Skywatcher Quattro f4 Imaging Newtonian telescopes

[DrRobin]

Hi,

Thanks Ben and Mike, great to know someone else is doing it. I have read about extending the shaft, keeps the overall weight down so I will be doing that in any case. I am an electronics engineer by trade, but have quite a bit of experience with control, mechanical and system design, so I have some understanding of weight, torque and the various reactions of movement.

Regarding a guide scope, I have no experience of guiding, I have an ST80, but was thinking of having a go with a 50mm finder first. As regards guide camera I could use an SPC900 or try the DFK31, both are fairly light.

As regards wind, at the moment the dob is fairly useless in any wind at all, so I suppose that the HEQ5 might be slightly better, but if it is windy (and my back garden is fairly sheltered) it's a TV and glass of wine night instead.

I do have a summerhouse, which I have put the dob in before when it's windy, but that seriously limits my field of view and polar alignment will be all but impossible.

Thanks again for the tips, I am looking forward to having a go with an EQ mount, I think it will have to be after Xmas now, I have no time to buy or assembly anything before.

[Dipper]

I'm planning on buying the 200/800 Quattro and have read this thread - it's a great read. Still I'd like to ask a few things.

First, I have an EQ5 mount complete with a Synscan GoTo upgrade. Will the Quattro telescope dovetail fit into EQ5 (does it have a standard size and dimensions)?

Second, regarding coma corrector which is suggested in FLO site First Light Optics - Baader MPCC Coma Corrector am I right to imagine that one end of coma corrector has a screw for T-ring and another end goes into the 2" focuser? I've never used a coma corrector and I have a T-ring for my Nikon DSLR. If this is how it works I can begin imaging straight away without buying any extra adaptors.

Third, someone mentioned that Quattro doesn't have such a wide focus travel as standard focusers and that might alter eyepiece choice. For the new scope I am planning to also buy one or two eyepieces. Would this eyepiece First Light Optics - Skywatcher PanaView 2" eyepieces have no problems with focusing? And what is a limitation in the choice of an eyepiece if any?

[DrRobin]

Hi,

I might not be the best person to answer your questions as I have only just got a 200 Quattro.

Mine is a carbon tube version and weighs 7kg which is well within the capacity of your mount. However, if you are going to use it for imaging then everyone says don't go over half the capacity. I think an EQ5 is about 10 kg so it probably wouldn't be too good.

If its the steel version you are looking at then it's right at the top end and you really need an HEQ5 or EQ6. If you are not imaging, just visual I suspect a 200 or 200 PDS would be a better option? The Quattros are really meant for imaging.

Regarding the dovetail, mine was supplied with rings and a Skywatcher /Vixen dovetail, which should fit on the EQ5. I am upgrading to Losmndy dovetail, but that is only because I have two scopes and the other is too big for the Skywatcher dovetail.

I confirm that the focus has relatively short travel. In fact I have to add a short extension tube for my eyepieces and remove it for my camera. This might be due to me buying it second hand and not getting all of the original accessories or it might be a common problem.

I haven't bothered with a coma corrector yet, thought I would give it a try without first. I am sure to an expert my pictures will show coma, but I am hard pressed to spot it. I don't really do any visual so couldn't comment on how much difference a coma corrector makes, but I suspect very little.

[Jammy]

Are these easy to colimate? I've read a few articles that suggest they're for the more experienced user.

[MikeWilson]

Are these easy to colimate? I've read a few articles that suggest they're for the more experienced user.

The faster the scope the more accurate the collimation needs to be. Physically collimating the scope is no harder than collimating the other Sky-Watcher newtonian designs.

I'd say the combination of weight and collimation requirements would make it a scope more for the experienced imager and ideally suits a fixed observing site such as a pier or observatory.

All the best,

Mike

[DrRobin]

Hi,

I find mine very easy to collimate. It seems easier than my 250 Skywatcher dob, but i don't suppose there is much difference. I collimated my dob 3 times in 8 months and it was never far out.

I have only had the Quattro for a month and have collimated it once. I had heard that you need to collimate them every time but I keep my scope at a cool temperature (near ambient) and I doesn't seem to drift very much.

Anyway I seem to spend ages polar aligning so an extra 5 minutes to collimate wouldn't be a problem. I don't have an obs, but haven't really experienced any more difficulty with the Quattro over the dob I own. I think it is fair to say that like any precision instrument to get the best out of it the more set up it takes. The higher the precision, the more set up or more frequently it should be done.

