John

13 minutes ago, GazOC said:

Just MHO but I'd be surprised if Skywatcher redesigned the scope to give it an extra 10mm aperture and then said nothing about it ? 🤷

Me too. At the very least they would have called it the "Plus" version or "Skymax Pro Mk II"

3 minutes ago, GazOC said:

That'll be me 😉

The mirror is 200mm. It could be that that baffle coming out of the primary is cutting out light but it looks very carefully graduated in width as it approaches the primary

 

Someone has put a lot of thought into the width of the baffle at any given point. That's not to say they've not just got it wrong but they've not just stuck a tube on and hoped it's correct 

Thanks Gaz - I'm glad I was not imagining it !

So I wonder just what Synta / Skywatcher did actually change to increase the effective aperture ?. Maybe nothing and the tales of the 180's operating at less than 180mm are myths ?

The ES 70 would be OK in that scope but not outstanding in any way. It is quite an old design - a 5 element modified Erfle. The 68 degree ES range is a more modern and sophisticated design which works well even in quite fast scopes - I used on in my F/5.3 12 inch dobsonian and it was pretty much sharp to the edge of the field.

I believe that the Bresser 70 degree eyepieces are the same as the ES 70's and the old Meade QX range are also the same.

3 hours ago, markleton said:

My barlow is the Celestron 93436 Luminous 2-Inch 2.5x. It's definitely not high end, but seems to be of good quality and has really given me some impressive views with the 12mm ES. I have no complaints with it. 

It's definitely a tall and heavy stack, but my focuser seems to handle it quite well. I haven't noticed any difference in terms of eye positioning, but I'm still kind of getting used to proper eye positioning in general (still a rookie!)

If you wear glasses while observing I can see that the ES 12mm 92 would be good. I don't wear glasses though and found that I needed to "hover" my eye some way off the eye cup of the eyepiece which is not how I like to observe - I prefer to nestle my eye socket gently into a soft eye cup so that the eye cup keeps stray light off the top of the eyepiece and acts as a eye positioning guide.  Because I could not do this with the 12mm 92 I let that one go to a new home. I still have the 17mm 92 though which suits me better although that has taken some getting used to as well.

They are excellent eyepieces optically though, quite probably the best that ES have produced to date.

The ES 70's are not as well corrected as the 68's.

If your scope is F/8 or slower they work fine. In faster scopes the 68's are much better.

55 minutes ago, johninderby said:

All the Skywatcher maks were actually smaller aperture than  the listed size. The 150 and 180 were revised a few years ago to bring them up to the stated aperture but nothing has been done about the 127 mak.

The problem is the size of the primary mirror which limits the usable aperture to about 118mm. 127mm is the diameter of the corrector.

I've seen a thread somewhere on the original gold tube 180 which showed that it has a primary the same diameter as the more up to date one that @Captain Magenta took apart recently. Is there some other modification that would increase the effective aperture such as a re-designed secondary baffle ?

57 minutes ago, Don Pensack said:

Just be aware that if you use magnifications above about 15x/inch of aperture, your best view will be without the filter.

The contrast enhancement at high powers is very minor, and the dimming of the nebula more important when the magnification is large.

My best view of the Catseye has been at 493x in the 12.5" but without a filter.

Up to now I have not used a filter on this target either. Generally I prefer not to use filters unless they are going to make a sigiificant difference. But it is fun to try new things out

Guess what my first target is going to be when I next have the 12 inch dob out ? - the Cats Eye with the Lumicon O-III filter

Well, the image is as good as the weakest link in the optical chain. As long as the barlow lens is of good optical quality it's impact on optical quality should be negligible.

The only snags that I can see are:

- The 12mm ES 92 (which I believe you said you have) is a very large 2 inch eyepiece. Adding a 2.5x barlow to that will make a heavy and tall "stack" to hang out of your focuser.

- The 12 ES 92 already has quite long eye relief and the barlow lens will extend that further. You might find that eye positioning becomes tricky ?

That sounds right. Its not much difference - 10% more:

Of those I think I would go for the Vixen 30mm NPL because I like it's ergonomics.

There is not a lot between any of them though, even the BST 25 is not too bad in an F/6 scope like yours.

I think I've owned all of them at one time or another

17 hours ago, ALZASCOPE said:

Thanks guys

Very new to this got myself the set of nirvana seem good also managed to obtain a televue 20mm plossl which is very nice

Also got a panaview 38mm which is excellent 

I just wander if im missing something maybe i would be better off with some es52 

If you have the Nirvana's (the 16, 7 and 4mm ?) I don't think the ES 52's are going to offer you anything more. The 16mm Nirvana will show you quite a bit more sky than the 20mm TV plossl can as well.

