John

Hopefully I'm now finished...............

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Very nice indeed 

Why stop at 22mm though ? 

because I'm not using motorised scope to track the target, so for more power eps I may enjoy the view longer if I choose ethos. unless if my scope is automatic tracking then I would just choose delos/naggler.

I use Ethos eyepieces for just this reason. The 6mm is an excellent high power eyepiece. They are very expensive though and the Explore Scientific 100 degree eyepieces are so very close in performance for considerably less outlay if you get hooked on 100 degree eyepieces. ES have recently released a 5.5mm in this series which is getting good feedback on another forum.

I wouldn't, since the optical axis hasn't moved.

Exactly. 

But remember that stopping down also requires recollimation of main mirror AFAIK.

Why ?

I don't seem to need to re-collimate my 12" when I stop it down to 4".

So if I have a 6" scope it will show up diffraction spikes and atmospheric effects whereas a 2" scope won't?

Or put another way if I have a 6" scope it's resolution is 1" while a 2" scope has a resolution of 3" so it presumably removes effects smaller than 3"? If that's the case though then is the improvement real? For example if I was using a 150mm / 1000 scope with a dslr with 5µ pixels that is 1" resolution from both scope and camera. I could stop the aperture down to 50mm to overcome effects but couldn't I just as well use 3x3 binning to obtain the same effect but not lose the light gathering power?

I don't know how it applies to imaging as I only do visual observing.

I have an aperture mask with a 4" hole which is the largest I can use with my 12" dobsonian. Using this I get the effective performance of a 4" unobstructed scope with a focal length of 1590mm so F/15.5. 

As I already have a rather nice 4" ED refractor which is actually much smaller and lighter than my 12" dob, it makes more sense for me to get that scope out if the seeing conditions are not good enough for the dob to make use of it's full aperture.

Why should that be the case? Reducing the aperture reduces resolution so why should a smaller aperture improve the view.

The smaller aperture reduces the effects of atmospheric disturbance and in the case of newtonians the diffraction caused by the secondary and it's supports so the image you do see does seem sharp and steadier. You are quite right though that the resolution and light grasp of the instrument are reduced the the size of the hole in the cap so in most cases you now have a 2" or smaller aperture scope so the amount of contrast, detail and resolution you will see will be reduced to that level as well. There is no "free lunch" so to speak !

Thanks john they look good quality I've got the stock 10mm and 25mm with x2 Barlow, which would be best to add to collection for planetary viewing??

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The 6mm and 8mm would be good with your scope.

Would these be a good option for a skywatcher skyhawk 114 with 1000mm focal length??

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Since I posted that the Vixen NPL's have come out which I think are better plossls than the Skywatcher SP's. They are a little more expensive though but nice eyepieces:

http://www.firstlightoptics.com/vixen-eyepieces/vixen-npl-eyepieces.html

Would something a little larger such as a custom pillar extension for a large mount be within the scope of this service ?

I think I would keep the SW 114/900.

I'd agree. I tried to collimate one of the Bird-Jones 114mm "catadioptrics" once and it was a nightmare because of the corrector lens inside the drawtube and the short focal length spherical primary. 

They were available under lots of brand names un the 1970's and 1980's including Tasco, Prinz, Revue, Greenkat, etc, etc.

They were one of what used to be termed "department store" telescopes. It wasn't a compliment ....

Nice report - thanks for posting it 

Good to remind people about the need to use the Skywatcher 2" adapter - it can get confusing !

The tip on the used one didn"t Pan out!!   See what I did there   The hunt goes on.....

Sorry to hear that Alan (and I didn't mean the pun !).

...... I have never seen coma that I can remember.....

Interestingly, coma is an aberration suffered by schmidt-cassegrains as well, according to this web page:

http://starizona.com/acb/basics/equip_optics101_schmidts.aspx

Presumably the relatively narrow field of view means it does not trouble observers too much ?

When the focal ratio gets faster than F/5 the Tele Vues really come into their own I think. There is also some satisfaction and confidence that comes from using one, in my opinion at least 

Luke and Sarah (members here) were using a 35mm Panoptic with their 12" and then 16" Skywatcher dobs and felt the views with the Pan suddenly seemed "washed out" when they moved to a 21mm Ethos so I reckon an overlarge exit pupil is probably to be avoided to get optimum contrast on deep sky objects. 

I think this leaves us with the GSO options - apparently they're as good as the Sky-watcher - if not better. 

Possibly as good, if you get one with a good mirror.

Thanks Alex. This seems doable actually. Having looked around though the only 12" dobs I could find were flexitube and I am actually after a solid tube. Any idea where to get the 12" Skyliner from?

I think the solid tube Skywatcher 12" went out of production a couple of years back. Shame because that would be my preference if I was looking for a 12" dob right now. It was less expensive than the Flextube is too.

Orion Optics are wholly made in the UK.

Orion (USA) dobs are made by Synta in China who own and make Skywatcher scopes and Celestron scopes, amongst others.

Orion Optics scopes are much more expensive to buy new than their chinese made equivalents but offer a range of focal lengths, tube and mirror specifications. They are quite reasonable to buy on the used market though and thats how I bought the OO scopes that I've owned including my current 12" F/5.3

Where do you get them from?

Orion Optics will make the aluminum ones for about £400. Shane made me mine along the same lines from 18mm Baltic ply and somewhat less cost   

It's really stable - 400x is no problem.

Skywatcher and Meade 12" dobs are somewhat heavier than Orion Optics ones but all can be moved around easily enough, on the level, in two sections. I'd not fancy going up and down stairs with one though.

Heres me with mine. I'm 6 foot tall. My dob is a little taller and slimmer than some as its an F/5.3 with a custom base. It gives the general idea though:

I would say they are plossls, there is a trend for bundling better quality ep's at the moment, anyway, it's how they perform that counts in my opinion.

I agree - I reckon they are both plossls - the 10mm has a "P" visible despite the faded printing. They are multi-coated rather than fully multi-coated and there are numerous manufacturers in Taiwan and China who make this pattern of eyepiece. Eye relief will be as per the normal plossl which is around 80% of the focal length in mm I believe.

These are an improvement over the 3 element MA types.

These are my 2 cases. Top my wide fields and general viewing. Lower is the specialty case with the planetaries should the conditions be good enough to take advantage. Many times I just go out wth the second case as it is smaller, lighter, and gets the job done.

Very nice

The top row in the second case has some class acts in it (all of them in fact !). Don't see many AP SPL's over here

I've not posted in this thread for a while and I now reckon I've completed my eyepiece buying for the foreseeable future (yes, really !) I thought I'd post a pic of where I've got to. In the big case are the 31mm Nagler, 20mm ES 100, 13mm, 8mm and 6mm Ethos's plus the 6mm Baader GO. The filters are the 2" Astromik O-III and a 1.25" 1000 Oaks H-Beta which is on loan from Mark at Beaufort. In the smaller case are the Pentax XW 5mm, Radian 4mm, XW 3.5mm and Radian 3mm.

With my scopes I think that's covered all eventualities

Looks a nice one - congratulations

I've owned a few 6" F/8 refractors - there is something about that large, unobstructed aperture that is very appealing