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Asbytec
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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: Sasa]
      #5551004 - 12/02/12 08:41 PM

Jupiter is quite beautiful this time around, Sasa. I am having the time of my life, and so are you, I'd guess. Yes, the festoons are ghostly lately. Earlier, there seemed to be more prominent blues and arcing wisps into the EZ. Those are no longer prevalent. Again, great observations. All of them, including the one's on your site.

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Sasa
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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: Sasa]
      #5555201 - 12/05/12 07:07 AM

Hello guys, two days ago I actually took out 130ED to watch Jupiter. The weather looked promising, at least it looked like that the clouds would be off for at least one hour. In fact, they came a little bit earlier in 45 minuts. To make it short, I did not see red junior at all, I could barely see rising GRS (but hey, it was at least of orange cast; last time I saw a color on it was in my former 250mm Newton).

The problem was big temperature drop (about 20C) between room and outside temperature. Well at least, I got a feeling how quickly this 130mm beast thermalizes. In about 20 minutes of being outside, the image was still very bad. Jupiter was hidden behind strong greenish misty veil. The veil was about 10" larger than Jupiter. I could barely discern main belt. In 30 minutes, veil shrink a little bit (it was now about 5" larger than Jupiter), image improved, but it was still very bad. In 40 minutes, the veil was very small and I could start to see interesting features, like rising GRS but no red junior yet. In another 5 minutes, the experiment was terminated by clouds.

So, the moral is: bigger is not always better. With AS80/1200 I would be done with observing in about 20 minutes and I'm sure, I would record much finer details.

Edited by Sasa (12/05/12 08:37 AM)


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Eddgie
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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: Sasa]
      #5555841 - 12/05/12 03:20 PM

This is interesting because there was a thread in the refractor forum about cool-down and many people seemed to think that refractors could cool very quickly.

My expeience was that the bigger they were, the more the cooldown time they needed and that at 6", it could take a couple of hours to cool (still faster than a big reflector or SCT which can literally go all night without cooling).

Anyway, glad you got to see the BA. It is actually very large and even a small aperture has sufficient angular resolution to show it, but it starts with very low contrast that even in larger telescopes, it doesn't really "jump out" like GRS. In smaller scopes though, the already soft edges are further softened makeing the transition from surrounding region to the only slighly higher contrast of the BA less easy to spot. Much "crisper" in bigger scopes, but at the same time, never really "Crisp" at the edges. At least not the times I have seen it. It is very pale pastel splotch rather than a hard spot. At least that is the way it looks to me even in the C14. Not hard to see, but not obvious at all.


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Sasa
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Reged: 11/03/10

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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: Eddgie]
      #5556912 - 12/06/12 05:45 AM

Eddgie, I agree with you, I would say since ED130 takes at least about 45 minutes with ~15-20C temperature drop to thermalize to some reasonable level (still far away from perfect) , it starts to be comparable with my former N250/1600. My experience in the similar weather with the dobson was that when I left it outside with running fan for about an hour, and then continue observing Jupiter with fan switched on, it was already providing visibly more detailed images than for example ED100. So it was worth to take it out. ED130 seems to operate at the same level as N250, even after 45 minutes it was still showing less details than AS80 after 20 minutes of beeing outside. So in my conditions in winter time, I would say than even 5" refractor (and we are talking about doublet, not triplets which are even worse) is at the edge with about 10" Newton concerning thermal effects.

Since I mostly operate on short sessions from my backyard (and I do enjoy all type of observation especially such type of observations that put my observing skills to my limit, from doubles, planets, Moon to DSO), I gain some experience about how quickly the telescopes thermalizes in order to be able to do this demanding type of observation.

For deeply frozen nights (we are talking about 35C temperature drop), in winner, clear winner is AS80. It needs only about 10-15 minutes and one can start with "serious" work. For example, last winter I was testing how long it will take AS80 to split Rigel. It took it 15 minutes before I started seeing the faint companion. This 15 minutes agrees more or less with what I see when observing Jupiter. Nice feature of AS80 (and AS110) is its removable lens. So if I decided to go out on short notice, I just put the lens outside on the window sill and I gain additional 10 minutes which usually takes me to prepare the staff for observing (dressing, atlases, papers, pencils, eyepieces...).

I have another 80mm telescope of different nature, the 80/480 Lomo triplet (SV80S). Some time ago I did direct comparison on Moon between AS80/1200 and SV80S. Difference was startling, even with ~10C temperature drop, the triplet was not there on the level of AS80 (there is a link to this report in some of my previous replies in this thread). So even tiny 3" refractor could be quite sensitive to thermalization. If I would not have an "etalon" (AS80) to compare the image with, I would probably not noticed it and I would classified it as a bad seeing.

Next step is ED100, this is very good compromise between the power (diameter) and thermalization speed. It is definitely slower in thermalization than AS80, but the difference is not that big if one does not operate in really cold nights. This is normally my choice number one. Except in winter time, when I prefer for short sessions AS80. For example during one night, with temperature drop of about 20-25C, I could not split theta Aur even after 30 minutes of observing (star test was still showing signs of pinched optics), after another 30 minutes, theta Aur was clear and nice split in ED100 (and the signs of pinched optics were gone).

