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Planetary observing with the travelscope


JeremyS

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Having struggled with Mars and Saturn so far this summer, I had the opportunity of travelling to the island of Lefkada in western Greece. I took my Tak FC76DCU in a back pack. Once again no problems thru airport security. The Neweer carbon fibre tripod and the TS altaz head travelled in my check in bag.

I was able to observe for 7 nights, the last 3 being truly excellent seeing. Some of the best I’ve seen . Just as well as the first 2 were awful; images were dancing around like at home.

Given the presence of the moon preventing deep sky observing, I concentrated on the planets (although I did look at eps Lyrae: see the “double double” thread). Also there was quite a bit of local light pollution.

I have to say that Mars and Saturn were amazing. Could see bands on the gas giant. But the most enjoyable was Mars. Although it’s the dull hemisphere was on view, I could see quite a lot of detail e.g. the Mare sirenim area and of course the polar cap. But it was the subtle colours that were most extraordinary especially the grey/ green of the Mare contrasted with the red of the rest of the planet.

Each evening I started with the Televue 3-6 zoom at 6 mm  (100x) then gradually racked up to 5 then 4 mm. Only on one night was it possible to use 3 mm (200x). I also tried the Vixen HR3.4 (175x) which also gave excellent views. There was hardly any difference between the TV and the Vixen at the same mag. If pushed, I’d say the Vixen was slightly preferable in terms of colour rendition.

So I’m pretty well pleased with the travel set up. I wish the Neweer CF tripod were a bit more steady as the image jumps around when focussing at high mags. But the whole point is the have something lightweight. And for low power viewing it's fine. And the performance of the 3-inch Tak is astounding for its size. Who’d have thought such a scope could be so easily carried by air - the fact that it breaks into two helps!

 

A103A900-DD13-4F6C-8C7B-4D30EB90C901.jpeg

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Lovely stuff Jeremy, a really cracking setup and it sounds like it delivered on those planets!

It very much reminds me of my FC76DC, again, a split tube which I took abroad with me. So easy to transport for such a capable scope. Wish I had had the additional extender though.

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Excellent! That reminds me... I need to see if I can attach my TeleVue Ranger to my camera ball head & Manfrotto 055PROB. I think the base plate saddle on the ball head is wide enough to accept a 'Vixen' type dovetail bar without attaching the quick release plate. I used to use the same tripod & Manfrotto 125RC video head, before I purchased the Giro GR-DXll, and was not to bad. A bit of vibration at high magnification too.

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25 minutes ago, Stu said:

Lovely stuff Jeremy, a really cracking setup and it sounds like it delivered on those planets!

It very much reminds me of my FC76DC, again, a split tube which I took abroad with me. So easy to transport for such a capable scope. Wish I had had the additional extender though.

Thanks Stu. I have an Extender Q x1.6 but didn’t take on this trip.

a couple things to add:

Views of Jupiter were not so good as when it was visible early evening it was just above the island’s mountains and I think they were contributing to poor seeing.

For the first time since I bought the scope in June, I was able to do a star test under excellent seeing conditions and I’m pleased to report that it was textbook perfect. Although I wouldnt have expected anything else from Takahashi.

Does anyone have any suggestions for double star tests for this aperture?  

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21 minutes ago, JeremyS said:

Does anyone have any suggestions for double star tests for this aperture?  

Why not give Pi Aquilae a go Jeremy. 1.4" separation. If I've done the maths right a 76mm scope should resolve to around 1.5" so you may just see it at high power.

You've presumably tried Izar? Should be fairly easy but very nice in the Tak.

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18 minutes ago, Ags said:

I really like that TS travel mount! I use it a lot with my ST80 and Skymax 102.

I must admit that I didn’t have much expectation of it, but I have found it pretty impressive. It’s certainly hugely better than the standard pan head I’ve used on standard photo tripods until now. So I highly recommend it for a lightweight travel set up. Certainly has no probs with the Tak FC 76.

i might add that I tried to increase the stability of the tripod by hanging a carrier bag containing two 1.5 litre water bottles off the central column. There is a hook to facilitate a weight being hung. However, whilst it helped a bit to damp the high frequency vibrations when focussing, it left a slow movement of the planet in the field of view as the weight slowly swaid backwards and forwards. Imperceptible when looking at the tripod, but pretty annoying at 200x thru the eyepiece!

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On 26/08/2018 at 10:52, Stu said:

Why not give Pi Aquilae a go Jeremy. 1.4" separation. If I've done the maths right a 76mm scope should resolve to around 1.5" so you may just see it at high power.

You've presumably tried Izar? Should be fairly easy but very nice in the Tak.

Had a go at pi Aql two nights ago and again last night, Stu. Could clearly see elongation at x200, but not resolved. Seeing was good last night and there were occasional views of a peanut shape, but the stars wouldn't pull apart.  Perhaps I need a night of perfect seeing, possibly with a bit more mag.

