Posts Made By: Phil Barker

I've had one for a week or two only used once I had to borrow a mount from a mate as mine is on the way.

Optics are very nice from what I saw I used it for 3 hours in average seeing.

Very portable and superb baffling the emission nebula around the LMC and SMC really stand out. If you are unaware there are dozens of distinct emmision nebula around both clouds including the amazing Tuarantula nebula.

Found a 40mm Pentax on Orion was pushing it with very slight sky flooding evident at the edge of the field. I expected this with the small obstruction.

The fan worked well and the cooldown was surprisingly reasonable in about 40-50 minutes with the fan on it was stable.

I needed to tweak the collimation a whisker also.

I suspect your're right re the bragging rights I was more interested in the fact the fan and ceramic mirror should be a faster coolerdown.

In saying that a startest should show the difference between 1/6th wave and 1/8th wave P-V and in the very best seeing I would expect to detail a little easier.

I recall reading somewhere the ceramic optics potentially have a better polish I took a punt and decided an xtra 500US was'nt too bad under the circumstances.

A 12 inch would need a lightweight mirror to fit on a G11.

It would probually need to be f-5 or less also.

That is quite an undertaking but if you can do a good job on a smaller mirror I see no reason not to attempt it.

I used my 13.25 inch dobbie last night which I figured and polsihed the mirror for.

It is BVC glass I don't recommend this to you as its difficult to figure well.

The views were stunning the mirror tests to around 1/10th wave p-v even at 80 X the 5th and 6th star of the trapezium are visible. I had her at 480 last night the seeing was so good.

The heart of 47 Tuk at this power has to be seen to be believed.

Its very satisfying seeing superb high contrast images from a large well corrcected parabola. Doing it yourself you can spend more time on the figure.

The maths theory etc can be trusted and potentially anyone can do this I don't intend talkign you out of it I say give it a go.


I'm goint to replace this mirror with a irror kits plate 14.5 inch as you've heard.

I don't know the guy but you'll love the eyepiece

Small field but superb sharpness inky black background a real winner.

I also have the 10mm I thoroughly enjoy using.

Ask him why he has no feedback? I have and I live in NZ

Phil B

A parabla at 6 inch f-8 has a lot of advantages over an 8 inch f-6 especially in the budget range as its 1/4 wave before figuring the 8 inch is more like 3/4 wave before figuring.

Time is money as they say and you generally get what you pay for.

The secondary mirror size and height of focuser play a part is whether its worthwhile trying 2 inch eyepieces.

Mel Bartell has a secondary sizing program on his atm webpage check that out.

Russian optics are highly regarded but I've seen ne review that mentions spherical optics make sure its a parabola if you go for that.

Do Meade still make the starfinder range i wonder?

Don't use so much pressure this means less control and can in my opinion cause tde.

Also how soft/hard is your pitch. you want good contact good pressing slow smooth 1/4 stroke with little sideways movement should fix it.

It will raise the centre like you say and turn the edge up dropping .7 area down but you can fix that later.

another method is simply trim the edge of the tool by a couple of mm and press then nice slow even 1/3 strokes. this should keep you closer to a sphere.
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Make sure you are not overdoing the length of the stroke which is the usual cause. get someone to look at the length from opposite you.

Don't give up you could also simply mask it. Good luck with the glass pushing remember slow even strokes less pressure.

I suggest you get someone with a tester to test the mirror or carefully startest it in good seeing at high power.

Large plate mirrors cool slower and it may be fine.

I can say from experience if you see minor greyness on the mirror it will cause some scattering around bright objects.

I did an early 6 inch f-9 mirror that showed this and when I repolished it further the smog around stars disapeared so yes greyness causes the effect you describe.

Of course its hard to say from your description how bad it is.

You have a very good mirror support going and truss design well done. I recently built a similar 13.3 inch instrument with my own mirror. It is 45mm thick BVC and blows away an 8 inch newt in good seeing as it should but takes some time to cool.

The fact the mirror is thin plate isn't a problem I've seen a 20 inch 19mm thick plate mirror work superbly but its maker was a master of the art and it was very nicely supported.

The suggestion of getting the mirror refigured by a master like Mr Swayze is a good one. He does this at very reasonable cost and I've seen his workmanship first hand he knows what he's doing.

Wonderful drawing.

I was observing Jupiter around this time (from NZ)in a IM 715 with the GRS near the centre I noted the spot is redder than i recall last year.

The seeing was'nt exactly stunning but the colour in the spot really stood out. The festoons and detail in the SEB(particularly close to the GRS)is very close to what I was seeing you've done a marvelous job of recording it.

I will try and toucam it this weekend willbe great to compare this with your drawing.

keep up the excellant drawings.

Phil B

Nice drawing Carlos

I shot this image from the west coast of the south island of New Zealand on 18.3.2005 Universal date/time 1400 hours approx.

7.1 inch f-15 maksutov with 2 x barlow.

Visually I could see a festoon very similar to the one you drew the webcam image showed more seeing 7/10.

Phil Barker

Fantastic shooting.

I assume its with the celestron 8 incredable.

A few years ago who would have believed this was possible with 20cm of aperture.

I hope to challenge when i get similar conditions will be doing f-36 not f-30 as in the images I showed.

All the best can't wait to see the other side in those conditions.

Phil B

here's a pickie of the dome as it is now.

I'll reply and post an earlier image showing the construction

Phil B