Skywatcher Evostar 6" Refractor first light

[jimlennie]

Hi,

Got my Evostar 6" F8 refractor today and as luck would have it a perfectly clear 'night'. First up was Jupiter and I could see the red spot although it looked beige to me. Saw lots of detail between the cloud bands and also saw a moon pass in front of the disk of Jupiter. I used a 7mm orthoscopic eyepiece and could easily see a star ( Ganymede ) right on the limb of Jupiter. False colour is minimal, just a slight purple tinge on the outside of Jupiter's disk. By now my 10" dob had cooled and I could see more detail on Jupiter with the same eyepieces as both scopes have the same focal length ( 1200mm ) so give the same magnification. Jupiter was much brighter at all times compared with the Evostar using the same oculars but the refractors image was sharper as the moons appeared to be much clearer than they did through the reflector... more starlike. Moving on to Albireo the Evostar easily gave a much cleaner and prettier image than the dob as the stars are much tighter and condensed in appearance than they are in the reflector. Also saw M57 and the dob clearly won that one ! a beautiful pastel smoke ring appeared in the reflector and was much nicer to look at than the image the refractor provided, which was still very good and clear as well. M13 next, the reflector wins again in light gathering and resolution but the image in the Evostar was more satisfying, mainly due I think to the intense dots of light right across the field of view with hardly any discernable coma. I put my 2" 38mm Q70 eyepiece in both scopes and I have to say that the Evostar won this contest easily as the images it showed of starfields and clusters were simply stunning to look at, I can't wait for dark skies ! The reflectors images were also good but were spoiled by coma in that eyepiece.

The focusser on the Evostar is probably the worst one I've had with lots of image shift and when that was adjusted out it then became tight to focus. I think that Steve at FLO will be supplying me with a new focusser soon ! I also discovered the the lens needs collimating as during a star test on Deneb the centre spot was slightly off centre, confirmed afterwards with my cheshire eyepiece. The HEQ-5 seems to handle the ota with no effort as vibration when trying to focus didn't cause much shaking and what there was damped out in a second or two.

All in all I'm really pleased with this scope as I've always wanted a big refractor and so far it has exceeded my expectations and the false colour is nowhere near as bad as been reported, at least in this example as I never saw any signs of it except on Jupiter. Venus and Saturn were unfortunately out of reach in the west due to our high hedge and I expect I'll see some ca on Venus.

Anyway, so far so good !

Jim

[barkis]

That's nice of you to give us your report on your new frac's first light exercise Jim. It is reasonable to compare performances of your two telesopes, and of course you will find that although the focal lengths are almost identical, there is a difference in light grasp.

I don't think you would get any surprises during your comparisons, The reflector and it's larger objective, will render brighter images, and any colour in the objects you viewed would be honestly delivered.

The refractor of course is going to triumph as far as star quality is concerned. Nice tight stellar points in the globs are a delight.

Planetary definition is another area where the refractor should come out the winner.

Of course, I am sure you know Jim, that making judgements on telescopes are better formulated over a period of time, to let different seeing, and atmospheric conditions, become part of the equations.

Anyway, you have had a good session, and I think I sense that your new acquisition, has not given you any cause for concern.

You are going to get a lot of enjoyment, from both your instruments. I have a six inch refractor too, and I love it.

Keep the reports coming Jim, we all like to hear how it goes.

Ron.

[geppetto]

Agreed, an honest report there Jim

How lucky you were to get such a good sky for first light. 8)

Have loads of fun with your new scope

[saturn5]

Hi Jim,i agree with you on the iffy focuser,the focuser on my skywatcher 250 explorer is not as good as i hoped, not rubbish but a bit sloppy.My lovely wife will be getting me a crayford for xmas.

Lovely clear night here,not a cloud to be seen,not a drop of darkness to be seen either and its 23.30.

Anyway, enjoy your new toy.

[Vega]

Thanks Jim for that excellent report. I took a particular interest as I have the 120/1000mm version of the Evostar with the hope of getting a 10" Skyliner. Nice to see yours together as a size comparison! I have had some fantastic planetary/double/starfield views with mine. With the right conditions I have been able to push the mag way over the recommended limit while still getting amazing views of Saturn (using 6mm Televue Radian & 2x Barlow = 333x !)

