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Big Dob purchase

Stargazer_00

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Stargazer_00

Stargazer_00

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So the day has finally come. My savings topped off this morning with the exact amount I need to buy a brand new Skywatcher 350p Flextube.

This is likely to be the last main scope I buy for a long long time so I figured it might be prundent to share my thoughts on the scope prior to purchase and check if I have missed anything obvious or not considered something important which may make me regret the decision.

Reasons for purchase

First of all, aperture. I wanted more aperture than my 10" 250px currently offers. This scope would offer double the light grasp of a 250px (96% increase I believe). A 12" would offer only a 40% upgrade which would probably equate to not much of an upgrade in reality.

I always said to my wife when I started astronomy that if I carried the hobby for more than a year then I'd buy a scope for at least £1000. So this is that.

The base on a 12" flextube doesn't deconstruct.

This model comes with a dual speed focuser, where the 12" does not.

Portability is not a concern for me. The scope will unlikely never travel more than 20 feet from the shed in which it will live. I expect set up to consist of taking the base apart, building it on the lawn and then loading the OTA onto the base. I expect this will never take more than 5 minutes.

I expect I will have to collimate the primary mirror often and occasionally the secondary. I am comfortable with collimation.

I do not expect to have to upgrade any of the primary mirror supports/springs. All my skywatchers to date have had no problem with this.

I know the scope is fast, but my 10" is F4.7 and this scope is, F4.5 so it's faster but not by too much. I expect to have to purchase a coma corrector.

I intend to purchase the astrozap light shield / coat thing as well. So the loss of contrasts from an open tube assembly should be mitigated.

The extra weight of this scope shouldn't cause a problem, in fact I'm thinking it might even introduce some stability at the eyepiece.

I am deliberatly not getting a 16" because I believe the eyepiece will be more often in an uncomfortable position. The 14" should put the eyepiece 1 inch under my eye at full zenith and I have a fully adjustable seat to take car of all the other elevation points.

I expect to have to counter balance the scope for my heavier 2" eyepieces.

I expect to mod the base with lazy susan and flock the inside of both parts of the OTA.

I expect to add a light shield to the top cage.

I will replace the secondary screws for thumbscrews.

I appreciate that I will lose maximum potential field of view from going from a 1200mm focal length to a 1600mm focal length. I intend to keep the 10" for such time as I can run the scopes side by side and see how good an upgrade it is and then sell the 10" on for someone to have as a main scope.

I appreciate that at low magnifications the exit pupil will be larger than my 10" on equal magnification and that this limits the lowest potential magnificaiton in comparison.

Equally I appreicate that the high power eyepieces I have purchased for the 250px / 150p set up will likely be unused in the 350p very often as they would offer very high mangifications (4.7mm = 340x)

I understand that a 16" scope gives a further 25% light grasp over a 14" and that once having purchased a 14" the step up to a 16" is a bit pointless and therefore unlikely.

I can find almost no user information on this scope whatsoever. It's a journey into the relatively unknown and that exciting to a point but also a little unnerving. I hope that the quality of mirrors I've found in my SW purchases to date carries over to this scope. As I expect sales of this model to be fantastically small there is every chance the scope I end up buying has sat on a shelf for a year or two waiting to be purchased. I would hope that nothing bad could happen to a scope that is stored in its packaging for a prolonged period of time. In particular the mirrors.

Is there anything else I should be considering? I would like to think in the 2-3 months its taken me to save for it I've spent enough time considering the pros and cons of the scope.

thanks for any input you can offer up. I intend to put the order in Monday to FLO for this scope, and a Rigel Quickfinder (used to a TelRad and want to try the RQF and it's much lighter)

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DirkSteele

DirkSteele

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Echo Michael's thoughts exactly. Sounds like you have thoroughly considered everything and have come to an excellent conclusion based on your needs.

I look forward to seeing some unboxing pictures and first light report.