I also have short experience with ED120. My friend came to visit me for common observations. I do not know the temperature drop, but it was summer, definitely not very cold night (but the telescope was in the car). Even after one hour one could see some signs of thermal effects when observing Saturn (our etalon was at that time my ED100).

I do not have too many experiences with AS110, but there are thermal effects as well. During October (so not so cold), I was observing some doubles and I noticed that in first 10-15 minutes, the lens was showing in star test signs of strong spherical aberration. In about 20 minutes they were gone. I t looks like it will be at the same level as ED100.

BTW, yesterday I was observing Jupiter, this time with AS80 since it was difficult to judge how long the sky will stay clear. Again, it was providing quite quickly images with high contrast and clarity :



No red spot junior this time, but I noticed towards the end of my observation very thin and hard to spot bend on the western hemisphere just south of SEB. Never noticed it before in 80mm refractor (but I saw it in ED100 a month ago).


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Asbytec
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Reged: 08/08/07

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Re: Jupiter 9.11.2012 - first time seeing oval BA [Re: Sasa]
      #5556941 - 12/06/12 06:33 AM

Yes, that STB "bend" is becoming more noticeable. Still pretty faint. Great catch!

Interesting on the cool down, I would expect a large refractor lens and Mak meniscus to cool /relatively/ quickly as they are exposed to the open air. The inner workings of Cats, however, are not and require a bit more time. As Eddgie said, I have seen Cats that never cool at all.

But, there are so many variables, it's easier to argue in generalities that probably do not apply equally across everyone. Contrary to their reputation, my Mak has zero cool down issues, after it's cooled down. That takes about an hour, then it's clear sailing all night.

You really nail Jupiter in your 80, Sasa.


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Sasa
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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: Asbytec]
      #5622082 - 01/14/13 03:28 AM

It is probably not worth starting new thread, so here is a short update. Finally, I was able to observe Jupiter through AS110:



Following the discussion about thermal effects, it looks like, unfortunately, that this old lens (from 1924) has serious problems at low temperatures (it was -9C at the time of observing). During summer, the optics was almost perfect (with only mild traces of undercorrection). In last autumn session, I already noticed very faint brightening in the first diffraction ring which was a little bit confusing when I was observing close unequal doubles stars. But two days ago, Jupiter moon's were accompanied by two relatively bright stars. Star test showed clear signs of pinched optics. Still, Jupiter was very nice and clean. I could observe a lot of details.


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Asbytec
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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: Sasa]
      #5622550 - 01/14/13 11:58 AM

You have a lens that old? Wow.

In any case, yes, it's a nice observation, Sasa. I've been hitting some doubles lately, too. Tight unequal pairs. They are interesting and challenging...and taking up all my time.


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ericj
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Reged: 02/17/05

Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: Sasa]
      #5639651 - 01/23/13 10:16 PM

Hi Sasa,

Very nice sketches, you recorded a lot of fine detail.

Here is some background information on oval BA.

In the late 1930's, three white ovals formed in Jupiter's South Temperate Belt (STB) and were designated as FA, BC and DE. Ovals BC and DE merged in 1998 formed the oval BE. These two ovals merged in March 2000 and formed oval BA.

Since 2000 BA has remained white in color, but at the end of 2005 oval BA began to change to a brown color, and on February 24, 2006 Filipino amateur astronomer Christopher Go noted that its color changed to that of the Great Red Spot. Dr. Tony Phillips gave it the name "Red Spot Jr." or "Red Jr." although professional astronomers still refer to it as oval BA.

Here is a link to my Jupiter Nomenclature page that shows BE and FA before these two ovals merged in March 2000 and formed oval BA:

http://ejamison.net/jupiter_nomenclature.html

And here are two sketches I made of oval BA in 2006:

http://ejamison.net/jupiter052806.html

http://ejamison.net/jupiter061606.html

Hope this helps.

Best,

Eric Jamison


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azure1961p
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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: ericj]
      #5640226 - 01/24/13 09:10 AM

Eric nice of you to mention the history on the white ovals leading up to BA. Unlike the white ovals we have now that trio was far more conspicuous and was seen even in average seeing. It was fun to watch how they shuttled about. Even a few nights passing and they were noticeably rearranged. The spots now though - wow - tinier and far less conspicuous. They'd morph into a specked muddle then smooth out into nothing leaving the surrounding grey spaces between the spots as the greater albedo. Those older pre BA spots, fat and bright. Small still but definately bigger than these micro spots we have now.

Pete


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Sasa
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Reged: 11/03/10

Loc: Ricany, Czech Republic
Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: ericj]
      #5643018 - 01/25/13 05:30 PM

Eric, it is very interesting. I had no idea about the origin of the "Red Jr.". Thanks for the story.

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ericj
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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: Sasa]
      #5651308 - 01/29/13 10:35 PM

Hi Pete and Sasa,

Glad to hear you found the information helpful.

Best,

Eric


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Rich (RLTYS)Moderator
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Re: Jupiter 9.11.2012 - first time seeing oval BA new [Re: ericj]
      #5651881 - 01/30/13 09:32 AM Attachment (11 downloads)

Here's an image I took of Jupiter last evening, 1-29-13, using the Slooh Remote Observatory. Oval BA is clearly seen.

Rich (RLTYS)


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