Skywatcher Quattro f4 Imaging Newtonian telescopes

[focaldepth]

Someone has to ask the daft question, so I will.

This is as good as it gets with the MPCC... http://img268.imageshack.us/img268/6...pic2resize.jpg

What is wrong with that image?

[Revs]

I know it's not bad and I'm probably expecting a bit much and/or being too fussy, but there's still a little coma the extremities which I wanted to clean up. I just wondered if I could get it perfect, but alas, the RCC-I came today and is unsuitable. The problem is that the monorail focuser that TS fit to this version of the GSO f/4 has a baffled (threaded) focuser tube which doesn't allow the RCC to fit all the way in. I don't want to start machining bits so it's back to the MPCC.

I'm still messing with the spacing for now. I'm not 100% but I think I need to move the MPCC closer to the sensor (<55mm), which will require a bit of juggling with adapters, which are on the way. I should be able to adjust the spacing from the default 55-56mm to 50-60mm ish once I've got em.

I don't seem to be able to find a definitive answer about whether using a scope that is faster than the designed f/4.5 requires the spacing closer of farther from the chip. My testing suggests spacing less than 55mm is required. If anyone knows for sure I'd really like to know

[Revs]

BTW, I read the Quattro has Pyrex mirrors, which if true is excellent!

[focaldepth]

I had a frustrating time finding a CCD to thread distance a short while ago. I do not understand why manufactures and supplies don't publish the data.

That along with thread sizes on things.

FLO are you listening.

Or maybe a thread on here just for known working back focus distances etc.

[MikeWilson]

I had a frustrating time finding a CCD to thread distance a short while ago. I do not understand why manufactures and supplies don't publish the data.

That along with thread sizes on things.

FLO are you listening.

Or maybe a thread on here just for known working back focus distances etc.

It's amazing isn't it?

I can't believe that Synta haven't even so much as published - I don't know.. tube length and weight information?!

It seems almost incredulous to suggest that a telescope manufacturer hasn't published such info that we have to wait for someone to purchase an expensive telescope and get it home before anyone even sees a real life picture of one!

"Does it have 3 vanes, or 4?", "Is that a new focuser?", "Does it have baffles?", "What's the mirror made of?", "How heavy is it?", "How long is the tube?"...

Synta/Skywatcher - are you listening?

All the best,

Mike

[FLO]

If anyone's interested, I'm gonna be trying out a Baader RCC-I on the f/4 as I've found the MPCC isn't quite up to the job.

We will be very interested to hear your findings as we have some Baader RCC-1 on order. We are thinking the extended backfocus will be perfect for the Atik OAG with EFW-2 filter wheel.

Steve

[FLO]

FLO are you listening.

We are

When the Quattro arrives we will be 100% behind it and will collate and make available as much information as we can

Steve

[FLO]

It seems almost incredulous to suggest that a telescope manufacturer hasn't published such info that we have to wait for someone to purchase an expensive telescope and get it home before anyone even sees a real life picture of one!

When the Quattro telescopes arrive we will measure their vital statistics and post them here and in our website's product description

"Does it have 3 vanes, or 4?"

Four

"Is that a new focuser?"

Yes

"Does it have baffles?"

The steel tubes do, not sure about the carbon-fiber models.

What's the mirror made of?", "How heavy is it?", "How long is the tube?"...

We don't know but will post details when they arrive here in the UK.

I know this is frustrating but we like to post news as soon as it comes in, even if incomplete.

HTH,

Steve

[FLO]

We will be very interested to hear your findings as we have some Baader RCC-1 on order.

James has just thrown a pen at me! Apparently we already have Baader RCC-1 here on the shelves but I forgot to put them on the website

We will make one available for an SGL review soon

Steve

[Revs]

We will be very interested to hear your findings as we have some Baader RCC-1 on order.

Steve

Scroll up to post #177

The question is; has the Quattro got the same threaded focuser tube design??

The RCC looks a nice bit of kit and the triplet design should result in a flatter image... if it'll fit in the tube

The only drawbacks I know of are; a/ it pushes the camera further out which may cause/increase flexing of the OTA round the focuser and b/ it apparently make collimation extremely critical.

