Skywatcher 14" Dobsonian first month's thoughts

[DaveGibbons]

Hi all,

 

I recently purchased a used but immaculate Skywatcher 350p non goto dobsonian. It was a little gift to myself upon retirement after 26 years at BT. This would be the largest aperture scope I have ever decided to live with, also the heaviest!

Many scopes have passed through my hands over the past 40 years and I have loved most of them! I currently own an APM152mm apo refractor and a Celestron CPC 925 sct both with excellent optics . But, as my eye’s get older I find the photon’s just don’t light up the receptors that they once did and as they are only going to get worse I figured it’s now or never for larger aperture.

I know some of you will be thinking why not go 16” or larger? I tend to observe every clear night possible and do not wish the set up and break down to become a chore. My garden is reasonably dark but I do use several observing positions to open up as much of the sky as possible and it is necessary for me to negotiate a couple of steps and traverse a short bit of decking, ultimately I need to be able to set up without breaking my back- more on that in a minute.

 

So a bit about my actual scope. It came with a few modifications to improve performance and usability:-

Bob’s knobs fitted on secondary

Focuser tube and secondary mirror edges blackened

lower tube assembly and upper cage opposite focuser flocked.

 

I have added :-

Astrozap light shroud

9x50 ra finder

Telrad with 2” riser .

Baader click lock adapter.

It’s a sin that Skywatcher still persist in shipping dobs with a straight through finder, keeps the after market 9x50 RA finder sales buoyant I suppose! If you want to keep cost down the “essential” item in that list is the light shroud. Improves contrast and has kept dew at bay on all observing sessions so far.

The standard dual speed Crayford style focuser is of decent quality and comes with 2” and 1 ¼” adapters. I just use the 2” with a Baader click lock 1 ¼ “ adapter. Focuser is super smooth and is more than up to the job.

The dreaded collimation and the collapsible tube. Well I keep my tube assembly fully extended and locked permanently! It saves faffing round with the light shroud and means only a small tweek usually needed when I take the tube out to the base . My secondary is in perfect position and has not needed adjustment and I use a simple short collimation eyepiece for the primary adjustment, it is good enough to get accurate alignment. Here's the thing at F 4.5 and 14” aperture this is not the scope for splitting sub arc second doubles, it’s forte are the faint grey galaxy smudges,  globular and galactic clusters and the beautiful rendition of true star colours. Yup atmosphere permitting it will easily show fainter E and F components in the trapezium but it is not a double star or planetary killer. I am learning to embrace it’s greatest strengths letting me see new objects for the first time and familiar vistas with greater detail than ever before.

Mirror quality, well you get what you pay for to a degree. Inside and outside focus differ (as does every other Skywatcher mirror I have ever seen) with what appears to be a turned down edge evident, par for the course on a big machine figured mirror, no hand finishing here! No other aberrations other than some surface roughness as usual. The mirror coatings themselves are immaculately applied. Difficult to give a true evaluation as I have not had good seeing conditions in the past month since purchase and it also takes a long time to reach thermal equilibrium.  I am quite sure it is representative  of a typical large  Skywatcher mirror and am satisfied  with the quality it offers.

In practice the views of the Orion Nebula and the double cluster nothing short of spectacular. M35, M81/82 best I have seen them. Nebulosity around the Pleiades is superb. Dark lane can be glimpsed in M31 and I am certain when better positioned overhead M51 the whirlpool galaxy will show the  nature of it's spiral arms. This is why I bought the scope.

Coma is most definitely evident in lower power eyepieces but it does not bother me that much,You may well differ. I may try a coma corrector at some point but I will not worry if I never do.

Now for the weight issue. It is heavy and you do need to consider this very carefully as it literally can be a back breaker. I keep my scope in an unheated workshop/shed and I move it in two pieces.The built up base approx 80lb and the permanently extended OTA about 60lb . Although the base is built to be taken apart with hand knobs and captive nuts aiding this operation. I find it a bit too fiddly and opt to pick it up in one lot. Now I do have a bad back, but I also train a lot with weights and have  above average body strength and find If I use the two cut outs in the front board and not the side handles I can lean back slightly and keep the base close to my body and manage the 15m or so to the garden. Again  the tube assembly can be carefully picked up using the bottom of the truss brackets as grips, keeping  it close to my body it is manageable for me without much trouble.

I must stress for many this will not be an option so either a permanent position outside or full breakdown of the base (5-10-min) would be order of the day.

