Quick session - Izar and Jupiter

[Piero]

Just back from a quick session. The seeing was okay but not as good as last week. 

Izar. A quite challenging double star for a 60mm is Izar (Epsilon Boo). This is the first time I use my new HR 2.4mm (150x) on a double star and it performed very well. In all my previous attempts (100x-150x), the companion was at most visible on the first diffraction ring of the primary, but tonight I could see a distinct black margin between the two. The primary appeared white/yellow, whereas the companion grey/blue. Light control was very good. 

Jupiter. I was a bit in a rush on this targets as the clouds were coming. In those few minutes I could not see striking features on the belts. The image at 150x (HR 2.4mm) was larger but provided as much detail as at 108x (SLV 5mm + VIP 1.5x).

 

Looking forward to Saturn..

[Charic]

I was out a little earlier, looked at Jupiter with my eyes!
I so wanted to cool the scope, test my Orthoscopics, but it will be a few hours before Jupiter is in a better position for the Dobsonian, and with an early start in the morning, another night wasted
However 5 satellites and a stationary  flash/burn satisfied my need tonight?

[scarp15]

That is a good achievement Piero, cleanly splitting Izar with your TV60mm and a good account of that eyepiece. Actually I read your account just as I was about to go out and also took a look at Izar. This was with my 8" dob, so therefore there were some diffraction spikes to contend with, now I have an eyepiece capable of 120X I will try with my TV76 sometime. So it was 11.45 before Jupiter approaching the meridian, cleared the chimney top. Much surface activity again and I was able to explore this at 200x, since the sky was quite clean after passing showers earlier on. I can still see those large barges (or are they festoons) in the NEB and dark mottling in the SEB, also hints of white ovals, as it began to appear the GRS was quite impressive, I could make out the hollow, this was around 1.15am and just before Jupiter would start to sink out of view behind my shed.

[Piero]

Thanks Iain, and great report from your side too! 

The next time the sky is clear and steady I will focus on the NEB at 150x.

You could try to see the barges with your 8" next to your 76mm. After observing them with your 8" you know their exact position. This could also be a nice way to improve pattern recognition I think.

[FenlandPaul]

Nice report Piero. Those HRs do look like interesting eyepieces; I remember reading the review in AN a while back.

looking a bit hazy tonight but hoping to catch the asteroid "flyby" and might try Izar too. Jupiter will no doubt get a look in too.

[Stu]

Nice one Piero. I love Izar as a test in small scopes. The Tak FS60C split it well, probably similar to your TV60 but I bet that HR2.4 adds a bit extra! I can't recall whether or not I've seen clean space between the two at this aperture or not. Haven't got the scope to check any more unfortunately.

It showed very well in my little TAL Alkor recently, showing the quality of the optics i.e.  65mm Newt given the secondary obstruction.

[Piero]

Thanks Paul and Stu. 

What surprised me wasn't just the split, but the fact that it was very neat. You know, when you are at short exit pupils, the stars start appearing larger (the Airy disc) and the borders become less and less defined as if they were vibrating. In this case the two stars were still of reasonable size and their contours were well defined. It didn't take much effort to see them and the little black lane between them.

I look forward to trying this eyepiece on some bright planetary nebula (e.g. M57).

[Littleguy80]

Just split Izar for the first time with my 5" newt tonight. Could make out the gap but at the very limit of my scope so not a clear image. I'm super impressed that you managed it with such a smaller aperture!

[Stu]

4 hours ago, Littleguy80 said:

Just split Izar for the first time with my 5" newt tonight. Could make out the gap but at the very limit of my scope so not a clear image. I'm super impressed that you managed it with such a smaller aperture!

Well done for the split. Small, high quality refractors seem to have an advantage when splitting these sorts of doubles. Nice neat star shapes which makes things easier.

EDIT When I say advantage, I more mean that they punch above their weight. A larger, high quality scope will generally always beat a smaller one

[Piero]

5 hours ago, Littleguy80 said:

Just split Izar for the first time with my 5" newt tonight. Could make out the gap but at the very limit of my scope so not a clear image. I'm super impressed that you managed it with such a smaller aperture!

Congratulations!

The seeing that night was very stable and that is an important factor. I believe the eyepiece also played a role because I never spotted a margin between the two stars with my other eyepieces.

Cooling the optics down properly is also crucial if you are using high-ish mags. My 60mm cools down in 5-10min.