Just now, Pixies said:

OK - you've persuaded me to see how it goes removing it!

If the mount for the finder is well designed it should slide on and off the scope and store while maintaining it's alignment accurately with the main scope. I use a similar 6 screw finder mount on my 130mm refractor and it holds the finder in alignment really solidly.

13 hours ago, Greymouser said:

Well, yes, that is hard to argue with and my heart agrees. However I cannot do without a decent PC, my mind says. I already have some decent scopes, even if not quite Tak quality. Also as I like to play games, some of which can be very demanding, an i9 and 32 gig or Ram is calling, to future proof me for a while. Added to which, can a Tak be justified, with Bortle 6 skies and little chance to travel for the foreseeable? Playing good games is not a weather dependant hobby either!

Not being a gamer or even in any sense a "power" PC user I didn't factor that in of course 

It sounds to me as if you have already talked yourself out of a Tak so that's the decision made

I think this is one of those "do what works for you" matters

I think the original poster has bought a rather meaty finder scope (60mm ?) so it's going to be quite a projection while it's on the scope:

If it gets a real clout the finder mount could possibly twist the tube wall ? - I've seen quite a few newtonian tubes where that has happened and the tube is slightly deformed where the finder mount shoe screws onto it as a result. One of the reasons that I remove my finders when the scope is not in use.

My finders come off my dob when it's not in use and go back on when I put the scope out. Mostly they stay aligned but sometimes I re-adjust the optical one on Polaris. I like it to be pointing precisely where the scope is even when a high power eyepiece is in the scope.

If you leave the finder on the scope and bump it even slightly when moving the scope, it will need re-aligning anyway.

I think that is why finders have quick release bases ?

It's not perfect by any means but I'm a heavy user of the Skytee II and have been for a number of years now. The stock dovetail clamps should certainly be upgraded ASAP as mentioned above. The 2 sides of the mount can point independently from each other. The slow motion knobs can be replaced with the same sort of flexible cables that Skywatcher and Vixen mounts use. I rarely have 2 scopes on mine.

I would agree with @johninderby that 10Kg is a more realistic load limit. This scope is 9.5kg but quite long:

I think I was pushing the Skytee II a bit too far here though !

10 minutes ago, markleton said:

Thanks. Any suggestions? I have a 30mm SuperView with a 68 degree FOV that came with the scope. I hardly ever use it anymore.  

What sort of budget do you have in mind ?

If I had your scope and your current eyepieces, I would be looking for a 6mm to give 200x. Very useful and usable high power.

Do you have anything with lower power than the ES 12mm ? - if not I think you have a niche or two there that might need filling.

Eyepieces that give more than 250x will not get a lot of use whereas the ones I mention above will

How long does an upgraded PC remain "state of the art" ?. A few months perhaps ?

How long does a Takahashi go on being a superb, top end performing scope ?. 50 years plus I would think.

11 minutes ago, Louis D said:

I'd go with a BST Starguider/HD-60/XCel LX over a Tele Vue Plossl except possibly at 18mm and 25mm in an f/4.7 scope.

I would probably do the same but I would not use low cost UWA's (~80 degrees) in an F/4.7 scope. Manufacturers seem to be able to pull off a decent 60 degree field these days for a moderate cost.

That said, I could quite easily live with a set of Tele Vue plossls plus a 2.5x Powermate for the higher powers in such a scope

43 minutes ago, Barry-W-Fenner said:

..My main concern is to find out if the focuser is out to far as I have very little outward focus left available currently.

 

 

My guess is that it might be something to do with the focuser upgrade. If the replacement unit is lower in profile than the one that it replaced, the drawtube will need to be racked out further to get eyepieces to focus.

I've marked the key distance on the image below. If this was a bit longer when the original focuser was installed, that would explain what is happening.

For use in what scope ?

(it could make quite a difference on the choice)

1 hour ago, Pixies said:

How do you find lining it up when you first start? With a straight-through, I keep both eyes open and usually find the starting target that way. I assume with a RACI, you will need to sight the whole tube in the right direction first?

 

That's why I use an illuminated reticule finder alongside my 50mm RACI.

Neptune can be seen with 30mm binoculars / finders so an 8 inch SCT is more than enough.

It's just a tiny blue/green disk though even at very high magnifications.