16 replies to this topic

[bluesilver]

Hi,  a bit of a random question i guess,  but thought it would be best to ask anyway.

I have the Skywatcher 16" collapsible Dobsonian with GOTO

 

I was interested to know if it is really worth while looking at upgrading to premium primary and secondary mirrors?

Would i actually notice any improvement with through the eyepiece?

I use Tele vue  Delos eyepieces

 

I don't have any clubs close by and definitely don't have any other Dobsonian with premium mirrors to look through to compare.

 

I have read that mass produced Dobsonians like Sywatcher don't have the premium mirrors,  but would i actually notice any difference to justify the extra cost?

 

I do realize this might be a bit of a broad question,  Just trying to get a general feel to see if it is worth looking into it a bit further.

There would be lots of Skywatcher Dobsonian out there,   and i am sure that the mirrors must be of reasonable quality or they just wouldn't sell.

 

So basically i not sure how to tell if i have a good mirror to start with.

There must be a general way of visually testing to see how good a mirror is to start with.

 

I do know if i was say looking a the planets like Jupiter and get a nice crisp clear view through the eyepiece and then slew over to Mars i can't make out any detail,  just a orange slightly blurred planet.  ( Collimation is good )

 

Not sure if that has anything to do with it though.

 

 

 

 

 

[spaceoddity]

Tough to say. If you can never get good high power views after many tries and you're sure it isn't collimation, thermal issues or seeing, then it's normal to wonder, but unless you have them tested you won't know. If i was unsatisfied with the views, I'd send them off to get them tested before I invested the money to upgrade. You can probably get the mirrors refigured if needed and it would be less expensive than buying new premium mirrors, although still costly. 

[TOMDEY]

A premium 16-inch mirror set will cost around $3500. It should make a world of difference. To somehow just stumble upon premium mirrors in a used economy scope is so unlikely, it may not be worth imagining. The original owner would have held onto something so magnificent and never let it go.   Tom

[StarryHill]

Skywatcher/Orion dobs can have very good mirrors. I've used them side-by-side with premium dobs like Obsessions and the differences in views have been subtle, not huge. In my experience, since Skywatcher/Orion uses thinner mirrors than many premium mirrors, they cool faster and can provide better views at first. On the other hand, the mass produced dobs may be more likely to have duds on occasion but I don't know this for sure. 

 

If it were me, I would not consider getting a new mirror unless I knew for sure that mine was a dud. Also, I'm not sure that I would put a lot of money into a premium mirror for a mass produced telescope anyway. Why not just get a premium dob since there are lots of other ways they are 'premium' besides the mirror such as smoothness of the motions, rigidity of the structure, longevity, focuser, etc.

[Astro-Master]

If you live or observe in an area where the seeing is just fair, or below average most of the time, its probably not worth spending the extra money on premium optics.  Many times its the secondary mirror that is the problem on mass produced scopes.  Get it tested and buy a premium secondary if needed.

 

Making sure the mirror has time to cool to the night time temperature is just as important as good collimation.  Make sure you use a shroud the block your body heat from the optical path, and keep your hands out of the path as well.  

 

Put a post on Cloudy Nights for someone in your area that has experience to give you some help.

[Michael Tomich]

I have the exact same telescope and I would not consider installing premium mirrors. Not that I would do this either, but I would sooner put the mirrors from the SW 16 in a premium structure. A very experienced astronomer briefly assessed my telescope and suggested that if I planned to keep it for a while, an upgraded focuser would be in order. Collimation can be hit or miss as eyepieces align or not in the cheap focuser. When collimation is on, views are impressive, when it's not, it kinda sucks. For now I will enjoy the telescope as is and make any attempts possible to stabilize the optics at the focuser (seriously I have heard suggestions like a layer of tape in the focuser tube to tighten things up). I added an O-ring to my 2" to 1.25" adapter so it seats squarely. I'm learning more about collimation and trying different techniques. Realistically, everything about the scope is from good to very good, I don't consider any of it to be excellent. I believe the structure and the mirrors deserve each other with the challenges being more in the structure. Don't get me wrong, I'm enjoying it and seeing all that amazes with the 16" aperture. I'll accessorize it, especially if the accessories could be used in a future telescope. I have some ES eyepieces and they do a great job. I'll enjoy the telescope as is and will sort out any issues as best as I can. Should I choose to upgrade, it would be to sell and replace with a premium dob.

Edited by Michael Tomich, 26 November 2020 - 01:31 AM.

[SeattleScott]

You can see the difference with premium mirrors. Just a certain clarity to the view. Is it worth thousands of dollars? Up to you. I might start with upgrading the secondary.

Scott

[Waynosworld]

Mars is a very tough planet to see detail, I have massive hours in front of the eyepiece and only a couple minutes of clarity at best, I was looking at Mars a few days ago and clouds moved in so I panned over to where the Orion Nebula was supposed to be as there were no clouds there, I had never looked for it before and it was crystal clear, it is 1344 light YEARS away and it is clear and Mars is 12 minutes away and I cannot see much at all but a flaming ball of light, but sometimes I can see a few moments of clarity, just enough to keep me interested, I have yet to get a good look at Jupiter or Saturn, they are so close to the horizon that all I see is a blurry planet with four moons and maybe a dark cloud band, I have seen Saturn slightly better, a white planet with one big white ring.