Refractors are also free of secondary spiders, so the image is cleaner. Because of this, the only times I saw some details on Venus clouds was with my 60mm under the right seeing conditions, in twilight, and using a single.polarising filter. I never spotted the equivalent detail with my 8" dob. 

 

If you observe under good sky conditions, using right magnifications, with equipment minimising light scattering and maximising light transmission, you can split that double even a with small aperture. And a larger aperture will beat a smaller one no doubt if the sky conditions are good.

[Littleguy80]

23 minutes ago, Piero said:

If you observe under good sky conditions, using right magnifications, with equipment minimising light scattering and maximising light transmission, you can split that double even a with small aperture. And a larger aperture will beat a smaller one no doubt if the sky conditions are good.

Thanks Piero. Really interesting info. Venus was the first planet I looked at through my scope. I was just impressed that I could make out it the crescent shape of it. Looking forward to seeing it again and trying to pick out some detail. Will be a  challenge from the sounds of it!

[Piero]

1 hour ago, Littleguy80 said:

Thanks Piero. Really interesting info. Venus was the first planet I looked at through my scope. I was just impressed that I could make out it the crescent shape of it. Looking forward to seeing it again and trying to pick out some detail. Will be a  challenge from the sounds of it!

Another thing that crossed my mind is the sky brightness. At the time of my first post, the sky was reasonably dark. This is important because you need contrast between the sky and the stars as you are essentially looking for a separation. Increasing the magnification decreases the exit pupil making the sky darker. This helps, but is not exactly equivalent to having a night sky. What I am saying is that splitting tight double stars can be quite tricky in twilight, because the contrast necessary for seeing the split ("the black line") is reduced. 

For planets like Jupiter and Venus, observing in twilight can help in my opinion. Maybe it's because our eye cones are still active and therefore our eyes are more capable to pick up colours. Enhancing colour contrast can help discern more faint features. 

Specifically on Venus, I was able to pick up a horizontal "V" shape in the clouds when observing in twilight using a single polarising filter at about 100x (0.6mm exit pupil) with my previous Nagler T6 3.5mm. It was not obvious of course. Venus is not an easy target. It is very bright. I believe the 60mm worked well because I was able to push the magnification sufficiently high (100x) while keeping the exit pupil down (0.6mm). This reduced the glare caused by Venus white atmosphere. In my 8" dobson, Venus is just too bright. I would need quite high magnifications (>200x) to reduce the exit pupil below 1mm. At these magnifications, the seeing must be very good / excellent. Despite this, I found the spikes caused by the secondary spiders were really damaging the image. 

[Littleguy80]

I've read a couple of posts where people have said that Jupiter is best seen in twilight. I did have really good views of Jupiter last night around 10 pm when the sky was still fairly bright. GRS was looking good. The seeing was better than earlier in the week, I could definitely pick up more detail. I was using a Neodymium filter to help with the brightness. Exit pupil is not something I've ever thought about before. My setup last night would have given an exit pupil of 0.87mm... I think. 130mm aperture / 150x magnification = 0.87, when rounded up.

I also have a variable polariser so I'll give that a go when Venus is next up. Thanks for all the tips

[Piero]

1 hour ago, Littleguy80 said:

I've read a couple of posts where people have said that Jupiter is best seen in twilight. I did have really good views of Jupiter last night around 10 pm when the sky was still fairly bright. GRS was looking good. The seeing was better than earlier in the week, I could definitely pick up more detail. I was using a Neodymium filter to help with the brightness. Exit pupil is not something I've ever thought about before. My setup last night would have given an exit pupil of 0.87mm... I think. 130mm aperture / 150x magnification = 0.87, when rounded up.

I also have a variable polariser so I'll give that a go when Venus is next up. Thanks for all the tips

 

Great observing on Jupiter!  

I consider seeing conditions more important than the exit pupil when observing planets. Venus is really bright though! 

I assume your variable polarising filter is made of two combined single polarising filters which rotate onto each other. If so, you should be able to separate them. I would use just one of them. 

[Littleguy80]

4 minutes ago, Piero said:

I assume your variable polarising filter is made of two combined single polarising filters which rotate onto each other. If so, you should be able to separate them. I would use just one of them. 

Exactly that. I've only used the two filters together a couple of times. One on it's own has normally been about right

[Les Ewan]

I've always found Izar a problem you really need to ramp up the magnification.

Les.