The biggest issue with the scope apart from weight is excesive stiction on initiating  movement with the altitude bearings, again a long standing complaint with Skywatcher dobs for as long as I can remember. I found cleaning both side bearings and nylon bushes with Isopropyl alcohol and then apply a few small drops of mineral oil helps minimise the jerky motion. Once done I can hand guide at over 500x with a 3mm eyepiece keeping ahead of a stars motion. The azimuth became nice and  smooth once I cleaned the accumilated dust and grime from the lazy Susan roller bearing and put a drop of oil on each roller.

 

Overall I am more than happy with the £750 I initially paid for the scope and it compliments well with what I already have.

 

Cheers

 

Dave

 

 

Edited January 30, 2022 by DaveGibbons
Spelling correction

[John]

Very interesting thoughts Dave. Thanks for posting them

 

[Sunshine]

It is certainly a big and beautiful dob! you describe M42 and the double cluster as "spectacular" this made my heart skip a beat! making me want a dob too!

[Mr Spock]

I would like a 350, but, in terms of weight and bulk it's a step too far for my dodgy back - like you I am strong though. I had the pleasure of looking through a StellaLyra 16" Dob a while ago. Fantastic views of the witch's broom, but it's huge - definitely a two man job to move it around.

My 'retirement' present is going to arrive early - I'm not waiting another 3 years! I'll be purchasing a 300mm shortly. I reckon that's the biggest scope I can safely move around.

[GordonD]

Thanks for posting this - it is all helpful and interesting to hear. Like others here I decided to get something of size whilst I can still manage it, so went for the 300 flex tube 18 months ago. Luckily just before the prices went skyward.

But I figured that I would only manage it on wheels so attached lockable castors and move it all in one with the tube collapsed. Of course this will only work if you have flat-ish surface to move it over and it does rattle alarmingly.

Glad to hear you are enjoying it. I had a 250mm previously but for me it has been globular clusters that has really shown the difference. You can just look deeper and deeper in to them with higher and higher magnification.. Also showed me the veil for the first time too.

A 350 would be even more fun, though.

[Space Hopper]

Mighty impressive beast.

It gives a good comparison of size next to the OO 10" 4.8 and i have one of those myself which i find a bit of a handful.

I had the 12" F4 scope 3 years ago and enjoyed the aperture, but i feel like 'i've been there, done that' now.

At nearly 55 and in not the best shape and health i'm much happier with refractors these days.

Enjoy the views through the 14 ! 🙂

[tomato]

Thanks for posting. I purchased a used 16” flextube last year which I transport from the garage to the back garden on a custom built 4 wheel trolley. I do have to extend the tubes and collimate each time but this is straightforward with a Hotech laser.

l’ll confess it is bit of a beast and given that I’m imaging first and foremost I only feel it’s worthwhile setting up if l have the prospect of a cloudless, clear, moonless night. Needless to say, It’s never going to get worn out through over use, but no regrets on acquiring a decent light bucket for visual use.

[Whistlin Bob]

Congratulations on your 14". I succumbed to the desire to go bigger around 4 years ago, and went for the same size. I've never regretted it.

Mine is a truss based Orion USA model, I keep it on a sack truck, so moving from garage to garden isn't a big deal. Assembly takes about ten minutes, which I don't find onerous, although I've kept my 8 inch dob for quickie grab n go sessions. At the zenith it's right at my eye level (I'm 6' tall), which makes the size really good for me, had I gone bigger I'd have needed a ladder or step and that has never felt comfortable in the dark.

On your aspiration to see the arms of m51, I'm in Bortle 5 and on the most transparent nights they're pretty clear in my 7mm Celestron ep, so I'm sure it's on for you.

I suspect our mirrors are of similar quality, so I would mostly agree on the strengths. However, I've made an aperture mask for mine, which gives me 160mm unobstructed aperture. This tightens stars up hugely, and makes it very competent for double star splitting. If the seeing is a bit wobbly it also improves lunar and planetary views, so I'd definitely recommend that.

I'd also recommend a little portable hairdryer- even with a shroud, the secondary is quite prone to dewing up on damper nights. It's soon sorted with a quick blow of warm air- that has prolonged many a session.

My other tip would be binoviewers: I use a Williams Optics pair, and on the right targets (esp globs and tighter/brighter open clusters) the views are bright, detailed and immersive. I have to Barlow mine to achieve focus, but I'm guessing the flextube system would give you some extra flexibility there.

As you can probably tell, I'm a bit in love with my 14" dob. It has shown me some wonderful sights and I'm hoping to have many more years of use out of it. I hope yours gives you the same satisfaction, and look forward to hearing of your adventures with it.