Lately I take a look at Mars with a smaller scope, if It looks crystal clear in that scope I pull out the 14.5" Starsplitter, I am about 50 percent on getting it set up before clouds roll in, and about 10 percent on being able to see details after sitting there for hours, and except for once it is always very late before I see any detail, but I live in a Bortle 8 area.

[RedzoneMN]

Moving to a site with darker skies, better seeing would produce a greater impact on your views than a premium mirror.

On planets it might make a small but noticeable difference in contrast.

[osbourne one-nil]

If my experience of larger mirrors is anything to go by, I think seeing is likely to be the culprit or minor collimation issues rather than the mirror, but it's impossible to tell really. I'd agree with those that say if you want a premium mirror, get a premium dob as I suspect that would represent better value for money...if that matters to you of course. 

[junomike]

IME the difference is subtle at best and only on Planetary/Lunar views.  Unless there's some issue with the OEM mirror I wouldn't bother replacing it.

[nof]

Hello, I have a 12” SW with a very good mirror and a premium Teeter STS 10” with a super Lightholder mirror. I use the 12” at home and take the 10” to darker skies. At first I considered asking Lightholder to reconfigure the 12” mirror, but then just upgraded the 12” with a moonlite focuser, added a fan and flocked the tube. It’s pretty good! If you want a premium scope that’s something else, it’s a different experience that doesn’t boil down to just optical quality. Change the focuser, flock the tube and add a fan and it will all make a difference for not much money or trouble. That said, the contrast in the Lightholder mirror seems better- there is a difference.

Edited by nof, 26 November 2020 - 09:09 AM.

[bigdob24]

Over the years I’ve had both.
Started out with a Coulter13.1 that was decent for the cost but when the next scope was made a 20” Telekit with a John Hall mirror the difference was evident not only in the size increase but contrast and detail.

Then a Starmaster 24” with a Zambuto mirror , WOW and my last scope a Starmaster FXQ20 Lockwood.

Ive been spoiled by premium mirrors and have done the comparison at countless dark sky starparties and premium wins

If you don’t have it when needed your missing out , no matter what size your considering

[Jon Isaacs]

My two cents:

 

The 16 inch Skywatcher's have a conical mirror. That has advantages, it cools more quickly than standard mirror.  But it does make replacing it or even refiguring it more difficult if not impossible. 

 

If you are not getting the good planetary views, the place to start is with seeing, collimation and cooldown.  These are the three important factors when it comes to getting the good planetary views.  

 

Seeing:  Where are you located?  How often is atmosphere rock solid stable, nice stars at high mags?

 

Collimation:  How are you collimating you scope, do you collimate before every use?

 

Cooldown:  What's the climate like?  What sort of fans are you using to cool the scope?

 

How do the views compare to other scopes you have owned and used?  

 

Do you have a shroud for your scope?  Air warmed by your body heat drifting across the optical path disturbs the image. 

 

 

Info on the 16 inch Skywatcher:

 

"It features an exceptionally large 16" aperture conical parabolic mirror to draw in copious amounts of light to make detailed observations of the Moon and planets, and still reach out past our solar system to discover dim deep-sky subjects that smaller scopes are unable to resolve. A conical mirror, as opposed to a standard parabolic, helps to reduce the mirror's weight while allowing it the ability to more evenly acclimate to the ambient temperature."

 

https://www.bhphotov...n.html/overview

 

Jon

[gatorengineer]

I have had many 16s over the years, and will be picking up probably my at least my 6th on Sunday.  Star test your optics and if possible bench test them, unless they are really bad, no, its not worth it.  I had a refigure done on a 16 and didnt see the benefit.  You are much more likely to have a bad secondary than a bad primary in mass produced dobs.

[Pinbout]

Those 2ndry’s are big. They don’t bother making them flat enough.

too much curvature makes it look like astig from primary

 

heres one, smooth but not flat enough.

 

astig ruins contrast at all mags. 

 

 https://www.youtube....uy-tf_Gb45PT43k

[wpostma]

I don't know anything but I do know that spending $3500 to MAYBE get better views and maybe nothing, would be the last thing I would try.

 

I would buy a whole other scope for $3500 and then sell it if it's not better. At least that way my losses if nothing worked, would be about 20% of my outlay.

 

What's a used "lower quality" mirror going to sell for used? Not much.

 

If your 16" isn't doing enough for you, and you're sure it's not seeing problems, viewfinders, or light pollution, I really would try to get someone else who looks through scopes to advise you after looking through yours.

 

The post above that suggests a "bad secondary mirror" sounds right on. But why not have someone look through your scope.  I live in a low population region, but there are times (when pandemics are not happening) that I might have a weekend in a big city and might be able to meet up with someone who can advise me after looking through the eyepiece of my beast.

Edited by wpostma, 27 November 2020 - 11:20 PM.