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14" Flextube GOTO - It Works!


Albireo380
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The 'scope arrived in two huge boxes and a small one (20" x 20" x 10"). The contents were an OTA, a flatpack base unit and a mirror cell.

On Monday evening I built the base unit in an hour. It was an easy build, the only confusing bit being that the instructions said there should be 8 hex screws and washers that were not there. This caused me a bit of concern, but as I looked at the pictorial instructions I realised they were never shown, their place being taken by 12 large bolts with black knobs on the end. The hex screws appear to be for the 10" or 12" versions.

I was out doing Astro Club things on Tuesday and Wednesday evenings and so it was Thursday before I approached the mounting of the mirror cell. I had previously got some images from Brantuk of his 10" Flextube mirror cell in situ, so I thought I knew what to do. I lowered the mirror into the OTA and left it resting on 3 flanges that it would later be bolted to. I had a bit of bubble wrap around the outside edge of the mirror (there was about an inch of clearance between the mirror's edge and the OTA tube wall). Then I slowly lowered the OTA until it was horizontal on the floor. My wife had helpfully held the mirror cell in place by reaching into the open base of the OTA and grabbing it.

On the flanges protruding from the central base of the mirror cell are 3 male bolts, these get a small spring put on them and then each bolt is inserted into a hole in an OTA base flange. You then screw on female bolt threaded to go over the male, through the hole in the OTA base flange. You thus have a secure, but sprung mirror. Locking bolts sit next to the threaded bolts, so that once collimation is achieved, you can lock the mirror in place. This took only 20 minutes to do and was pretty straight forward. Collimation was a snap with a laser collimator (5 minutes).

I then mounted the 'scope onto the base, added a 20mm plossl and pointed at the roof of the high flats half a mile away - I couldn't focus, not enough back/outward focus, by about 10mm. Oh Dear - Panic stations. I tred several other EPs, all the same. I fretted and posted on SGL - Andrew replied saying that in such a fast 'scope half a mile was not the same focus point as infinity. It was 100% cloud, so i fretted for 24hrs

At 6.30pm this evening I et up the 'scope (10 mins) and pointed at the Moon - FOCUS :D. I tried a variety of EPs, all achieved focus.

at 7pm it was dark enough to see stars and so I followed the GOTO instructions - the aignment failed and the 'scope slewed all over the place. I tried again, with the same result. I reread the instructons, set the scope level and pointing North, set Lat/Long, date and time then put the scope in autotracking mode. Okay, what next? I then went through the GOTO procedure, manually slewing the scope to point near the chosen bright star, then using the handset to sync, then onto a second bright star. The scope slewed to within about a degree of the star and I used the handset to get the star in the 16mm Nagler EP.

Alignment successful! Yippee!. It is really a very similar process to the 2 star align procedure with an HEQ5 Pro.

I then decided to GOTO M13, and off she went - bang on the nail in the EP at x100 magnification. I let her track for 20 minutes and M13 stayed in the centre of the FOV.

I then used the GOTO to observe Jupiter - again the 'scope slewed accurately and Jupiter was half way to the centre of the FOV at x100. I again tracked for 20 minutes and the Planet stayed in the centre of the FOV. I could observe several cloud bands and the 3 inner moons (the 4th was outside the FOV).

So, after a few days of concern, all seems okay. I have a MASSIVE 'scope that I can move myself (I may invest in a small trolly to ease the potentail back pain from lifting the base). The GOTO functions reasonably well and the tracking seems good.

The next thing is to get out to a dark sky site and away from my light polluted city back garden. Then I can really see what the 'scope is capable of.

Thanks to Brantuk and Andrew for their help when I was concerned about mounting the mirror and it's apparent inability to get focus.

Tom

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Thanks Tom for that report, I almost got excited as you! It's usually the case that there always seems to be this time difference between when the boxes arrive and actually getting at its contents - effects of the real world. At least you got to make a start by constructing the base.

Congratulations on getting everything to work which must be a bit of a relief - everytime I buy something there is always something not quite right or something that needs fettling. Can't wait for you take her to a dark site to what she can really do (...the scope I mean :D:D:D)

Thanks again Tom and await the next installment!

James

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Thanks Tom for that report, I almost got excited as you! It's usually the case that there always seems to be this time difference between when the boxes arrive and actually getting at its contents - effects of the real world. At least you got to make a start by constructing the base.

Congratulations on getting everything to work which must be a bit of a relief - everytime I buy something there is always something not quite right or something that needs fettling. Can't wait for you take her to a dark site to what she can really do (...the scope I mean :D:D:D)

Thanks again Tom and await the next installment!