I too have had no end of problems with my skywatcher focuser. I even lost/replaced a rack screw once! I have tried to resolve image shift as best I can but it's still there slightly. I'm trying to resist the idea of buying one of those yummy but horrifically expensive Moonlight crayford focusers from FLO.

Enjoy your new toy, it's a fantastic all rounder with an added edge on planetary/doubles IMO

Matt

[Hipolito]

Thanks for the review. This was one of the scopes I was considering, but boy, does that look like a big scope! I'm slightly leaning more towards to Startravel simply because it is far more compact and I am limited for space.

[jimlennie]

Hi Jim,i agree with you on the iffy focuser,the focuser on my skywatcher 250 explorer is not as good as i hoped, not rubbish but a bit sloppy.My lovely wife will be getting me a crayford for xmas.

Lovely clear night here,not a cloud to be seen,not a drop of darkness to be seen either and its 23.30.

Anyway, enjoy your new toy.

Hi,

Thanks for that, btw I got a new Orion Crayford focusser for my Skyliner 10" Dob, it's excellent with really smooth movement and zero image shift, I paid £50.00 for it new from SCS Astro in Wellington and I think it's worth every penny, plus I got to see it before I bought it as I live quite close to SCS.

Jim

[jimlennie]

Thanks Jim for that excellent report. I took a particular interest as I have the 120/1000mm version of the Evostar with the hope of getting a 10" Skyliner. Nice to see yours together as a size comparison! I have had some fantastic planetary/double/starfield views with mine. With the right conditions I have been able to push the mag way over the recommended limit while still getting amazing views of Saturn (using 6mm Televue Radian & 2x Barlow = 333x !)

I too have had no end of problems with my skywatcher focuser. I even lost/replaced a rack screw once! I have tried to resolve image shift as best I can but it's still there slightly. I'm trying to resist the idea of buying one of those yummy but horrifically expensive Moonlight crayford focusers from FLO.

Enjoy your new toy, it's a fantastic all rounder with an added edge on planetary/doubles IMO

Matt

Hi Vega,

The focusser on my new Evostar is really 'pants'. My old Evostar 120's focusser was quite good though, luck of the draw I think ! I'm ordering a moonlight from FLO tonight in gold as I can't really live with my present 'focusser' as it won't work with my Accufocus electric unit either as it's too stiff to move without wobble.

Best wishes.

Jim

[jimlennie]

Thanks for the review. This was one of the scopes I was considering, but boy, does that look like a big scope! I'm slightly leaning more towards to Startravel simply because it is far more compact and I am limited for space.

Hi,

The Evostar 150/F8 is rather large but it is also relatively light. It is front heavy due to the lens and cell/dew shield. I find it no more difficult to mount onto my HEQ-5 than it's smaller brother the 120/F8.3 Evostar. When I move my stuff outside I find that the 10" dob is easy to move as is the 150 ota, it's the HEQ-5 that needs the effort !! Can't imagine what the EQ6 must be like to move ! Mind you, I move the completely assembled mount including the counterweights ( 2 x 5kg ) in one go.

Jim

[Father Ted]

Hi Jim,

I have a 2001 Celestron version, the CR150. The optical quality and performance of the Objective is very good, the tube looks impressive, and the 50mm Finder is sweet. That's it really, the rest of the scope, mount and tripod were not fit for purpose. The focuser was junk from day one and only got worse with wear and tear. The 1.25 star diagonal was cheap and nasty. The EQ5 mount, with aluminium legs, was not up to carrying the weight of the OTA, the whole package wobbled like a jelly.

So if anyone is thinking of buying one of the early versions secondhand, be prepared to upgrade the star diagonal, focuser, the mount and tripod. In my experience, these early Chinese made scopes were capable of very good optical performance, but they were often let down by the use of mediocre accessories. Quality control was also variable, as was the honesty of some of the dealers selling them. Some owners ended up very pleased, whilst unlucky others began to wonder what a star might really look like through a decent quality Refractor such as those made by Vixen and TeleVue.

