PST etalon as Quark contrast booster mods: Log & Result

[minhlead]

So as titled. I am going to make a PST mods that use the PST etalon as contrast booster for my Quark. This will be a log of the result achieved to be used as reference for any future endeavour like myself.
First I bought 2 used PSTs to be used in my mods. I figure I'd use one in the mods and 1 as a visual scope.
The first problem arises with the arrival of the second etalon: the etalon came decontacted.
I was lucky all the spacers are still intact.
I cleaned all the surface with 99.7% isopropyl and a lot of kimwipes, blows them with a compressor then put them together. Luckily I managed to get them clicked and contacted again.

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A quick test with the scope shows the etalon worked fine. I dont know If there are any decrease in uniformity since the etalon came decontacted out of the box. But the scope showed good proms and surface detail with noticable "sweetband".
The second scope is fine.
I asked my neighbour machinist to CNC 2 adapter for me to connect the PST etalon to my Quark and the camera behind it.

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If anyone wonder, the threads of the etalon chamber is M50x1mm and my adapters output to the common M48 that easily adapts to M42.

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Now I wait for the sun to come again which definitely will take quite sometime.

[minhlead]

https://photos.app.goo.gl/aPosAUxHC1NAydyY9
The etalon after recontacting. Note the pile of Kimwipes in the background.
For anyone who would run into the same situation:
1. Use Kimwipes. Any other tissue will have dust and messes up your surface.
2. Use reagent grade isopropyl (99.7%) to clean up the surfaces. Dab the kimwipes in the solvent and give the surface a few good wipes to washes out any oil that is on the surface.
3. Get a Qtip, wrap it in 2 layers of kimwipes to clean the spacer surface. Stroke in 1 direction and change the kimwipes after each stroke. NEVER use 1 kimwipes for the second stroke.
4. Clean the other side of the etalon with kimwipes and change the tissue with each time stroke. Remember, only wipe in 1 direction.
5. Use a compressor with filtered air input to blows on the surface. DO NOT use canned compressed air
6. Clean them again in 3 and 4
7. Put the 2 piece together, make sure the spacers are 90* apart. Put alot pressure into the etalon while twisting the 2 plates together. Just VERY slight twisting. There should be a clicking sound if it sticks. Check underlight to see if all 4 spacer sticks.
The bond should be very strong.
8. If it does not stick repeat from 2. Be patient. It took me 2 nights trying to recontact the etalon. But once it worked it's like magic.

[Highbury Mark]

Impressive - good job on the recontacting. Hope the results reward your endeavour.

[marktownley]

Good work Minh!

[christian viladrich]

Very nice Minh !
You are now the master of optical contacting.

[minhlead]

Thanks guys if only the sky clears for a few days.

[minhlead]

Okay so today I got some clear sky and got the PST out and tested it.
The result was amazing. It gives out even flatter image than the good etalon. No sign of sweet band that I can see.

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The proms were really good visually and even better imaged.

[marktownley]

Excellent results!

[minhlead]

Excellent results!

Okay so I got a few hours of clear sky this morning and despite just testing positive with Covid-19, I decided to give it a spin.
Here is the Quark + the "good" etalon.
I managed to get focus, a few turns of PST tuning ring, and WHAM BAM!

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The contrast JUMPED.
- The proms look 10x better than just with the Quark, the filaments are now pitch dark and 3D looking instead of lying flat on the surface.
- The filament transition into proms now can be seen clearly which I have never seen it on my Quark before.
- The annoying uniformity of the Quark is somehow gone. I had to crop about 1/3 of the FOV before due to uniformity. Now there is some unevenness in brightness that I think can be solved with flats. But NO loss in DETAIL which is a HUGE deal for me.
Tried some etalon angle/tuning ring combinations and all looks great. There is definitely some polarizing effect between the PST etalon and the Quark with some relative position gives out darker images and a 90* turn brightens it again. But not much. the difference was just about 25% of the histogram at best.
The only sacrifice was exposure time. I was using 0.5ms exposure time before and now I have to use 6ms (a 12 fold increase) but quite frankly, it's not a problem for me.
In your face, Daystar!!! ( They said double stacking your Quark is unnecessary, anyone who needs more contrast should just shell out $$$ to buy their higher graded etalons). I beg to differ! I have never had my Quark perform this well (and my PST alone also)
So success on the first try. The target for the next experiment: Try other tuning positions, see if I can squeeze out some more contrast. Try the "recontacted" etalon to see if it works any difference.
See you next time.

[Rusted]

Congratulations! Well done!

My Lunt B1200S BF needs to be carefully orientated relative to the PST etalon.
I marked them both with red tape to ensure quick rotational alignment every time.
There may well be certain orientations, within your own system.
Which offer increased improvements in image quality.

[minhlead]

Congratulations! Well done!

My Lunt B1200S BF needs to be carefully orientated relative to the PST etalon.
I marked them both with red tape to ensure quick rotational alignment every time.
There may well be certain orientations, within your own system.
Which offer increased improvements in image quality.

Thanks, Chris!
I did try to rotate the PST and the Quark and indeed there are some changes to the image. But I did not have the time to assess them. I'll try again the next time the sun comes up. Thanks again!

[marktownley]

Excellent results Minh!

Rotational clocking (IMHO) is an essential part of all solar systems, self and professionally made to extract the last bit of performance optimally.

[minhlead]

Excellent results Minh!

Rotational clocking (IMHO) is an essential part of all solar systems, self and professionally made to extract the last bit of performance optimally.

I think there are some kind of polarizing effect with the PST etalon going behind the Quark since each 90* rotation, there are peak and trough of brightness, do you tune for the highest brightness or lowest or somewhere in between?

[marktownley]

I always tune for the most even field.

[minhlead]

I always tune for the most even field.

Thanks Mark. That make sense. Let me try it

[christian viladrich]

Excellent results Minh!

Rotational clocking (IMHO) is an essential part of all solar systems, self and professionally made to extract the last bit of performance optimally.

I think there are some kind of polarizing effect with the PST etalon going behind the Quark since each 90* rotation, there are peak and trough of brightness, do you tune for the highest brightness or lowest or somewhere in between?

Very good results there Minh !

I am not sure there is a polarization effect there. To the best of my knowledge, the PST etalon has no polarizing effect. I suspect that what you observe when rotating the etalons is more about alignment (or not) of the non uniformities of each etalon.

This makes me think I have to tune this on my mica etalon + fused silica etalon combination ;-)

[minhlead]

I tried a 12 panels mosaics. A lot of work but the result was alright (I think?)

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[Jordan Konisky]

Minh, nice set of images today. Thanks for posting.

[marktownley]

Nice disk Minh!

[minhlead]

Thanks, guys. I think I am having some light leaks. Trying to address the problem by some electrical tape and cloth but still not quite sure if I ellimimate them all.

[minhlead]

Bought a new solar camera (Apollo M-Max) with bigger chip than the IMX174. The mosaic now takes less tiles (4 instead of 12) and the proms is now better.

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[marktownley]

That's very nice Minh! The camera seems to be a winner.

[minhlead]

It is, Mark

[Oak]

Great results! I've done something similar with a Lunt 40mm etalon after a Quark and it also works.