Scope pimp - mirror upgrade

[Stargazer_00]

I have a geniunie attachment to my explorer 150p grab and go and am looking for ways to pimp it up and get the absolute most out of it.

I've found this:

£300 for a 1/10 PV mirror set (F5)

http://www.orionoptics.co.uk/OPTICS/opticsultragrade.html

Does anyone know if this would directly replace the Skywatcher mirror set? Would I need to buy anything else? Assuming the spider vanes and holder would be reused and that this secondary would screw directly into the place of the existing one.

Also I'm assuming the primary would fit inside a sky watcher cell. It wouldn't be significantly thicker, or require different mounting/fixings, springs etc to work.

[Stargazer_00]

I'm assuming of course that a Hilux coated 1/10 PV mirror set would offer a signifcant improvement over the supplied optics in the OTA?

[jambouk]

Why not get spend a similar amount of money and get significantly more light capture with an explorer 200?

Just a thought.

James

[Stargazer_00]

I specifically want to pimp this scope. It's my grab and go. I like the ergonomics of the tube and it's mount and I dont want to do anything but improve this set up as much as possible.

My main scope is a 10" and believe me that is going to grow soon enough as well

[nicks90]

wouldnt you get just as much improvement by flocking the tube, adding a 2" crayford and maybe investing in a catseye collimation kit for absolute perfect collimation?

maybe the more experienced techy types can say how much image degredation occurs between perfect colly and the sweet spot being off 1mm, 2mm, 3mm etc and if this is more advantageous than 1/10pv mirror.

I would also love a nice dual speed focusser, as I think the ability to really accurately fine tune the focus is probably more beneficial than any mirror can deliver!

[Stargazer_00]

wouldnt you get just as much improvement by flocking the tube, adding a 2" crayford and maybe investing in a catseye collimation kit for absolute perfect collimation?

maybe the more experienced techy types can say how much image degredation occurs between perfect colly and the sweet spot being off 1mm, 2mm, 3mm etc and if this is more advantageous than 1/10pv mirror.

I would also love a nice dual speed focusser, as I think the ability to really accurately fine tune the focus is probably more beneficial than any mirror can deliver!

The tube is flocked, it has a 2" crayford as standard (which I will upgrade to a 10:1 anyway) and I use a high end laser collimator already for my newts

Some further reading indicates that the high accuracy PV would allow the scope to show better images at high magnification and show little to no visible improvment at low manification. So essentially the investment would serve to broaden the usability of the scope so that it would be a better instrument for higher manifications. Obviously the like for like aperture wouldn't boost brightness, per se (although HiLux would improve reflectivity so that would actually improve brightness) but the resolution would be improved meaning finer detail could be resolved at the eyepiece.

It may prove to be worthwhile.

I'm just looking at what a full Orion Optics VX6 costs compared to just the mirrors and there is only about £180 in it and I could write part of that off by not upgrading the focuser on the current OTA. So maybe £100 in it when all is said and done. I think I'd sooner have an OO scope than a pimped 150p that I've had to mount mirrors myself. It's worth the £100 extra to let the experts hand build it in my opinion.

I think a VX6 might even be lighter overall as well... I'll probably opt to upgrade the 150p entirely for a brand new OOUK VX6 OTA after my main scope gets an upgrade to 14" and sell the explorer 150p on. It's my first scope though so that'd be hard.

[russ.will]

There's been a couple of threads, plus links to the source of all knowledge - Cloudy Nights - posted on this very subject recently.

The general consensus seems to be that there is virtually no discernable difference between 1/4 and 1/10 PV optics in visual use.

The PV rating alone might tell you how good the shape of the mirror is, but ignores how smooth the figure is. So that brings in the issue of Strehl ratings and it's interdependance on the PV/Wave rating. Further compounding this is the fact that, people will *tend* to assume that their current, mass produced far eastern mirror is a good example of the ilk and that one of the premium mirrors will be *needed* to improve on it. The truth is that the stock mirrors can languish in the 1 to 1/2 PV territory and that, with rare exceptions, can be significantly improved on with a 1/4PV mirror of a tested and certificated quality.

I personally can't see an issue with pimping a cherished and much used scope, regardless of size. I think getting a decent set of 1/4 or 1/6 mirrors will see you with a 6" Newt for life and the money saved can be spent optimising other aspects of it's performance, if you haven't already.

And anyway, this is a hobby which means it's okay to spend money on frivolity.

Russell

[russ.will]

Sorry, our postes crossed in the ether. Looks like you've ddrawn a sensible conclusion.

Russell

[Stargazer_00]

That's a good point. A 1/4 PV set is £155 and a 1/10 PV is £300. I know that is still £150 but, well, it's not actually much difference is it? Especially when you think it could be for life.

I think it'd just be nice to own a best in class as well. I'll probably end up pimping the scope by replacing it entirely with a brand new VX6 (or S/H if one comes up with 1/8+ optics)

[russ.will]

It's probably more sensible. You get a better mirror, cell, OTA and focuser all into the bargain, with a lot less faffing around.

Then again, it depends on your outlook, faffing around is half the fun of a hobby for some.

Russell

[SkyGibbon]

Go to agenaastro. They sell 1/16th wave set for about $145.00. Awesome mirrors. Built a great 6" for under $175.00 total cost. I swear I get better views at times than with my Orion 10". It uses 1/10th wave mirrors.

