's out - up to 18 degrees. 

Whatever it is, the seeing definitely "came and went" last night and if I hadn't stuck at this one star for a good 20-25 minutes I might well have not been able to resolve eta draconis with real certainty - yet, when it was there, it was definitely there!

The whole experience reminded me of resolving Sirius and the Pup for the first time..

Hope that makes sense?

Dave

[F15Rules]

1 hour ago, Nik271 said:

I'm actually very thrilled by the success of the small Mak, it just keeps giving.

Excellent, Nik! 

You and your scope did really well👍. I've owned a couple of good Russian Maks in the past, and they could rival the best fracs on good nights..sounds like you have a good one!

Dave

[scotty38]

Would it be a fair assumption to say these would not be possible with a Stellamira 80 ED?  I'm new to this so I'm still unsure of whether it's eyes or scope that limits me.

I've found a fair few doubles but I've not recorded which ones to then check if they're "easy" or not....

[John]

49 minutes ago, scotty38 said:

Would it be a fair assumption to say these would not be possible with a Stellamira 80 ED?  I'm new to this so I'm still unsure of whether it's eyes or scope that limits me.

I've found a fair few doubles but I've not recorded which ones to then check if they're "easy" or not....

Under a very dark, transparent sky and with an experienced observer Eta Draconis may well be possible with an 80mm scope. The split and the B star magnitude are within the grasp of the aperture.

[Nik271]

49 minutes ago, scotty38 said:

Would it be a fair assumption to say these would not be possible with a Stellamira 80 ED?  I'm new to this so I'm still unsure of whether it's eyes or scope that limits me.

I've found a fair few doubles but I've not recorded which ones to then check if they're "easy" or not....

You should be able to see Polaris B without a problem, for Eta Draconis you will need very good conditions, first try something easier while still challenging, for example Izar (Epsilon Bootis). Have fun!

[scotty38]

Thanks both and will look at the others. I think I may have seen Izar but as mentioned I didn't record them so I could be mistaken.