I replaced the focuser on my scope with one of the very well made and smart looking Crayford's made by Antares. OK, not as flashy looking as the Moonlight Crayfords, but it works a treat and does not require a second mortgage. I would recommend one of these scopes as a second hand purchase, because if they have been properly sorted by their owner, or you are willing to do the required upgrading, it is possible to end up with a scope that will give an average quality 10inch Newtonian Reflector a good run for its money. Not in terms of raw light grasp, but certainly in terms of producing very crisp images that are full of contrast.

Best Wishes

FT

[jimlennie]

Hi Jim,

I replaced the focuser on my scope with one of the very well made and smart looking Crayford's made by Antares. OK, not as flashy looking as the Moonlight Crayfords, but it works a treat and does not require a second mortgage. I would recommend one of these scopes as a second hand purchase, because if they have been properly sorted by their owner, or you are willing to do the required upgrading, it is possible to end up with a scope that will give an average quality 10inch Newtonian Reflector a good run for its money. Not in terms of raw light grasp, but certainly in terms of producing very crisp images that are full of contrast.

Best Wishes

FT

Hi,

I've ordered a gold coloured moonlight from FLO so should have it installed by next weekend. Like you I believe that 90% of the cost of the ota is the lens itself. I always remember though that years ago a 6" Refractor would have cost an arm and a leg for an achro so I still believe that we are getting fantastic value despite some shortcomings, as long as you get one with decent optics. My first ED80 ( Skywatcher ) was a 'lemon' and it's replacement has been brilliant. Quality control is what is skimped on at the moment but despite that you have every chance of getting a fine instrument at a relatively bargain price. My 10" Skywatcher reflector cost about £400, a new Tak 100mm refractor costs 5 times as much but the Skywatcher will simply blow it away under the night sky, period. It's not as portable but pound for pound it's a clear winner by a light year !

I think that we are very lucky to be living in a time when such scopes a few years ago would have been considered 'observatory class' size wise but are very affordable for the casual observer or serious amateur astronomer.

All the best

Jim

[huwbellamy]

Hi Jim,

I have a C6R - same scope as your evostar - it's nice to know it compares well to some extent with your dob. I know I sacrificed on aperture by choosing a refractor but the image quality is excellent and it seems very tough. I may have to check my collimation - how do you do that with a frac?

My focusser was loose, slack, floppy, sticky and seemed to almost bind at times - right in the useful part of focuser travel. I took it apart and cleaned with white spirit then regreased. Still lots of rotational play even after fiddling with the grub screws. Took it apart again and superglued thin plastic shims to the cutaway part of the focuser body through which the rack slides - this eliminates rotational play and so firms up the racking as well. I also put wafer thin shims in the wells that the axle sits in - this stopped play and relieved some pressure on the rack - which has made a big difference to the smoothness, I used to be able to "feel" every tooth engaging.

I am happy with the result for now but will be asking Steve for a Baader Crayford as soon as funds allow. They are less expensive than the Moonlights. It's a bit of a shame that so many of us have the same problem - I would be lost without the help and reassurance I've had from SGL and the likes of Adam and Steve as to what is "normal".

M13 is the only deep object I've found so far but it did have a definite grainy edginess the first time when I was in a darker area. No real planetary stuff yet - what sort of EP's would be good with this scope if I was willing to spend £80ish? I have a meade 5000 2" 32mm and it's lovely - works well with my revelation 2" ED barlow which was excellent value. I also upgraded to a 2" dielectric revelation diagonal - it is built like a tank but I couldn't tell you if it's better than the original - I never used it.

It's big but I love it. Huw.

[jimlennie]

Hi Jim,

I have a C6R - same scope as your evostar - it's nice to know it compares well to some extent with your dob. I know I sacrificed on aperture by choosing a refractor but the image quality is excellent and it seems very tough. I may have to check my collimation - how do you do that with a frac?

What sort of EP's would be good with this scope if I was willing to spend £80ish? .

It's big but I love it. Huw.