[John]

The Agena Astro mirrors are made by GSO - same people that make the Meade Lightbridge, Zhumell, Telescope Services and other mirrors and mirror cells. Their spec is given as 1/16th wave RMS but I believe that equates to around 1/4th wave PV.

The Orion Optics 1/10th, 1/8th and 1/6th wave mirrors, all of which are PV figures, are supplied with Zygo reports. Hence the price difference - it takes time to get to the higher optical accuracy and time costs money.

[Bukko]

Please ignore this if you think I am overcomplicating things..

I have a 12" OO VX, with the 1/10 wave. Purchased for imaging.

As Russell says, the Strehl is important and this seems to improve with the figuring. Mine is over 99%. On the P-V figures, I wonder how they would drop off when the first layer of dust and stuff starts to layer on the mirror?

If you are looking to get a new VX from OO, then here's a few things you might consider.

The OTA is Aluminium, rather than steel. Much lighter, but will dent easier. It also has a higher thermal expansion rate, but as mine is permanently outside, I have not noticed much focus shift.

The costs of a 1/10 wave is high, I wonder if there is a better compromise going for an 1/8 wave? In the UK, we would probably not see the difference anyway.

The OTA would also benefit from flocking.

OO will customise whatever you want. Bigger secondary, change the Primary/secondary distance, anything, so you don't need to keep to the basic options.

The same for the focuser. The std OO unit is OK, but quite expensive for what it is. Mine struggled to firmly hold the imaging train without needing some extra tightening (it weighs a couple of kg, though). They can fit anything, the Baader, Moonlight, Feathertouch. Get it from new, as the hole spacings from the OO focuser is different to others if you want to upgrade later.

I you are looking to exchange parts with your existing, then I suspect the OO tube will be a different diameter, so the OO cell would probably not transfer well.

HTH.

Gordon.

[Astrobits]

Why don't you get hold of a local mirror maker and get your mirror checked before rushing out to purchase another one? It might be that it is typical Chinese production but it just might be better ( or worse ) than average. At least then you will know where you are coming from.

Nigel

[SkyGibbon]

The Agena Astro mirrors are made by GSO - same people that make the Meade Lightbridge, Zhumell, Telescope Services and other mirrors and mirror cells. Their spec is given as 1/16th wave RMS but I believe that equates to around 1/4th wave PV.

The Orion Optics 1/10th, 1/8th and 1/6th wave mirrors, all of which are PV figures, are supplied with Zygo reports. Hence the price difference - it takes time to get to the higher optical accuracy and time costs money.

Aaah. It didn't mention whaat was what and I thoughtthe price was a little too good. They do perform well, for what they are. Thanks for the heads up.

[Moonshane]

Why don't you get hold of a local mirror maker and get your mirror checked before rushing out to purchase another one? It might be that it is typical Chinese production but it just might be better ( or worse ) than average. At least then you will know where you are coming from.

Nigel

great point - don't throw the baby out with the bathwater.

I only use OOUK scopes although I buy used. personally, I wouldn't pay a premium for a 1/4 PV or possibly even a 1/6PV mirror but 1/8PV and 1/10PV I feel are worth it. Realistically the difference is greatest for high brightness/contrast/magnification subjects. Therefore you will see less light scatter on things like Jupiter and the moon and possibly finer splits on double stars. If that's what you like to observe then it's worth it. If you rarely observe them then it's probably not as only aperture really affects the lower magnification faint objects.

Another option is to contact someone like John Nichol as he could test the mirror (although would probably tell you it's not really worth it for a mirror that size). This might be worth a read too http://www.nicholoptical.co.uk/Optical%20Standards.pdf

I have been told by several people that John makes very smooth mirrors which reduces the light scatter drastically. I am pretty sure he uses OOUK for the coatings.

[Stargazer_00]

Thanks guys.

I honestly don't think my eyes are good enough. So my current thinking is; save a bit of money, when I have a bit start posting wanted ads for a 14" used OO, keep saving until I hit the amount needed for a 14" flextube and if no response to the wanted ads then buy this scope and be happy with it. The tube lists as 23.5kg which I can manage without any issue I believe. The base is deconstructable and is apparently quick to set up. Probably has around 1/4 PV optics, I think I'll be fine with these scopes really. Can't justify buying one new and there is no guarantee that a s/h one will ever pop up. Not many people seem to have 14"

[Astrobits]

great point - don't throw the baby out with the bathwater.

Another option is to contact someone like John Nichol as he could test the mirror (although would probably tell you it's not really worth it for a mirror that size). This might be worth a read too http://www.nicholopt...l Standards.pdf

I have been told by several people that John makes very smooth mirrors which reduces the light scatter drastically. I am pretty sure he uses OOUK for the coatings.

Quite right Moonshane. It's unlikely to be worthwhile paying for a test but an experienced mirror maker can give you a good idea of the quality of your existing mirror and whether it is smooth or rough.

Smooth mirrors will have higher Strehl ratios than rough mirrors even if the PV is the same.

Have you done a star test ( in and out of focus ) and compared it to the published patters you can expect? It might take some time before you get a steady enough night for the definitive airy disc and rings to be clear so be patient.

Nigel

[Stargazer_00]

star tests opn both my newts are pretty good although any issues i put down to atmospherics. can't recall ever having had a perfect night for a star test.