Oh and don't forget to apologise for all the clouds that the 350p will come packed in! :grin:

Clear skies,

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Bart

Bart

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You might be able to wheel it out to the garden on a sack truck or construct wheelbarrow handles. I use the sack truck for the 10", only takes a couple of mins to get it out there, and wheelbarrow handles for the 16", takes same little time as the 10"

Pic shows sack truck. If you look closely, you might see the fixing points on the LB for the removable handles (2x1" wood handles) and the handles behind it. The wheels are self evident. Don't get in the way at all, which was my fear. Very portable, really, if you're just rolling it outside

Barry

post-11876-137180219316_thumb.jpg

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swamp thing

swamp thing

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I reckon Barry's suggestion (above) is the way to go.

edi: My seventy two year old father was pushing my 20" Dob around on wheelbarrow handles no probs the other week, even up and down terraces in a lawn.

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Stargazer_00

Stargazer_00

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Thanks for your replies so far.

I had considerd getting a large truck type assembly too. I'd need to make some sort of ramp to get it in and out of the shed but that's not really very difficult. I'll see how much of a pain in the back it is to deconstruct/build the base each time. I don't think the weight of the tube is any concern.

I guess if I were planning on moving it on a truck is there any justification to not push on and get a revelation 16"? One reason I'm steering clear of that scope is that I read the GSO mirrors are much more likely to be poorly figured comapred to Skywatchers. An article i read on CN about a guy who refigures mirrors and said the bulk of his work were GSOs and he rarely ever saw Synta mirrors.

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brantuk

brantuk

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Sounds well thought out. Wheelbarrow handles and air filled tyres are the way to go - it'll absorb ground vibrations and ramp bumps. I look forward to your comparison with the ten inch. Just as a rough guide you might find the M13 comparison on this page interesting:

http://www.obsessiontelescopes.com/telescopes/20/index.php

(It's about 1/3rd the way down the page on the right) :)

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RikM

RikM

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Sounds like you have done your due diligence :)

James at FLO uses (or has used) a 350 flextube, so if you intend purchasing from them, you would be able to get some first hand user knowledge.

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SnakeyJ

SnakeyJ

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Painstakingly thought through Graham and I will be looking out for that unboxing and first light report. It sounds like you've thoroughly researched all bases and I hope the hard work and investment is rewarded with excellent views (above and beyond the 250PX).

You've built up a good collection of the ES82s, so sure the EPs will perform well at F4.5 - how much research have you done on the coma corrector, I believe the standard SW Coma Corrector is optimised for F5 and up - though not sure how much difference this would make for visual use. The SW Aplanatic is rated for F4, but this looks orientated towards imaging. TV Paracorr's seem to get the vote from most of the dob mob, but not a cheap addition to the EP case.

I'll watch out for the Mordor like murk overhanging Hertfordshire - hopefully the prevailing winds will keep this well away from me ;)

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SnakeyJ

SnakeyJ

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I have contacted R&D at ES and am on the short list for the coma corrector which is due to go into beta test imminently. I'm trying to get right ahead of that particular curve :)

I didn't know they were developing one, but this is very interesting and sure many here will want to hear how this performs - it would be nice to run this up against the SW, Baader CCs and Paracorr for a comparison, though suspect it will be reviewed very soon after launch - if not then SGL9?

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michael.h.f.wilkinson

michael.h.f.wilkinson

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You might be able to wheel it out to the garden on a sack truck or construct wheelbarrow handles. I use the sack truck for the 10", only takes a couple of mins to get it out there, and wheelbarrow handles for the 16", takes same little time as the 10"

Pic shows sack truck. If you look closely, you might see the fixing points on the LB for the removable handles (2x1" wood handles) and the handles behind it. The wheels are self evident. Don't get in the way at all, which was my fear. Very portable, really, if you're just rolling it outside

Barry

post-11876-137180219316_thumb.jpg

Nice solution. I have a sack truck lying around somewhere, might even push me to joining the Dob Mob.

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