Hi Huw,

I take it that your scope has 3 pairs of screws 120 deg apart on the lens cell ? If so that is how you adjust your collimation with the aid of a cheshire eyepiece. Keep the lens cap on and place the cheshire directly into your drawtube ( no diagonal ) then rotate the cheshire towards a light source such as a bright sky/light etc. You should see a single disk of light in the centre of your view. If you see 2 overlapping or apart disks then you need to play with the collimation lock and adjustment screws in your lens cell. Before all this...... make sure that your focusser is mechanically aligned central to the lens. I use a laser for this which I insert into the drawtube ( as the cheshire) I then take the smaller cap of the main cap into which I've placed a circle with a centre dot in it ( paper ) and turn the laser on. If the beam does not illuminate the centre dot then I loosen the 3 screws that hold the focusser into the main tube and move it about until it does align, then tighten the screws carefully. Then I do the cheshire collimation procedure check.

As for eyepieces I would recommend the Baader Ortho's which I bought from FLO, they give superb contrasty views but to be honest I haven't had the chance to use mine yet with the Evostar 150. This eyepiece worked extremely well with my old Evostar 120 and my 10" dob and ED80. I have the 7mm version.

All the best.

Jim

[huwbellamy]

Thanks Jim,

I think I had a cheshire with the scope but haven't tried it. What laser, where from and how is it attached/aligned properly in the drawtube?

Cheers, Huw.

[Father Ted]

Hello Jim,

Yes you are right, we are lucky to be living at a time when good quality telescopes are affordable to many. Of course we would be even luckier if the prices we pay, for the same scopes and accessories, were similar to the prices in the USA.

Perhaps with the strength of the pound and the spread of computer literacy, more people will be tempted to buy goods from the USA. Perhaps not the big stuff, but certainly eyepieces, diagonals, focusers and filters. I have spent around £1200 on telescope bits and pieces so far this year, for myself and others, nearly all of it from dealers in Germany and the USA. If an old git like me is doing it, I wonder how many others are ?

Best Wishes,

FT

[jimlennie]

Thanks Jim,

I think I had a cheshire with the scope but haven't tried it. What laser, where from and how is it attached/aligned properly in the drawtube?

Cheers, Huw.

Hi Huw,

I have a Astro-Engineering laser which I bought for my reflector, I got it from MC2 scopes in Frome ( Somerset ). Steve at FLO has the Baader laser which is reported to be very good. These lasers fit in the drawtube in the same way as a 1.25" eyepiece, it's best to avoid using your diagonal as this could introduce further errors. Make sure that your laser is a snug fit in the drawtube ( you will using a 2" to 1.25" adaptor with it ) some people build the laser fitting up with cellotape etc if it is 'loose'. That's all there is to it except from making sure that the laser itself is collimated, you can do this in a lathe or drill and you spin the laser slowly to make sure that the beam does not wander, if it does there are usually 3 grub screws to adjust to get it right. My Astro-Engineering laser was spot-on and is nicely machined for a good sliding fit in the eyepiece holder.

All the best.

Jim

[GazOC]

Is a f8 refractor anymore sensitive to collimation than a f8 Newt?

[jimlennie]

Is a f8 refractor anymore sensitive to collimation than a f8 Newt?

Hi Gaz,

Not sure about that one, but as a Evostar has 2 elements to it's primary I suppose that initially they are more sensitive to collimation than a single mirror element in a newtonian. I know that in a reflector you also have a secondary mirror as well but most refractors employ a mirror diagonal but they are not usually adjustable to the same degree as a reflectors secondary.

When I received my Skyliner I knew that the collimation was slightly out but even though it's a fast reflector at F4.7 it still gave a sharp and detailed view of Saturn. A reflector at F8 would be even more forgiving as would a refractor at F8. I think that once set a refractor will hold it's collimation much longer than a reflector.

I had my 2 refractors for about a year before I bought my dob and laser and I was suprised how far off my ED80 was as far as the focusser alignment was concerned. The spot was about 10mm off centre. After adjustment I didn't notice any difference and as the ED80 operates at F7.5 I would say that refractors are pretty forgiving about collimation, just as well really as the ED80 hasn't got a collimatable lens cell anyway. My old Evostar 120 was spot on when I checked it with my then new laser.

I would say that a refractor at F8 is less sensitive than an equivalent focal ratio reflector of the same aperture simply because there is more to go out of alignment in a reflector's optical train. A refractors lens cell holds the lens more securely than a reflectors mirror cell and probably won't need collimating again once set.

All the best.

Jim