Here are some pics of the problem with the TS MR focuser...

As you can see, the RCC sticks out 2" more than it should, making focusing beyond 15m impossible.

[Revs]

Oh yeah, I've also read the 8" Steel Tube Quattro weighs in at 9.5kg. Again, that could be wrong.

[FLO]

The question is; has the Quattro got the same threaded focuser tube design??

We won't know until it arrives. Let's hope it is compatible with the RCC-1 as it has potential for those wanting to use off-axis-guiders.

b/ it apparently make collimation extremely critical.

Synta mirror cells are better than most, we are not expecting problems.

Paul, when you are ready, we have a solution for your GSO

Steve

[Revs]

We won't know until it arrives. Let's hope it is compatible with the RCC-1 as it has potential for those wanting to use off-axis-guiders.

Synta mirror cells are better than most, we are not expecting problems.

It's not a question of the cell quality, it's a question of how good you are at collimation. It's hard enough getting an f/4 bang on, but the RCC apparently makes it far harder, which is scary As for OAG's.. the RCC is the only OAG compatible corrector that doesn't effect the FL

Paul, when you are ready, we have a solution for your GSO

Steve

oooh that looks nice, and the price is reasonable. I'll have a think, cheers

[FLO]

It's not a question of the cell quality, it's a question of how good you are at collimation.

Granted you need to know 'how' to collimate but anyone who has tried to collimate a Newtonian fitted with a weak and poorly designed mirror cell will tell you - the cell is a major factor.

[Revs]

I agree it ain't as easy with these cells and they don't hold collimation as well as the SW ones, but accurate collimation is still achievable. There a bit of a technique to it for sure

I meant other factors like secondary positioning and offset will have to be bang on, too.

[Macavity]

I agree it ain't as easy with these cells and they don't hold collimation as well as the SW ones, but accurate collimation is still achievable. There a bit of a technique to it for sure

I meant other factors like secondary positioning and offset will have to be bang on, too.

I must admit, the first thing I did was <cough> "re-centralise" the secondary.... Ooops! But perhaps it doesn't matter overmuch? I think Bob's knobs (or shop-bought equivalent) might be a significant addition. Not to mention recycled "milk bottle" washers etc. The main mirror cell might need some fiddling, but seems workable...

The TS Steeltrack focusser and now the (ultimately) "Rigel Systems" motor focus are seriously CUTE!

Onwards and upwards to my 8" F4 VIDEO imaging system...

[Tim]

Need to rewind a little here.

Go back to Pauls pic. From what I can see there is some stretched stars towards the bottom of the picture, however the stars at the top appear to be well rounded.

I am not saying there isn't a little coma evident, just that there is something else amiss, probably collimation or the focuser not being square to the optical plane. If the camera was pointed dead centre at the optical plane, the coma in evidence in the pic might well disappear. There could be several factors at play, likely focuser droop, or misalignment of the optics. FWIW, I found the Baader MPCC more than capable when used with an f4 8" newt.

It is also possible to use an OAG with a fast newt and a coma corrector, but I think probably only using the TS 9mm OAG, especially if you want to use a filter wheel. Works for me

As it happens, I have just read "New perspectives on Newtonian Collimation" a few times, and armed with all the extra info decided to have another crack at collimating the 8" GSO f4 I have. I stripped everything down to bare bones and carefully reassembled, measuring the spiders vanes, centralising the mirror centre dot and so on. One shockingly cheap and nasty component is the secondary mirror holder, which without careful packing with thin tape spacers actually made it more or less impractical to collimate nicely, as the mirror flops around in the holder, and is held at a skew to the focuser axis. After a good few hours of head scratching I achieved a very reasonable collimation, but sure enough, while gently mimicking the movements of the scope on a mount, the primary mirror slipped a mile off of true. Oh well, back to using it for a coffee stand...