James

LOL I know wha you mean :)

I usually pace around the boxes, then make myself a cup of coffee with a nice biscuit, pace the boxes again, then sit next to them and say to myself "right lets start then" :p

Edited by callisto
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Sounds great! How was collimation - was it easily achieved after inserting the mirror cell, and does it hold it well after setting up and breaking down etc? Also, is the base unit manageable for carrying through a doorway?

Thanks,

Ant

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Hi Ant, collimation only took a few minutes. Inserted the skywatcher laser collimater into the 1 1/4" EP holder, switched on. I could see two red dots in the secondary, one bright and one dim (about an inch apart). The dim one was the reflected light from the primary. Looking at the primary, the dot was ablout a half inch from the centre spot. I loosened all 3 hex screws on the seconday and then partly retightened 2 of them, The red dot was now bang in the middle of the circle/dot in the middle of the primary.

I then moved the OTA to horizontal, loosened the locking nuts on the back of the primary and loosened/tightened the collimation screws until the reflected red dot was in the centre of the laser collimator screen. The twin red dots on the secondary had now merged into one.

I then locked the primary mirror in position and was ready to observe - it all took only a few minutes.

The collimation holds resonably well. The following night I set up again and it took only a sight tweak of the primary to get collimation perfect. I will collimate every time I observe, as it only takes a minute to do.

Cheers

Tom

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They're MASSIVE, lol

I saw the images of you and your son next to your 14" FT. They give the size of this 'scope nicely. VERY BIG INDEED.

Andrew - I will take sunglasses with me when I point this 'scope at the Moon. I suspect that M31 will be light pollution through this baby.

Tom

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TOM I'm writing from Italy Hello, congratulations for the Dobsonian, I'm too indecisive for 35-inch 14 cm, 40 cm or 16 inches that is due out in January 2011, I want to ask questions of the tube and the base separately when they weigh? if you feel light and good if the goto el iseguimento are ok, and if it transportable, I salute you, good luck again

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Great report - infectious!!!! I must say that a scope like this would be great for me because when called on to find things in the big Dob I am as blind as a bat from the imaging-computer side of the site and can't find the bloomin' EP, never mind Stephan's Quintet...

Like you I use a laser and step two (after getting the beam into the primary centre ring) is to get the return beam to hit the secondary at the same point as the incident beam. This is obviously easier than trying to go straight to the target on the laser. I rarely bother to do a star test adjustment after that.

I'll be keen to hear how it performs on Jupiter. It is one planet that my big Dob really does like despite being f4. The brick coloured dust lanes show beautifully.

Who would have thought ten years ago that a go-to, alt-az, tracking Newtonian of this size would be available at such a price. We are all dead lucky. Well, you certainly are!

Olly

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Told you they were good..

The 12" was so good, we bought it for Spain...this review lark is chuffin expensive I can tell you..

Great report and so so glad to see others saying that they work as I saw it at SSP and in the month I had one.. truly brilliant scopes IMHO

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...at local prices atm, one of these 14"ers here in Oz would go for about the same as a 9.25" SCT OTA.... ..14", GoTo, ..short Planetary avi's.. .. and all that DSO viewing-power besides.. can you hear my thoughts whirrrrring ?? :)

Prices I've seen in Australia are £300 cheaper than here in the UK. As long as the GOTO wrinkles are sorted it would be a great scope at a great price.

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Okay, I took the 14" GOTO FT out to a dark sky site tonight, and tested the GOTO as best I could.

I have found that one has to ensure the base is level. 1 degree out whilst aligning in the Northern part of the sky means 1 degree error using the GOTO for an object in the South. This can be overcome by using the Pointing Accuracy Enhancement (PAE) function. In effect, this lets you realign on one or two stars near the object you want to observe, thus the inaccuracies caused by big slews (45 degrees or more) can be negated.

Tonight (Full moon) I used th GOTO for M27, M13, M92, M81 and M82. All were within my EP FOV at x 100 (0.82 degrees tFOV). M13 and M92 were resolved to the core, M27 was a definite dumbell within a globe and I could see hints of the spiral arms of M81 - all at Full Moon. It was so bright out there I could read the paper!

Jupiter also showed several cloud bands, a nice polar region and the Great Red Spot - all this only 45 degrees away from a light polluting Full Moon.

So - the GOTO is accurate only to a degree or so over long slews, but the PAE function overcomes this. Having the base absolutely level is VERY important. The optics seem reasonably good and produce good views even at Full Moon.

Cheers

Tom

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Nice to hear, I was more concerned about the tracking accuracy and the optics quality then the goto. Now I know the optics are good and the tracking is good enough, I'm even more anxious to get one of this!

Unfortunately I'll have to wait on some other financial priorities and I'm not sure who will be willing to ship it over to Portugal... :s

Please keep the reports coming as you use it in different conditions! :)

Edited by pvaz
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