The Quattros are really meant for imaging and there is the warning on the shops websites that they take more setting up but I am finding it quite easy to live with. Mine is a Carbon tube and it's lightness makes for easy handling. I also like the 800mm focal length, it's a great starting point for good wide field views.

I would rather spend 10 - 15 minutes setting up the scope at the start, than having to fiddle half way through an imaging session.

[Arringar]

I recently purchased an almost identical F3.9 10" Orion scope (steel tube). I have a Celestron CGEM mount. Anyone had any experience with this combination (large newt on CGEM)? I'd be interested to hear any woes you may have had with imaging with this setup.

[DrRobin]

Hi,

I checked the weight limit of a CGEM and it is 18Kg, similar to an HEQ5. I am not sure how much your Orion 10" weighs, 11.5kg perhaps?

It's slightly over 50% and once you add a finderscope and camera it's going to come in about 12.5 - 13kg so it might be a bit heavy for long exposure astrophotography.

Anyone on here used one?

[Ransu]

I am using 250mm f/5 Newton with CGEM, total weight with TS 60mm finderquider/QHY5 and canon 600D is about 17kg, so it is possible. I have permanent setup for CGEM in obsy.

Sampleimages with this setup in this topic

http://stargazerslounge.com/imaging-deep-sky/164436-m81-m82.html

[Arringar]

That is good news. Thank you, Rauno. Great images!

[Dipper]

What is the weight different between steel and carbon fibre versions? I am interested in 8" version.

[DrRobin]

Hi,

My 200mm carbon tube weighs 7kg with the scope rings and Vixen dovetail. I think that the steel version weighs around 9 kg with rings and dovetail, so not much more.

The main advantage of the carbon tube is the lower expansion hence cool down is not quite as important.

[Dipper]

And the main disadvantage is price.

[Tim]

The main advantage of the carbon tube is the lower expansion hence cool down is not quite as important.

That isn't quite accurate.

The carbon tube holds the tube length pretty much stationary. This means that the distance between the primary and secondary mirrors does not alter during the course of a session when the temperature is dropping and the steel tubes would be getting slightly smaller due to contraction.

At F4 the depth of focus is very shallow, so it is easy for even small amounts of contraction to pull your image out of focus.

The Carbon tubes can often be at exact focus night after night without alteration

But cool down time is something else, and refers to the mirror settling to ambient temperature. If anything, a steel tube would help with this as it may absorb and radiate heat coming from the mirror. Again at F4, non-cooled mirrors will produce poor results until they are properly thermally balanced.

A fan conversion is worth doing to help speed up cool down time.

HTH

Tim

[DrRobin]

Hi,

Glass (especially the type used telescope mirrors) has a very low coefficient of thermal expansion, about one quarter of that of Aluminium or Steel, although I do accept that the mirrors make up most of the mass of a telescope.

So as a telescope cools some of the heat stored in the glass will be transmitted to the body of the scope before been lost to the air. If the body of the scope is not affected to any great degree by changes in temperature then the heat lost by the mirrors as it cools down won't significantly change the focus position.

I also doubt that mirror temperature alone contributes too greatly to changes in focal length and since glass is a very poor conductor of heat it will only cool very slowly, again minimising or slowing the changes in focal length.

Modern mirrors are made very thin to both reduce cool down time but the amount of expansion/contraction is also reduced, again making the expansion in the tube more important than the mirror.

A fan will reduce cool down times, or do as I do and store the telescope at or close to ambient.

[Shibby]

I occasionally like to ponder what I might upgrade to if the opportunity ever arises in the future..!

So, can anyone tell me, does the focuser tube protrude far into the OTA of these Quattros when focusing with a DSLR? This is an annoying "characteristic" of my 150PDS and something I'd preferrably like to avoid in the future...

Thanks

[skarven]

while following this thread, I have still not seen the weight of the Skywatcher carbon fibre 10 inch stated.

I resently bought one, and the weight including focuser, rings and the standard dovetail is 14.2kg. I was a bit disappointed, because it was supposed to be a lot lighter than the steel one.

Living at 64 deg. North, I have had no chance to test it yet, but I have great expectations, both visually and with my new Canon EOS650D.