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28 minutes ago, JeremyS said:

Had a go at pi Aql two nights ago and again last night, Stu. Could clearly see elongation at x200, but not resolved. Seeing was good last night and there were occasional views of a peanut shape, but the stars wouldn't pull apart.  Perhaps I need a night of perfect seeing, possibly with a bit more mag.

Nice one Jeremy, yes I suspect perfect seeing would be needed for this to split, assuming I’ve got my maths right! I did try with the 72mm and would say I got elongation, possibly a rather fat waisted peanut ( ;) ) but very marginal.

I wonder if @chiltonstar could confirm whether this is theoretically possible?

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50 minutes ago, Stu said:

Nice one Jeremy, yes I suspect perfect seeing would be needed for this to split, assuming I’ve got my maths right! I did try with the 72mm and would say I got elongation, possibly a rather fat waisted peanut ( ;) ) but very marginal.

I wonder if @chiltonstar could confirm whether this is theoretically possible?

Hmm..... at 1.4 arcsec (2017) I would say it is below the Dawes limit of about 1.6 arcsec, although you might do slightly better with a blue filter (shrinks the limit to 1.2 arcsec in theory).

With white light viewing, a perfect 72 mm scope view of Pi Aql should look like this (Aberrator).

Chris

piaq72b.jpg

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11 minutes ago, chiltonstar said:

Hmm..... at 1.4 arcsec (2017) I would say it is below the Dawes limit of about 1.6 arcsec, although you might do slightly better with a blue filter (shrinks the limit to 1.2 arcsec in theory).

With white light viewing, a perfect 72 mm scope view of Pi Aql should look like this (Aberrator).

Chris

piaq72b.jpg

Thanks Chris. Looks quite like my fat waisted peanut ;) ?, visible occasionally in the 72mm. Jeremy has a little aperture advantage at 76mm.

Will give the blue filter a go next time to see.

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46 minutes ago, chiltonstar said:

Hmm..... at 1.4 arcsec (2017) I would say it is below the Dawes limit of about 1.6 arcsec, although you might do slightly better with a blue filter (shrinks the limit to 1.2 arcsec in theory).

With white light viewing, a perfect 72 mm scope view of Pi Aql should look like this (Aberrator).

Chris

piaq72b.jpg

Thanks Chris. That’s pretty much how I saw it thru the the Tak FC76.

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You can see how the pair open up with aperture in this composite using Aberrator; the brightness of each image is not comparable as obviously the view through a 72mm scope will be less than 1/4 as bright as through a 150mm scope.

Chris

piaqlcomp.png

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1 minute ago, chiltonstar said:

You can see how the pair open up with aperture in this composite using Aberrator; the brightness of each image is not comparable as obviously the view through a 72mm scope will be less than 1/4 as bright as through a 150mm scope.

Chris

piaqlcomp.png

Thanks Chris - that’s really helpful

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41 minutes ago, chiltonstar said:

You can see how the pair open up with aperture in this composite using Aberrator; the brightness of each image is not comparable as obviously the view through a 72mm scope will be less than 1/4 as bright as through a 150mm scope.

Chris

piaqlcomp.png

Thanks Chris.

I get the fact that the airy disk size theoretically reduces with increased aperture, but that has not always matched my experience. I guess seeing conditions and cooling issues often mean that a larger scope shows a larger/messier disk. I think I’m right in saying I’ve yet to split anything in a larger Newt that I haven’t been able to do in the Tak.

Now my OMC140 is sorted I need to do some more side by side with it to see how they compare. It generally beats the Tak on resolution for globs, small OCs etc, but so far for planetary and doubles I prefer the Tak.

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31 minutes ago, Stu said:

I guess seeing conditions and cooling issues often mean that a larger scope shows a larger/messier disk. I think I’m right in saying I’ve yet to split anything in a larger Newt that I haven’t been able to do in the Tak.

 

Interesting. I find that with my 180 Mak, if  the seeing is poorish my ED80 will appear to give a "cleaner" view of a close pair, but if I use a ND filter to cut the brightness a bit, the views are as expected - the Mak gives smaller, more separated disks. You can of course dim the image with more mag.

If you run an Aberrator simulation for this pair with say a 200 mm scope, they are well separated as shown, but if you increase the intensity, they run together and the clean split disappears.

Chris

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I had another go at pi Aql this evening. I realise it’s not going to be possible from the info Chris has presented, but the seeing was again very good indeed and I’m a bit stubborn! But Ivcould still only get a peanut. I have no filters with me to test.

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Since the seeing was very steady last night, with great views of Mars and Saturn, I had one last try on pi Aql. It was tantalisingly close to pulling the two stars apart. Best I've seen, but still not good enough.

Instead, I moved onto some deep sky objects including M22 and M11. I must say, scanning around Sagittarius with the Televue Pan 24 in the Tak 76 was delightful. Glad i purchased it. It makes the scope a bit back end heavy (easily taken care of by shifting the scope in the tube ring, albeit a bit of a pain when changing backwards and forwards with lighter shorter FL eyepieces). but it is so much lighter that my ES 24 and the Pentaxl XL. There’s a lot to be said for compact and lighter weight low power eyepieces for a travel setup.

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