For the stepper motor control you might want to consider the MyFocuser system by Robert Brown. It was developed for controlling a focuser remotely for astrophotography but the operation would work perfectly for this application as well. It is very easy to build has many option like temperature compe...

On my PST's ( I have two ) the Teflon ring that comes in contact with the upper surface of the Etalon is on a slight angle. So it doesn't make contact evenly. So to reduce any possibility of tilting you might consider placing your silicon ring above the Etalon so the Etalon is against a hard surface...

Bob, If you own a PST all you have to do is look down at the Etalon as you turn the ring and you easily see it tilting and as we know tilting is easy way to tune them Valery's statement using a laser is again showing that the Etalon is tilting and that is mechanism of how it is tuned If you wanted t...

I'm sorry but the Etalon in a PST is a simple tilt tune mechanism and not pressure tuned by mechanical force applied to deform the Etalon. The patent is red herring about pressure tuning by applying force to the Etalon. It is not used in a PST. The end of the tuning ring is machined on a slight angl...

Nope. Chris provides the 0 ring because the active area of his filters is slight smaller then the original so it is to prevent any light leaks. On of the keys to making these filters last is to seal them against O2 and water. So the coatings are not applied out it the very edge like the original Mea...

Alexandra,
Yes that is the Maier's filter I'm using.

- Dave

Hi All, Happy 2023 ! I finally had both some free time and clear skies to use my repaired CaK PST that I used a Maier Photonics filter to replace the bad one in mine. Visually today I could see the CaK features and was very pleased with the images it was producing with my ZWO 120 monochrome camera. ...

Alexandra,
I have not imaged through my CaK with the new filter but it is on my list and will post images when I do. I can say that the image is much bright and I see it visually pretty well and even see some CaK features on the disk when I cover my head with dark cloth.

- Dave

Bob, Here is what is listed on Maier's site for his 393 filter that I used 393 Bandpass Filter - sulfur line gas chromatography Center wavelength=393 nm +/- 2 nm Bandwidth=13 nm +/- 2 nm Size=12.0 mm dia. x 5.0 mm thick Out of band blocking > optical density 4.0 (xray to 2000 nm) Coating type= Non h...

Like others that own a CaK PST, the filters will hazy over with age. So far the main yellow one in the OTA is still in good shape but the blocking filter in the eyepiece tube had hazied over. I took it into work and measured it. It was only passing less than 2% at the CaK wavelength . I was still ab...

Both of my Maiers filters are still perfectly clear and my two are the first two he made.

- Dave

With it being 24 years old the odds are very good that it has drifted off the CWL of 656 and is also cloudy. It should look perfectly clear so if you see any hazy it has problems.

- Dave

Have you checked the narrow band filter ? If your unit is 10 years old then the filter might have aged and is no longer on band.

- Dave

You can assembly the unit minus the narrow band filter and see if you can get an eyepiece to focus of the edge of the cone. Since the Moon is about the same diameter as the Sun you can try the unit out again without the narrow band filter in place to see if you can get the Moon and the occulting con...

The key is that H2 that contains the Iris is located at the aperture stop of the system So V2 might not be in the correct position. Here is a link to my math that shows how to calculate the spacing for all the elements in a solar coronagraph. http://considine.net/dgroski/promscope/prom3.gif so you c...

The main parts should be the tube with the lens and occulting disk, with the occulting disk facing the focuser of the telescope. Next, what screws on the back of that tube ( end without the lens/disk) is the tube with the iris, and screwed on to that is the tube with the second lens without the disk...

Hi, Having designed and built coronagraphs from scratch I'll be happy to try to happy. http://considine.net/dgroski/promscope/ The first issue you might have are the occulting cones. The diameter is determined by the size of the solar disk produced by the telescope. The Sun's disk is approximately 1...

A Q-tip that is only slight damp with isopropyl alcohol can be used to clean the surface of the filters without any damage. It is possible that the spot your seeing are on the ITF filter and the coating are known to go bad. The ITF filter is not the small 5mm that you see when you remove the eyepiec...

Last weekend I was in Vermont at the 80th Stellafane convention. Stellafane has a legendary Swap meet on Saturday morning and you'll never know what you'll find. In the piles of treasures was a PST that the owner stated gave a sharp image but the Etalon needed adjusting since his kids had dropped it...

Walter,
I think it is some type of artifical star. Light is reflected off the big mirror onto the little mirror, then back off the big mirror and then brightly illuminates the pin hole.

- Dave

Walter, You need to do the final alignment on a defocused star. You most likely only need to adjust the primary in the "M" plane so the primary mirror is tilted a little bit more away from the secondary. Remember to recenter the star in the eyepiece after each adjustment. - Dave

Walter, You might consider this filter from Omega on Ebay. It is cheaper then the Andover filter and narrower in bandwidth. - Dave http://www.ebay.com/itm/Optical-Interference-Filter-656-3-H-Alpha-0-15nm-Band-Pass-Double-Pass-/310516117756?pt=Educational_Toys_US&hash=item484c33f0fc#ht_1173wt_1074

Hi David step four done. I'm not far of the 62.5 mm depending on where I hold the ruler on. Looking up the tube I see nothing but the primary. I wonder how that looks on the moon ;-) . I guess I have to wait a couple of days. the laser still points to the middle of the primary give or take a Millim...

Walter, Excellent alignment so far. You just need to tilt the primary away from the secondary so it is no longer is visible in the when you look up the focuser. In your picture, showing what you see when looking up the tube, your at Step 3 in my drawing. The primary mirror is looking at the secondar...

Walter, When the primary is aligned correctly, the laser being reflected off it should be around 62.5mm (125/2) from the edge of the secondary. It may be much more depending on the design. So if you taped a piece of paper off the back of the secondary mirror cell you can use that as a target to alig...