6" PST Stage II progress.

[Peter Drew]

My 6" Ha mod shows good surface and prominence details at the same setting, I have scribed a line to indicate this. It is very interesting to observe the changes in appearance of details, particularly those of filaments as you slowly retune the etalon. PST etalons do not all have the same performance level, mine is the best so far from several examples. 

[Rusted]

Without more examples I cannot make a comparison.

However, I am very happy with the clarity of prominences with the Cemax 12mm.

The detail is extraordinary.

I still haven't done more than crude adjustment of the DERF angle yet.

My PST eyepiece holder now has three x 4mm thumbscrews.

So I can finally use the T-S GPC safely if I need to.

Pushing the etalon away from the tailpiece has thrown my earlier binoviewer success out of the window.

I can't get even close to focus now.

I tried the Orion Shorty 2 x Barlow in the binov. nose-piece with greater success.

I'm just going to have to order the 2.6x GPC to get enough back focus.

They claim it is neutral regarding back focus with their binoviewer.

My understanding of the Shorty Barlows is that they are much stronger than normal Barlows.

A bit too much cloud today but I'll try the Shorty in place of the GPC.

For single eyepieces I have returned to the optimum 200mm inside focus for the PST etalon.

With the T-S diagonal and T2-2" adapter I have about 20mm of spare back focus.

[Peter Drew]

Do I see your aluminium backplate held on to the OTA with strips of double sided? If you don't have plate thick enough to fit normally, you can "grow" some length by attaching three lengths of bar to the inner face equispaced and then turn their outer surfaces to the fitting diameter with a short register on the thin plate for location.   

[Rusted]

Thank you for the clever idea, Peter.

The first disk cost me hours of work cutting it out from a sheet of 10mm plate.

It was a good fit by the time I was finished.

So I just added some electrical tape to be certain and then jammed it into the tailpiece casting.

Crude but effective.

Another full 10mm disk would be ideal for adding some serious tail end "welly" [i.e.moment] to the nose heavy OTA.

 

The image below shows the binoviewer focused with almost no extension beyond the etalon.

This could be overcome by cutting off an AOK rear etalon adapter to accept a short 2">1.25" EP adapter.

Its present depth is 40mm. A 2">1.25" adapter is only about 15mm deep. [As shown]

I've ordered a T-S low profile, helical focuser and 2.6x GPC, instead, and hope these will solve the lack of back focus.

[Rusted]

My T-S helical focuser and T-S 2.6x binoviewer GPC have arrived.

Contrary to T-S claims the 2.6x does not fully compensate for their T-S binoviewer.

The 2.6x GPC, unlike the 1.6x, is the correct diameter of 31.8mm for the 1.25" standard. 

The helical focuser was a nice addition to the single 12mm Cemax set-up. 

It just shows how it is all but impossible to achieve perfect focus using push pull and clamping thumbscrews on a 2" adapter barrel.

I still lost about an inch [25mm] of focus using the T-S Binoviewer with the 2.6x GPC and Meade Plossls in 26mm and 32mm pairs.

This meant that the helical focuser was unusable. Grr! 

The high magnification was rather startling in stereo but well worthwhile for incredible surface detail when the sky was clear. 

The new AR was spread out before me and surface detail far easier to settle on with both eyes.

The earlier AR was almost central on the disk and far easier to see than in cyclops mode.

Then came thin high cloud in increasing thickness so I had to pack up.

The complete Stage 2 H-alpha + Binoviewer weighs 3lbs without EPs so must be  struggle to hang off smaller telescopes and mountings.

I use my Vixen 90mm f/11 to precisely measure GPC in white light so can confirm that tomorrow.

In summary: Despite the high magnification, binoviewing the Sun is well worthwhile for relaxed viewing of fine, surface detail. 

My warm thanks to all those who helped to accelerate me up the steep learning curve  and [only slightly] less severe depletion of my wallet.

 

[Rusted]

An update on focal path shortening by common components:

All measurements were visually assessed using my Vixen 90M f/11, 1000mm fl aimed at 450 yard distant trees.

The silvery drawtube was marked with a sharp pencil where the drawtube entered the casting at best focus for each test.

I then measured the differences between the lines with a steel rule.

I used Meade 4000 26mm and 32mm EPs throughout.

The Teleskop-Service 90° diagonal used up 86mm of the original 1000mm focal length.

The Baader 45° diagonal used up 100mm.

The T-S 2.6x GPC in the binoviewer's nose-piece uses up 15mm in combination. So not the complete binoviewer neutralization promised.

The resulting high magnification is pointless for terrestrial use with this 90mm aperture. Soft, colourful and dim!

I had to shorten the Vixen's main tube by 15mm to allow me to reach focus with some combinations.