I hope there is a ring of truth about the Quattro's mirrors being Pyrex, they are in the MN190 and have proved to be very stable. As for the wieght, 9.5kg for an 8" seems on the heavy side though, not sure that is correct, the MN190 only weighs 10kg and is longer, has baffles, and a very heavy cell/corrector at the end.

@ Steve, if you need that corrector reviewing, just shout

Cheers

Tim

[Macavity]

<wibble> I think I'm going to try to restore the TS/GSO (previous?) "secondary offset" - According to the formula: (minor axis) / 4 * F-number. Hmmm... ~70/4*4 = 4-5mm i.e. quite a bit! Not strictly necessary, but I sense some of the screws were "bedded in" at this previous setting. <G> A ~0.3(?) deg shift of main axis MIGHT return me to the joys of "cone errors". But who really knows...

Aside: I would hope Quattros are a tad less "stick and string" tho'? <G> But I sense MOST budget Newtonians (Astronomers?) have "delusions of accuracy" when matching theoretical adjustment requirements to hardware limitations? As a consolation, at least for my smaller-chip VIDEO imaging, these seem within the inherent, practical limitations of the technique?

P.S. The primary cell seems fairly stable, albeit of limited adjustment and tightened quite a bit. I keep hoping (want to check!) no screws are pressing on glass? As I "Give it a bit o' Wellie", I'd dread to hear a sudden glass-like <craaaaak>.

[George]

Paul, when you are ready, we have a solution for your GSO

Steve

I'd buy one just to look at it , Beautiful craftsmanship.

[DrNeb]

Joking aside, I cannot be the only one who observes the actual sky through one eye and the magnified finderscope view with cross-hair simultaneously through the other. Once you get the hang of it it is a quick way to centre something.

Steve

I thought everyone did it this way? :| i love my stock skywatcher finder :|

[Revs]

Steve, I think I'll give one of those cells a go. Do you have stock? Any discount to SGL members?? One concern is how the mirror is secured (clipless). Might be worth starting a thread about them coz I have a few questions and don't want to get this thread too off track.

BTW TJ, I have a TS alu. secondary support on the way to replace the GSO one. If you want I'll let you know how I get on. I'll be a good chance to set the offset, too. Also, does anyone know what to use to bond the secondary on?

[ollypenrice]

If anyone's interested, I'm gonna be trying out a Baader RCC-I on the f/4 as I've found the MPCC isn't quite up to the job. Despite my best efforts playing with the MPCC's spacing, it seems f/4 is a bit much for it. I'll post my findings once I've done some testing. Hopefully this weekend, weather permitting. The MPCC is optimised for f/4.5, whereas the RCC-I is optimised for f/4, with a triplet design.

EDIT: This is as good as it gets with the MPCC... http://img268.imageshack.us/img268/6436/lrpic2resize.jpg

Is it me or do you think the best stars are in the upper left of the posted image? Odd. If so, non-orthogonality might lie behind it?

Olly

[Revs]

As far as I can tell, it's tube distortion around the focuser. The focuser itself is very solid, but there is deffo a bit of movement when I add the 1000d. I'm 100% sure the collimation is bang on, but the collimator is a lot lighter than the camera (I'm thinking about weighting the laser colli.). There are several tweaks and mods I'm on with at the mo, it's a learning process, but the cloud is putting a stopper on testing. I've mod'd the T-ring adapter to allow 54mm spacing on the MPCC, too. Cheers Olly

[Macavity]

Aside: My TS was certainly... "well-screwed". LOL. At some stage, by "Tighteners are Us"?

- The OTA is quite dented around the various external fixations. <sigh>

It seems to have fun DIY prospects though. How nice it would be to have (such) a compact Newt as a "main" scope. I tire of the MAK's long focal length. I can't afford a "posh" Refractor - Doubtless a common lament! If only one can only get the hardware to function optimally... But perhaps worth working on, even if it involves replacement?

[Revs]

I'm using this as my main scope for now. I'm yet to see how it performs on local objects. I got myself a x5 Barlow so fingers crossed it'll do the job. I'm hoping to get a C9.25HD next year, but we'll see.

Do you have any pics taken with the f/4, Chris?