[DrRobin]

Hi,

I can recommend getting the matching F4 coma corrector as well. I have just used mine for the first time and the difference is huge compared to the scope without a coma corrector. Stars are sharp all the way across a Canon 600D frame.

14.2Kg for the 10" carbon version sounds quite heavy, I am sure my 8" is around 7Kg.

Robin

[laser_jock99]

Hi,

I can recommend getting the matching F4 coma corrector as well. I have just used mine for the first time and the difference is huge compared to the scope without a coma corrector. Stars are sharp all the way across a Canon 600D frame.

14.2Kg for the 10" carbon version sounds quite heavy, I am sure my 8" is around 7Kg.

Robin

A coma corrector is essential for AP work. As the mirror dia goes so does the weight the 12" F4 Revelation/GSO scope is pushing 20kg!

[skarven]

14.2Kg for the 10" carbon version sounds quite heavy, I am sure my 8" is around 7Kg.

I know this is an old thread, but...

I agree it sounds heavy, but if you take the (10"/8") raised to the 3rd power, you come to 1.95 and 1.95x7.0kg is 13.65kg!

I have not been able to use my 10" Quattro. (this is partly due to the fact that I have been 3 weeks in Tucson, Arizona with my Skywatcher Equinox 120D. Now THAT was an interesting experience!!!) Here at 64° North I have only had one clear night to try out the 10" Quattro, and I think it performed well. The moon was up, and conditions were not ideal, but there was one astonishing fact that really stood out.  The outside of the telescope was, after about 5 hours outside in a temp of -1 or 2 C, covered with about half a millimeter of ICE. Still there was no problem with dew on the mirror. Might this be the great advantage of the carbon tube. I wonder.

Has anybody had a similar experience?

Kai

[FLO]

I haven't heard of carbon fibre tubes reducing dew on a secondary mirror but the main advantage of carbon-fibre is that it is more dimensionally stable than a traditional rolled steel tube. If you are imaging at a location where significant temperature changes are the norm then a CF tube is best. It is also warm to the touch and looks rather classy  

Steve 

[ollypenrice]

I haven't heard of carbon fibre tubes reducing dew on a secondary mirror but the main advantage of carbon-fibre is that it is more dimensionally stable than a traditional rolled steel tube. If you are imaging at a location where significant temperature changes are the norm then a CF tube is best. It is also warm to the touch and looks rather classy

Steve 

Actually I think they might. I've heard quite a few people say that CF is a better insulator so it's a mixed blessing, thermally. Cooldown can take longer but the mirror is more insulated. This is only me listening to Newtonian imagers, though. The 14 inch CF reflector I use here is remarkably immune to dewed mirrors, to my surprise.

Olly

[Macavity]

Rigidity is always going to be useful. As to the "thermal effect" of various materials... I guess it's still "experimental"?

Black OTAs absorb (radiate) heat? Telescopes once USED to be White mostly! lol. Insulation versus conduction? I have seen a composite (layered) structure (seriously) advocated. Maybe some R & D? I sense such things might not be beyond the wit etc. 

[tonedeaf]

.....

Modern mirrors are made very thin to both reduce cool down time but the amount of expansion/contraction is also reduced, again making the expansion in the tube more important than the mirror.

A fan will reduce cool down times, or do as I do and store the telescope at or close to ambient.

as a small note regarding the thermal stability of the steel tube:

as an example

at delta-t ~20°C and 1000mm length, the steel elongates ~0,2-0,3mm !!

L=~ a x L0 x delta T = ~11,5x10^-6 x 1000 x 20

may have an effect on colmination....(depends at which temperature the scope was colminated)

[Starbucky]

I just bought the steel tube Quattro 10" today and yes it has baffles, however, the circumference of the tube is 11" not 10". At the store we took it out of the box and I instantly thought it was a 12". The baffles appear to be about 1/2" thick give or take a hair. I also purchased for it a secondary heater and eye piece/autoguider heater, should have grabbed the primary heater while I was at it, might as well.

Here's the catch, I talk big but am relatively new, no idea why the baffles are there, not in my 8"? Last year I bought the SW EQ6 with Orion Starshoot guider, and now I added this here scope for Xmas this year, but the steel tube version.

It's very impressive matched up with the EQ6, the focuser is very nice low speed doesn't stick very smooth, high speed is a slight stick likely because it's new. Mounted on the SW EQ6 the weight extension bar must be used, will not balance without it, perhaps the CF version doesn't have that for an issue?